Skeptical Science

2012 SkS Weekly Digest #19

Mon, 14 May 2012 14:55:24 EST

SkS Highlights

The first article out of the chute, Dana's Lindzen's Clouded Vision, Part 1: Science created the biggest buzz of comments for the week. MarkR's Turbines in Texas mix up nighttime heat stirred-up the second highest number of comments. Coming in third was Dana's Tom Harris' Carleton University Climate Misinformation Class. Tom Harris himself actually dropped a couple of comments on the thread.

Toon of the Week

Quote of the Week

"We have known since the 1800s that carbon dioxide traps heat in the atmosphere. The right amount keeps the climate conducive to human life. But add too much, as we are doing now, and temperatures will inevitably rise too high. This is not the result of natural variability, as some argue. The earth is currently in the part of its long-term orbit cycle where temperatures would normally be cooling. But they are rising — and it’s because we are forcing them higher with fossil fuel emissions."

Source: "Game Over for the Climate" Op-ed by James Hansen, New York Times, May 9, 2012

Issue of the Week

Are you reluctant to ask a "dumb question" on a comment thread for fear of being lectured to by one or more of members of the SkS author team?

Words of the Week

Climate: Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. In various chapters in this report different averaging periods, such as a period of 20 years, are also used.

Climate system: The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere, and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations and anthropogenic forcings such as the changing composition of the atmosphere and land-use change.

Climate change: Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that the Unite Nations Framework Convention on Climate Change (UNFCCC), in its Article 1, defines climate change as: ‘a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods’. The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition, and climate variability attributable to natural causes. See also Climate variability; Detection and Attribution.

Source: Annex I (Glossary) to Climate Change 2007: Working Group I: The Physical Science Basis, IPCC Fourth Assessment Report.

The Week in Review

A complete listing of the articles posted on SkS during the past week.

Analysis of Speed of Greenland Glaciers Gives New Insight for Rising Sea Level by John Hartz
Arctic Winter Analysis by Neven
Two Centuries of Climate Science: part three - Manabe to the present day, 1966-2012 by John Mason
Tom Harris' Carleton University Climate Misinformation Class by Dana
Turbines in Texas mix up nighttime heat by Mark R
101 responses to Ian Plimer's climate questions by John Cook
Lindzen's Clouded Vision, Part 2: Risk by Dana
New research from last week 18/2012 by Ari Jokimäki
Lindzen's Clouded Vision, Part 1: Science by Dana

Coming Soon

A list of articles that are in the SkS pipeline. Most of these articles, but not necessarily all, will be posted during the week.

CRUTEM4: A detailed look (Kevin C)
New research from last week 19/2012 (Ari Jokimäki)
Climate Change Consequences - Often Unexpected (Dana)
David Evans: All at Sea about Ocean Warming and Sea Level Rise (Rob Painting)
Resolving Confusion about Modeled and Observed Ocean Heat Content (Dana)
Open letter to an anonymous climate scientist (Dumb Scientist)
In Search Of: Himalayan Ice Loss (mspelto, Daniel Bailey)
Latest Southern Ocean research shows continuing deep ocean change (John Hartz)

SkS in the News

Lessons from Past Predictions: Hansen 1981 was re-posted by Climate Progress.

Lindzen's Clouded Vision, Part 1: Science and Part 2: Risk was re-posted by Climate Progress and PlanetSave.

SkS Spotlights

The Alfred Wegener Institute for Polar and Marine Research: Polar and Marine research are central themes of Global system and Environmental Science. The Alfred Wegener Institute conducts research in the Arctic, the Antarctic and at temperate latitudes. It coordinates Polar research in Germany and provides both the necessary equipment and the essential logistic back up for polar expeditions. Recent additional research themes include North Sea Research, contributions to Marine Biological Monitoring, Marine Pollution Research, Investigation of naturally occuring marine substances and technical marine developments.

The Institute was established as a public foundation in 1980. The Foundation Alfred Wegener Institute for Polar and Marine Research includes the Alfred Wegener Institute in Bremerhaven the Potsdam Research Unit (1992), the Biologische Anstalt Helgoland and the Wadden Sea Station Sylt. It is a member of the Helmholtz Association of German Research Centres; the German Federal Ministry of Education and Research (BMBF) covers 90% of financing, the state of Bremen 8% and the states of Brandenburg and Schleswig-Holstein provide 1% each. The Foundation employs over 900 staff and has a total budget of 100 million Euro in 2005.

Analysis of Speed of Greenland Glaciers Gives New Insight for Rising Sea Level

Mon, 14 May 2012 03:50:25 EST

This is a reprint of a news release posted by the National Science Foundation on May 4, 2012.

Researchers determine that although glaciers continue to increase in velocity, the rate at which they can dump ice into the ocean is limited.

The north branch of Jakobshavn Isbrae is in the upper left corner of the image, with several newly calved icebergs in front of it. The larger, faster moving, south branch is located near the upper right corner. Prior to about 2003, both branches merged to create a large floating ice tongue that extended beyond the iceberg covered area visible in this image. Since the 1990, the glacier calving front (terminus) has retreated about 18 km (11 miles). Now, it is only in the winter that both branches sometimes merge to form a much smaller seasonal ice tongue, which breaks up in the spring.

Credit: Polar Science Center, Applied Physics Laboratory, University of Washington

Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland's contribution to rising sea level in the 21st century could be significantly less than the upper limits some scientists thought possible.

The finding comes from a paper funded by the National Science Foundation (NSF) and NASA and published in today's (May 4, 2012) journal Science.

While the study indicates that a melting Greenland's contributions to rising sea levels could be less than expected, researchers concede that more work needs to be done before any definitive trend can be identified.

Studies like this one are designed to examine more closely and in greater detail what is actually happening with the ice sheets, often using newer and more precise tools and thereby better defining the parameters that scientists use to make predictions, such as the upper limits of sea-level rise.

"This study provides more evidence that the rate at which these glaciers can dump ice into the ocean is indeed limited," said Ian Howat, assistant professor of Earth sciences and member of the Byrd Polar Research Center at Ohio State University, a co-author on the paper. "What remains to be seen is how long the acceleration will continue--but it appears that our worst-case scenarios aren't likely."

The fate of the Earth's ice sheets and their potential contributions to sea-level rise as the globe warms are among the major scientific uncertainties cited in the Fourth Assessment of the Intergovernmental Panel on Climate Change (IPCC). This is in part because the Greenland and Antarctic ice sheets have historically been, and in large measure continue to be, relatively sparsely monitored, as compared to other parts of the globe.

The faster the glaciers move, the more ice and melt water they release into the ocean.

In previous studies, scientists trying to understand the contribution of melting ice to rising sea level in a warming world considered a scenario in which the Greenland glaciers would either double or increase by as much as ten-fold their velocity between 2000 and 2010 and then stabilize at the higher speed.

This new study shows Greenland ice would likely move at the lower rate--a doubling of its speed--and contribute about four inches to rising sea level by 2100. The previous studies used the higher speed and estimated the glaciers would contribute nearly 19 inches by the end of this century.

In the new study, the scientists extracted a decade-long record of changes in Greenland outlet glaciers by producing velocity maps using data from the Canadian Space Agency's Radarsat-1 satellite, Germany's TerraSar-X satellite and Japan's Advanced Land Observation Satellite. They started with the winter of 2000-01 and then repeated the process for each winter from 2005-06 through 2010-11 and found that the outlet glaciers had not increased in velocity as much as had been speculated.

"So far, on average we're seeing about a 30 percent speedup in 10 years [of Greenland glaciers, which gives new insight for rising sea level]," said Twila Moon, a University of Washington doctoral student in Earth and space sciences and lead author of the paper documenting the observations.

"This study is a great example of the power of high-resolution data sets in both space and time, and the importance of looking carefully at as much data as possible in helping make the best predictions we can of future changes", said Henrietta Edmonds, program director for Arctic Natural Sciences in NSF's Office of Polar Programs.

The scientists saw no clear indication in the new research that the glaciers will stop gaining speed during the rest of the century, and so by 2100 they could reach or exceed the scenario in which they contribute four inches to sea level rise.

The record showed a complex pattern of behavior. Nearly all of Greenland's largest glaciers that end on land move at top speeds of 30 to 325 feet a year, and their changes in speed are small because they are already moving slowly. Glaciers that terminate in fjord ice shelves move at 1,000 feet to a mile a year, but didn't gain speed appreciably during the decade.

In the East, Southeast and Northwest areas of Greenland, glaciers that end in the ocean can travel seven miles or more in a year. Their changes in speed varied (some even slowed), but on average the speeds increased by 28 percent in the Northwest and 32 percent in the Southeast during the decade.

Moon said she was drawn to the research from a desire to take the large store of data available from the satellites and put it into a usable form to understand what is happening to Greenland's ice. "We don't have a really good handle on it and we need to have that if we're going to understand the effects of climate change," she said. "We are going to need to continue to look at all of the ice sheet to see how it's changing, and we are going to need to continue to work on some tough details to understand how individual glaciers change."

Climate Change Consequences - Often Unexpected

Wed, 16 May 2012 02:38:51 EST

An increasingly common fallback position once climate change "skeptics" accept that the planet is warming and humans are the dominant cause is the myth that climate change won't be bad. In fact, this particular myth comes in at #3 on our list of most used climate myths. It's an ideal fallback position because it allows those who reject the body of scientific evidence to believe that if they are wrong on the science, it's okay, because the consequences won't be dire anyway.

One of my colleagues, Molly Henderson recently completed a Masters Degree program class on scientific research which focused on climate change, which she aced (way to go, Molly!). For her final research paper, she examined the consequences of climate change on the prevalence of water-borne diseases in the US Great Lakes region.

This is obviously a very focused topic on a specific region and predicted consequence of climate change, but I think it also provides a perfect example as to why this notion that the effects of climate change will somehow be benign or good is fundamentally flawed. As a general rule, climate change is not a good thing, because all species are adapted to the current climate in the region in which they reside. There is a certain amount of climate change to which species can adapt and survive, but adaptation can be a difficult and ugly process.

As Molly's paper makes clear, while humans are a very adaptable species, at the same time we've built a lot of infrastructure whose specifications are based on the current climate. We have large agricultural farms which depend on a relatively constant climate in order to successfully grow crops, for example. As Molly's paper shows, there are some other climate change consequences on our infrastructure which we might not even normally think about.

The Problem

Molly states the problem as follows.

"Many cities that surround the Great Lakes are equipped with sewer systems that capture and combine sanitary sewage and stormwater as they are conveyed to wastewater treatment plants (McLellan et al., 2007). The EPA estimates that 150 communities within the Great Lakes drainage basin are serviced by combined sewer systems (CSS) (U.S. EPA, 2012). Extreme precipitation events can overcome the conveyance capacity of CSS and cause overflows, known as combined sewer overflows (CSO). These overflow events result in untreated sanitary sewage and stormwater discharges into receiving waters (i.e, rivers, streams, lakes, etc.).

Urban stormwater and sewage overflow water contains human pathogens including viruses, protozoans, and pathogenic bacteria that can cause adverse health effects if ingested. The Great Lakes provide drinking water for an estimated 40 million people and there are more than 500 recreational beaches along lake shores (Great Lakes Legislative Caucus, 2012). Waterborne disease outbreaks result when water supplies are contaminated with pathogens that infect humans.

It is well known that extreme precipitation events that cause CSO in the Great Lakes Region can lead to waterborne disease outbreaks, as seen in the 1993 outbreak of intestinal illness in Milwaukee, Wisconsin which affected an estimated 403,000 people (Curriero et al., 2001). Observed and projected climate changes due to global warming infer that more frequent extreme precipitation events are on the horizon for this region, thus potentially leading to a higher incidence of waterborne disease outbreaks if mitigation measures are not taken to improve existing CSS infrastructure and reduce greenhouse gas emissions."

Personally when I think about the consequences of climate change, the possibility that increased heavy precipitation events could cause combined sewer systems to overflow, thus introducing pathogens into drinking water sources has never previously crossed my mind.

Climate Literature Investigating this Problem

In retrospect this is a perfectly logical climate change consequence in regions which will receive increased precipitation, and indeed Molly shows that a great deal of research has been done on this specific concern in the specific region of the Great Lakes. Sousounis & Grover (2002) used the the Canadian Coupled Climate Model and the Hadley Coupled Climate Model to show that an increase in heavy precipitation events is among the expected climatic changes in the Great Lakes region. A paper led by Katharine Hayhoe (who we've previously seen here and here responding to the wave of hate directed her way when she was asked to write a climate chapter for a Newt Gingrich book) also examined some of the expected climatic changes in the Great Lakes region, as described by Molly:

"Some positive impacts such as a decrease in energy use in the winter and risk of cold-related illnesses may result; however, a higher demand for energy in the summer and higher rates of heat-related mortality is likely to offset this positive impact. This study also highlights the economic impacts on the Great Lakes due to projected lake level reductions and the article places emphasis on reducing greenhouse gas emissions."

Patz et al. (2008) hypothesized that extreme precipitation events may overwhelm the common combined sewer systems in the Great Lakes region, causing potentially dangerous overflows into sources of drinking water and recreational waterways, and recommended upgrading sewage/stormwater infrastructure and greater protection of watersheds.

A National Resource Defense Council (NRDC) fact sheet highlights the fact that that more than half of the waterborne disease outbreaks in the United States over the past 50 years are linked to heavy rain events, lending additional credibility to this potential problem. Curriero et al. (2001) examined the association between extreme rainfall and waterborne disease outbreaks in the United States between 1948 and 1994, and their conclusions were consistent with the NRDC fact sheet, finding that 51% of outbreaks in their study sample were preceded within a 2-month lag by an extreme level of precipitation.

Adaptation Has a Cost

The good news is that while most of us probably haven't considered this particular climate change consequence, obviously a number of scientists have investigated it. While it may seem on the surface like a relatively minor regional concern, Molly notes that 40 million people rely on the Great Lakes Region as a water supply, and the recreational beaches along the shores of the Great Lakes are an important economic contributor to the region. Additionally, combined sewer systems serve roughly 772 communities containing about 40 million people in the USA. It's also a larger region - over 30 million people live within the Great Lakes basin area; that's 10% of the US population plus 25% of Canada's.

However, since we are aware of the problem, the Great Lakes region can adapt to it. The bad news is of course that upgrading sewage and stormwater infrastructure is not a cheap undertaking. As another example we recently discussed, adjusting to a rising frequency of heat waves resulting from continued climate change will be another costly adaptation, as will shifting the geography of our agricultural production.

There are alternatives to facing these types of climate change costs. We can try to prevent the problems from occurring by addressing the source (greenhouse gas emissions), which is likely the cheapest option, or we can simply allow them to happen and face the consequences. As renowned paleoclimatologist Lonnie Thompson put it:

"Three options remain for dealing with the crisis: mitigate, adapt, and suffer...Sooner or later, we will all deal with global warming. The only question is how much we will mitigate, adapt, and suffer."

Molly's research provides one specific example of this choice. If we fail to mitigate these types of consequences, we will either have to pay the cost to adapt to them, or suffer the consequences of failing to act. The good news is that we are aware of the problem both on a global and local scale. Now we just have to decide how we want to address it.

References

McLellan, Sandra L., Hollis, Erica J., Depas, Morgan M., VanDyke, Meredith, Harris, Josh, and Scopel, Caitlin O. (2007). Distribution and Fate of Escherichia coli in Lake Michegan Following Contamination with Urban Stormwater and Combined Sewer Overflows. Journal of Great Lakes Research, (33), 566-580.

