Global warming drains the water of life
Melting snowpack in Turkey’s Lesser Caucasus mountains. Image: Dario Martin-Benito
New research warns that rising temperatures are reducing the mountain snow on which billions of people in lowland areas depend for their water supply.
LONDON, 13 November, 2015 – Up to two billion people who depend on winter snow to deliver their summer water could see shortages by 2060 as upland and mountain snowpacks continue to dwindle.
An estimated 300 million people could find, 45 years on, that they simply won’t have enough water for all their needs, according to new research.
Climate change driven by rising atmospheric levels of carbon dioxide – in turn, fed by human combustion of fossil fuels – may already be affecting global precipitation. Researchers have consistently found that much of the world’s drylands will increase as global average temperatures rise.
But warmer temperatures increasingly also mean the water that once fell as snow, to be preserved until the summer, now falls as winter rain, and runs off directly. The snow that does fall is settling at ever higher altitudes and melting ever earlier.
Reliable flow
This is bad news for agricultural communities that depend on a reliable flow of meltwater every summer.
California is already in the grip of a sustained drought, made worse by lower falls of snow. Great tracts of Asia depend on summer meltwater from the Himalayan massif and the Tibetan plateau.
Justin Mankin, an environmental scientist at Columbia University’s Earth Institute in the US, and colleagues report in Environmental Research Lettersjournal that they studied 421 drainage basins across the northern hemisphere
They took account of the water used now and the patterns of population growth, and tested the impact of global warming, using computer simulations of a range of possible future patterns.
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