much, and in what sense regional temperatures have systematically
changed, around the world, in the last fifty years. The contours
express the temperature change in degrees C: in this case, the difference
between the mean temperature for 1981-1997 and that for 1951-1980.
The mean temperature increase in this time, averaged over the globe,
was about 0.4°C. The greatest changes, as expected,
were generally at higher latitudes, although surface readings over
isolated portions of the North Atlantic and North Pacific Oceans
have cooled by about as much. (As in Figure 1, courtesy of J. Hurrell;
adapted from data provided by the Hadley Center, UKMO, and CRU,
University of East Anglia).