Physical effects

J. Climate 21, 4647–4663 (2008)

Credit: © BJORN NISSEN/MÉDECINS SANS FRONTIÈRES

Establishing a physical link between warming in the tropical Pacific and the regional climate of Bangladesh could allow researchers to predict how climate change will influence future outbreaks of cholera there.

Now scientists say that increased rainfall, rather than temperature, may be the main factor that causes a surge in the water-borne disease in El Niño years in Bangladesh. El Niño-Southern Oscillation events — anomalous rises in tropical Pacific sea surface temperatures associated with shifts in atmospheric circulation that occur every three to seven years — have previously been linked to cholera outbreaks in Bangladesh, but until now a physical explanation for this relationship has been lacking.

Benjamin Cash of the Center for Ocean–Land–Atmosphere Studies, Maryland, and colleagues used a global circulation model to investigate the effects of El Niño-induced warming in the tropical Pacific on the climate of Bangladesh. Simulated increases in sea surface temperature altered wind patterns to the west of Bangladesh, leading to an accumulation of moisture in the region and greater rainfall during the summer monsoon season. The researchers suggest that this increase in rainfall, which exacerbates the risk of flooding and thus disease proliferation, is the cause of the more frequent outbreaks of cholera in El Niño years.

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Armstrong, A. Physical effects. Nature Clim Change 1, 138 (2008). https://doi.org/10.1038/climate.2008.107

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