U.S. Environmental Protection Agency (2012). National Pollutant Discharge Elimination System (NPDES). Retrieved April 27, 2012 from http://cfpub.epa.gov/npdes/.

Great Lakes Legislative Caucus (2012). Great Lakes Facts and Figures. Retrieved on April 27, 2012 from http://greatlakeslegislators.org/.

Curriero, Frank C., Patz, Jonathan A., Rose, Joan B., Lele, Subhash (2001). The Association Between Extreme Precipitation and Waterborne Disease Outbreaks in the United States, 1948-1994. American Journal of Public Health, 91(8), 1194-1199.

Sousounis, Peter J. and Grover, Emily K. (2002). Potential Future Weather Patters over the Great Lakes Region. Journal of Great Lakes Research. 28(4), 496-520.

Hayhoe, Katharine, VanDorn, Jeff, Croley, Thomas II, Schlegal, Nicole, and Wuebbles, Donald (2010). Regional Climate Change Projections for Chicago and the U.S. Great Lakes. Journal of Great Lakes Research, 36, 7-21.

Patz, Jonathan A., Vavrus, Stephen J., Uejio, Christopher K., McLellan, Sandra L. (2008). Climate Change and Waterborne Disease Risk in the Great Lakes Region of the U.S. American Journal of Preventative Medicine, 35(5), 451-458. doi:10.1016/j.amepre.2008.08.026.

National Resources Defense Council (2010). Rising Tide of Illness: How Global Warming Could Increase the Threat of Waterborne Diseases. Retrieved March 12, 2012 from http://www.nrdc.org/health/files/GWillness4pgr_08.pdf.

New research from last week 19/2012

Tue, 15 May 2012 18:55:14 EST

Wouldn't it be nice to see something like following headlines in popular news media:

"Growth change of oak and beech are related to climate time series and N deposition trends!"

"Atmospheric lifetime of methane only 9.1 ± 0.9 years!"

"WAIS Divide was colder than the last 1000-year average from 1300 to 1800 C.E.!"

"Concentrations of rBC in the ice cores displayed significant variability at annual to decadal time scales!"

I bet papers with these in their frontpage would be sold out in minutes.

Contrary to expectations, British butterflies don't utilise an increased range of habitat types with global warming

Habitat associations of thermophilous butterflies are reduced despite climatic warming - Oliver et al. (2012)

Abstract: "Climate warming threatens the survival of species at their warm, trailing-edge range boundaries, but also provides opportunities for the ecological release of populations at the cool, leading edges of their distributions. Thus, as the climate warms, leading-edge populations are expected to utilise an increased range of habitat types, leading to larger population sizes and range expansion. Here, we test the hypothesis that the habitat associations of British butterflies have expanded over three decades of climate warming. We characterise the habitat breadth of 27 southerly-distributed species from 77 monitoring transects between 1977 and 2007 by considering changes in densities of butterflies across 11 habitat types. Contrary to expectation, we find that 20 out of 27 (74%) butterfly species showed long term contractions in their habitat associations, despite some short-term expansions in habitat breadth in warmer-than-usual years. Thus, we conclude that climatic warming has ameliorated habitat contractions caused by other environmental drivers to some extent, but that habitat degradation continues to be a major driver of reductions in habitat breadth and population density of butterflies."

Citation: Tom H. Oliver, Chris D. Thomas, Jane K. Hill, Tom Brereton, David B. Roy, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02737.x.

Droughts have become more intense and last longer in Urmia Lake Basin, Iran

Observed climate variability and change in Urmia Lake Basin, Iran - Delju et al. (2012)

Abstract: "This paper analyzes climate variability and change in the Urmia Lake Basin, northwest of Iran. Annual average of the following data time series has been analyzed by statistical methods: dry bulb temperature, maximum and minimum temperature, precipitation, and number of rainy and snowy days. We have also used mean monthly temperature and precipitation data for analysis of drought spells for the period 1964–2005 to find out whether fluctuations in the lake level are attributable to natural drought. Our results indicate that mean precipitation has decreased by 9.2 % and the average maximum temperature has increased by 0.8°C over these four decades. The seasonal changes are particularly visible in winter and spring. Results of the Palmer Drought Severity Index show that on average, drought episodes have hit the Urmia Lake Basin every 5 years and most of them reached severe levels, but recent droughts have become more intense and last longer."

Citation: A. H. Delju, A. Ceylan, E. Piguet and M. Rebetez, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0651-9.

Asian summer monsoon intensity has decreased with global warming

Decreasing Asian summer monsoon intensity after 1860 AD in the global warming epoch - Xu et al. (2012)

Abstract: "The trend of the Indian summer monsoon (ISM) intensity and its nature during the past 100 and 200 years still remain unclear. In this study we reconstructed the ISM intensity during the past 270 years from tree ring δ¹⁸O at Hongyuan, eastern edge of the Tibet Plateau. The monsoon failures inferred from δ¹⁸O_{tree ring} correlate well with those recorded in ice cores, speleothem, and historical literature sources. 22.6, 59.0, and 110.9-years frequency components in the Hongyuan δ¹⁸O_{tree ring} series, which may be the responses to solar activities, synchronize well with those recorded in other ISM indices. A notable feature of the reconstructed ISM intensity is the gradually decreasing trend from about 1860 to the present, which is inversely related to the increasing temperature trend contemporaneously. Such “decreasing ISM intensity–increasing temperature” tendency can also be supported by ice core records and meteorological records over a wide geographic extension. The decrease in sea surface temperature gradient between tropical and north Indian Ocean, and the decrease in land-sea thermal contrast between tropical Indian Ocean and “Indian sub-continent–western Himalaya” are possibly responsible for the observed decreasing ISM trend."

Citation: Hai Xu, Yetang Hong and Bin Hong, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1378-0.

Sunshine hour decline in China since 1960's due to air pollution

The magnitude of the effect of air pollution on sunshine hours in China - Wang et al. (2012)

Abstract: "This study investigates the changes in sunshine hours in relation to API (Air Pollution Index) across China. Data were collected from a total of 38 cities over the period of 1960–2009. Sunshine hours in over 84% of the cities significantly (p < 0.05) decline with an average of 16.7% for the 1960s–2000s. This decline is mainly prevalent over Sichuan Basin (22.4%), North China Plain (18.8%), and Yangtze River Delta (18.2%). While the sunshine hour decline is largely in the 20th century (with the strongest drop in the 1980s and the least in the 1990s), it rebounds by 0.3% after 2000. For especially in winter seasons and the North China region, API is negatively related with sunshine hours. For days with API > 80, sunshine hours are on the average 0.7 h d⁻¹ (8.4%) shorter than for days with API ≤ 80 under clear-sky condition for 2001–2005. In cities with average daily API ≤ 80 and >80 for the 2000s, sunshine hour decline for the 1960s–2000s is 0.8 h d⁻¹ (13.4%) and 1.0 h d⁻¹ (15.9%) respectively. Winter seasons with high API (90) exhibit the highest sunshine hour decline (21.5%). The study shows that spatiotemporal changes in sunshine hours in China could largely be explained in terms of API."

Citation: Wang, Y., Y. Yang, N. Zhao, C. Liu, and Q. Wang (2012), The magnitude of the effect of air pollution on sunshine hours in China, J. Geophys. Res., 117, D00V14, doi:10.1029/2011JD016753.

In 2007 there were lot of melt ponds on Arctic sea ice and in 2011 there were even more

Exceptional melt pond occurrence in the years 2007 and 2011 on the Arctic sea ice revealed from MODIS satellite data - Rösel & Kaleschke (2012)

Abstract: "Melt ponds contribute to the ice-albedo feedback as they reduce the surface albedo of sea ice, and hence accelerate the decay of Arctic sea ice. Here, we analyze the melt pond fraction, retrieved from the MODIS sensor for the years 2000–2011 to characterize the spatial and temporal evolution. A significant anomaly of the relative melt pond fraction at the beginning of the melt season in June 2007 is documented. This is followed by above-average values throughout the entire summer. In contrast, the increase of the relative melt pond fraction at the beginning of June 2011 is within average values, but from mid-June, relative melt pond fraction exhibits values up to two standard deviations above the mean values of 30 ± 1.2% which are even higher than in Summer 2007."

Citation: Rösel, A., and L. Kaleschke (2012), Exceptional melt pond occurrence in the years 2007 and 2011 on the Arctic sea ice revealed from MODIS satellite data, J. Geophys. Res., 117, C05018, doi:10.1029/2011JC007869.

Signal of human influence on climate has strengthened over the first decade of the 21st century

Observed 21st century temperatures further constrain likely rates of future warming - Stott & Jones (2012)

Abstract: "We carry out a detection and attribution analysis of observed near-surface temperatures to 2010 and demonstrate that the signal of human influence on climate has strengthened over the first decade of the 21st century. As a result, we show that global warming is set to continue, with the second decade of the 21st century predicted to be very likely warmer than the first. Estimates of future warming rates consistent with observations of past climate change are now better constrained than they were a decade ago. The highest rates of warming previously consistent with past warming now appear to be unlikely."

Citation: Peter A. Stott, Gareth S. Jones, Atmospheric Science Letters, DOI: 10.1002/asl.383.

Antactic ice core records of black carbon deposition since 1850

Changes in black carbon deposition to Antarctica from two high-resolution ice core records, 1850–2000 AD - Bisiaux et al. (2012) [FULL TEXT]

Abstract: "Refractory black carbon aerosols (rBC) emitted by biomass burning (fires) and fossil fuel combustion, affect global climate and atmospheric chemistry. In the Southern Hemisphere (SH), rBC is transported in the atmosphere from low- and mid-latitudes to Antarctica and deposited to the polar ice sheet preserving a history of emissions and atmospheric transport. Here, we present two high-resolution Antarctic rBC ice core records drilled from the West Antarctic Ice Sheet divide and Law Dome on the periphery of the East Antarctic ice sheet. Separated by ~3500 km, the records span calendar years 1850–2001 and reflect the rBC distribution over the Indian and Pacific ocean sectors of the Southern Ocean. Concentrations of rBC in the ice cores displayed significant variability at annual to decadal time scales, notably in ENSO-QBO and AAO frequency bands. The delay observed between rBC and ENSO variability suggested that ENSO does not directly affect rBC transport, but rather continental hydrology, subsequent fire regimes, and aerosol emissions. From 1850 to 1950, the two ice core records were uncorrelated but were highly correlated from 1950 to 2002 (cross-correlation coefficient at annual resolution: r = 0.54, p < 0.01) due to a common decrease in rBC variability. The decrease in ice-core rBC from the 1950s to late 1980s displays similarities with inventories of SH rBC grass fires and biofuel emissions, which show reduced emission estimates over that period."

Citation: Bisiaux, M. M., Edwards, R., McConnell, J. R., Curran, M. A. J., Van Ommen, T. D., Smith, A. M., Neumann, T. A., Pasteris, D. R., Penner, J. E., and Taylor, K.: Changes in black carbon deposition to Antarctica from two high-resolution ice core records, 1850–2000 AD, Atmos. Chem. Phys., 12, 4107-4115, doi:10.5194/acp-12-4107-2012, 2012.

Most temperature proxies really are linear functions of annual mean temperature

A test for non-linearity in temperature proxy records - Støve et al. (2012)

Abstract: "Are temperature proxy records linear recorders of past temperature conditions? We apply a statistical test for linearity to 15 millennial-long proxy records with annual resolution that where shown to significantly respond to Northern Hemisphere annual mean temperature selected from a collection of 30 proxies. The test, based on generalized additive modeling, shows that most of the proxies can indeed be shown to be linear functions of annual mean temperature, but two proxy records do not appear to have a linear relationship with temperature -- this supports the assumption of linearity in most climate reconstruction work. The method tests for non-linearity in a proxy relative to the group of proxies it is being used together with. We test robustness of the results and find that the results are stable to choice of proxies. The linearity-testing method is quite general and could in the future be used for larger and more extensive sets of proxies."

Citation: Bård Støve, Fredrik Charpentier Ljungqvist, Peter Thejll, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00632.1.

New technique for measuring past methane mixing ratios from ice cores

Continuous measurements of methane mixing ratios from ice cores - Stowasser et al. (2012) [FULL TEXT]

Abstract: "This work presents a new, field-deployable technique for continuous, high-resolution measurements of methane mixing ratios from ice cores. The technique is based on a continuous flow analysis system, where ice core samples cut along the long axis of an ice core are melted continuously. The past atmospheric air contained in the ice is separated from the melt water stream via a system for continuous gas extraction. The extracted gas is dehumidified and then analyzed by a Wavelength Scanned-Cavity Ring Down Spectrometer for methane mixing ratios. We assess the performance of the new measurement technique in terms of precision (±0.8 ppbv, 1σ), accuracy (±8 ppbv), temporal (ca. 100 s), and spatial resolution (ca. 5 cm). Using a firn air transport model, we compare the resolution of the measurement technique to the resolution of the atmospheric methane signal as preserved in ice cores in Greenland. We conclude that our measurement technique can resolve all climatically relevant variations as preserved in the ice down to an ice depth of at least 1980 m (66 000 yr before present) in the North Greenland Eemian Ice Drilling ice core. Furthermore, we describe the modifications, which are necessary to make a commercially available spectrometer suitable for continuous methane mixing ratio measurements from ice cores."

Citation: Stowasser, C., Buizert, C., Gkinis, V., Chappellaz, J., Schüpbach, S., Bigler, M., Faïn, X., Sperlich, P., Baumgartner, M., Schilt, A., and Blunier, T.: Continuous measurements of methane mixing ratios from ice cores, Atmos. Meas. Tech., 5, 999-1013, doi:10.5194/amt-5-999-2012, 2012.

Evidence for global Little Ice Age from West Antarctic borehole temperatures

Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide - Orsi et al. (2012)

Abstract: "The largest climate anomaly of the last 1000 years in the Northern Hemisphere was the Little Ice Age (LIA) from 1400–1850 C.E., but little is known about the signature of this event in the Southern Hemisphere, especially in Antarctica. We present temperature data from a 300 m borehole at the West Antarctic Ice Sheet (WAIS) Divide. Results show that WAIS Divide was colder than the last 1000-year average from 1300 to 1800 C.E. The temperature in the time period 1400–1800 C.E. was on average 0.52 ± 0.28°C colder than the last 100-year average. This amplitude is about half of that seen at Greenland Summit (GRIP). This result is consistent with the idea that the LIA was a global event, probably caused by a change in solar and volcanic forcing, and was not simply a seesaw-type redistribution of heat between the hemispheres as would be predicted by some ocean-circulation hypotheses. The difference in the magnitude of the LIA between Greenland and West Antarctica suggests that the feedbacks amplifying the radiative forcing may not operate in the same way in both regions."

Citation: Orsi, A. J., B. D. Cornuelle, and J. P. Severinghaus (2012), Little Ice Age cold interval in West Antarctica: Evidence from borehole temperature at the West Antarctic Ice Sheet (WAIS) Divide, Geophys. Res. Lett., 39, L09710, doi:10.1029/2012GL051260.

