AGW Observer

Observations of anthropogenic global warming

New research from last week 10/2012

Posted by Ari Jokimäki on March 12, 2012

This week we wonder if there’s a monsoon in Europe and if data archiving practices of ecologists could be improved. We also have a paper on skating in Canada. Doesn’t sound much like a batch of climate papers, right? We do have studies also on maize in United States, double cropping in China, and soil microbial communities. Still not about climate, you say? Ok, there are also studies on Twentieth Century Reanalysis, hurricane classifications over time, Saudi Arabia temperature trends, and carbon dioxide transport in upper atmosphere. Does that satisfy your hunger for climate papers?


United States maize yields are projected to decrease and become more variable

Projected temperature changes indicate significant increase in interannual variability of U.S. maize yields – Urban et al. (2012)

Abstract: “Climate change has the potential to be a source of increased variability if crops are more frequently exposed to damaging weather conditions. Yield variability could respond to a shift in the frequency of extreme events to which crops are susceptible, or if weather becomes more variable. Here we focus on the United States, which produces about 40% of the world’s maize, much of it in areas that are expected to see increased interannual variability in temperature. We combine a statistical crop model based on historical climate and yield data for 1950–2005 with temperature and precipitation projections from 15 different global circulation models. Holding current growing area constant, aggregate yields are projected to decrease by an average of 18% by 2030–2050 relative to 1980–2000 while the coefficient of variation of yield increases by an average of 47%. Projections from 13 out of 15 climate models result in an aggregate increase in national yield coefficient of variation, indicating that maize yields are likely to become more volatile in this key growing region without effective adaptation responses. Rising CO2 could partially dampen this increase in variability through improved water use efficiency in dry years, but we expect any interactions between CO2 and temperature or precipitation to have little effect on mean yield changes.”

Citation: Daniel Urban, Michael J. Roberts, Wolfram Schlenker and David B. Lobell, Climatic Change, DOI: 10.1007/s10584-012-0428-2.


New paper urges ecologists to archive and share their data

Advances in global change research require open science by individual researchers – Wolkovich et al. (2012)

Abstract: “Understanding how species and ecosystems respond to climate change requires spatially and temporally rich data for a diverse set of species and habitats, combined with models that test and predict responses. Yet current work is hampered by the long-known problems of inadequate management of data and insufficient description of analytical procedures, especially in the field of ecology. Despite recent institutional incentives to share data and new data archiving infrastructure, many ecologists do not archive and publish their data and code. Given current rapid rates of global change, the consequences of this are extreme: because an ecological dataset collected at a certain place and time represents an irreproducible set of observations, ecologists doing local, independent research possess, in their file cabinets and spreadsheets, a wealth of information about the natural world and how it is changing. Although large-scale initiatives will increasingly enable and reward open science, we believe that change demands action and personal commitment by individuals—from students and PIs. Here, we outline the major benefits of sharing data and analytical procedures in the context of global change ecology, and provide guidelines for overcoming common obstacles and concerns. If individual scientists and labs can embrace a culture of archiving and sharing we can accelerate the pace of the scientific method and redefine how local science can most robustly scale up to globally-relevant questions.”

Citation: Elizabeth M. Wolkovich, James Regetz, Mary I. O’Connor, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02693.x.


Possibly artificial shift in Twentieth Century Reanalysis over central United States

Detecting inhomogeneities in the Twentieth Century Reanalysis over the central United States – Ferguson & Villarini et al. (2012)

Abstract: “The Twentieth Century Reanalysis (20CR), which spans the 138 year period from 1871 to 2008, was intended for a variety of climate applications, including long-term trend assessment. Because over land 20CR only assimilates surface pressure observations and their count increases by an order of magnitude over the course of the record, a key question is whether the 20CR is homogenous and hence suitable for detecting climate-related changes. We use three statistical methods (Pettitt and Bai-Perron tests and segmented regression) to detect abrupt shifts in multiple hydrometeorological variable mean and uncertainty fields over the central United States. For surface air temperature and precipitation, we use the Climate Research Unit (CRU) time series data set for comparison. We find that for warm-season months, there is a consensus change point among all variables between 1940 and 1950, which is not substantiated by the CRU record. While we cannot say with certainty that these shifts in the 20CR analysis fields are artificial, our statistical analyses, coupled with a visual inspection of the underlying assimilated observational count time series, strongly point to this conclusion. Our recommendation is therefore for users to restrict climate trend applications over the central United States to the second half century of the 20CR record, after observational density has stabilized.”

Citation: Ferguson, C. R., and G. Villarini (2012), Detecting inhomogeneities in the Twentieth Century Reanalysis over the central United States, J. Geophys. Res., 117, D05123, doi:10.1029/2011JD016988.


