Climate Change Shifts Snow to Rain, Amplifying Extreme Rainfall and Flooding Worldwide

A recent study, titled "A Warming-Induced Reduction in Snow Fraction Amplifies Rainfall Extremes" published in the journal Nature, reveals that as the climate warms, mountainous regions will experience more intense rainfall than previously anticipated, along with an increase in associated hazards such as floods, landslides, and soil erosion.

While previous research focused on the overall increase in extreme precipitation due to climate change, this study specifically examines the distribution between rainfall and snowfall during these events. The findings highlight the significance of the shift from snow to rain, as rain tends to pose greater risks to human populations.

Mountainous Regions At Risk of Extreme Rainfall and Flood

The study, conducted by researchers at Lawrence Berkeley National Laboratory, reports that climate change is causing a shift from snowfall to rainfall in mountainous regions across the Northern Hemisphere. According to Science Daily, this transition to more liquid water poses distinct dangers, including the increased risk of floods, landslides, and soil erosion.

Mohammed Ombadi, the first author of the study, highlighted the significance of this finding. Ombadi noted that approximately one-fourth of the global population resides in or downstream from mountainous areas, directly exposing them to these risks.

While scientists have previously anticipated that climate change would lead to greater volumes of water during extreme weather events, this study is the first to examine the distribution between rain and snow within these events. The researchers observed a decrease in the proportion of precipitation falling as snow in mountainous regions, with more precipitation occurring as rain.

This shift makes mountains particularly susceptible to the hazards associated with heavy rain. The study revealed that for every 1 degree Celsius increase in global temperature, there is an average of 15% more rainfall at high elevations.

Furthermore, Ombadi emphasized that the increase in extreme rainfall is not a future prediction but rather an ongoing phenomenon. As New York Times reported, the increase in extreme rainfall with rising elevation was not linear, and different mountain ranges in the Northern Hemisphere had varying risks of extreme rainfall.

Implications of Increased Rainfall to Human Populations

Mountain regions and areas downstream are home to around 25% of the world's population, making them vulnerable to various hazards, according to WION's report. Landslides primarily affect localized areas, while floods can have widespread impacts on communities located downstream.

Moreover, soil erosion can further aggravate the risks of floods and landslides, leading to the degradation of agricultural lands and natural ecosystems. These challenges are compounded by the melting of glaciers in mountain ranges and river valleys, posing additional threats to these regions.

Although the shift from snow to rain affects all mountain ranges in the Northern Hemisphere, the North American Pacific mountain ranges, including the Cascades, Sierra Nevada, and coastal ranges, and the Himalayas are particularly at risk, as per Science Daily.

The researchers are still investigating the reasons behind the heightened vulnerability of these regions compared to other mountain ranges like the Rockies or the Alps.

Ombadi suggested that the susceptibility may be attributed to the unique temperature conditions in the North American Pacific ranges, where slight temperature changes can result in the transformation of snowfall into rainfall, unlike other regions where snowfall occurs at lower temperatures.

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