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Large rainfall changes consistently projected over substantial areas of tropical land


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.

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Figure 1: Tropical land precipitation changes in two climate models, and observations of Sahel drought.
Figure 2: Tropical land precipitation change.
Figure 3: Relationship between area of tropical land with large precipitation change and global mean temperature change.
Figure 4: Regions most likely to experience large precipitation changes.

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All authors were supported by the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups for producing and making available their model output. For CMIP the US Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. We thank G. J. van Oldenborgh for making the CMIP5 data easily available via the KNMI Climate Explorer tool.

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R.C. conceived the original idea for the study, and performed the analysis. All authors provided additional ideas, helped to refine the methodology, and contributed towards writing the manuscript.

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Correspondence to Robin Chadwick.

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The authors declare no competing financial interests.

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Chadwick, R., Good, P., Martin, G. et al. Large rainfall changes consistently projected over substantial areas of tropical land. Nature Clim Change 6, 177–181 (2016).

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