Arguments
1998 is not the hottest year on record
Posted on 23 December 2009 by John Cook
The argument "global warming stopped in 1998" still enjoys popularity (in fact, #7 on the skeptic leaderboard). The nuanced response to this line of thought is to point out that global warming is fundamentally due to the planet accumulating heat. Direct observations find the planet's total heat content has continued to rise past 1998 (Murphy 2009). Recent ocean heat measurements show the planet has been in positive energy imbalance to the end of 2008 (Schuckmann 2009). Global warming is still happening. Nevertheless, there is a simpler response to the argument that 1998 is the hottest year on record. It's not true. 1998 is not the hottest year on record.
The most prominent global temperature records come from the Hadley Centre at the University of East Anglia (HadCRUT), a branch of NASA called the Goddard Institute of Space Studies (NASA GISS) and the National Climatic Data Center which is part of the USA government’s National Oceanographic and Atmospheric Administration (NOAA). Of these three records, only the HadCRUT record shows 1998 as the hottest year on record. While all three records show near identical long term trends, there are differences on a year-to-year basis. GISS and NOAA both find 2005 is the hottest year on record (with 2009 possibly on track to pip 1998 as the second hottest year on record).
A new independent analysis of the HadCRUT record sheds light on this discrepancy. The analysis is by the European Centre for Medium-Range Weather Forecasts (ECMWF) who calculated global temperature, utilising a range of sources including surface temperature measurements, satellites, radiosondes, ships and buoys. They found recent warming has been higher than that shown by HadCRUT. This is because HadCRUT is sampling regions that have exhibited less change, on average, than the entire globe.
Figure 1 shows the regions that HadCRUT have sampled compared to the regions ECMWF included in their dataset. The ECMWF analysis shows that in data-sparse regions such as Russia, Africa and Canada, there is strong warming over land that is not included in the HadCRUT's sampling data. This leads the ECMWF to infer with high confidence that the HadCRUT record is at the lower end of likely warming.
Figure 1: Increase in mean near-surface temperature (°C) from (1989-98) to (1999-2008). Top figure shows HadCRUT sampling regions, lower figure shows ECMWF analysis (ECMWF 2009).
This result is not unexpected. NASA GISS found a major contributor to the record hot 2005 was the extreme Arctic warming (Hansen 2006). As there are few meterological stations in the Arctic, NASA extrapolated temperature anomalies from the nearest measurement stations. They found the estimated strong Arctic warmth was consistent with infrared satellite measurements and record low sea ice concentrations.
Figure 2: Surface temperature anomaly for the first half decade of the 21st century (Hansen 2006).
For the record, I've updated the "global warming stopped in 1998" page, adding the ECMWF analysis. However, I've still kept the discussion of total heat content as more prominent in the hope that this will lead to greater scientific understanding.
Rest assured you are not the only one who has had difficulty obtaining data form HadCRUT :)
RE: the NASA plot of temperature above for 2001 to 2005, why is the major part of the temperature increase concentrated in N. Canada, Greenland and Siberia ?
Also there are places on the map where in one area the temp has risen by say 1.8 degrees while at the same time, relatively close-by the temp has decreased by about 0.4 degrees. How do you explain this ?
So if you were thinking such a situation is physically impossible, so divergent temperature changes must be due to measurement error, you were wrong.
I was thinking more of the difference in temps between the areas north and south of the Persian Gulf. I am not talking about local temp differences on the scale of cities - the hot spot north of the Persian Gulf for example is about the size of India.
Have the original temp data been kriged to get the "blocked" temp data ? If so this produces a smoothing effect which means that the original ( raw ) temp differences were even greater than shown.
Simmons, A. J., K.M. Willett, P.D. Jones, P. W. Thorne, and D. Dee (2009),
Low-frequency variations in surface atmospheric humidity, temperature and precipitation: Inferences from reanalyses and monthly gridded observational data sets,
J. Geophys. Res., doi:10.1029/2009JD012442, in press.
Thanx John for your time and patience. May Santa be kind to you and yours!
Conversely, if the heat source was homogeneous, you would expect to see exception (last vestiges of cooler zones) appearing as remanant localized cold spots, yet the data indicates just the opposite.
http://www.jpl.nasa.gov/news/news.cfm?release=2009-196
Some interesting things happening right now in the science, as more results start arriving from better equipment.
(quote)"The implication of these studies is that, should greenhouse gas emissions continue on their current course of increase, we are virtually certain to see Earth's climate warm by several degrees Celsius in the next century, unless some strong negative feedback mechanism emerges elsewhere in Earth's climate system," Dessler said(end quote)
Lovely phrasing here. Dressler is a true scientist, IMHO.
