Warming causes more extreme rain, not snow, over mountains. Scientists say that’s a problem
The Hindu
A warming world is transforming some major snowfalls into extreme rain over mountains instead, somehow worsening both dangerous flooding and long-term water shortages
A warming world is transforming some major snowfalls into extreme rain over mountains instead, somehow worsening both dangerous flooding like the type that devastated Pakistan last year as well as long-term water shortages, a new study found.
Using rain and snow measurements since 1950 and computer simulations for future climate, scientists calculated that for every degree Fahrenheit the world warms, extreme rainfall at higher elevation increases by 8.3% (15% for every degree Celsius), according to a study in Wednesday’s journal Nature.
Heavy rain in mountains causes a lot more problems than big snow, including flooding, landslides and erosion, scientists said. And the rain isn't conveniently stored away like snowpack that can recharge reservoirs in spring and summer.
“It is not just a far-off problem that is projected to occur in the future, but the data is actually telling us that it’s already happening and we see that in the data over the past few decades,” said lead author Mohammed Ombadi, a Lawrence Berkeley National Laboratory hydrologist and climate scientist.
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As the world has warmed to the brink of the 1.5 degree Celsius (2.7 degrees Fahrenheit) internationally agreed threshold to stem the worst effects of climate change, this study shows “every degree (Celsius) matters because it comes with an additional 15% increase” in extreme rain over mountains, Ombadi said. That per-degree rainfall boost in the mountains is more than twice the increase the rest of the world gets from warming air holding more water.
The study looked at only the heaviest rains each year over six decades in the Northern Hemisphere, finding that as altitude rose, so did the turbocharging of rain. The biggest increase in rains were noticed at about 10,000 feet (3,000 meters). That includes much of the American West, where Ombadi said “it’s very pronounced,” as well as parts of the Appalachian Mountains. Another big hotspot in Asia is the Himalayas, Tian Shan and Hindu Kush mountains, with the Alps also affected.
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