20TH-CENTURY SEA-SURFACE TEMPERATURE TRENDS

An analysis of historical sea surface temperatures provides evidence f or global warming since 1900, in line with land-based analyses of glob al temperature trends, and also shows that over the same period, the e astern equatorial Pacific cooled and the zonal sea surface temperature gradient strengthened. Recent theoretical studies have predicted such a pattern as a response of the coupled ocean-atmosphere system to an exogenous heating of the tropical atmosphere. This pattern, however, i s not reproduced by the complex ocean-atmosphere circulation models cu rrently used to simulate the climatic response to increased greenhouse gases. Its presence is likely to lessen the mean 20th-century global temperature change in model simulations.