On can think about it in this way:
Since water vapor dominating the green house effect, and since water vapor varies in concentration in the atmosphere, and if CO2 is uniformly distributed, and if CO2 has a significant effect, then it follows the warming will be greater at those places where water vapor has less concentration. Therefore, since water vapor concentration is lower at the polar region the prediction is that warming due to CO2 should be greater at the polar regions.
http://www.youtube.com/watch?v=B7OdCOsMgCw
(This Peter Sinclair video may not be appropriate [strays from scientific discourse in places] but it does some nice things with maps of heat and people.)
But on the ECMWF map, (1998-2008)the reverse is shown. The location of the hot spot in figure 1 has actually cooled by 0.3 degrees and in general the south of Angola has cooled.
Or to put it another way, figure 2 shows appreciable warming in South Central Africa while the ECMWF map shows cooling to no change in the same area. How is this explained ?
Approximately Angola, the Antarctic Peninsula, north of the Faulkland Islands, Siberia, Uzbekistan, Siberia, and the Western Arctic seem to be the reddest. Please explain.
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I already explained above, and I did watch the video. The link is very apropo and appreciated, however the style is defensive and biased giving it a political campaign type feel.
I would like to answer your question in part by asking another question. Are red and purple splotches random, or might there not be a particular reason why some parts of the world are warming in general more than others? And if we had maps comparing temperatures over ten year intervals going back in time 1000 years, would one expect temperature cycles to have a homogeneous distribution, or resemble the kind of thing we are seeing here?
I would assume that even in a totally non anthropogenic scenario, you would have uneven warming, for whatever the causes. However in the case here, these patterns are due in part by nature and in part by man.
Drivers such as waste heat may be local or downwind as I was saying. The cumulative effect of an urban continent such as Europe, or metropolis such as Los Angeles, Mexico City cannot be cooling the Earth. I dont think anyone is denying this. (Maybe the video is and exception)
I would also ask if polar zones arent more prone intrincially to have their average temperatures change given that they are dry, and represent the tail "edge" of the planet's net thermal energy reservoir.
The Arctic is supposed to warm quickly, the Antarctic is not. I don't know why you persist in insinuating that regional patterns of warming are unexpected from AGW theory. I thought you were cured of that
(http://www.skepticalscience.com/Was-there-a-Medieval-Warm-Period.html see your much appreciated response at comment #42). Your response in #17 above is a bit of a jumble, and it's probably not worth delving into here (even if I had the expertise) because (1) this post is about how hot 1998 was, and (2) the figures we're discussing (esp Fig 2) have observational periods that are too brief.
Finally, I didn't notice in the video someone saying that cities cooled the Earth. Did you? The only time I ever heard that was at a talk given by Hadi Dowlatabadi who gave the example of Pittsburgh -- the aerosols from post-war industry there apparently reduced the temperature of the city by quite a bit. I can't find the ref. But if you want a big picture view, go no further than our host's other pages. For example:
http://www.skepticalscience.com/urban-heat-island-effect.htm
http://tamino.wordpress.com/2009/12/15/how-long/
http://skepticalscience.com/CO2-is-not-the-only-driver-of-climate.html
' If ever asked how much CO2 contributes to global warming, you could say "all of it... and some!" '
Large industrial cities are responsible for a good proportion of the aerosols, so let me be the first one you've heard say, "cities cool the planet, with the exception of greenhouse gas production."
Sorry for the off-topic, John. I don't know how to make this more relevant to your post.
To answer your question about what I meant. I suppose a very different picture is conceivable. One where the entire planet's temperature is raised slightly, everything one color for the most part, and possibly some holes where the trend is lagging. This being a situation where the temperature is increasing globally and in general unison.
"For rates of global warming (large spatial scale), somewhere over 15 years is recommended in this post"...
So I can disregard NASA's temperature map above as it reflects weather and not climate ? In that case, why was the map posted here?
I have had a look at NASA's data and the current hot spot in Antarctica started around 1982, about the same time as the hot spot in Angola. That is based on 27 years of data and therefore I would argue reflects climate and not simpy weather.
Also, with regard to which year has been hottest, taking into consideration the accuracy of the temp measurements ( +/- about 0.1 degree C according to NASA ) the years 1998, 2002,2003, 2005, 2006 and 2007, can be regarded as being of similar temperature.
It's seems like HadCRUT's result was not acceptable but GISS & NOAA's were.
The funny thing is, if you look at figure 1 above comparing both their samplings some interesting things come out:
1. ECMWF looks like they have averaged down the southern hemisphere
2.Apart from more infill on the northern hemisphere, there doesn't seem to be much difference between the two. Except for the west coast of the United States of America(how could HadCRUT got this area so wrong).