Yet another analysis suggests that greenhouse gases and aerosols controlled temperature after 1950

A fractal climate response function can simulate global average temperature trends of the modern era and the past millennium - van Hateren (2012) [FULL TEXT]

Abstract: "A climate response function is introduced that consists of six exponential (low-pass) filters with weights depending as a power law on their e-folding times. The response of this two-parameter function to the combined forcings of solar irradiance, greenhouse gases, and SO₂-related aerosols is fitted simultaneously to reconstructed temperatures of the past millennium, the response to solar cycles, the response to the 1991 Pinatubo volcanic eruption, and the modern 1850–2010 temperature trend. Assuming strong long-term modulation of solar irradiance, the quite adequate fit produces a climate response function with a millennium-scale response to doubled CO₂ concentration of 2.0 ± 0.3 °C (mean ± standard error), of which about 50 % is realized with e-folding times of 0.5 and 2 years, about 30 % with e-folding times of 8 and 32 years, and about 20 % with e-folding times of 128 and 512 years. The transient climate response (response after 70 years of 1 % yearly rise of CO₂ concentration) is 1.5 ± 0.2 °C. The temperature rise from 1820 to 1950 can be attributed for about 70 % to increased solar irradiance, while the temperature changes after 1950 are almost completely produced by the interplay of anthropogenic greenhouse gases and aerosols. The SO₂-related forcing produces a small temperature drop in the years 1950–1970 and an inflection of the temperature curve around the year 2000. Fitting with a tenfold smaller modulation of solar irradiance produces a less adequate fit with millennium-scale and transient climate responses of 2.5 ± 0.4 and 1.9 ± 0.3 °C, respectively."

Citation: J. H. van Hateren, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1375-3.

New derivations for atmospheric lifetimes of some GHG's

Reactive greenhouse gas scenarios: Systematic exploration of uncertainties and the role of atmospheric chemistry - Prather et al. (2012)

Abstract: "Knowledge of the atmospheric chemistry of reactive greenhouse gases is needed to accurately quantify the relationship between human activities and climate, and to incorporate uncertainty in our projections of greenhouse gas abundances. We present a method for estimating the fraction of greenhouse gases attributable to human activities, both currently and for future scenarios. Key variables used to calculate the atmospheric chemistry and budgets of major non-CO₂ greenhouse gases are codified along with their uncertainties, and then used to project budgets and abundances under the new climate-change scenarios. This new approach uses our knowledge of changing abundances and lifetimes to estimate current total anthropogenic emissions, independently and possibly more accurately than inventory-based scenarios. We derive a present-day atmospheric lifetime for methane (CH₄) of 9.1 ± 0.9 y and anthropogenic emissions of 352 ± 45 Tg/y (64% of total emissions). For N₂O, corresponding values are 131 ± 10 y and 6.5 ± 1.3 TgN/y (41% of total); and for HFC-134a, the lifetime is 14.2 ± 1.5 y."

Citation: Prather, M. J., C. D. Holmes, and J. Hsu (2012), Reactive greenhouse gas scenarios: Systematic exploration of uncertainties and the role of atmospheric chemistry, Geophys. Res. Lett., 39, L09803, doi:10.1029/2012GL051440.

Causes and differences of temperature response of tree species radial growth

Radial growth change of temperate tree species in response to altered regional climate and air quality in the period 1901–2008 - Kint et al. (2012)

Abstract: "Both increasing and decreasing 20th century growth trends have been reported in forests throughout Europe, but only for few species and areas suitable modelling techniques have been used to distinguish individual tree growth (operating on a local scale) from growth change due to exogenous factors (operating on a broad geographical scale). This study relates for the first time observed growth changes, in terms of basal area increment (BAI) of dominant trees of pedunculate oak, common beech and Scots pine, in north-west European temperate lowland forests (Flanders) to climate, atmospheric CO₂ and tropospheric O₃ concentrations, N deposition, site quality and forest structure for more than a century (the period 1901–2008), applying mixed models. Growth change during the 20th century is observed for oak (increasing growth) and beech (increasing growth until the 1960s, growth decline afterwards), but not for pine. It was possible to relate growth change of oak and beech to climate time series and N deposition trends. Adding time series for CO₂ and O₃ concentration did not significantly improve model results. For oak and beech a switch from positive to negative growth response with increasing nitrogen deposition throughout time is observed. Growth increase for oak is mainly determined by the interaction between growing season temperature and soil water recharge. It is reasonable to assume that the observed growth trend for oak will continue for as long as early season water availability is not compromised. The decreasing trend in summer relative air humidity observed since the 1960s in the study area can be a main cause of recent beech BAI decrease. A further growth decline of beech can be expected, independent of site quality."

Citation: Vincent Kint, Wim Aertsen, Matteo Campioli, Dries Vansteenkiste and Andy Delcloo, et al., Climatic Change, 2012, DOI: 10.1007/s10584-012-0465-x.

CLASSIC OF THE WEEK: Lord Kelvin (1864)

On the secular cooling of the earth - Lord Kelvin (1864) [FULL TEXT (partial)]

Abstract: No abstract. Quote from the beginning of the paper: "For eighteen years it has pressed on my mind, that essential principles of Thermo-dynamics have been overlooked by those geologists who uncompromisingly oppose all paroxysmal hypostheses, and maintain not only that we have examples now before us, on the earth, of all the different actions by which its crust has been modified in geological history, but that these actions have never, or have not on the whole, been more violent in the past time than they are at present."

Citation: Lord Kelvin (William Thomson), Transactions of the Royal Society of Edinburgh, Vol. XXIII, pp. 167169, 1864. Read April 28, 1862.

This is a cross-post from AGW Observer. When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. At least some of these are also retweeted in Skeptical Science Twitter page. Here's the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.

Tom Harris' Carleton University Climate Misinformation Class

Thu, 10 May 2012 13:19:08 EST

A few months ago, the Canadian Committee for the Advancement of Scientific Skepticism (CASS) issued a report regarding a slew of climate misinformation being taught at Carleton University in Ottawa, Canada by Tom Harris. Somehow Harris, who is an engineer and communications specialist with zero climate research experience, and is the Executive Director of the Heartland Institute-funded International Climate Science Coalition, was put in the position to teach a class on climate and Earth science at Carleton University. More recently, Harris has taken to denouncing what he terms "climatism," which appears to be a disparaging synonym for "climate science." How an anti-climate science engineer was made lecturer of a climate science class at Carleton University is something of a mystery, and a poor decision by the university.

The CASS report followed the growing trend of climate misinformation debunkings using the Skeptical Science database. In this post we will examine just a few of the myths identified by CASS as regrettably being used by Harris to misinform Carleton University students.

Galactic Cherries

A popular climate myth, coming in at #21 on the list of most used climate myths, is that global warming is being caused by galactic cosmic rays. The reason this myth is so popular is that it's a relatively new hypothesis, and thus has only been investigated by climate researchers in recent years. However, the vast majority of studies on the subject have found little if any relationship between galactic cosmic rays and global temperatures.

That didn't stop Harris from exhibiting one of the 5 characteristics of scientific denialism to claim otherwise in his lectures - cherrypicking. As John Cook wrote two years ago in describing this denialism characteristic,

"[cherrypicking] involves selectively drawing on isolated papers that challenge the consensus to the neglect of the broader body of research..."

This is precisely how Harris taught his class, picking out the few scientific studies which seemed to indicate a relationship between cosmic rays and global temperatures, and completely neglecting to mention the vast majority of studies finding little to no correlation between the two. More importantly, galactic cosmic ray flux on Earth has been flat on average over the past six decades, and therefore could not be responsible for a long-term global warming trend over that period. As Figure 1 shows, starting around 1925, the cosmic ray increase lagged behind the temperature increase, and temperatures continued to rise after 1970 while cosmic ray flux did not.

Figure 1: Reconstructed cosmic radiation (solid line before 1952) and directly observed cosmic radiation (solid line after 1952) compared to global temperature (dotted line). All curves have been smoothed by an 11 year running mean (Krivova 2003).

Additionally, there was a record high cosmic ray flux observed in 2009 (Figure 2). The hypothesis espoused by Harris claims that cosmic rays are supposed to cause cooling by increasing cloud cover, yet 2009 was one of the hottest years on record.

Figure 2: Record cosmic ray flux observed in 2009 by the Advanced Composition Explorer (NASA)

Harris chose simply not to teach these inconvenient facts to his students, instead only presenting the cherrypicked bits of information which seemed to support the case he wanted to present them.

Downplaying the Human Influence on Climate

Along similar lines as his cosmic ray cherrypick, Harris decided to toss physics aside and claim that human effects on the climate are too small to measure.

"Until we understand natural cycles of climate without humans, it’s very very tough to tease out what affect humans are having because it’s much smaller. It’s not the big carrier wave that nature is doing anyways, it’s a smaller affect on top of that...There isn’t a good correlation between temperatures and CO2 over the record."

This myth fails on two levels. First, as Richard Alley has discussed, CO2 has historically been the principle control knob for the Earth's temperature, and the current human influence on the climate involves a rapid increase in the amount of CO2 and other greenhouse gases in the atmosphere. Second, many different studies have shown that the human influence on global temperatures has dominated the natural influence over the past century, especially over the past half-century (Figure 3). Once again, Harris neglects to mention the vast body of scientific research and literature which contradicts the assertions he makes in his lectures.

Figure 3: Net human and natural percent contributions to the observed global surface warming over the past 50-65 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, green), Lean and Rind 2008 (LR08, purple), Huber and Knutti 2011 (HK11, light blue), and Gillett et al. 2012 (G12, orange).

Denying the CO2 Control Knob Again

CASS caught Harris downplaying the influence of CO2 on climate once again, repeating the myth that water vapor is the most important greenhouse gas.

"[the] most important greenhouse gas is water vapour...."

Harris of course neglects to mention that the amount of water vapor in the atmosphere is dictated by the temperature of the atmosphere - water vapor is a feedback, not a forcing. Thus something else has to initiate global warming before water vapor can kick in and amplify it. This inconvenient fact makes it very difficult to argue that water vapor is "the most important" greenhouse gas.

Indeed, as Lacis et al. (2010) noted in a paper titled Atmospheric CO2: Principal Control Knob Governing Earth's Temperature (emphasis added),

"Ample physical evidence shows that carbon dioxide (CO₂) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO₂, like ozone, N₂O, CH₄, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does...Without the radiative forcing supplied by CO₂ and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state."

Once again, Harris failed to accurately portray the body of scientific research and evidence, which contradicts the information he taught his students.

CO2 is a Pollutant

Harris also decided to delve into the realm of laws and policy, repeatedly claiming that CO2 is not a pollutant.

"Carbon dioxide of course is a greenhouse gas, but it is not a pollutant. it’s invisible, odourless, it’s essential to plant photosynthesis...It’s not a pollutant and it’s probably a benefit....The debate of course is not whether it’s a pollutant – because it’s not a pollutant. Carbon footprint is not a pollution..."

In fact, CASS documents Harris claiming that CO2 is not a pollutant at least four times, showing two additional videos in which it is again claimed that CO2 is not a pollutant, and also twice claiming that another greenhouse gas - nitrous oxide - is not a pollutant.

Why, in a class entitled "Climate Change: An Earth Sciences Perspective", is Harris so focused on the legal and policy issue of the definition of a pollutant? As it so happens, CO2 and other greenhouse gases are indeed pollutants, at least based on the U.S. Clean Air Act. The U.S. Environmental Protection Agency correctly determined that greenhouse gases meet the definition of air pollutants because they pose a threat to public health and welfare through climate change, and Canadian scientific organizations certainly concur with this conclusion. However, the definition of this term is primarily a legal question, and thus it is puzzling why Harris placed so much emphasis on the issue in a climate and Earth science class.

It's also worth noting that while we often hear this argument from climate denialists that CO2 isn't a pollutant because it's tasteless and odorless, human sensory perceptions generally have little to do with whether a substance is is deemed a pollutant. As noted above, pollutants are characterized by the threat they pose to public health and welfare, not based on whether they're ugly or stinky.

Denying Settled Science

In his lectures, Harris even goes as far as to deny some of the most settled aspects of climate science.

"...the majority of the rise of CO2 has nothing to do with humans....One of the things I find astounding about this whole climate debate is that some of the most basic tenets – you know, the idea that CO2 rise is mainly caused by humans, the idea that temperature rise is definite, its occurring, - many of these things are either not true or are simply unknown, or highly debatable."

Of course we know for a fact that the planet is warming, and similarly there simply is no question that the CO2 increase is due to human emissions. The easiest way to prove this is through a simple accounting approach (i.e. see Cawley 2011) - human emissions are roughly twice as large as the increase in atmospheric CO2 (most of the rest is absorbed by the oceans, which leads to ocean acidification). Harris disputes this with yet another cherrypick:

"I’m getting emails now from scientists, one in particular from Poland, who just authored a paper with a guy from Norway, very leading scientists on CO2 studies, who say that they’ve shown in fact the majority of the rise of CO2 has nothing to do with humans."

Once again Harris rejects the body of scientific evidence in favor of one paper which somebody emailed him about, and apparently expects his students to exhibit the same lack of skepticism.

Climate Denial 101

We have only touched on a few of the many climate myths identified in Harris' lectures by CASS, who in fact documented over 100 such myths in their report. Tamino also takes Harris to task for his minsinformation regarding warming in the United States in a recent Open Mind post.

Harris' Carleton University course was clearly less of a climate and Earth science class and more of a climate cherrypicking denial class, teaching students how to ignore the vast body of scientific evidence and only consider the few bits of information which appear to support one's pre-determined conclusion. However, such denial is entirely anti-science, and this behavior should certainly not be taught in a university classroom. Hopefully Carelton University will learn from this error and disservice to their students.

2012 SkS Weekly Digest #18

Mon, 7 May 2012 14:47:19 EST

SkS Highlights

In the second installment of the Why Are We Sure We're Right? series, SkS authors Rob Honeycutt, Dana Nuccitelli, and Andy S. explain why they embrace what mainstream scientists are telling us about climate change. Needless to say, this post generated the highest number of comments during the week. Coming in second and third respectively were Dana's John Nielsen-Gammon Comments on Continued Global Warming and John Mason's Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965.

Toon of the Week

Another climate change solution

Source: Royalty Free Cartoons

Quote of the week

“The big damages come if the climate sensitivity to greenhouse gases turns out to be high,” said Raymond T. Pierrehumbert, a climate scientist at the University of Chicago. “Then it’s not a bullet headed at us, but a thermonuclear warhead.”

Source: "Clouds’ Effect on Climate Change Is Last Bastion for Dissenters" by Justin Gillis, New York times, Apr 30, 2012

Issue of the Week

When it comes to manmade climate change, what do you consider to be the most significant "canary in the coal mine"?

Words of the Week

Greenhouse effect Greenhouse gases effectively absorb thermal infrared radiation, emitted by the Earth’s surface, by the atmosphere itself due to the same gases, and by clouds. Atmospheric radiation is emitted to all sides, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system. This is called the greenhouse effect. Thermal infrared radiation in the troposphere is strongly coupled to the temperature of the atmosphere at the altitude at which it is emitted. In the troposphere, the temperature generally decreases with height. Effectively, infrared radiation emitted to space originates from an altitude with a temperature of, on average, –19°C, in balance with the net incoming solar radiation, whereas the Earth’s surface is kept at a much higher temperature of, on average, +14°C. An increase in the concentration of greenhouse gases leads to an increased infrared opacity of the atmosphere, and therefore to an effective radiation into space from a higher altitude at a lower temperature. This causes a radiative forcing that leads to an enhancement of the greenhouse effect, the so-called enhanced greenhouse effect.