Analysis of the effect of classification method changes to hurricane categories

On the Classification of Extreme Atlantic Hurricanes Utilizing Mid-20th Century Monitoring Capabilities – Hagen & Landsea et al. (2012)

Abstract: “An investigation is conducted to determine how improvements in observing capabilities and technology may have affected our ability to detect and monitor Saffir-Simpson Hurricane Wind Scale Category 5 hurricanes in the Atlantic basin during the mid-20th century. Previous studies state that there has been an increase in the number of intense hurricanes and attribute this increase to anthropogenic global warming. Other studies claim that the apparent increased hurricane activity is an artifact of better observational capabilities and improved technology for detecting these intense hurricanes. The present study focuses on the ten most recent Category 5 hurricanes recorded in the Atlantic from Hurricane Andrew (1992) through Hurricane Felix (2007). These ten hurricanes are placed into the context of the technology available in the period of 1944-1953, the first decade of aircraft reconnaissance. A methodology is created to determine how many of these ten recent Category 5s likely would have been recorded as Category 5s if they had occurred during this period using only the observations that likely would have been available with existing technology and observational networks. Late 1940s and early 1950s best track intensities are determined for the entire lifetime of these ten recent Category 5s. It is found that likely only two of these ten – both Category 5 landfalling hurricanes – would have been recorded as Category 5 hurricanes if they had occurred during the late 1940s period. The results suggest that intensity estimates for extreme tropical cyclones prior to the satellite era are unreliable for trend and variability analysis.”

Citation: Andrew B. Hagen, Christopher W. Landsea, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00420.1.


Double cropping may amplify regional warming in northern China

Observational evidences of double cropping impacts on the climate in the northern China plains – Ho et al. (2012)

Abstract: “The impacts of harvested cropland in the double cropping region (DCR) of the northern China plains (NCP) on the regional climate are examined using surface meteorological data and satellite-derived normalized difference vegetation index (NDVI) and land surface temperature (LST). The NDVI data are used to distinguish DCR from single cropping region (SCR) in the NCP. Notable increases in LST in the period May-June are found in the area identified as DCR on the basis of the NDVI data. The difference between the mean daily maximum temperature averaged over the DCR and SCR stations peaks at 1.27°C in June. The specific humidity in DCR is significantly smaller than in SCR. These results suggest that the enhanced agricultural production by multiple cropping may amplify regional warming and aridity to further modify the regional climate in addition to the global climate change. Results in this study may also be used as a quantitative observed reference state of the crop/vegetation effects for future climate modeling studies.”

Citation: C.-H. Ho, S.-J. Park, S.-J. Jeong, J. Kim, and J.-G. Jhun, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00224.1.


In Saudi Arabia temperatures have increased and precipitation has decreased significantly

Recent climate change in the Arabian Peninsula: annual rainfall and temperature analysis of Saudi Arabia for 1978–2009 – Almazroui et al. (2012) [FULL TEXT]

Abstract: “The rainfall and temperature climatology over the Arabian Peninsula are analysed on an annual basis using various gridded datasets. For Saudi Arabia, the area of which represents almost 80% of the Peninsula, the climatic datasets from its 27 ground observations are analysed for the period 1978–2009, with additional gridded datasets used to describe the observed state and change of the present climate. The gridded datasets represent well the very dry (40–80 mm) area over the world’s largest sand desert (Rub Al-Khali), the dry (80–150 mm) area over middle-to-north of Saudi Arabia, and the wettest (>150 mm) region in the southwest of the Peninsula. The annual temperature is relatively high (24–27 °C) in the middle-to-south of the Peninsula and low (27 °C) is obtained over the Rub Al-Khali. Over Saudi Arabia, the observed annual rainfall showed a significant decreasing trend (47.8 mm per decade) in the last half of the analysis period, with a relatively large interannual variability, while the maximum, mean and minimum temperatures have increased significantly at a rate of 0.71, 0.60, and 0.48 °C per decade, respectively. This information is invaluable to consider in any climate impact assessment studies in Saudi Arabia.”

Citation: Mansour Almazroui, M. Nazrul Islam, H. Athar, P. D. Jones, M. Ashfaqur Rahman, International Journal of Climatology, DOI: 10.1002/joc.3446.


