Global warming continues.

Abstract

The second warmest global surface temperature in more than a century of instrumental data ([1][1]) was recorded in the 2001 meteorological year (December 2000 through November 2001) (see panel A). The calendar year 2001 will also be the second warmest year on record, as the 11-month temperature anomaly exceeds that in the next warmest years (1990 and 1995) by almost 0.1°C. For our analysis, we used recently documented procedures for data over land ([1][1]) and for sea surface temperatures ([2][2]). The global warmth in 2001 is particularly meaningful because it occurs at a phase of the Southern Oscillation in which the tropical Pacific Ocean is cool (see panel B). The record warmth of 1998, in contrast, was bolstered by a strong El Nino that raised global temperature 0.2°C above the trend line (see panel A). Global surface air warming over the past 25 years is ~0.5°C, and in the past century is ~0.75°C ([1][1]). The recent surface warming contrasts with warming of only ~0.1°C in the troposphere over the past 22 years ([3][3]); however, surface and tropospheric warmings are similar over the past 50 years ([4][4]). The greatest warm anomalies in 2001 were in Alaska-Canada, in a band from North Africa to Central Asia, and in the Antarctic peninsula (Palmer Land). The Indian and Western Pacific oceans were unusually warm, continuing a trend of recent decades ([1][1]). The North Atlantic Ocean is notably warmer than the 1951-1980 climatology. Unusually cool conditions of recent decades, which were centered in Baffin Bay and extended south and southeast of Greenland ([1][1]), have given way to warm anomalies in the past 5 years. Overall, the 2001 temperature extends the unusual global warming of recent decades. This warming is considered to be a consequence of anthropogenic greenhouse gases ([5][5]), and thus the high 2001 temperature will likely invigorate discussions about how to slow global warming. 1. [↵][6]1. J. Hansen 2. et al. , J. Geophys. Res. 106, 23947 (2001). [OpenUrl][7] 2. [↵][8]1. R. W. Reynolds, 2. N. A. Rayner, 3. T. M. Smith, 4. D. C. Stokes, 5. W. Wang , J. Climate, in press. 3. [↵][9]1. J. R. Christy, 2. R. W. Spencer, 3. W. D. Braswell , J. Atmos. Oceanic Technol. 17, 1153 (2000). [OpenUrl][10][CrossRef][11] 4. [↵][12]National Research Council. Reconciling Observations of Global Temperature Change (2000) Washington, DC, National Academy of Scences. 5. [↵][13]1. J. T. Houghton 2. et al. Intergovernmental Panel on Climate Change (IPCC), Climate Change 2001 (Cambridge Univ. Press, New York, 2001). [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5 [6]: #xref-ref-1-1 View reference 1 in text [7]: {openurl}?query=rft.jtitle%253DJ.%2BGeophys.%2BRes.%26rft.volume%253D106%26rft.spage%253D23947%26rft.atitle%253DJ%2BGEOPHYS%2BRES%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [8]: #xref-ref-2-1 View reference 2 in text [9]: #xref-ref-3-1 View reference 3 in text [10]: {openurl}?query=rft.jtitle%253DJ.%2BAtmos.%2BOceanic%2BTechnol.%26rft.volume%253D17%26rft.spage%253D1153%26rft_id%253Dinfo%253Adoi%252F10.1175%252F1520-0426%25282000%2529017%253C1153%253AMTTDCA%253E2.0.CO%253B2%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [11]: /lookup/external-ref?access_num=10.1175/1520-0426(2000)017 2.0.CO;2&link_type=DOI [12]: #xref-ref-4-1 View reference 4 in text [13]: #xref-ref-5-1 View reference 5 in text