Greenhouse gas (GHG) Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, the atmosphere itself, and by clouds. This property causes the greenhouse effect. Water vapour (H₂O), carbon dioxide (CO₂), nitrous oxide (N₂O), methane (CH₄) and ozone (O₃) are the primary greenhouse gases in the Earth’s atmosphere. Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Beside CO₂, N₂O and CH₄, the Kyoto Protocol deals with the greenhouse gases sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).

Source: Annex I (Glossary) to Climate Change 2007: Working Group I: The Physical Science Basis, IPCC Fourth Assessment Report.

The Week in Review

A complete listing of the articles posted on SkS during the past week.

West Antarctic Ice Shelves Tearing Apart at the Seams by John Hartz
Report Warns of Rapid Decline in U.S. Earth Observation Capabilities by John Hartz
rbutr Puts Climate Information In Front of Those Who Need It Most by Shane Greenup
HadSST3: A detailed look by Kevin C
Why Are We Sure We're Right? #2 by Rob Honeycutt, Dana Nuccitelli, and Andy S.
Lessons from Past Predictions: Hansen 1981 by Dana
Two Centuries of Climate Science: part two - Hulburt to Keeling, 1931- 1965 by John Mason
New research from last week 17/2012 by by Ari Jokimäki
John Nielsen-Gammon Comments on Continued Global Warming by Dana

Coming Soon

A list of articles that are in the SkS pipeline. Most of these articles, but not necessarily all, will be posted during the week.

Lindzen's Clouded Vision, Part 1: Science (Dana)
New research from last week 18/2012 (Ari Jokimäki)
Lindzen's Clouded Vision, Part 2: Risk (Dana)
Turbines in Texas helping to cool the planet? (MarkR)
Two Centuries of Climate Science: part three - Manabe to the present day, 1966-2012 (John Mason)
Arctic Winter Analysis (Neven)
101 responses to Ian Plimer's climate questions (John Cook)
Open letter to an anonymous climate scientist (Dumb Scientist)
In Search Of: Himalayan Ice Loss (mspelto & Daniel Bailey)
CRUTEM4: A detailed look (Kevin C)

Simple Myth Debunking of the Week

Anyone who argues There is no consensus is denying the many different studies and surveys which demonstrate that approximately 97% of climate scientists agree that humans are the main cause of the current global warming.

SkS Spotlights

The Max Planck Institute for Meteorology (MPI-M), located in Hamburg, Germany, is an internationally renowned institute for climate research. Its mission is to understand Earth's changing climate.

The MPI-M comprises three departments:

and three independent research groups:

Scientists at the MPI-M investigate what determines the sensitivity of the Earth system to perturbations such as the changing composition of its atmosphere, and work toward establishing the sources and limits of predictability within the Earth system. MPI-M develops and analyses sophisticated models of the Earth system, which simulate the processes within atmosphere, land and ocean. Such models have developed into important tools for understanding the behaviour of our climate, and they form the basis for international assessments of climate change. Targeted in-situ measurements and satellite observations complement the model simulations.

Together with several other non-university research institutions the MPI-M and the University of Hamburg constitute the KlimaCampus, a centre of excellence for climate research and education in Hamburg, Germany.

Report Warns of Rapid Decline in U.S. Earth Observation Capabilities

Sun, 6 May 2012 16:18:45 EST

This is a reprint of a news release posted by the US National Research Council on May 2, 2012.

A new National Research Council report says that budget shortfalls, cost-estimate growth, launch failures, and changes in mission design and scope have leftU.S.earth observation systems in a more precarious position than they were five years ago. The report cautions that the nation's earth observing system is beginning a rapid decline in capability, as long-running missions end and key new missions are delayed, lost, or cancelled.

This photo from NASA's Suomi NPP satellite shows the Eastern Hemisphere of Earth in "Blue Marble" view. The photo, released Feb. 2, 2012, is a companion to a NASA image showing the Western Hemisphere in the same stunning detail. This photo was taken on Jan. 23. CREDIT: NASA/NOAA

"The projected loss of observing capability will have profound consequences on science and society, from weather forecasting to responding to natural hazards," said Dennis Hartmann, professor of atmospheric sciences at theUniversityofWashington,Seattle, and chair of the committee that wrote the report. "Our ability to measure and understand changes in Earth's climate and life support systems will also degrade."

The report comes five years after the Research Council published "Earth Science and Applications From Space: National Imperatives for the Next Decade and Beyond," a decadal survey that generated consensus recommendations from the earth and environmental science and applications community for a renewed program of earth observations. The new report finds that although NASA responded favorably and aggressively to the decadal survey, the required budget was not achieved, greatly slowing progress. Changes in program scope without commensurate funding, directed by the Office of Management and Budget and by Congress, also slowed progress. A further impediment, the report says, is the absence of a highly reliable and affordable medium-class launch capability.

Despite these challenges, NASA has been successful in launching some of the missions in development when the survey report was published. It has also made notable progress in establishing the "Venture-class" program, as recommended in the decadal survey. The suborbital program and the airborne science program are additional areas where significant progress is being made. In accord with the decadal survey's recommendations, NASA also aggressively pursued international partnerships to mitigate shortfalls and stretch resources.

In the near term, the report concludes, budgets for NASA's earth science program will remain inadequate to meet pressing national needs. Therefore the agency should focus on two necessary actions: defining and implementing a cost-constrained approach to mission development, and identifying and empowering a cross-mission earth system science and engineering team to advise on the execution of decadal survey missions.

The report also reviews the state of NOAA's satellite earth observation program, an integral part of the decadal survey's overall strategy and tied to the success of NASA's program. Budget shortfalls and cost overruns in NOAA's next generation of polar environmental satellites account for the slow rate of progress. An interagency framework, recommended in the decadal survey to assist NASA and NOAA in optimizing resources, has yet to be realized. This framework is even more crucial now that both agencies face fiscal constraints, and its importance is reiterated in the present report.

The study was sponsored by NASA. The National Academy of Sciences, National Academy of Engineering, Instituteof Medicine, and National Research Council make up the National Academies. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter. The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. For more information, visit http://national-academies.org.

Turbines in Texas mix up nighttime heat

Thu, 10 May 2012 00:12:59 EST

Satellite measurements of temperatures near wind farms in Texas from 2003-2011 have suggested that wind turbines have mixed up the nighttime atmosphere, bringing warmer air down to the ground (Zhou et al, 2012). When looking at the physics it turns out that this suggests the chance of a (very, very small) global cooling effect.

The satellites measure that downwind from wind farms the surface is warming more than other places nearby, but only at night. In the windier Texan summer the night warming has been 0.73°C per decade, but the calmer winter months have only gone up at 0.46°C per decade.

The authors blame wind farms because the warming happened where turbines were built, as shown in Figure 1 below. The patterns also match expectations from physics: the effect is stronger when it's windier, downwind from turbines and at night.

Figure 1 - map of changes in temperature across Texas in degrees Celsius. Crosses represent places where there are wind turbines, and the prevailing wind is from the south. The area average temperature has been subtracted from each point, so a blue area doesn't necessarily mean it cooled, just that it warmed less quickly than the turbine areas.

At night the Earth's surface cools quickly as it radiates efficiently to space and the cold dense air right next to it can't rise. The air above is warmer and less dense so it floats on top and heat becomes 'trapped' (rather like the alcohol content in the layers of a B-52 cocktail) unless something helps mix it up - and this is where the chopping blades of wind turbines come in (stirring a B-52 does the same job).

During the day the Sun quickly warms the surface and the lower air heats up and rises. The extra chopping of the turbines doesn't make a difference because the atmosphere is already well mixed (to try this at home, try pouring a B-52 the wrong way round and too quickly, then see how much difference stirring it makes!).

What does this mean for climate change?

Lead scientist Liming Zhou from the University of Albany released a Q&A to explain that the effect is local, and that

Very likely, the wind turbines do not create a net warming of the air and instead only redistribute the air’s heat near the surface...fundamentally different from the large-scale warming effect caused by increasing atmospheric concentrations of greenhouse gases due to the burning of fossil fuels.

However, newspaper headline writers and political commentators disagree with physics, measurement and scientific experts and think that the results mean "Wind Farms Cause Global Warming". As Professor Zhou explained, this just ain't the case.

Tiny and local effect, but physics suggests wind farms cause small global cooling!

It's possible that the global effect of this would be a (very small) cooling. It works like this: the Earth's surface can emit in the atmospheric 'windows' where heat leaks easily to space. This is why the Earth's surface cools down faster at night than the atmosphere.

Typically the upper air stores this heat at night, but if it's mixed up by wind turbines, it loses it to the ground and the ground then leaks this heat efficiently into space. Like the radiator fins on a car: the radiator warms up, but it helps keep to cool the whole engine.

When contacted, Professor Zhou responded that "Your explanation is interesting and physically correct to me but the warming-induced emission is very small." He also commented that there might be other effects related to the efficiency of Earth's heat loss which could work in the opposite direction and that more research is needed. Regardless, the effect on global temperatures will be too tiny to measure.

Effect important locally, and a good reminder to stay skeptical

The nighttime warming measured by satellite is quite large compared with the global warming signal of ~0.2°C per decade. But it's only in a very small region and doesn't have much effect on global warming.

As Professor Zhou says, more research is needed. Is this effect widespread in other places? Does it explain some of the night warming measured by near surface thermometers? The area of atmosphere affected is too low for satellites, but maybe nearby weather balloons could be used to check these results.

The media confusion shows us how important it is to stay skeptical and try and think of the whole picture. The turbines are just mixing up heat that was already there and by only measuring where the heat is moving to you can easily get confused and draw the wrong conclusions.

101 responses to Ian Plimer's climate questions

Wed, 9 May 2012 12:16:04 EST

The Australian Department of Climate Change and Energy Efficiency have put together a handy and recommended resource: Accurate Answers to Professor Plimer's 101 Climate Change Science Questions (direct link to 1.4Mb PDF). This is in response to Plimer's book How To Get Expelled From School, a compilation of climate misinformation targeted at school children. One section of the book features 101 questions that he suggests children ask their teachers. The DCCEE summarise it well:

"Many of the questions and answers in Professor Plimer’s book are misleading and are based on inaccurate or selective interpretation of the science. The answers and comments provided in this document are intended to provide clear and accurate answers to Professor Plimer’s questions. The answers are based on up-to-date peer reviewed science, and have been reviewed by a number of Australian climate scientists."

As well as a direct response to Plimer's misleading questions, the document is an interesting and useful resource in its own right. As I explain in a workshop with the Climate Literacy & Energy Awareness Network (CLEAN), responding to misinformation can be educational opportunity, a chance to put myths in proper context and explain the science. So I recommend reading through the document which explains the science behind many common climate myths.

There are also numerous references to Skeptical Science graphs and resources, as we have already tackled many of the myths propounded by Plimer. In fact, SkS content has been appearing in a number of sources of late. Most notably, weather website Wunderground have published a section on climate myths, reproducing the SkS rebuttals of the top climate myths. Apparently they tweaked some of the text where they thought they could improve on our content (I haven't got around to checking where exactly, will be interesting to check).

SkS material is also being adopted in colleges and universities, with our rebuttals and graphs included in textbooks covering on topics such as geology, climate and psychology. The Debunking Handbook has been adopted into the curriculum of a philosophy course at Portland State University and a Science Communication course at the University of Western Australia. So kudos and credit must go to the SkS team who continue to produce content of high quality and quantity, that is not only being read on the SkS website but also being reproduced by scientists, communicators and educators across the globe.

Note: an alternative response to Plimer's 101 questions is provided by Ian Enting in the document Ian Plimer’s questions deconstructed. Analysis of ‘How to get expelled from school ..”

CRUTEM4: A detailed look

Tue, 15 May 2012 02:04:32 EST

CRUTEM is a version of the surface temperature record based on weather station data spanning the last one and a half centuries. It is produced by the Climatic Research Unit (CRU) at the University of East Anglia, and provides the land component of the widely quoted HadCRUT global temperature record. Version 3 of this dataset (CRUTEM3) was the current version from 2006-2012, however in the past few months a new version, CRUTEM4, has been released.

Why produce a new version? Studies from the ECMWF and GISS identified a significant bias in the CRUTEM3 record: The dataset has been under-reporting recent temperatures, owing to poor sampling of high Northern latitudes which have displayed the fastest warming over the last decade. The coverage issue has been examined in previous articles on HadCRUT3 and GISTEMP.

CRUTEM4 (Jones et al, 2012) takes the existing CRUTEM3 dataset and adds a significant number of new records. 344 stations were added in the Russian federation, 223 in other former USSR states, 125 in the Arctic and 7 in Greenland. A number of other records were updated. 312 records which were adjusted by CRU in the 1980s for inhomogeneity were either replaced with other records or had their adjustments reassessed. The total number of temperature series in the dataset is now ~5500, although only about 3000 can be updated on a monthly basis.

Does the update address the issues?

Let's take a look. Figure 1 shows a coverage map for the last 15 years, with an indication of temperature change given by color. The figure shows the difference in temperature between the mean for 2006-2011 and the mean for 1996-2001 (red=+2°C and blue=-2°C). Note that the rectangular projection used here does exaggerate area at higher latitudes, so this figure does not give an accurate representation of the area covered.

Coverage of Canada, Asia and Australia has improved significantly in the new dataset. Coverage of Africa and Antarctica remains poor.

A more representative measure of coverage is the fraction of the land surface area which is covered by the dataset. This is shown in Figure 2. (This figure was calculated using a high-resolution land mask, and thus the numbers are slightly lower than the corresponding figures in the distributed CRUTEM data files.)

Apart from a recent anomaly in 2010 land coverage has improved from around 60 to 70%. (Antarctica, which is still largely uncovered, comprises about 10% of the Earth's land surface.)

A confusion of conventions

How have the global land temperature estimates been affected by the new dataset? Unfortunately at this point we run into a problem. There are several ways of calculating a land temperature estimate. First there is a choice of how to calculate the average:

A global area average over all the land.
Hemispheric averages, combined according to the formula (0.68xT_NH + 0.32xT_SH), where the coefficients are the fractions of the global land area in each hemisphere. This gives a result similar to method 1 (or identical if coverage is uniform).
Hemispheric averages, combined according to the formula 0.5x(T_NH + T_SH).

Then, there is a choice of how to treat coastal map cells:

Weight them according to the proportion of land in that cell.
Treat them as 100% land.

NCDC and BEST seem to use method 1A for their land products (i.e. a true land-area average). CRUTEM3 used method 3B (equal weighted hemispheres, no weighting of coastal cells). CRUTEM4 changed to method 2B (land area weighted hemispheres, no weighting of coastal cells). The GISTEMP dTs land products don't fit any of the above categories.

When it comes to calculating a global land-ocean temperature average, all the options give roughly the same answers, because the hemispheric land-ocean distribution cancels, and both parts of coastal cells are used. However for land-only temperature indices, the results can differ significantly. When calculating a difference between two series, such as CRUTEM3 and CRUTEM4 the same convention must used for both. For subsequent calculations we will use the CRUTEM4 convention (i.e. 2B).

Temperature series

Figure 3 provides a comparison of the CRUTEM3 and CRUTEM4 temperature series using a 12 month moving average.

1900-2010 1980-2010

Note that with the temperature estimate for the strong El-Nino year of 1998 has decreased, however temperature estimates for the subsequent years have generally increased. El-Nino is a tropical phenomena, thus it is to be expected that increasing high latitude coverage would reduce the impact of the El-Nino cycle on the temperature record.

