Large rainfall changes consistently projected over substantial areas of tropical land

Abstract

This study quantifies a direct link between global greenhouse gas emissions and rainfall changes over tropical land, and identifies regions most at risk of large changes, such as southern and east Africa. Many tropical countries are exceptionally vulnerable to changes in rainfall patterns, with floods or droughts often severely affecting human life and health, food and water supplies, ecosystems and infrastructure1. There is widespread disagreement among climate model projections of how and where rainfall will change over tropical land at the regional scales relevant to impacts2,3,4, with different models predicting the position of current tropical wet and dry regions to shift in different ways5,6. Here we show that despite uncertainty in the location of future rainfall shifts, climate models consistently project that large rainfall changes will occur for a considerable proportion of tropical land over the twenty-first century. The area of semi-arid land affected by large changes under a higher emissions scenario is likely to be greater than during even the most extreme regional wet or dry periods of the twentieth century, such as the Sahel drought of the late 1960s to 1990s. Substantial changes are projected to occur by mid-century—earlier than previously expected2,7—and to intensify in line with global temperature rise. Therefore, current climate projections contain quantitative, decision-relevant information on future regional rainfall changes, particularly with regard to climate change mitigation policy.