James Hansen - Global Temperature in 2020.

 

14 January 2021 James Hansena, Makiko Satoa, Reto Ruedyb,c, Gavin Schmidtc, Ken Lob,c, Michael Hendricksonb,c

Abstract.  Global surface temperature in 2020 was in a virtual dead-heat with 2016 for warmest year in the period of instrumental data in the Goddard Institute for Space Studies (GISS) analysis.  The rate of global warming has accelerated in the past several years.  The 2020 global temperature was +1.3°C (~2.3°F) warmer than in the 1880-1920 base period; global temperature in that base period is a reasonable estimate of ‘pre-industrial’ temperature.  The six warmest years in the GISS record all occur in the past six years, and the 10 warmest years are all in the 21st century.  Growth rates of the greenhouse gases driving global warming are increasing, not declining.       Update of the GISS (Goddard Institute for Space Studies) global temperature analysis (GISTEMP)1,2,3 (Fig. 1) finds 2020 to be the warmest year in the instrumental record, but by an amount so slight (<0.01°C) that the difference with the 2016 temperature is insignificant.  More detail is available at http://data.giss.nasa.gov/gistemp/ and http://www.columbia.edu/~mhs119/Temperature.  Figures shown here are available from Makiko Sato on the latter web site.       We use 1880-1920 as baseline, i.e., as the zero-point for temperature anomalies, in part because it is the earliest period with substantial global coverage of instrumental measurements.  Global temperature in 1880-1920 should approximate ‘preindustrial’ temperature, because the small warming from human-made greenhouse gases in that period tends to be offset by unusually high volcanic activity then.4             The six warmest years in the GISS record are the past six years, 2015-2020.  Figure 2 compares the temperature anomalies for each of these years relative to the 1951-1980 base period.  We use 1951-1980 as base period for global maps because it allows good global coverage, including data for Antarctica.

Fig. 1.  Global surface temperatures relative to 1880-1920 based on GISTEMP data, which employs GHCN.v4 for meteorological stations, NOAA ERSST.v5 for sea surface temperature, and Antarctic research station data1.

a Earth Institute, Columbia University, New York, NY b SciSpace LLC, New York, NY c NASA Goddard Institute for Space Studies, New York, NY

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