More than a third of the difference over recent years comes from the switch from reporting the mean of the hemispheric means to the more conventional global average. Using only the weighted hemispheric series to ensure a like-for-like comparison, the trends in the series shown above over the 15 year period 1996-2010 are 0.213°C/decade for CRUTEM3 and 0.274°C/decade for CRUTEM4.

How have the global land temperature estimates changed between the datasets? Figure 4 shows the difference between the estimated global land temperature.

The effect of increasing the high latitude coverage has increased the global land temperature anomaly, as more of the rapidly warming high-latitude regions are included in the data. The impact of the change matches the onset of rapid Arctic warming as expected. The actual differences show significant inter-annual variability.

Comparison to other land temperature series?

NCDC and the Berkeley Earth project also report land-only temperature records, and it is interesting to make a comparison of the series. However the significant impact of the choice of averaging convention complicates the comparison. In their draft paper the BEST team state the problem as follows:

We note that the difference in land average trends amongst the prior groups has not generally been discussed in the literature. In part, the spread in existing land-only records may have received little attention because the three groups have greater agreement when considering global averages that include oceans ... . We strongly suspect that some of the difference in land-only averages is an artifact of the different approaches to defining “land-only” temperature analyses.

A second issue is that the interpretation of a comparison can be affected by the choice of baseline. As a result of these issues, while you can compare the published series at Wood for Trees the results should be treated with caution.

My own attempt at a like-for-like comparison will be presented in a later article which will gather together some more tentative analysis of the Hadley/CRU datasets and look at possible sources of bias in the resulting records.

Summary

The CRUTEM4 update set out to reduce a known bias in the dataset, identified in multiple studies, by improving land coverage. While coverage is still far short of complete it has improved significantly. The effects on the temperature record are minimal before 1990, but have resulted in a significant increase in the trend over the past 15 years. This corresponds well to the period over which the Arctic has shown rapid warming.

Additionally, a change in the definition of global land temperature has been made bringing CRUTEM4 somewhat into line with the other records. While this change has a significant impact on the recent land temperature trends it has minimal impact on the more frequently quoted land-ocean indices.

The CRUTEM4 land data is primarily of interest for its contribution to the global surface temperature series, HadCRUT4. This will be the focus of the next article in the series.

Lindzen's Clouded Vision, Part 1: Science

Tue, 8 May 2012 01:58:32 EST

When it comes to global climate change, there are two critical and intertwined, but distinct issues: science, and policy. We generally focus on the science, because that is what dictates the appropriate policy response, or at least what our climate policy needs to accomplish.

Justin Gillis had an excellent article published in The New York Times this past week, which addresses both science and policy. The science aspect of the article bears some resemblance to one of our posts from a year ago, Climate Sensitivity: The Skeptic Endgame. The fundamental premise of both articles involves the fact that, because of the sound basic science supporting the human-caused global warming theory, there only remains one fallback position for the remaining relatively credible climate contrarians. That fallback position involves climate sensitivity being lower than the body of scientific evidence indicates.

Gillis' article focuses mainly on Richard Lindzen, who is one of the relatively more credible climate contrarians (although he has a long history of taking contrarian positions on nearly every climate-related issue, and being almost universally wrong on those issues). Lindzen embodies the low climate sensitivity fallback position perfectly, but as we will see here, the basis of Lindzen's argument, which itself is the basis of all remaining relatively credible climate contrarianism, is entirely false and undermined by three inescapable flaws.

Lindzen's Three Sensitive Achilles' Heels

We know that humans are rapidly increasing the level of CO2 and other greenhouse gases (GHGs) in the atmosphere, we know that this GHG increase is causing some amount of warming, and will continue to cause additional warming as long as GHG levels continue to rise. The remaining relatively credible climate contrarians like Lindzen acknowledge these realities; where they differ from mainstream climate science is in exactly how much warming the GHG increase will cause. This is known as the climate sensitivity - how much the planet will warm in response to increasing GHGs, including feedbacks.

For contrarians like Lindzen, climate sensitivity must be low, or they have no case to make. They have acknowledged that GHGs will cause warming, and their only argument against taking serious action to reduce GHG emissions is this premise that the GHG increase won't cause very much warming. That is why we described this argument as the 'skeptic' endgame, and Gillis accurately described it as the dissenters' "last bastion."

So what is Lindzen's case for low climate sensitivity? He summed it up in the recent ABC documentary discussed by John Cook, I Can Change Your Mind About Climate (see minute 21 in this video). In response to a comment that the average global surface temperature has warmed about three-quarters of a degree Celsius, Linzen responds:

"Yeah, and we should have seen 3[°C]"

This is a very brief encapsulation of Lindzen's pet argument, Earth hasn't warmed as much as expected. I call it his 'pet argument' because he makes it in virtually every talk and presentation he gives, and has been making it since at least 1989, despite the fact that it's been debunked time and time again (i.e. Skeptical Science alone has debunked it here and here and here and here and here and here).

In short, if climate sensitivity is lower than resulting in climate models, then the climate should have warmed less than climate models have predicted. In order to argue that this is the case, Lindzen claims that CO2-equivalent (the total radiative forcing for all greenhouse gases in units equivalent to CO2-caused warming) has already doubled from pre-industrial levels; therefore, if climate sensitivity is around 3°C for doubled CO2 (as in climate models), the planet should have warmed 3°C. It has not warmed nearly so much; therefore, Lindzen asserts, climate sensitivity is low.

The problem with Lindzen's argument for low sensitivity is that it contains three separate fundamental flaws:

CO2-equivalent has not increased by 100%, but rather by about 76% above pre-industrial levels.

Lindzen has completely neglected all non-GHG influences on the climate. The second-largest influence (behind CO2) is from human aerosol emissions, which have a cooling effect. Lindzen seizes on the uncertainty associated with aerosols - the strength of their cooling effect is not well-known; however, the scientific evidence does clearly indicate that they have a cooling effect. In fact, Lindzen's own sources on the subject conclude that aerosols have a strong cooling effect. Yet in his argument, he has completely failed to account for this cooling effect. In short, Lindzen treats the GHG forcing as equivalent to the net radiative forcing (which is what the climate responds to), but the two are not equivalent.

3°C is the equilibrium climate sensitivity - the amount the planet will eventually warm once it reaches a new energy balance. The planet currently has an energy imbalance (mostly stored as heat in the oceans), so there is still more warming "in the pipeline" from the GHGs we have already emitted. Lindzen fails to account for this effect.

By themselves, each of these fundamental errors completely invalidates Lindzen's argument. Taken together, they form a trio of Achilles' Heels which leave us puzzled as to how Lindzen has continued to make this obviously and grossly fundamentally flawed argument for over two decades.

Lindzen also Disproven by Reality

In addition to these three glaring errors, we know the Earth has warmed as much as expected because climate scientists compare their model runs to observational data. We've done a whole series of posts looking at the accuracy of past climate model predictions, our most recent entry being Hansen et al. 1981 (Figure 1).

Figure 1: Hansen et al. (1981) global warming projections under a scenario of high energy growth (4% per year from 1980 to 2020) (red) and slow energy growth (2% per year from 1980 to 2020) (blue) vs. observations from GISTEMP with a 2nd-order polynomial fit (black). Actual energy growth has been between the two Hansen scenarios at approximately 3% per year. Baseline is 1971-1991.

Thus not only do we know Lindzen's argument is wrong due to its three Achilles' Heels, we know it's wrong just by comparing actual model results to observational data, which show the Earth has warmed consistent with model predictions.

There simply is no question - Lindzen's claim that the Earth hasn't warmed as much as expected, which is the basis of his low climate sensitivity argument, which is the basis of all remaining relatively credible climate contrarianism, is entirely false based on three fundamental physical flaws in his argument, as demonstrated by simply comparing the models and observations.

Lindzen's Cloudy Iris

In Gillis' Times article, Lindzen brings up his Iris hypothesis. Back in 2001, Lindzen proposed that in response to global warming, increased sea surface temperature in the tropics would result in reduced cirrus cloud formation and thus more infrared radiation leakage from Earth's atmosphere. This radiation leakage in turn would have a cooling effect, dampening global warming as a negative feedback (like the iris in a human eye contracting to allow less light to pass through the pupil in a brightly lit environment - hence the term 'iris effect').

However, within a year of the publication of Lindzen's iris paper, there was one study published concluding that Lindzen had significantly overestimated the iris effect, a second concluding that if the iris effect existed, it would lead to increased warming, and a third and fourth papers finding no evidence for the iris effect. The vast majority of subsequent research has simply not substantiated Lindzen's iris hypothesis - it has not withstood the test of time.

All of Lindzen's Eggs in the Cloud Basket

In another challenge for the low sensitivity crowd, research has shown that the water vapor feedback (which appears to be the largest single feedback) is positive, amplifying global warming. Therefore, contrarians like Lindzen need a large negative feedback to offset the water vapor effect, and the only credible candidate is cloudcover. Thus, as Andrew Dessler notes in Gillis' article,

"If you listen to the credible climate skeptics, they’ve really pushed all their chips onto clouds."

Not only is climate sensitivity the 'skeptic' endgame, but clouds are the low climate sensitivity endgame. Climate contrarians need a strongly negative cloud feedback to argue that climate sensitivity is low, which they need to be the case in order to argue that global warming is nothing to worry about. It all boils down to clouds.

Lindzen hasn't actually published any subsequent research to support his iris hypothesis, but he has attempted to show that climate sensitivity is low, and then proposed his iris hypothesis as the physical explanation for that low sensitivity, even though as noted above, the hypothesis has not withstood the test of time.

The Inconvenient Truth About Clouds and Sensitivity

Unfortunately, most recent climate research has indicated that clouds probably act as yet another positive feedback, amplifying rather than dampening global warming. The most prominent and recent such paper was Dessler (2010), which found that the short-term cloud feedback is probably positive, although slightly negative values could not be ruled out.

Contrarians like Lindzen still hold out hope because clouds do remain one of the biggest climate uncertainties. However, it's not just climate models and studies of climate feedbacks that undermine the low sensitivity argument. Paleoclimate studies (examining climate data from hundreds to millions of years ago) are also consistent with the climate model sensitivity, and inconsistent with low climate sensitivity arguments (Figure 2).

Figure 2: Distributions and ranges for climate sensitivity from different lines of evidence. The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability). Dashed lines indicate no robust constraint on an upper bound. The IPCC likely range (2 to 4.5°C) and most likely value (3°C) are indicated by the vertical grey bar and black line, respectively. Adapted from Knutti and Hegerl (2008).

Don't Bet on the Climate Contrarians

In short, the evidence is heavily stacked against the low climate sensitivity argument. The premise of the argument - that the Earth should have warmed more if climate models were right about climate sensitivity - is unquestionably wrong on many different levels. The argument's last hope lies in a strongly negative cloud feedback, but so far the evidence is pointing in the other direction. Data from the Earth's history is also inconsistent with an insensitive climate.

That's not to say that a low climate sensitivity is an impossibility. Science is about probabilities, not certainties. However, as we will explore in Part 2 tomorrow, while there is a very low probability that they are right, the problem is that contrarians like Lindzen refuse to even consider the possibility that they are wrong, and expect us to risk the welfare of future generations on that slim chance that they are right.

New research from last week 18/2012

Tue, 8 May 2012 23:11:45 EST

Last week scientists moved the borders of unknown little further in following subjects (among others): astronomical climate forcing, NAO-snow cover relation, global temperature analysis, daily mean temperature, hurricane activity, ocean acidification, mass extinction, AMO, insect ice toleration, lake ice, sea ice, climate system annual cycle, growing season, 18th century meteorology, bark beetle outbreaks, summer monsoon, and iceberg distribution.

Astronomical forcing as a pacemaker of climate

Is the astronomical forcing a reliable and unique pacemaker for climate? A conceptual model study - De Saedeleer et al. (2012) [FULL TEXT]

Abstract: "There is evidence that ice age cycles are paced by astronomical forcing, suggesting some kind of synchronisation phenomenon. Here, we identify the type of such synchronisation and explore systematically its uniqueness and robustness using a simple paleoclimate model akin to the van der Pol relaxation oscillator and dynamical system theory. As the insolation is quite a complex quasiperiodic signal involving different frequencies, the traditional concepts used to define synchronisation to periodic forcing are no longer applicable. Instead, we explore a different concept of generalised synchronisation in terms of (coexisting) synchronised solutions for the forced system, their basins of attraction and instabilities. We propose a clustering technique to compute the number of synchronised solutions, each of which corresponds to a different paleoclimate history. In this way, we uncover multistable synchronisation (reminiscent of phase- or frequency-locking to individual periodic components of astronomical forcing) at low forcing strength, and monostable or unique synchronisation at stronger forcing. In the multistable regime, different initial conditions may lead to different paleoclimate histories. To study their robustness, we analyse Lyapunov exponents that quantify the rate of convergence towards each synchronised solution (local stability), and basins of attraction that indicate critical levels of external perturbations (global stability). We find that even though synchronised solutions are stable on a long term, there exist short episodes of desynchronisation where nearby climate trajectories diverge temporarily (for about 50 kyr). As the attracting trajectory can sometimes lie close to the boundary of its basin of attraction, a small perturbation could quite easily make climate to jump between different histories, reducing the predictability. Our study brings new insight into paleoclimate dynamics and reveals a possibility for the climate system to wander throughout different climatic histories related to preferential synchronisation regimes on obliquity, precession or combinations of both, all over the history of the Pleistocene."

Citation: Bernard De Saedeleer, Michel Crucifix and Sebastian Wieczorek, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1316-1.

North Atlantic Oscillation is related to European snow cover, particularly in January and February

Physical mechanisms of European winter snow cover variability and its relationship to the NAO - Kim et al. (2012)

Abstract: "Annual snow cover in the Northern Hemisphere has decreased in the past two decades, an effect associated with global warming. The regional scale changes of snow cover during winter, however, vary significantly from one region to another. In the present study, snow cover variability over Europe and its connection to other atmospheric variables was investigated using Cyclostationary Empirical Orthogonal Function (CSEOF) analysis. The evolution of atmospheric variables related to each CSEOF mode of snow cover variability was derived via regression analysis in CSEOF space. CSEOF analysis clearly shows that the North Atlantic Oscillation (NAO) is related to European snow cover, particularly in January and February. A negative NAO phase tends to result in a snow cover increases, whereas a positive NAO phase results in snow cover decreases. The temporal changes in the connection between the NAO and European snow cover are explained by time-dependent NAO-related temperature anomalies. If the NAO phase is negative, the temperature is lower in Europe and snow cover increases; by contrast, when the NAO phase is positive, the temperature is higher and snow cover decreases. Temperature and snow cover variations in Europe are associated with the thermal advection by anomalous wind by NAO. CSEOF analysis also shows an abrupt increase of snow cover in December and January and a decrease in February and March since the year 2000, approximately. This abrupt change is associated with sub-seasonal variations of atmospheric circulation in the study region."

Citation: Yoojin Kim, Kwang-Yul Kim and Baek-Min Kim, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1365-5.

NOAA introduces improvements to Merged Land-Ocean Surface Temperature analysis

NOAA's Merged Land-Ocean Surface Temperature Analysis - Vose et al. (2012)

Abstract: "This paper describes the new release of the Merged Land-Ocean Surface Temperature analysis (MLOST version 3.5), which is used in operational monitoring and climate assessment activities by the NOAA National Climatic Data Center. The primary motivation for the latest version is the inclusion of a new land dataset that has several major improvements, including a more elaborate approach for addressing changes in station location, instrumentation, and siting conditions. The new version is broadly consistent with previous global analyses, exhibiting a trend of 0.076 °C dec⁻¹ since 1901, 0.162 °C dec⁻¹ since 1979, and widespread warming in both time periods. In general, the new release exhibits only modest differences with its predecessor, the most obvious being very slightly more warming at the global scale (0.004 °C dec⁻¹ since 1901) and slightly different trend patterns over the terrestrial surface."

