Scientists Warn: Global Warming Transforms Snowfall into Devastating Mountain Rain

A recent study has revealed that the warming climate is causing a significant shift in precipitation patterns over mountains, replacing major snowfalls with extreme rain events. This transformation is exacerbating the risks of dangerous flooding, similar to the catastrophic floods that devastated Pakistan last year, as well as contributing to long-term water shortages. Researchers analyzed rainfall and snowfall data dating back to 1950, along with computer simulations of future climate scenarios, and determined that for every degree Fahrenheit of global warming, there is an 8.3% increase in extreme rainfall at higher elevations (15% increase per degree Celsius). These findings were published in the journal Nature.

Scientists emphasized that heavy rain in mountainous regions leads to numerous issues, including flooding, landslides, and erosion, which pose far greater challenges than significant snowfall. Unlike snowpack, which can gradually melt and replenish reservoirs during spring and summer, rainwater flows away rapidly, failing to provide a convenient water supply.

The study’s lead author, Mohammed Ombadi, a hydrologist and climate scientist at Lawrence Berkeley National Laboratory, emphasized that this phenomenon is not a future projection but an observable trend over the past few decades. Ombadi stated, “The data is actually telling us that it’s already happening.”

The research holds critical implications as the world approaches the internationally agreed threshold of 1.5 degrees Celsius to mitigate the worst impacts of climate change. Ombadi emphasized that each degree of warming results in an additional 15% increase in extreme rainfall over mountains, more than double the increase experienced in the rest of the world due to the atmosphere holding more moisture.

The study focused on the most intense precipitation events each year over the past 60 years in the Northern Hemisphere. It revealed that as altitude increases, the intensity of rainfall intensifies as well. The greatest surge in rainfall was observed at approximately 10,000 feet (3,000 meters). This phenomenon affects various regions, including the American West, the Appalachian Mountains, the Himalayas, Tian Shan, Hindu Kush, and the Alps.

According to Ombadi, approximately one in four people on Earth lives in close proximity to mountains or downstream, putting them at risk of extreme rain and subsequent flooding.

The consequences of this transformation are already evident. Ombadi highlighted the similarity between the flooding caused by mountain runoff, resulting from excessive rainfall, and the devastating floods that claimed more than 1,700 lives in Pakistan, submerging one-third of the country. While the researchers did not specifically study the 2022 floods in Pakistan, there are likely to be resemblances.

UCLA climate hydrologist Park Williams, who was not involved in the study, supported its findings, stating, “The implications are serious.” While warmer temperatures are expected to bring increased precipitation, the impact of heavy snowfall on flooding is somewhat mitigated due to the gradual melting process, which allows for better monitoring of snowpack conditions. However, as the proportion of mountain precipitation falling as snow diminishes, the risk of floods can rapidly escalate.

The American West experiences the consequences of this shift in two distinct ways, as explained by study co-author Charuleka Varadharajan, a climate scientist and hydrologist. Extreme rainfall exacerbates flooding while also raising concerns about water management. Varadharajan cited the Tulare Lake flooding in the Sierras as a current example of the serious issues caused by these events.

Moreover, these extreme rain events pose long-term challenges for water supply. Winter snowfall gradually melts and fills reservoirs during spring and summer, ensuring a reliable water source when needed. However, as Varadharajan warned, the decrease in snowfall will reduce future water supplies. This leads to increased short-term runoff, contributing to more frequent floods, while the diminished snowpack fails to replenish groundwater and maintain stream flows.

Given that mountainous systems provide a significant portion of the water supply in the Western region, any reduction in water availability would have profound implications for water management. Water managers currently maintain high reservoir levels during drought periods using snowpacks, as they melt slowly. However, this strategy is ineffective for handling heavy rainfall.

As warming continues to fuel rainier extremes, society faces difficult choices. Water usage may need to be curtailed due to low reservoir levels to accommodate sudden and substantial mountain runoff, or substantial investments may be required to construct additional reservoirs, as explained by Park Williams.

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