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Goyal et al., paper presented at the 2004 Annual Peer Review of the U.S. Superconductivity Program for Electric Systems, Washington, DC, 27 to 29 July 2004 (www.energetics.com/meetings/supercon04/pdfs/ presentations/f_rabits_strategic_talk_ffy04_final.pdf). 18. A. Goyal et al., Supercond. Sci. Technol. 18, 1533 (2005). 19. Y. Yamada et al., Appl. Phys. Lett. 87, 132502 (2005). 20. A. Goyal thanks Q. Jia at Los Alamos National Laboratory for useful discussions pertaining to pulsed laser deposition of YBCO. S. Kang, J. Li, and A. A. Gapud thank Oak Ridge Associated Universities for a postdoctoral fellowship. The research was sponsored by the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability– Superconductivity Program, under contract DE-AC05- 00OR22725 with UT-Battelle, LLC managing contractor for Oak Ridge National Laboratory. Supporting Online Material www.sciencemag.org/cgi/content/full/311/5769/1911/DC1 SOM Text 11 January 2006; accepted 2 March 2006 10.1126/science.1124872 Significant Warming of the Antarctic Winter Troposphere J. Turner,* T. A. Lachlan-Cope, S. Colwell, G. J. Marshall, W. M. Connolley We report an undocumented major warming of the Antarctic winter troposphere that is larger than any previously identified regional tropospheric warming on Earth. This result has come to light through an analysis of recently digitized and rigorously quality controlled Antarctic radiosonde observations. The data show that regional midtropospheric temperatures have increased at a statistically significant rate of 0.5- to 0.7-Celsius per decade over the past 30 years. Analysis of the time series of radiosonde temperatures indicates that the data are temporally homogeneous. The available data do not allow us to unambiguously assign a cause to the tropospheric warming at this stage. M eteorological observations from the Antarctic research stations provide the most accurate data to investigate long-term climate change across the conti- nent. Many of the surface records extend back to the International Geophysical Year of 1957 to 1958. These records indicate that the western side of the Antarctic Peninsula has experienced the largest measured annual near-surface warming (0.55-C per decade at Faraday/Vernadsky station) on Earth over the past 50 years (1). However, there have been few statistically significant temperature changes at the surface across the rest of the continent (2, 3), and some studies have suggested a slight cooling in recent decades (4). This is in con- trast to a mean near-surface warming across the Earth of 0.11-C per decade during the past 50 years (5). Although there have been several investiga- tions concerned with surface temperature change across the Antarctic (6–8), there have not been any comparable investigations of changes at up- per levels, because many of the radiosonde ob- servations were not available. Recently, many of the important radiosonde records have been digitized and intensively quality controlled in a project funded by the Scientific Committee on Antarctic Research (9). In particular, the Russian radiosonde observations are now avail- able (www.antarctica.ac.uk/met/READER/). This represents a considerable increase in the coverage and completeness over the Antarctic component of previous global radiosonde com- pilations (10–12). A summary of the annual and seasonal tem- perature trends at the 500-hPa level for the period from 1971 to 2003 is presented in Fig. 1A. We have concentrated on nine stations (most of which are in East Antarctica) that have reasonably complete records for this period; only five of these stations were included in the Angell studies of global upper air temperature trends (10, 11). In this study, a monthly mean temperature was only computed if at least 30% of the daily ascents were available. Only 8% of the monthly means (9) were missing across the records of the nine stations, allowing reliable temperature trends to be computed. Figure 1A shows that there have been statistically signifi- cant increases in seasonal temperature at many of the stations across the continent, both in the coastal region, where most of the stations are located, and at Amundsen-Scott station at the South Pole. We examined the mean vertical profile of the temperature trends for winter for the nine stations (Fig. 1B), because this is the season of maximum warming across most of the conti- nent (compare with Fig. 1A). Warming has oc- curred throughout the troposphere, with the maximum increase in temperature in the mid- troposphere (400 to 600 hPa). The mean winter trend for the nine stations from 1971 to 2003 was a 0.15-C increase per decade at the sur- face and a 0.70-C increase per decade in the midtroposphere. In the stratosphere, there has been cooling between 200 and 50 hPa, and the largest decrease in temperature was –0.16-C per decade at 100 hPa. The standard deviation (SD) of the station trends is large at the surface (Fig. 1B) because the pattern of change at this level is variable across the continent, and in the stratosphere because the impact of the Ant- arctic ozone hole has varied around the conti- nent. However, the SD values are small in the midtroposphere, indicating that a fairly uniform warming has occurred across the Antarctic at this level. The Angell analysis of global radiosonde data (10, 11) considered changes over the layer from 850 to 300 hPa. For the period from 1971 to 2003, there was an annual global warming trend of 0.11-C per decade; the largest trend of 0.15-C per decade was during the Austral winter. The annual trend for the Southern Hem- isphere was 0.07-C, and the greatest change took place during the winter when the trend was 0.10-C per decade. Within the Southern Hemisphere winter, the trends vary strongly by latitude: Equatorward of 60-S, the trend is 0.06-C per decade (13), whereas the data from the nine Antarctic stations analyzed in this paper have a mean temperature trend of 0.43-C per decade for 850 to 300 hPa. Thus, the trend for the Southern Hemisphere is dominated by the changes that have taken place across the Antarctic. The 40-year European Centre for Medium- Range Weather Forecasts (ECMWF) reanalysis data set (ERA-40) (www.ecmwf.int/research/ era) provides an extremely valuable means of examining spatial variability of atmospheric parameters and change in recent decades. Al- though ERA-40 begins in 1957, there are prob- lems with the quality of the high-latitude fields before 1979 (14, 15). Therefore, we compared the 500-hPa temperature trends in ERA-40 (Fig. 2) with equivalent values from the radio- sonde data for the period from 1979 to 2001 (the last full year of the reanalysis). The general pattern of the ERA-40 temperature trends is in broad agreement with the trends from the radiosonde data. However, ERA-40 has larger warming trends than the in situ data, except over the Antarctic Peninsula. For example, British Antarctic Survey, Natural Environment Research Council, Cambridge CB3 0ET, UK. *To whom correspondence should be addressed. E-mail: j.turner@bas.ac.uk 31 MARCH 2006 VOL 311 SCIENCE www.sciencemag.org 1914 REPORTS