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GISS Surface Temperature Analysis

Global Temperature Trends: 2002 Summation

Figure 1

Figure 1: Trend of global annual surface temperature relative to 1951-1980 mean. Click for full-size GIF or PDF of this graph.

The 2002 meteorological year is the second warmest year in the period of accurate instrumental data (since the late 1800s). The global surface temperature for 12 months from December 2001 through November 2002 is 0.51°C above the climatological mean (1951-1980 average) in the GISS analysis, which uses meteorological station measurements over land and satellite measurements of sea surface temperature over the ocean.

Figure 1 shows that the warmest temperature occurred in 1998, while the third warmest year was 2001. As this figure shows, there has been a strong warming trend over the past 30 years, a trend that has been shown to be due primarily to increasing greenhouse gases in the atmosphere. El Niños, in which warm water spreads over the tropical Pacific Ocean, are one major cause of fluctuations about the long-term trend. There was a very strong El Niño in 1998, while a weak El Niño has existed for the last several months of 2002. The fact that 2002 is almost as warm as the unusual warmth of 1998 is confirmation that the underlying global warming trend is continuing.

The map of surface temperature anomalies in 2002 (Figure 2) shows that the largest warm anomalies occurred in Siberia and in the Arctic. Averaged over the 12 months, most places in the world were warmer than normal, although the western half of the United States was near normal.

Figure 2

Figure 2: Global map of temperature anomalies for the 2002 meteorological year (Dec. 2001-Nov. 2002) relative to the 1951-1980 baseline. Click for full-size GIF or PDF of this map.


Figure 3

Figure 3: Global map of temperature anomalies for November 2002. (Note color scale is not the same as in Fig. 2.) Click for full-size GIF or PDF of this map.

The temperature anomalies for November 2002 (Figure 3) show that the monthly fluctuations of temperature in any given region are generally larger than the magnitude of global warming. Thus November was much cooler than normal in the eastern two-thirds of the United States, in northern Europe, and in China and Japan. These short-term fluctuations are natural variations of climate.

Further Information

Related webpages on the GISS website include:

Contacts

Other GISS scientists involved in this research were Drs. James E. Hansen, Reto A. Ruedy and Makiko Sato.

References

Christy, J.R., R.W. Spencer, and W.D. Braswell 2000. MSU tropospheric temperatures: Dataset construction and radiosonde comparisons. J. Atmos. Oceanic Tech. 17, 1153-1170.

Hansen, J., R. Ruedy, M. Sato, M. Imhoff, W. Lawrence, D. Easterling, T. Peterson, and T. Karl 2001. A closer look at United States and global surface temperature change. J. Geophys. Res. 106, 23947.

Intergovernmental Panel on Climate Change 2001. Climate Change 2001 (J.T. Houghton et al., Eds.), Cambridge Univ. Press, New York.

National Research Council 2000. Reconciling Observations of Global Temperature Change. National Academy Press, Washington, DC, 85 pp.

Reynolds, R.W., N.A. Rayner, T.M. Smith, D.C. Stokes, and W. Wang 2002. An improved in situ and satellite SST analysis for climate. J. Climate 15, 1609-1625.

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