New research from last week 23/2012
Posted on 12 June 2012 by Ari Jokimäki
One important thing in science is method development. Science works at the edge between known and unknown, and in order to reveal little bit more of unknown, it is quite often needed to improve our research methods and even come up with some new ones. That is because the studied issues, or at least some aspects of them, have not been known for long, and research methods developed originally to study something else might not be suitable for studying the new issue.
We have some studies this week, that are at least partially method development papers. There is a paper about a meeting of statisticians, mathematicians, and climate scientists, where they discussed how uncertainties should be quantified in climate observations. One paper makes an effort to determine surface air temperatures using satellite measurements. Ice core syncronisation is the subject of one paper. Speaking of ice cores, there's another paper on ice cores which is borderline method development. Ice cores are used to study past climates but they have limited reach back in time. Currently longest ice core reaches back 800,000 years. Now researchers have studied ice flows in Allan Hills icefield and found out that there old ice has moved upwards, so old ice is there at the surface presenting possibility to extend ice core records beyond 800,000 years.
Other studies this week are touching the unknowns of carbon cycle, temperatures in European Alps, atmospheric carbon dioxide effects, Greenland glaciers, Southern Ocean wind, climate change scepticism, tropical and African rainfall, and atmospheric methane.
Carbon cycle uncertainty is larger than thought and could strongly amplify climate warming
Abstract: "Projections of greenhouse gas concentrations over the 21st century generally rely on two optimistic, but questionable, assumptions about the carbon cycle: 1) that elevated atmospheric CO2 concentrations will enhance terrestrial carbon storage, and 2) that plant migration will be fast relative to climate changes. This paper demonstrates that carbon cycle uncertainty is considerably larger than currently recognized and that plausible carbon cycle responses could strongly amplify climate warming. This has important implications for societal decisions that relate to climate change risk management because it implies that a given level of human emissions could result in much larger climate changes than we now realize or that stabilizing atmospheric greenhouse gas concentrations at a “safe” level could require lower human emissions than currently understood. These results also suggest that terrestrial carbon cycle responses could be sufficiently strong to account for the changes in atmospheric carbon dioxide that occurred during transitions between ice age and interglacial periods."
Citation: Paul A. T. Higgins and John Harte, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00089.1.
Let's synchronise our ice cores
Abstract: "This study aims at refining the synchronisation between the EPICA Dome C (EDC) and Vostok ice cores in the time interval 0–145 kyr BP by using the volcanic signatures. 102 common volcanic events were identified by using continuous electrical conductivity (ECM), di-electrical profiling (DEP) and sulfate measurements while trying to minimize the distortion of the glaciological chronologies. This is an update and a continuation of previous works performed over the 0–45 kyr interval that provided 56 tie points to the ice core chronologies (Udisti et al., 2004). This synchronisation will serve to establish Antarctic Ice Core Chronology 2012, the next synchronised Antarctic dating. A change of slope in the EDC-depth/Vostok-depth diagram is probably related to a change of accumulation regime as well as to a change of ice thickness upstream of the Lake Vostok, but we did not invoke any significant temporal change of surface accumulation at EDC relative to Vostok. No significant phase difference is detected between the EDC and Vostok isotopic records, but depth shifts between the Vostok 3G and 5G ice cores prevent from looking at this problem accurately. Three possible candidates for the Toba volcanic super-eruption ~73 kyr ago are suggested in the Vostok and EDC volcanic records. Neither the ECM, DEP nor the sulfate fingerprints for these 3 events are significantly larger than many others in the records."
Citation: Parrenin, F., Petit, J.-R., Masson-Delmotte, V., Wolff, E., Basile-Doelsch, I., Jouzel, J., Lipenkov, V., Rasmussen, S. O., Schwander, J., Severi, M., Udisti, R., Veres, D., and Vinther, B. M.: Volcanic synchronisation between the EPICA Dome C and Vostok ice cores (Antarctica) 0–145 kyr BP, Clim. Past, 8, 1031-1045, doi:10.5194/cp-8-1031-2012, 2012.