Aircraft observations show the interhemispheric transport of CO2 in the upper atmosphere

Aircraft observation of the seasonal variation in the transport of CO2 in the upper atmosphere – Sawa et al. (2012)

Abstract: “A large number of in situ carbon dioxide (CO2) measurements from 5224 flights were taken by commercial airliners from 2005 to 2010. We analyzed the seasonal cycles in tropospheric CO2 in wide areas of the world over the Eurasian continent, the North Pacific, Southeast Asia, and Oceania. In the Northern Hemisphere, large seasonal changes of CO2 in the upper troposphere are found from spring through summer at northern midlatitudes to high latitudes with significant longitudinal differences; seasonally low CO2 mixing ratios are vertically transported from the surface over the Eurasian continent and then transported eastward to the North Pacific. In the Southern Hemisphere, the CO2 in the upper troposphere increases rapidly from April to June, indicating clearly the interhemispheric transport of high CO2 from the Northern Hemisphere winter. The rapid increase in the upper southern lower latitudes is equivalent to about 0.2 Pg increase in carbon. This interhemispheric transport should be adequately represented in general circulation models for source/sink estimates by inverse methods, because it is comparable to the seasonal or net fluxes estimated for a current inversion area size or a typical subcontinental domain. Estimation for transport of CO2 through the high altitudes will be more important than ever with increasing data from aircraft observations.”

Citation: Sawa, Y., T. Machida, and H. Matsueda (2012), Aircraft observation of the seasonal variation in the transport of CO2 in the upper atmosphere, J. Geophys. Res., 117, D05305, doi:10.1029/2011JD016933.


Soil microbial communities might react more to nitrogen deposition than to climate

Microbial communities and their responses to simulated global change fluctuate greatly over multiple years – Gutknecht et al. (2012)

Abstract: “We used microbial lipid analysis to analyze microbial biomass and community structure during six years of experimental treatment at the Jasper Ridge Global Change Experiment (JRGCE), a long-term multi-factor global change experiment in a California annual grassland. The microbial community fingerprint and specific biomarkers varied substantially from year to year, in both control and experimental treatment plots. Possible drivers of the variability included plant growth, soil moisture, and temperature. Surprisingly, background variation in the microbial community was of a larger magnitude than even very significant treatment effects, and this variation appeared to constrain responses to treatment. Microbial communities were mostly not responsive or not consistently responsive to the experimental treatments. Both AMF biomarker abundance (16:1 ω5c) and the fungal to bacterial ratio were lower under nitrogen addition in most years. Bacterial lipid biomarker abundances (15:0 iso and 16:1 ω7c) were higher under nitrogen addition in 2002, the year of largest microbial biomass, suggesting that bacteria could respond more to nitrogen addition in years of better growth conditions. Nitrogen addition and warming led to an interactive effect on the Gram-positive bacterial biomarker and the fungal to bacterial ratio. These patterns indicate that in California grassland ecosystems, microbial communities may not respond substantially to future changes in climate and that nitrogen deposition may be a determinant of the soil response to global change. Further, year-to-year variation in microbial growth or community composition may be important determinants of ecosystem response to global change.”

Citation: Jessica LM Gutknecht, Christopher B Field, Teri C Balser, 2012, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02686.x.


Canadian outdoor skating season has gotten shorter

Observed decreases in the Canadian outdoor skating season due to recent winter warming – Damyanov et al. (2012) [FULL TEXT]

Abstract: “Global warming has the potential to negatively affect one of Canada’s primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada.”

Citation: Nikolay N Damyanov et al 2012 Environ. Res. Lett. 7 014028 doi:10.1088/1748-9326/7/1/014028.


There might be a monsoon in Europe too

Some evidence on European monsoon existence – Radinović & Ćurić (2012)

Abstract: “Large-scale European atmospheric circulation induced by temperature differences between the continent and the North Atlantic Ocean causes thermodynamic and climatic conditions that initiate a European monsoon. In Eastern Europe, the rainy season occurs in early summer, and the dry season occurs in winter. In Western Europe, the rainy season is in the early winter and the dry season is in the spring. This precipitation trend, as well as other climatic features, suggests the existence of a European monsoon.”

Citation: D. Radinović and M. Ćurić, Theoretical and Applied Climatology, DOI: 10.1007/s00704-012-0609-y.


CLASSIC OF THE WEEK: Alexander & Mobley (1976)

Monthly Average Sea–Surface Temperatures and Ice–Pack Limits on a 1° Global Grid – Alexander & Mobley (1976) [FULL TEXT]

Abstract: “Climatological monthly ocean-surface temperatures obtained from the National Center for Atmospheric Research and from Fleet Numerical Weather Central are merged and interpolated onto a 1° global grid. Monthly distributions of the main ice packs of the Arctic and Antarctic are digitized from Fleet Weather Facility ice charts and Navy atlases, and are incorporated into the global arrays. Machine-analyzed maps of the resulting distributions for the months of January, March, May, July, September and November are presented to indicate the seasonal variations of temperature and ice extent.”

Citation: Alexander, Richard C., Robert L. Mobley, 1976: Monthly Average Sea–Surface Temperatures and Ice–Pack Limits on a 1° Global Grid. Mon. Wea. Rev., 104, 143–148.


When each paper is published, it is notified in AGW Observer Facebook page and 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.

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