In recent years, as extreme weather events have intensified across the globe, the term “atmospheric rivers” has transitioned from scientific to everyday language, particularly in heavily impacted regions, according to AP News.
A comprehensive study published in the latest issue of the Journal of Climate reveals that atmospheric rivers—known for delivering torrential rains and strong winds, particularly in California and other parts of the western United States—have become larger, wetter, and more frequent over the past 45 years as global temperatures have risen.
Atmospheric rivers are long, narrow bands of water vapour that transport moisture from the oceans and release it as heavy rainfall. According to the study, such weather systems have expanded their coverage by 6 to 9% since 1980, increased in frequency by 2 to 6%, and are now slightly wetter than in previous decades.
Scientists have long theorised that climate change, driven by the burning of coal, oil, and gas, would lead to warmer air capable of holding more moisture. This, in turn, would result in larger and more intense atmospheric rivers. The findings of this week’s study suggest that this more moisture-laden future has already arrived.
While atmospheric rivers can provide much-needed rainfall to drought-affected regions, they often pose serious risks when they are intense and prolonged. Just over a year ago, a series of atmospheric rivers triggered hundreds of mudslides and claimed several lives in California. In the 1860s, an atmospheric river caused such severe flooding that California was forced to relocate its capital from Sacramento.
The events are not confined to California. They occur across the United States and around the world, though they are not always recognised as atmospheric rivers, study lead author Lexi Henny, an atmospheric scientist at the University of North Carolina who did her research while at NASA, explained. For instance, an atmospheric river in New England in 2023 brought a foot of rain and winds of up to 50 mph, whereas a 2020 event dumped 99 inches of snow on Alaska.
Christine Shields, a water scientist at the National Centre for Atmospheric Research who was not involved in the study, praised the paper for its insightful new details and data. She noted that the research will help scientists better understand the future behaviour of the intense rain and snow events.
As the world continues to warm, the study underscores the growing importance of monitoring and preparing for the impacts of atmospheric rivers, which are likely to become even more extreme in the years to come.