Using satellites to measure surface air temperature
Abstract: "Air surface temperature (Tair) is an important parameter for a wide range of applications such as vector-borne disease bionomics, hydrology and climate change studies. Air temperature data is usually obtained from measurements made in meteorological stations, providing only limited information about spatial patterns over wide areas. The use of remote sensing data can help overcome this problem, particularly in areas with low station density, having the potential to improve the estimation of Tair at both regional and global scales. Some studies have tried to derive maximum (Tmax), minimum (Tmin) and average air temperature (Tavg) using different methods, with variable estimation accuracy; errors generally fall in the 2–3 °C range while the level of precision generally considered as accurate is 1–2 °C. The main objective of this study was to accurately estimate Tmax, Tmin and Tavg for a 10 year period based on remote sensing—Land Surface Temperature (LST) data obtained from MODIS—and auxiliary data using a statistical approach. An optimization procedure with a mixed bootstrap and jackknife resampling was employed. The statistical models estimated Tavg with a MEF (Model Efficiency Index) of 0.941 and a RMSE of 1.33 °C. Regarding Tmax and Tmin, the best MEF achieved was 0.919 and 0.871, respectively, with a 1.83 and 1.74 °C RMSE. The developed datasets provided weekly 1 km estimations and accurately described both the intra and inter annual temporal and spatial patterns of Tair. Potential sources of uncertainty and error were also analyzed and identified. The most promising developments were proposed with the aim of developing accurate Tair estimations at a larger scale in the future."
Citation: A. Benali, A.C. Carvalho, J.P. Nunes, N. Carvalhais, c, A. Santos, Remote Sensing of Environment, Volume 124, September 2012, Pages 108–121, http://dx.doi.org/10.1016/j.rse.2012.04.024.
Highest summer temperatures in European Alps during 1053-1996 happened in the end of 20th century
Abstract: "We present a multi-archive, multi-proxy summer temperature reconstruction for the European Alps covering the period AD 1053–1996 using tree-ring and lake sediment data. The new reconstruction is based on nine different calibration approaches and errors were estimated conservatively. Summer temperatures of the last millennium are characterised by two warm (AD 1053–1171 and 1823–1996) and two cold phases (AD 1172–1379 and 1573–1822). Highest pre-industrial summer temperatures of the 12th century were 0.3 °C warmer than the 20th century mean but 0.35 °C colder than proxy derived temperatures at the end of the 20th century. The lowest temperatures at the end of the 16th century were ∼1 °C lower than the 20th century mean."
Citation: Mathias Trachsel, Christian Kamenik, Martin Grosjean, Danny McCarroll, Anders Moberg, Rudolf Brázdil, Ulf Büntgen, Petr Dobrovolný, Jan Esper, David C. Frank, Michael Friedrich, Rüdiger Glaser, Isabelle Larocque-Tobler, Kurt Nicolussi, Dirk Riemann, Quaternary Science Reviews, Volume 46, 16 July 2012, Pages 66–79, http://dx.doi.org/10.1016/j.quascirev.2012.04.021.
Atmospheric carbon dioxide concentration affects land water balance
Abstract: "Numerous studies have shown that increased atmospheric CO2 concentration is one of the most important factors altering land water balance. In this study, we investigated the effects of increased CO2 on global land water balance using the dataset released by the Coupled Model Intercomparison Project Phase 5 derived from the Canadian Centre for Climate Modelling and Analysis second-generation Earth System Model. The results suggested that the radiative effect of CO2 was much greater than the physiological effect on the water balance. At the model experiment only integrating CO2 radiative effect, the precipitation, evapotranspiration (ET) and runoff had significantly increased by 0.37, 0.12 and 0.31 mm year−2, respectively. Increases of ET and runoff caused a significant decrease of soil water storage by 0.05 mm year−2. However, the results showed increases of runoff and decreases of precipitation and ET in response to the CO2 fertilisation effect, which resulted into a small, non-significant decrease in the land water budget. In the Northern Hemisphere, especially on the coasts of Greenland, Northern Asia and Alaska, there were obvious decreases of soil water responding to the CO2 radiative effect. This trend could result from increased ice–snow melting as a consequence of warmer surface temperature. Although the evidence suggested that variations in soil moisture and snow cover and vegetation feedback made an important contribution to the variations in the land water budget, the effect of other factors, such as aerosols, should not be ignored, implying that more efforts are needed to investigate the effects of these factors on the hydrological cycle and land water balance."
Citation: Jing Peng, Wenjie Dong, Wenping Yuan, Jieming Chou and Yong Zhang, et al., Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0673-3.
