During the Little Ice Age, the Pacific section of the circumglobal tropical rainbelt was up to 500 km south of its present position. Published online in this week's Nature Geoscience, these results indicate a very sensitive response of tropical rainfall patterns ― which many people in Africa, Asia and South America rely on for subsistence agriculture ― to small changes in Earth's radiation budget.
Julian Sachs and colleagues use microbiological, molecular and isotopic analyses of lake sediments from three islands in the eastern, central and western equatorial Pacific Ocean, respectively, to determine wet and dry periods on each island. The periods of humidity they identify in the three locations suggest that the intertropical convergence zone ― which marks the position of the most vigorous rainfall events ― were substantially further south than today between about ad 1400 and 1850. At this time, European temperatures were relatively cool, possibly owing to low solar radiation.