Citation: Russell S. Vose, Derek Arndt, Viva F. Banzon, David R. Easterling, Byron Gleason, Boyin Huang, Ed Kearns, Jay H. Lawrimore, Matthew J. Menne, Thomas C. Peterson, Richard W. Reynolds, Thomas M. Smith, Claude N. Williams, Jr., David L. Wuertz, Bulletin of the American Meteorological Society 2012, doi: http://dx.doi.org/10.1175/BAMS-D-11-00241.1.

So, how do we determine daily mean temperature then?

Estimating daily mean temperature from synoptic climate observations - Ma & Guttorp (2012) [FULL TEXT]

Abstract: "We compare some different approaches to estimating daily mean temperature (DMT). In many countries, the routine approach is to calculate the average of the directly measured minimum and maximum daily temperature. In some, the maximum and minimum are obtained from hourly measurements. In other countries, temperature readings at specific times throughout the day are taken into account. For example, the Swedish approach uses a linear combination of five temperature readings, including the minimum and the maximum, with coefficients that depend on longitude and month. We first look at data with very high temporal resolution, and compare some different approaches to estimating DMT. Then, we compare the Swedish formula to various averages of the daily minimum and maximum, finding the latter method being substantially less precise. We finally compare the Swedish formula to hourly averages, and find that a recalibrated linear combination improves estimation accuracy."

Citation: Yuting Ma, Peter Guttorp, International Journal of Climatology, DOI: 10.1002/joc.3510.

Eastern North Pacific hurricane season 2010 was one of the least active seasons on record

Eastern North Pacific Hurricane Season of 2010 - Stewart & Cangialosi (2012)

Abstract: "The 2010 eastern North Pacific hurricane season was one of the least active seasons on record. Only seven named storms developed, which is the lowest number observed at least since routine satellite coverage of that basin began in 1966. Furthermore, only three of those storms reached hurricane status, which is also the lowest number of hurricanes ever observed in the satellite era season. However, two tropical storms made landfall – Agatha in Guatemala and Georgette in Mexico, with Agatha directly causing 190 deaths and moderate to severe property damage as a result of rain-induced floods and mud slides. On average, the National Hurricane Center track forecasts in the eastern North Pacific for 2010 were quite skillful."

Citation: Stacy R. Stewart and John P. Cangialosi, Monthly Weather Review 2012, doi: http://dx.doi.org/10.1175/MWR-D-11-00152.1.

Expected ocean acidification from human actions seems to be unprecedented in the geologic past

History of Seawater Carbonate Chemistry, Atmospheric CO2, and Ocean Acidification - Zeebe (2012) [FULL TEXT]

Abstract: "Humans are continuing to add vast amounts of carbon dioxide (CO₂) to the atmosphere through fossil fuel burning and other activities. A large fraction of the CO₂ is taken up by the oceans in a process that lowers ocean pH and carbonate mineral saturation state. This effect has potentially serious consequences for marine life, which are, however, difficult to predict. One approach to address the issue is to study the geologic record, which may provide clues about what the future holds for ocean chemistry and marine organisms. This article reviews basic controls on ocean carbonate chemistry on different timescales and examines past ocean chemistry changes and ocean acidification events during various geologic eras. The results allow evaluation of the current anthropogenic perturbation in the context of Earth's history. It appears that the ocean acidification event that humans are expected to cause is unprecedented in the geologic past, for which sufficiently well-preserved records are available."

Citation: Richard E. Zeebe, Annual Review of Earth and Planetary Sciences, Vol. 40: 141-165 (Volume publication date May 2012), DOI: 10.1146/annurev-earth-042711-105521.

End-Permian mass extinction may be important ancient analog for 21st century oceans

End-Permian Mass Extinction in the Oceans: An Ancient Analog for the Twenty-First Century? - Payne & Clapham (2012)

Abstract: "The greatest loss of biodiversity in the history of animal life occurred at the end of the Permian Period (~252 million years ago). This biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of Earth's largest continental flood basalt provinces, the Siberian Traps. Volatile release from basaltic magma and sedimentary strata during emplacement of the Siberian Traps can account for most end-Permian paleontological and geochemical observations. Climate change and, perhaps, destruction of the ozone layer can explain extinctions on land, whereas changes in ocean oxygen levels, CO₂, pH, and temperature can account for extinction selectivity across marine animals. These emerging insights from geology, geochemistry, and paleobiology suggest that the end-Permian extinction may serve as an important ancient analog for twenty-first century oceans."

Citation: Jonathan L. Payne and Matthew E. Clapham, Annual Review of Earth and Planetary Sciences, Vol. 40: 89-111 (Volume publication date May 2012), DOI: 10.1146/annurev-earth-042711-105329.

Greenland ice cores show highly variable Atlantic Multidecadal Oscillation

Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation - Chylek et al. (2012)

Abstract: "The Greenland δ¹⁸O ice core record is used as a proxy for Greenland surface air temperatures and to interpret Atlantic Multidecadal Oscillation (AMO) variability. An analysis of annual δ¹⁸O data from six Arctic ice cores (five from Greenland and one from Canada's Ellesmere Island) suggests a significant AMO spatial and temporal variability within a recent period of 660 years. A dominant AMO periodicity near 20 years is clearly observed in the southern (Dye3 site) and the central (GISP2, Crete and Milcent) regions of Greenland. This 20-year variability is, however, significantly reduced in the northern (Camp Century and Agassiz Ice Cap) region, likely due to a larger distance from the Atlantic Ocean, and a much lower snow accumulation. A longer time scale AMO component of 45–65 years, which has been seen clearly in the 20th century SST data, is detected only in central Greenland ice cores. We find a significant difference between the AMO cycles during the Little Ice Age (LIA) and the Medieval Warm Period (MWP). The LIA was dominated by a ∼20 year AMO cycle with no other decadal or multidecadal scale variability above the noise level. However, during the preceding MWP the 20 year cycle was replaced by a longer scale cycle centered near a period of 43 years with a further 11.5 year periodicity. An analysis of two coupled atmosphere-ocean general circulation models control runs (UK Met Office HadCM3 and NOAA GFDL CM2.1) agree with the shorter and longer time-scales of Atlantic Meridional Overturning Circulation (AMOC) and temperature fluctuations with periodicities close to those observed. However, the geographic variability of these periodicities indicated by ice core data is not captured in model simulations."

Citation: Chylek, P., C. Folland, L. Frankcombe, H. Dijkstra, G. Lesins, and M. Dubey (2012), Greenland ice core evidence for spatial and temporal variability of the Atlantic Multidecadal Oscillation, Geophys. Res. Lett., 39, L09705, doi:10.1029/2012GL051241.

Did some insects survive in Greenland during last glacial stage?

Interglacial insects and their possible survival in Greenland during the last glacial stage - Böcher (2012)

Abstract: "Sediments from the last interglacial (Eemian) in Jameson Land, East Greenland, and the Thule area, NW Greenland, have revealed a number of insect fragments of both arctic and more or less warmth-demanding species. Altogether, the interglacial fauna of Coleoptera (beetles) indicates boreal conditions. Undoubtedly, a large fraction of the insect fauna succumbed when the mild Eemian climate cooled drastically during the last glacial stage. However, a group of hardy species now found far north into the High Arctic might be glacial survivors. It is, however, still puzzling why well-adapted arctic beetle species such as Amara alpina and Isochnus arcticus did not survive the last glacial stage in Greenland. Two factors that have not been sufficiently considered when discussing survival contra extinction are the importance of microclimate and the number of sun-hours during the Arctic summer. Even among the Coleoptera, which as a group fares quite badly in the Arctic, there might be survivors, at least among those found both during the interglacial and as fossils during the early Holocene. First of all, glacial survival applies to the seed bug Nysius groenlandicus, which was widespread during the Eemian, was found soon after the last deglaciation, and is now almost omnipresent in Greenland."

Citation: Jens Böcher, Boreas, DOI: 10.1111/j.1502-3885.2012.00251.x.

Lakes in eastern North America already have up to 21 day longer ice free season

Local climatic drivers of changes in phenology at a boreal-temperate ecotone in eastern North America - Beier et al. (2012)

Abstract: "Ecosystems in biogeographical transition zones, or ecotones, tend to be highly sensitive to climate and can provide early indications of future change. To evaluate recent climatic changes and their impacts in a boreal-temperate ecotone in eastern North America, we analyzed ice phenology records (1975–2007) for five lakes in the Adirondack Mountains of northern New York State. We observed rapidly decreasing trends of up to 21 days less ice cover, mostly due to later freeze-up and partially due to earlier break-up. To evaluate the local drivers of these lake ice changes, we modeled ice phenology based on local climate data, derived climatic predictors from the models, and evaluated trends in those predictors to determine which were responsible for observed changes in lake ice. November and December temperature and snow depth consistently predicted ice-in, and recent trends of warming and decreasing snow during these months were consistent with later ice formation. March and April temperature and snow depth consistently predicted ice-out, but the absence of trends in snow depth during these months, despite concurrent warming, resulted in much weaker trends for ice-out. Recent rates of warming in the Adirondacks are among the highest regionally, although with a different seasonality of changes (early winter > late winter) that is consistent with other lake ice records in the surrounding area. Projected future declines in snow cover could create positive feedbacks and accelerate current rates of ice loss due to warming. Climate sensitivity was greatest for the larger lakes in our study, including Wolf Lake, considered one of the most ecologically intact ‘wilderness lakes’ in eastern North America. Our study provides further evidence of climate sensitivity of the boreal-temperate ecotone of eastern North America and points to emergent conservation challenges posed by climate change in legally protected yet vulnerable landscapes like the Adirondack Park."

Citation: Colin M. Beier, John C. Stella, Martin Dovčiak and Stacy A. McNulty, Climatic Change, 2012, DOI: 10.1007/s10584-012-0455-z.

With 2007 wind, 2010 and 2011 would have reached record lows in Arctic summer sea ice extent

The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011 - Ogi & Wallace (2012)

Abstract: "Strong summertime anticyclonic wind anomalies over the Arctic Ocean, with anomalous flow toward the Fram Strait, during summer months of 2007 contributed to the record-low the Arctic sea-ice extent observed in September of that year. Had the summer winds over the Arctic during the summers of 2010 and 2011 been the same as those in 2007, September sea ice extent would have reached new record lows in those years as well. By regulating the flow of ice toward and through the Fram Strait, variations in low-level winds over the Arctic have contributed to the month-to-month, year-to-year, and decade-to-decade variability of sea ice extent."

Citation: Ogi, M. and J. M. Wallace (2012), The role of summer surface wind anomalies in the summer Arctic sea ice extent in 2010 and 2011, Geophys. Res. Lett., 39, L09704, doi:10.1029/2012GL051330.

Global warming is accompanied by amplification of the annual cycle of the climate system

What drives the global summer monsoon over the past millennium? - Liu et al. (2012) [FULL TEXT]

Abstract: "The global summer monsoon precipitation (GSMP) provides a fundamental measure for changes in the annual cycle of the climate system and hydroclimate. We investigate mechanisms governing decadal-centennial variations of the GSMP over the past millennium with a coupled climate model’s (ECHO-G) simulation forced by solar-volcanic (SV) radiative forcing and greenhouse gases (GHG) forcing. We show that the leading mode of GSMP is a forced response to external forcing on centennial time scale with a globally uniform change of precipitation across all monsoon regions, whereas the second mode represents internal variability on multi-decadal time scale with regional characteristics. The total amount of GSMP varies in phase with the global mean temperature, indicating that global warming is accompanied by amplification of the annual cycle of the climate system. The northern hemisphere summer monsoon precipitation (NHSMP) responds to GHG forcing more sensitively, while the southern hemisphere summer monsoon precipitation (SHSMP) responds to the SV radiative forcing more sensitively. The NHSMP is enhanced by increased NH land–ocean thermal contrast and NH-minus-SH thermal contrast. On the other hand, the SHSMP is strengthened by enhanced SH subtropical highs and the east–west mass contrast between Southeast Pacific and tropical Indian Ocean. The strength of the GSMP is determined by the factors controlling both the NHSMP and SHSMP. Intensification of GSMP is associated with (a) increased global land–ocean thermal contrast, (b) reinforced east–west mass contrast between Southeast Pacific and tropical Indian Ocean, and (c) enhanced circumglobal SH subtropical highs. The physical mechanisms revealed here will add understanding of future change of the global monsoon."

Citation: Jian Liu, Bin Wang, So-Young Yim, June-Yi Lee, Jong-Ghap Jhun and Kyung-Ja Ha, Climate Dynamics, 2012, DOI: 10.1007/s00382-012-1360-x.

Growing season and freeze-free period are getting longer in Colorado at high elevation

Growing season expansion and related changes in monthly temperature and growing degree days in the Inter-Montane Desert of the San Luis Valley, Colorado - Mix et al. (2012)

Abstract: "Most climate change studies on high elevation ecosystems identify changes in biota, while several report abiotic factors. However, very few report expansion of the freeze-free period, or discuss monthly changes of temperature and growing degree days (GDD) during the growing season. This study provides initial data on agriculturally-related aspects of climate change during the growing season (M-J-J-A-S) in the inter-montane desert of the San Luis Valley (SLV), Colorado. Temperature data were gathered from 7 climate stations within the SLV. Based on ordinal days, the last vernal freeze is occurring (p < 0.05) earlier at 3 stations than in prior years, ranging between 5.52 and 11.86 days during 1981–2007. Significantly-later autumnal freezes are occurring at 5 stations by 5.95–18.10 days, while expansion of the freeze-free period was significantly longer at all stations by 7.20–24.21 days. The freeze-free period averaged about 93 days prior to the 1980s, but now averages about 107 days. Increases (p < 0.05) in daily mean, maximum, minimum temperature occurred at nearly all stations for each month. Increases in GDD₁₀, GDD_4.4 (potato) and GDD_5.5 (alfalfa) also occurred at nearly all stations for all months during 1994–2007. Higher temperatures increase the number of GDD, quickening crop growth and maturity, and potentially reducing yield and quality unless varieties are adapted to changes and water is available for the season extension and increased evapotranspiration."

Citation: Ken Mix, Vicente L. Lopes and Walter Rast, Climatic Change, 2012, DOI: 10.1007/s10584-012-0448-y.

Meteorological observations from 18th century Brazil

The meteorological observations of Bento Sanches Dorta, Rio de Janeiro, Brazil: 1781–1788 - Farrona et al. (2012)

Abstract: "Bento Sanches Dorta was an astronomer and geographer in the Portuguese colony of Rio de Janeiro in Brazil from 1781 to 1788. He recorded daily readings of meteorological and geomagnetic variables during that period. This dataset provides, to the best of our knowledge, the earliest known continuous 8-year-long instrumental meteorological observations for any South American site. His data show that the winters in this period were relatively cool, and that 1785 was the rainiest and hottest year, and 1787 the driest and coolest. The records display a distinct seasonal cycle and a variability that are comparable with the modern data."

Citation: A. M. M. Farrona, R. M. Trigo, M. C. Gallego and J. M. Vaquero, Climatic Change, 2012, DOI: 10.1007/s10584-012-0467-8.

