Researchers at the US Department of Energy’s Lawrence Berkeley National Laboratory found that climate change is turning snowfall into rain in the mountains of the northern hemisphere.
According to Mohammed Ombadi, the author of the study, a quarter of the world’s population lives in mountainous areas or downstream and will be directly affected by this risk.
Scientists already assume that climate change will increase the amount of water that falls during extreme events. However, this is the first time researchers have studied whether these extreme precipitation events occur as rain or snow.
They found that the proportion of water that fell as snow decreased in mountainous regions and instead fell as rain, making mountains particularly vulnerable to the threat of extreme precipitation.
They explained that for every one degree Celsius rise in global temperature, an average of 15 percent more rain can be expected at high altitudes.
While all mountain ranges in the Northern Hemisphere experience the change from snow to rain, those in the North American Pacific (the Cascades, the Sierra Nevada, and the coastal ranges from Canada to California) are most threatened by extreme precipitation events in the Himalayas and high-latitude regions.
This is because, according to Ombadi, a significant portion of the snowfall in this region typically occurs at temperatures just below zero degrees Celsius.
“The slightest change in air temperature will turn that snowfall into rain. This is unlike other mountain ranges where snow can occur at very low sub-zero temperatures.”
Ombadi hopes other climate scientists will consider the distinction between snowfall and precipitation to improve global climate models, and that civil engineers and planners will use the data to better prepare for heavy rain events.
rgh/lpn