Robust direct effect of carbon dioxide on tropical circulation and regional precipitation

• Published in: Nature geoscience Vol. 6; no. 6; pp. 447 - 451
• Main Authors: Bony, Sandrine, Bellon, Gilles, Klocke, Daniel, Sherwood, Steven, Fermepin, Solange, Denvil, Sébastien
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-06-2013; Nature Publishing Group
• Subjects: 21st century; 704/106; 704/106/35; Atmosphere; Atmospheres; Atmospheric circulation; Atmospherics; Bgi / Prodig; Carbon dioxide; Circulation; Climate change; Climate models; Climatology; Earth science; Earth Sciences; Earth System Sciences; Fossil fuels; General circulation models; Geochemistry; Geoengineering; Geology; Geophysics/Geodesy; Global temperatures; Global warming; Hydrologic cycle; letter; Mathematical models; Ocean, Atmosphere; Physical geography; Precipitation; Prediction models; Rain; Rainfall; Regional; Sciences of the Universe; Surface temperature; Temperature; Tropical environments; Warm and intertropical climates; Water vapor; Weather forecasting; World; France; Impact; Atmospheric circulation; Twenty-first century; Climate; Precipitation; Climatic change; Tropical zone; Carbon dioxide
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/ngeo1799

Predicting the response of tropical rainfall to climate change remains a challenge. An analysis of climate model simulations suggests that in an emission scenario without mitigation, a large fraction of tropical precipitation change will be independent of global surface warming over the twenty-first century.
Predicting the response of tropical rainfall to climate change remains a challenge
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. Rising concentrations of carbon dioxide are expected to affect the hydrological cycle through increases in global mean temperature and the water vapour content of the atmosphere
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,
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. However, regional precipitation changes also closely depend on the atmospheric circulation, which is expected to weaken in a warmer world
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. Here, we assess the effect of a rise in atmospheric carbon dioxide concentrations on tropical circulation and precipitation by analysing results from a suite of simulations from multiple state-of-the-art climate models, and an operational numerical weather prediction model. In a scenario in which humans continue to use fossil fuels unabated, about half the tropical circulation change projected by the end of the twenty-first century, and consequently a large fraction of the regional precipitation change, is independent of global surface warming. Instead, these robust circulation and precipitation changes are a consequence of the weaker net radiative cooling of the atmosphere associated with higher atmospheric carbon dioxide levels, which affects the strength of atmospheric vertical motions. This implies that geo-engineering schemes aimed at reducing global warming without removing carbon dioxide from the atmosphere would fail to fully mitigate precipitation changes in the tropics. Strategies that may help constrain rainfall projections are suggested.