Spruce forest damaging bark beetle outbreaks are more severe in warmer climate

Climate affects severity and altitudinal distribution of outbreaks in an eruptive bark beetle - Marini et al. (2012)

Abstract: "Temperature warming and the increased frequency of climatic anomalies are expected to trigger bark beetle outbreaks with potential severe consequences on forest ecosystems. We characterized the combined effects of climatic factors and density-dependent feedbacks on forest damage caused by Ips typographus (L.), one of the most destructive pests of European spruce forests, and tested whether climate modified the interannual variation in the altitudinal outbreak range of the species. We analyzed a 16-year time-series from the European Alps of timber loss in Picea abies Karsten forests due to I. typographus attacks and used a discrete population model and an information theoretic approach to compare multiple competing hypotheses. The occurrence of dry summers combined with warm temperatures appeared as the main abiotic triggers of severity of outbreaks. We also found an endogenous negative feedback with a 2-year lag suggesting a potential important role of natural enemies. Forest damage per hectare averaged 7-fold higher where spruce was planted in sites warmer than those within its historical climatic range. Dry summers, but not temperature, was related to upward shifts in the altitudinal outbreak range. Considering the potential increased susceptibility of spruce forests to insect outbreaks due to climate change, there is growing value in mitigating these effects through sustainable forest management, which includes avoiding the promotion of spruce outside its historical climatic range."

Citation: Lorenzo Marini, Matthew P. Ayres, Andrea Battisti and Massimo Faccoli, Climatic Change, DOI: 10.1007/s10584-012-0463-z.

Global warming might be responsible for recent weakening of East Asian summer monsoon

Recent weakening of northern East Asian summer monsoon: A possible response to global warming - Zhu et al. (2012)

Abstract: "We investigate the possible causes of the weakening of northern East Asian summer monsoon (EASM) from 1954 to 2010. We found that the decreased intensity of northern EASM as measured by a circulation index (EASMI) is significantly correlated with the increase of the surface air temperature (SAT) averaged over the Lake Baikal region (45°–65°N, 80°–130°E) defined as SATI. Corresponding to increasing SATI, an anomalous low-level anticyclone occurs with northeasterly prevailing over northern East Asia (30°–50°N,100°–130°E), resulting in a weakened southwesterly monsoon winds and drier climate in this region. Numerical experiments with the community atmosphere model version 3 (CAM3) show that the joint forcing induced by greenhouse gases (GHG), sea surface temperature (SST), solar radiance (SR), and volcano activity (VC) can replicate the observed trend of SATI and its related circulation anomalies, but without GHG forcing the model failed to simulate the warming trend of SATI after 1970s. This implies that the global warming is likely responsible for the local warming around the Lake Baikal, which in turn weakens the northern EASM in recent decades."

Citation: Zhu, C., B. Wang, W. Qian, and B. Zhang (2012), Recent weakening of northern East Asian summer monsoon: A possible response to global warming, Geophys. Res. Lett., 39, L09701, doi:10.1029/2012GL051155.

Increased accuracy for mapping Antarctic iceberg distribution

Antarctic icebergs distributions, 2002–2010 - Tournadre et al. (2012)

Abstract: "Interest for icebergs and their possible impact on southern ocean circulation and biology has increased during the recent years. While large tabular icebergs are routinely tracked and monitored using scatterometer data, the distribution of smaller icebergs (less than some km) is still largely unknown as they are difficult to detect operationally using conventional satellite data. In a recent study, Tournadre et al. (2008) showed that small icebergs can be detected, at least in open water, using high resolution (20 Hz) altimeter waveforms. In the present paper, we present an improvement of their method that allows, assuming a constant iceberg freeboard elevation and constant ice backscatter coefficient, to estimate the top-down iceberg surface area and therefore the distribution of the volume of ice on a monthly basis. The complete Jason-1 reprocessed (version C) archive covering the 2002–2010 period has been processed using this method. The small iceberg data base for the southern ocean gives an unprecedented description of the small iceberg (100 m–2800 m) distribution at unprecedented time and space resolutions. The iceberg size, which follows a lognormal distribution with an overall mean length of 630 m, has a strong seasonal cycle reflecting the melting of icebergs during the austral summer estimated at 1.5 m/day. The total volume of ice in the southern ocean has an annual mean value of about 400 Gt, i.e., about 35% of the mean yearly volume of large tabular icebergs estimated from the National Ice Center database of 1979–2003 iceberg tracks and a model of iceberg thermodynamics. They can thus play a significant role in the injection of meltwater in the ocean. The distribution of ice volume which has strong seasonal cycle presents a very high spatial and temporal variability which is much contrasted in the three ocean basins (South Atlantic, Indian and Pacific oceans). The analysis of the relationship between small and large (>5 km) icebergs shows that a majority of small icebergs are directly associated with the large ones but that there are vast regions, such as the eastern branch of the Wedell Gyre, where the transport of ice is made only through the smaller ones."

Citation: Tournadre, J., F. Girard-Ardhuin, and B. Legrésy (2012), Antarctic icebergs distributions, 2002–2010, J. Geophys. Res., 117, C05004, doi:10.1029/2011JC007441.

CLASSIC OF THE WEEK: Walker (1937)

World weather, VI - Walker (1937) [FULL TEXT]

Abstract: "The fluctuations of pressure, temperature, and rainfall in winter in the region of the North Atlantic had been studied as a connected system in the last paper of this series; and a similar system is now shown to hold in the spring, summer, and autumn. But the amount of persistence is small, so that the results are of little value for foreshadowing weather; nor does a consideration of the trade wind region lead to success in this respect. Similarly the Southern Oscillation which was found active in the summer and winter seasons over a large part of the globe is now shown to function in the two remaining seasons: and while that of March to May has little control over the following quarter, the Southern Oscillation of September to November has a correlation coefficient of .90 with the Oscillation of December to February. Thus there are a number of relationships of between .60 and .82 available for foreshadowing weather."

Citation: Sir Gilbert T. Walker, 1937, Memoirs of the Royal Meteorological Society, Vol. IV, No. 39.

2012 SkS Weekly Digest #17

Mon, 30 Apr 2012 05:15:42 EST

SkS Highlights

Dana's Global Warming Causing Heat Fatalities garnered a goodly number of heated comments by SkS readers and authors this past week. John Cook's ABC documentary demonstrates the how and why of climate denial drew the second highest number of comments. A "must see" video of Naomi Oreskes is embedded in it. Levitus et al. Find Global Warming Continues to Heat the Oceans by Dana rounded out the top three comment generators of the week.

Toon of the Week

Source: Royalty Free Cartoons

Quote of the week

"We have tended to look at climate change, food security and poverty challenges separately. We know that 60% of our people live in rural areas, we also know that 90% of our rural population depend on agriculture; most important of all, we do know the future climate predictions give a much more uncertain climatic condition for agriculture, with potentially devastating negative consequences.

"We also know that the situation in my country is not peculiar to us; the situation is the same for the whole of SADC and Africa in general. It is for this reason that my government attaches great importance to this initiative we are launching."

Dr John Phiri, Zambia's Minister of Education, Science, Vocational Training and Early Education

Source: "Southern Africa: Region Most Affected By Climate Change", Nambia Economist posted on AllAfrica.com, Apr 27, 2012

Issue of the Week

Should a prohibition against the "hijacking of a comment thread" be incoporated into the SkS Comments Policy? How would you define "hijacking"?

Words of the Week

Insolation: The amount of solar radiation reaching the Earth b ylatitude and by season. Usually insolation refers to the radiation arriving at the top of the atmosphere. Sometimes it is specified as referring to the radiation arriving at the Earth’s surface. See also: Total Solar Irradiance

Total solar irradiance (TSI) The amount of solar radiation received outside the Earth’s atmosphere on a surface normal to the incident radiation, and at the Earth’s mean distance from the Sun.

Reliable measurements of solar radiation can only be made from space and the precise record extends back only to 1978. The generally accepted value is 1,368 W m−2 with an accuracy of about 0.2%. Variations of a few tenths of a percent are common, usually associated with the passage of sunspots across the solar disk. The solar cycle variation of TSI is of the order of 0.1% (AMS, 2000). See also Insolation.

Source: Annex I (Glossary) to Climate Change 2007: Working Group I: The Physical Science Basis, IPCC Fourth Assessment Report.

The Week in Review

A complete listing of the articles posted on SkS during the past week.

Richard Alley on Today's CO2 Levels by Dana
Richard Alley - We Can Afford Clean Energy by Dana
Alberta’s bitumen sands: “negligible” climate effects, or the “biggest carbon bomb on the planet”? by Andy S
Lessons from Past Predictions: Vinnikov on Arctic Sea Ice by Dana
ABC documentary demonstrates the how and why of climate denial by John Cook
Two Centuries of Climate Science: part one - Fourier to Arrhenius, 1820-1930 by John Mason
Levitus et al. Find Global Warming Continues to Heat the Oceans by Dana
New research from last week 16/2012 by Ari Jokimäki
Global Warming Causing Heat Fatalities by Dana

Coming Soon

A list of articles that are in the SkS pipeline. Most of these articles, but not necessarily all, will be posted during the week.

John Nielsen-Gammon Comments on Continued Global Warming (Dana)
New research from last week 17/2012 (Ari Jokimäki)
Two Centuries of Climate Science: part two - Hulbert to Keeling, 1931- 1965 (John Mason)
Lessons from Past Predictions: Hansen 1981 (Dana)
Why Are We Sure We're Right? #2 (Rob Honeycutt, Dana, AndyS)
HadSST3: A detailed look (Kevin C)
Open letter to an anonymous climate scientist (Dumb Scientist)
In Search Of: Himalayan Ice Loss (mspelto, Daniel Bailey)
Two Centuries of Climate Science: part three - Manabe to the present day, 1966-2012 (John Mason

Simple Myth Debunking of the Week

If you think Renewable energy is too expensive, Richard Alley begs to differ.

SKS in the News

John Cook had articles related to the ABC documentary I Can Change Your Mind about Climate published in ABC News and The Conversation.

SkS Spotlights

Potsdam Institute for Climate Impact Research (PIK) was founded in 1992 and currently has a staff of about 300 people. The historic buildings of the institute and its high-performance computer are located on Potsdam’s Telegraphenberg campus. The institute is a member of the Leibniz Associationand receives core funding of about 10 million euros from the German federal government and the Federal State of Brandenburg. A similar amount of additional project funding is raised from external sources in competition with other institutions, a large part coming from grant programmes of the European Union.

At PIK, researchers in the natural and social sciences from all over the world work closely together to study global change and its impacts on ecological, economic and social systems. Researchers examine the earth system's capacity for withstanding human interventions and devise strategies and options for a sustainable development of humankind and nature. Interdisciplinary and solution-oriented approaches are a distinctive characteristic of the institute.

Research at PIK is organized in four Research Domains: Earth System Analysis, Climate Impacts and Vulnerabilities, Sustainable Solutions and Transdisciplinary Concepts & Methods.

PIK generates fundamental knowledge for sustainable development primarily through data analysis and computer simulations of the dynamic processes in the earth system, but also of social processes. PIK members publish their research findings in international publications and advise policymakers in Germany and abroad. In addition to the Federal Government of Germany, the European Commission and a number of other governments, international organizations like the World Bank also benefit from the institute´s expertise. Through institutions like the Climate-KIC (Knowledge and Innovation Community) of the European Institute of Innovation and Technology (EIT), whose German branch was founded with PIK support, the institute is in continuous exchange with the business community.

Understanding climate change and its impacts is a huge task that no institution or country can tackle alone. PIK is part of a global network of scientific and academic institutions working on questions of global environmental change. PIK plays an active role in activities such as the Intergovernmental Panel on Climate Change (IPCC), also known as the world´s climate council, whose working group on the mitigation of climate change is coordinated by PIK researchers. PIK initiated and has co-hosted the biennial Nobel Laureate Symposium on questions of global sustainability since 2007.

Arctic Winter Analysis

Sat, 12 May 2012 01:49:47 EST

This is a re-post from the Arctic Sea Ice blog.

I'm starting this blog post off with a conclusion that was reached a while back already: sea ice on the Atlantic and Russian side of the Arctic
looks vulnerable, sea ice on the Pacific and North American side
should be thicker.

Right, with that out of the way we can now look at various aspects of the 2011/2012 freezing season, and compare them to previous years, to be precise the previous freezing season of 2010/2011, and the freezing seasons leading up to and following that other record year: 2006/2007 and 2007/2008. Simply put: I'll be comparing 2007, 2008, 2011 and 2012 before their respective start of the melting season.

I'll try not to use too many words, but I'll be using a lot of images. A bigger version of these images can be found by clicking on them in the original blog post.

Ice age

I'll start with the AARI ice age maps. These images are for the end of April, and they look upside down, because it's from the perspective of the Russians who produced them:

This year, at the end of April, the Arctic seems to hold less of the brown 'old ice' than last year and 2007 (older version), and a tad more than 2008, that had relatively little multi-year ice (MYI) after the 2007 melting season/massacre.

Another source that was already mentioned in the A first clue blog post, were these images based on data compiled by NASA senior research scientist Josefino Comiso from NASA's Nimbus-7 satellite and the U.S. Department of Defense's Defense Meteorological Satellite Program (credit: NASA/Goddard Scientific Visualization Studio). The images show the amount of MYI at its maximum, I presume:

These images look similar to the ones from AARI, with 2012 showing less old ice/MYI than 2007 and 2011, and a bit more than 2008 (look at the graph in the bottom right image). However, at the time a flag was raised by Spanish blogger Diablobanquiso on his excellent blog, maintaining there was more MYI than AARI and Comiso indicated. He based himself on ASCAT radar images, where slightly brighter white represents older ice. The following image shows March 16th 2011 and March 15th 2012 side by side (unfortunately there are no radar images available from 2007 and 2008), with 2012 merging into an image made by Diablobanquisa, showing what part was missing from AARI and Comiso:

In my view he was proven right when James Maslanik and Chuck Fowler produced their bi-yearly graph/map for NSIDC, showing March ice age distribution, compared here with our other years of interest:

Here we see the zone delineated by Diablobanquisa on the ASCAT radar images that reaches much further towards the East Siberian Sea. Could it be that Comiso and AARI overlooked it because it stands out less clear than the rest of the MYI on the radar images? Maybe there's a difference in the way the respective teams define old ice/MYI. Either way, it still looks like 2012 has less old ice/MYI than 2011 and 2007, but more than 2008.

This isn't surprising as there has been a lot of transport of ice towards Greenland and the Canadian Archipelago, and through Fram Strait.

Sea level pressure and ice drift

The movement of ice floes is largely determined by wind, and wind is largely determined by sea level pressure gradients. So let's first have a look at SLP maps from NOAA's Earth Science Research Laboratory (daily mean composites page). I have divided the freezing season up into 3 parts with a duration of two months each:

Obviously the mean of two months of SLP patterns will look similar from year to year, but there is still some interesting info here. Take a look for instance at the purple-blue region of low pressure around Greenland. Low pressure means winds blowing counter-clockwise, so the intensity of this low pressure area tells us something about ice transport through Fram Strait and towards Greenland and the Canadian Archipelago. Darker purple means more transport, and particularly the Dec-Jan row looks intense in this sense for this winter and the winter preceding the 2007 melting season.

