| description abstract | A preliminary analysis based primarily on historical records of sea surface temperature (SST) gives estimates of the change since 1880 of global, hemispheric and zonal average surface temperatures. The global change with time is roughly similar in shape and magnitude to that derived by Mitchell from land station data alone, but lags the Mitchell curve by 10-20 years. That is, the present data show a minimumof temperature somewhere between 1900 and 1925 and a maximum somewhere between 1945 and 1970. Comparing the means of these 25-year periods, the rise from minimum to maximum was (roughly) 0.6 K for the Northern Hemisphere and 0.9 K for the Southern Hemisphere. Comparing the means of the 50 years before 1930 and the 48 years from 1930 to 1977, the rise was 0.3 K for the Northern Hemisphere and 0.6 K for the Southern Hemisphere. The figures do not take into account the polar regions which, on linear extrapolation from lower latitudes, may have risen in temperature by twice the hemispheric averages. The temperature of the tropical zone (l0°N-10°S) has not changed over the years, so that the meridionaltemperature gradient has decreased in both hemispheres. The detail of the various conclusions may be revised later in the light of further analysis of the errors associated with the SST data sets. This furtheranalysis is underway at the Environmental Research Laboratories of NOAA. | |