Glaciers are melting away in Ammassalik region, southeast Greenland
Abstract: "Landsat imagery was applied to elucidate glacier fluctuations of land- and marine-terminating outlet glaciers from the Greenland Ice Sheet (GrIS) and local land-terminating glaciers and ice caps (GIC) peripheral to the GrIS in the Ammassalik region, Southeast Greenland, during the period 1972–2011. Data from 21 marine-terminating glaciers (including the glaciers Helheim, Midgaard, and Fenris), the GrIS land-terminating margin, and 35 GIC were examined and compared to observed atmospheric air temperatures, precipitation, and reconstructed ocean water temperatures (at 400 m depth in the Irminger Sea). Here, we document that net glacier recession has occurred since 1972 in the Ammassalik region for all glacier types and sizes, except for three GIC. The land-terminating GrIS and GIC reflect lower marginal and areal changes than the marine-terminating outlet glaciers. The mean annual land-terminating GrIS and GIC margin recessions were about three to five times lower than the GrIS marine-terminating recession. The marine-terminating outlet glaciers had an average net frontal retreat for 1999–2011 of 0.098 km yr−1, which was significantly higher than in previous sub-periods 1972–1986 and 1986–1999. For the marine-terminating GrIS, the annual areal recession rate has been decreasing since 1972, while increasing for the land-terminating GrIS since 1986. On average for all the observed GIC, a mean net frontal retreat for 1986–2011 of 0.010 ± 0.006 km yr−1 and a mean areal recession of around 1% per year occurred; overall for all observed GIC, a mean recession rate of 27 ± 24% occurred based on the 1986 GIC area. Since 1986, five GIC melted away in the Ammassalik area."
Citation: Mernild, S. H., Malmros, J. K., Yde, J. C., and Knudsen, N. T.: Multi-decadal marine- and land-terminating glacier recession in the Ammassalik region, southeast Greenland, The Cryosphere, 6, 625-639, doi:10.5194/tc-6-625-2012, 2012.
Wind speed has been increasing in recent decades over Macquarie Island
Abstract: "Most studies of trends in regional climate focus on temperature, however for maritime environments in particular, changes in the wind are equally important. An analysis of trends in the wind over Macquarie Island is performed with a radio-sonde database spanning nearly four decades. The results indicate that the surface wind speed is increasing, with the trend for the upper levels being less well defined. The surface wind is highly correlated with the upper level winds, and the wind at all levels are moderately correlated with the Southern Annular Mode. ECMWF ERA-Interim reanalysis data shows significant trends in wind speed over several levels, however slightly smaller than trends in the soundings over a similar time period. The correlations in ERA-Interim are similar to those in the soundings. A clustering analysis of the wind reveals four distinct regimes, with a trend towards a regime characterised by strong north westerly winds."
Citation: Hande, L. B., S. T. Siems, and M. J. Manton (2012), Observed Trends in Wind Speed over the Southern Ocean, Geophys. Res. Lett., 39, L11802, doi:10.1029/2012GL051734.
Analysis of Australian climate change scepticism
Abstract: "Public scepticism surrounding climate change is an obstacle for implementing climate change mitigation measures in many countries. However, very little is known about: (1) the nature and sources of climate change scepticism; and (2) its influence on preferences for climate change mitigation policies. In this paper, we investigate these two issues using evidence and analysis from an Australian public survey and choice experiment. The study has three key findings. First, the intensity of scepticism varies depending on its type; we observed little scepticism over the cause, trend and impact of climate change and widespread scepticism over the effectiveness of mitigation measures and global co-operation. Second, cause and mitigation scepticism play significant roles in determining public support for climate change abatement. Respondents who believed in human-induced climate change were significantly more supportive of mitigation. Likewise, respondents who believed that mitigation would be successful in slowing down climate change were significantly more likely to be supportive. Third, the general public tend to give the benefit of the doubt to supporting mitigation. Those who expressed higher uncertainty about climate outcomes were more supportive of mitigation than others with similar expectations but lower uncertainty."
Citation: Sonia Akter, Jeff Bennett, Michael B. Ward, Global Environmental Change, http://dx.doi.org/10.1016/j.gloenvcha.2012.05.004.
