Global Mean Surface Temperature

Research teams from the US, Great Britain, and Russia have independently analyzed global records of air temperature taken at surface. These data sets begin about 1860 and extend to the present.

Studies of global warming that rely on surface air temperature measurements generally use plots of global (or hemispheric) mean temperature that are expressed relative to some base temperature (Figure 1). Typically, the 1951-1980 average or the 1961-1990 average is used as a reference, and individual annual temperatures are expressed as their departure from this mean value.

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