Also noteworthy is how far the purple blot stretches towards Siberia. Looking at Dec-Jan for this year and last year we see that the low doesn't stretch all the way over Novaya Zemlya, which partially explains why that region showed a retreat of ice earlier on in 2012 and 2011: westerly winds blowing between high and low pressure systems.

One last thing I noted is that comparing Dec-Jan from year to year, and also Feb-Mar from year to year, the pressure over Siberia seems to be getting higher every winter. Whether this means anything with regards to the WACC theory (Warm Arctic, Cold Continents), I wouldn't know. Either way, it's not relevant to this Winter Analysis.

The effect of the various SLP patterns can also be seen on these excellent IFREMER/CERSAT sea ice drift maps (hat-tip yet again to Diablobanquisa). I've made an animation covering the October-March period of 2011/2012:

In December and January there are a lot of long arrows, pointing towards Fram Strait, but also to Greenland, the Canadian Archipelago and the Beaufort Sea. This explains in large part why the ice pack looks vulnerable on the Atlantic/Siberian side of the Arctic, and should be stronger on the Pacific/North American side of the Arctic. But there are other factors as well.

Air and sea surface temperatures

For SAT and SST images we turn again towards that most excellent tool: the daily mean composites page from NOAA's Earth Science Research Laboratory. First of all the surface air temperatures of the four freezing seasons, divided into two periods:

With regards to the first half of the freezing season we see that in 2006/2007 and 2007/2008 large parts of the Arctic are anomalously warm, and the freezing season of 2010/2011 had a very big anomaly over Baffin Bay and the Canadian Archipelago. In the second half of the last freezing season the contrast between the positive anomaly in the Barentsz/Kara region and the negative anomaly in the Bering Sea is very pronounced.

And now for the SSTs:

I'm not really sure how useful this is, because it would seem to me that satellites can't measure SSTs when the sea is covered by ice (maybe I did something wrong while entering the parameters on the daily mean composites page), but nevertheless we see again a big contrast between the Atlantic and Pacific sides of the Arctic for the second half of the past freezing season, a contrast that translated into record anomalies in the Barentsz and Bering Seas.

Ice thickness

One final comparison to look at are the thickness maps generated by the Naval Research Laboratory's PIPS model and its follow-up, the Arctic Cap HYCOM/CICE/NCODA Nowcast/Forecast System (ACNFS):

There seems to be a lot more of the thickest 4-5 meter thick ice north of Greenland and the Canadian Archipelago when compared to 2008. But then again, PIPS wasn't the best tool for ice thickness projections, so I'll just have a look at higher-resolution ACNFS images and compare 2012 to 2011.

There seems to be less thick ice now than last year, but overall it's thicker, which makes sense, after all those winds pushing the winds from Siberia towards Greenland, the Canadian Archipelago and the Beaufort Sea in December and January. Here too the Atlantic side of the Arctic looks vulnerable, compared to last year, and there's a lot more (thin) ice in the Bering Sea.

---

So that was all the evidence for the conclusion given at the start of this blog post. The big questions now are of course:

How thick is the ice on the North American and Pacific side of the Arctic?
Will it be able to fend off the attacks from the west/south, just like in 2010 and 2011?
How fast will the ice on the Atlantic and Russian side disappear?
What will the effect of that be on local SSTs and the adjacent ice edge?

How this plays out, mostly depends on the weather, albeit less so than in the past when ice was thicker. We will be keeping a close watch through the (bi-)weekly ASI updates, the monthly NSIDC and PIOMAS updates, comparisons of sea ice concentration maps and an animation here and there.

Lessons from Past Predictions: Hansen 1981

Thu, 3 May 2012 01:57:39 EST

In previous Lessons from Past Predictions entries we examined Hansen et al.'s 1988 global warming projections (here and here). However, James Hansen was also the lead author on a previous study from the NASA Goddard Institute for Space Studies (GISS) projecting global warming in 1981, which readers may have surmised from my SkS ID, is as old as I am. This ancient projection was made back when climate science and global climate models were still in their relative infancy, and before global warming had really begun to kick in (Figure 1).

Figure 1: Annual global average surface temperatures from the current NASA GISS record through 1981

As Hansen et al. described it,

"The global temperature rose by 0.2°C between the middle 1960's and 1980, yielding a warming of 0.4°C in the past century. This temperature increase is consistent with the calculated greenhouse effect due to measured increases of atmospheric carbon dioxide. Variations of volcanic aerosols and possibly solar luminosity appear to be primary causes of observed fluctuations about the mean trend of increasing temperature. It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980's."

This analysis from Hansen et al. (1981) shows a good understanding of the major climate drivers, even 31 years ago. The study was also correct in predicting warming during the remainder of the 1980s. The Skeptical Science Temperature Trend Calculator reveals that the trend from 1981 to 1990 was 0.09 +/- 0.35°C per decade - not statistically significant because this is such a short timeframe, but most likely a global warming trend nonetheless.

Global Warming Skeptics Stuck in 1981?

Hansen et al. noted that the human-caused global warming theory had difficulty gaining traction because of the mid-century cooling, which ironically is an argument still used three decades later to dispute the theory:

"The major difficulty in accepting this theory has been the absence of observed warming coincident with the historic CO2 increase. In fact, the temperature in the Northern Hemisphere decreased by about 0.5°C between 1940 and 1970, a time of rapid CO2 buildup."

However, as we will see in this post, despite these doubts, the global warming projections in Hansen et al. (1981), based on the human-caused global warming theory, were uncannily accurate.

Climate Sensitivity

Hansen et al. discussed the range of climate sensitivity (the amount of global surface warming that will result in response to doubled atmospheric CO2 concentrations, including feedbacks):

"The most sophisticated models suggest a mean warming of 2° to 3.5°C for doubling of the CO2 concentration from 300 to 600 ppm"

This is quite similar to the likely range of climate sensitivity based on current research, of 2 to 4.5°C for doubled CO2. Hansen et al. took the most basic aspects of the climate model and found that a doubling of CO2 alone would lead to 1.2°C global surface warming (a result which still holds true today).

"Model 1 has fixed absolute humidity, a fixed lapse rate of 6.5°C km-1 in the convective region, fixed cloud altitude, and no snow/ice albedo feedback or vegetation albedo feedback. The increase of equilibrium surface temperature for doubled atmospheric CO2 is ∆Ts ~1.2°C. This case is of special interest because it is the purely radiative-convective result, with no feedback effects."

They then added more complexity to the model to determine the feedbacks of various effects in response to that CO2-caused warming.

"Model 2 has fixed relative humidity, but is otherwise the same as model 1. The resulting ∆T, for doubled CO2 is ~1.9°C. Thus the increasing water vapor with higher temperature provides a feedback factor of ~1.6."

"Model 3 has a moist adiabatic lapse rate in the convective region rather than a fixed lapse rate. This causes the equilibrium surface temperature to be less sensitive to radiative perturbations, and ∆T ~1.4°C for doubled CO2."

"Model 4 has the clouds at fixed temperature levels, and thus they move to a higher altitude as the temperature increases. This yields ∆T ~2.8°C for doubled CO2, compared to 1.9°C for fixed cloud altitude. The sensitivity increases because the outgoing thermal radiation from cloudy regions is defined by the fixed cloud temperature, requiring greater adjustment by the ground and lower atmosphere for outgoing radiation to balance absorbed solar radiation."

"Models 5 and 6 illustrate snow/ice and vegetation albedo feedbacks. Both feedbacks increase model sensitivity, since increased temperature decreases ground albedo and increases absorption of solar radiation."

Overall Hansen et al. used a one-dimensional model with a 2.8°C climate sensitivity in this study. In today's climate models, water vapor is generally a stronger feedback than modeled by Hansen et al. (i.e. see Dessler et al. 2008) and clouds generally weaker (i.e. see Dessler 2010), but their overall model sensitivity was very close to today's best estimate of 3°C for doubled CO2.

Natural Temperature Influences

Hansen et al. discussed the effects of solar and volcanic activity on temperatures, which are the two main natural influences on global surface temperature changes. Solar activity in particular posed a difficult challenge for climate modelers three decades ago, because it had not been precisely measured.

"for small changes of solar luminosity, a change of 0.3 percent would modify the equilibrium global mean temperature by 0.5°C, which is as large as the equilibrium warming for the cumulative increase of atmospheric CO2 from 1880 to 1980. Solar luminosity variations of a few tenths of 1 percent could not be reliably measured with the techniques available during the past century, and thus are a possible cause of part of the climate variability in that period."

"Based on model calculations, stratospheric aerosols that persist for 1 to 3 years after large volcanic eruptions can cause substantial cooling of surface air...Temporal variability of stratospheric aerosols due to volcanic eruptions appears to have been responsible for a large part of the observed climate change during the past century"

The study compared the various potential global temperature influences of both natural and human effects in Figure 2 below.

Figure 2: Surface temperature effect of various global radiative perturbations, based on the one-dimensional model used in Hansen et al. Aerosols have the The ∆T for stratospheric aerosols is representative of a very large volcanic eruption. From Hansen et al. (1981)

Hansen et al. ran their model using combinations of the three main effects on global temperatures (CO2, solar, and volcanic), and concluded:

"The general agreement between modeled and observed temperature trends strongly suggests that CO2 and volcanic aerosols are responsible for much of the global temperature variation in the past century."

Due to the uncertainty regarding solar activity changes, they may have somewhat underestimated the solar contribution (Figure 3), but nevertheless achieved a good model fit to the observed temperature changes over the previous century.

Figure 3: Percent contributions of various effects to the observed global surface warming over the past 100-150 years according to Tett et al. 2000 (T00, dark blue), Meehl et al. 2004 (M04, red), Stone et al. 2007 (S07, green), Lean and Rind 2008 (LR08, purple), Stott et al. 2010 (S10, gray), Huber and Knutti 2011 (HR11, light blue), and Gillett et al. 2012 (G12, orange).

Projected Global Warming

Now we arrive at the big question - how well did Hansen et al. project the ensuing global warming? Evaluating the accuracy of the projections is something of a challenge, because Hansen et al. used scenarios based on energy growth, but did not provide the associated atmospheric CO2 concentrations resulting as a consequence of that energy growth. Nevertheless, we can compare their modeled energy growth scenarios to actual energy growth figures.

Figure 4 shows the projected warming based on various energy growth scenarios. The fast scenario assumes 4% annual growth in global energy consumption from 1980 to 2020, and 3% per year overall from 1980 through 2100. The slow scenario assumed a growth of annual global energy rates half as rapid as in the fast growth scenario (2% annual growth from 1980 to 2020). Hansen et al. also modeled various scenarios involving fossil fuel replacement starting in 2000 and in 2020.

Figure 4: Hansen et al. (1981) projections of global temperature. The diffusion coefficient beneath the ocean mixed layer is 1.2 cm² per second, as required for best fit of the model and observations for the period 1880 to 1978. Estimated global mean warming in earlier warm periods is indicated on the right.

Since 1981, global fossil fuel energy consumption has increased at a rate of approximately 3% per year, falling between the Hansen et al. fast and slow growth scenarios. Thus we have plotted both and compared them to the observed global surface temperatures from GISTEMP (Figure 5).

Figure 5: Hansen et al. (1981) global warming projections under a scenario of high energy growth (4% per year from 1980 to 2020) (red) and slow energy growth (2% per year from 1980 to 2020) (blue) vs. observations from GISTEMP with a 2nd-order polynomial fit (black). Actual energy growth has been between the two Hansen scenarios at approximately 3% per year. Baseline is 1971-1991.

The global surface temperature record has improved since 1981, at which time the warming from 1950 to 1981 had been underestimated. Thus Figure 5 uses a baseline of 1971 to 1991 (sets the average temperature anomaly between 1971 and 1991 at zero), because we are most interested in how well the model projected the warming since 1981. As the figure shows, the model accuracy has been very impressive.

The linear warming trends from 1981 through 2011 are approximtely 0.17°C per decade for Hansen's Fast Growth scenario, 0.13°C per decade for the Slow Growth scenario, vs. 0.17°C per decade for the observed global surface temperature from GISTEMP. Estimating that the actual energy growth and greenhouse gas emissions have fallen between the Fast and Slow Growth scenarios, the observed temperature change has been approximately 15% faster than the projections of the Hansen et al. model.

If the model-data discrepancy were due solely to the model climate sensitivity being too low, it would suggest a real-world climate sensitivity of approximately 3.2°C for doubled CO2, although there are other factors to consider, such as human aerosol emissions, which are not accounted for in the Hansen et al. model, and the fact that we don't know the exact atmospheric greenhouse gas concentrations associated with their energy growth scenarios.

Predicted Climate Impacts

Hansen et al. also discussed several climate impacts which would result as consequences of their projected global warming:

"Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climatic zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage."

We can check off all of these predictions.

The southwestern United States and Central Asia have experienced frequent droughts in recent years;

The West Antarctic ice sheet has eroded;

Global sea level has risen; and

The Northwest Passage opened in 2007

Christy's Poor Critique

Climate "skeptic" John Christy, whose poor analysis of Hansen et al. (1988) we previously discussed, has also recently conducted a poor analysis of Hansen et al. (1981), posted on Pielke Sr.'s blog. Christy attempts to compare the warming projections of Hansen et al. with his lower atmosphere temperature record from the University of Alabama at Huntsville (UAH). However, Christy is comparing modeled surface temperatures to lower atmosphere temperature measurements; this is not an apples-to-apples comparison.

Christy's justification for this comparison is that surface temperature records and UAH show a similar rate of warming over the past several decades, but according to climate models, the lower atmosphere should warm approximately 20% faster than the surface. Christy believes the discrepancy is due to a bias in the surface temperature record, but on the contrary, the surface temperature record's accuracy has been confirmed time and time again (i.e. Peterson et al. 2003, Menne et al. 2010, Fall et al. 2011 [which includes Anthony Watts as a co-author!], Muller et al. 2011 [the BEST project], etc.). There are good reasons to believe the discrepancy is primarily due to problems in the atmospheric temperature record, but regardless, a surface temperature projection should be compared to surface temperature data.

In addition, Christy removes the influence of volcanic eruptions (which have had a modest net warming effect over the past 30 years due to a couple of volcanic eruptions causing cooling during the early part of that timeframe) before comparing UAH record to the Hansen model projections, but he fails to remove other short-term effects like the El Niño Southern Oscillation (ENSO) and solar activity (as was done by Foster & Rahmstorf [2011]), which have had cooling effects over that period. As a result, Christy's analysis actually biases the data in the cool direction prior to comparing it to the model, and as a result he arrives at the incorrect conclusion, wrongly claiming that Hansen et al. had over-predicted the ensuing global warming.

From Intrigue to Concern

The concluding paragraph of Hansen et al. expresses fascination at the global experiment we are conducting with the climate:

"The climate change induced by anthropogenic release of CO2 is likely to be the most fascinating global geophysical experiment that man will ever conduct. The scientific task is to help determine the nature of future climatic effects as early as possible."

While the grand global experiment humans are running with the climate remains a fascinating one, climate scientists have concluded that the nature of future climatic effects will be predominantly bad if we continue on our current greenhouse gas emissions path, and potentially catastrophic. Over the decades James Hansen's tone has grown increasingly alarmed, as he and most of his fellow climate scientists worry about the consequences of human-caused climate change.

Hansen et al. (1981) demonstrates that we have every reason to be concerned, as three decades ago these climate scientists understood the workings of the global climate well enough to predict the ensuing global warming within approximately 15%, and accurately predict a number of important consequences. It's high time that we start listening to these climate experts and reduce our greenhouse gas emissions.