Statisticians, mathematicians, and climate scientists discussed uncertainty quantifications in climate observations
Abstract: "Approximately 60 statisticians, mathematicians, and climate scientists from academia and governmental institutions met in Asheville, NC, USA in January 2012 to discuss the issues surrounding uncertainty quantification in the context of climate observations. This workshop was an opportunity to engage with and understand the different concerns and perspectives from the largely academic mathematical and statistical communities and climate data product scientists and providers. Major outcomes of the workshop include the realization of interest in collaboration as well as identification of possible steps to work towards the mutual goal of robustly characterizing uncertainty in climate observation."
Citation: Jessica L. Matthews, Elizabeth Mannshardt, Pierre Gremaud, Bulletin of the American Meteorological Society 2012, doi: http://dx.doi.org/10.1175/BAMS-D-12-00042.1.
Allan Hills icefield in Antarctica has potential to extend ice core record beyond 800 000 years
Abstract: "We present a new surface-balance and ice-motion dataset derived from high-precision GPS measurements from a network of steel poles within three icefields of the Allan Hills blue-ice area, Antarctica. The surveys were conducted over a 14 year time period. Ice-flow velocities and mass-balance estimates for the main icefield (MIF) are consistent with those from pre-GPS era measurements but have much smaller uncertainties. The current study also extends these measurements through the near-western icefield (NWIF) to the eastern edge of the mid-western icefield (MWIF). The new dataset includes, for the first time, well-constrained evidence of upward motion within the Allan Hills MIF, indicating that old ice should be present at the surface. These data and terrestrial meteorite ages suggest that paleoclimate reconstructions using the surface record within the Allan Hills MIF could potentially extend the ice-core-based record beyond the 800 000 years currently available in the EPICA Dome C core."
Citation: Spaulding, Nicole E.; Spikes, Vandy B.; Hamilton, Gordon S.; Mayewski, Paul A.; Dunbar, Nelia W.; Harvey, Ralph P.; Schutt, John; Kurbatov, Andrei V., Journal of Glaciology, Volume 58, Number 208, April 2012 , pp. 399-406(8), DOI: http://dx.doi.org/10.3189/2012JoG11J176.
Tropical land regions are projected to have more wet and dry months with global warming
Abstract: "Quantifying how global warming impacts the spatiotemporal distribution of precipitation represents a key scientific challenge with profound implications for human systems. Utilizing monthly precipitation data from Coupled Model Intercomparison Project (CMIP3) climate change simulations, the results here show that the occurrence of very dry (10 mm/day) months comprises a straightforward, robust metric of anthropogenic warming on tropical land region rainfall. In particular, differencing tropicswide precipitation frequency histograms for 25-year periods over the late 21st and 20th centuries shows increased late-21st-century occurrence of both histogram extremes in the model ensemble and across individual models. Mechanistically, such differences are consistent with the view of enhanced tropical precipitation spatial gradients. Similar diagnostics are calculated for two 15-year subperiods over 1979-2008 for the CMIP3 models and three observational precipitation products to assess whether the signature of late-21st-century warming has already emerged in response to recent warming. While both the observations and CMIP3 ensemble-mean hint at similar amplification in the warmer (1994-2008) subinterval, the changes are not robust, as substantial differences are evident among the observational products and the intraensemble spread is large. Comparing histograms computed from the warmest and coolest years of the observational period further demonstrates effects of internal variability, notably the El Niño/Southern Oscillation, which appear to oppose the impact quasi-uniform anthropogenic warming on the wet tail of the monthly precipitation distribution. These results identify the increase of very dry and wet occurrences in monthly precipitation as a potential signature of anthropogenic global warming but also highlight the continuing dominance of internal climate variability on even bulk measures of tropical rainfall."
Citation: Lintner, B., M. Biasutti, N. S. Diffenbaugh, J.-E. Lee, M. J. Niznik, and K. L. Findell (2012), Amplification of wet and dry month occurrence over tropical land regions in response to global warming, J. Geophys. Res., doi:10.1029/2012JD017499.
Atmospheric methane concentration is increasing again
Abstract: "Trends of column-averaged methane for the time period (1996, Sep 2011) are derived from the mid-infrared (mid-IR) solar FTIR time series at the Zugspitze (47.42° N, 10.98° E, 2964 m a.s.l.) and Garmisch (47.48° N, 11.06° E, 743 m a.s.l.). Trend analysis comprises a fit to the de-seasonalized time series along with bootstrap resampling for quantifying trend uncertainties. We find a positive trend during [1996, 1998] of 9.0 [3.2, 14.7] ppb yr−1 for Zugspitze (95% confidence interval), an insignificant growth during [1999, mid 2006] of 0.8 [−0.1, 1.7] ppb yr−1 (Zugspitze), and a significant renewed increase during [mid 2006, Sep 2011] of 5.1 [4.2, 6.0] ppb yr−1 for Garmisch, which is in agreement with 4.8 [3.8, 5.9] ppb yr−1 for Zugspitze. The agreement of methane trends at the two closely neighboring FTIR sites Zugspitze and Garmisch within the uncertainties indicates a good station-to-station consistency as a basis for future trend analyses by the ground-based mid-IR FTIR network on the global scale. Furthermore, the Zugspitze FTIR trend for the time interval [Jul 2006, Jun 2009] is found to agree with the trend derived from SCIAMACHY (WFM-DOAS v2.0.2) data within the 95% confidence intervals. In case a 1000-km pixel selection radius around the Zugspitze is used, the confidence interval is narrower for the FTIR trend (6.9 [4.2, 9.5] ppb yr−1) compared to SCIAMACHY (7.1 [5.1, 8.6] ppb yr−1). If, however, a loosened pixel selection is used (≈1000-km half-width latitudinal band), the SCIAMACHY trend significance interval is narrower (6.8 [5.1, 8.6] ppb yr−1) compared to Zugspitze FTIR (5.7 [3.0, 8.3] ppb yr−1). While earlier studies using surface network data revealed changes of 8.0 ± 0.6 ppb in 2007, 6.4 ± 0.6 ppb in 2008, and 4.7 ± 0.6 ppb in 2009 (Dlugokencky et al., 2011), our updated result proves that the renewed methane increase meanwhile has been persisting for >5 years [mid 2006, Sep 2011]. This is either the longest and largest positive trend anomaly since the beginning of systematic observations more than 25 years ago or the onset of a new period of strongly increasing CH4 levels in the atmosphere. Several scenarios have been developed to explain the persistent increase observed, mainly invoking an increase in emissions from natural wetlands, an increase in fossil fuel-related emissions or a decrease in OH concentrations. However, more work is needed to fully attribute this increase to a particular source or sink."
Citation: Mark Sussmann, R., Forster, F., Rettinger, M., and Bousquet, P.: Renewed methane increase for five years (2007–2011) observed by solar FTIR spectrometry, Atmos. Chem. Phys., 12, 4885-4891, doi:10.5194/acp-12-4885-2012, 2012.
River flows and rainfall have increased in sub-Saharan Africa
Abstract: "Climatic trends over sub-Saharan Africa are described using major river flows, European Community Medium-Range Weather Forecasts, Coupled Forecast System, global land surface data assimilation and National Center for Environmental Prediction reanalysis, Global Precipitation Climate Center gauge data, and satellite observations in the period 1995–2010. The Niger and Zambezi rivers reached flow levels last seen in the 1950s (2,000 and 5,000 m3 s−1, respectively), and rainfall across the Congo Basin increased steadily ~+0.16 mm day−1 year−1. Weather events that contributed to flooding are studied and include the Zambezi tropical trough of 4 January 2008 and the Sahelian easterly wave of 19 July 2010. Diurnal summer rainfall increased threefold over the 1995–2010 period in conjunction with a strengthened land–sea temperature contrast, onshore flow, and afternoon uplift. 700 mb zonal winds over East Africa became easterly after 2001, so clean Indian Ocean air was entrained to the Congo, improving convective efficiency. Relationships between the African monsoon circulation and global teleconnections are explored. Zonal wind convergence around the Congo appears related with the tropical multi-decadal oscillation and signals in the Atlantic during the study period."
Citation: Mark R. Jury, Theoretical and Applied Climatology, 2012, DOI: 10.1007/s00704-012-0677-z.
CLASSIC OF THE WEEK: Huntington (1913)
Abstract: No abstract.
Citation: Ellsworth Huntington, The American Historical Review , Vol. 18, No. 2 (Jan., 1913), pp. 213-232.
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.