Atmospheric rivers are getting bigger, wetter and more frequent, study shows

LOS ANGELES - Atmospheric rivers, a meteorological phenomenon responsible for heavy rain and wind events, have become more frequent and intense over the past 45 years due to global warming. 

A recent study in the Journal of Climate highlights the increasing impact of these weather events, particularly in California and other parts of the West.

What we know:

Atmospheric rivers are long, narrow bands of water vapor that transport moisture from oceans and release it as rain. 

The study reveals that since 1980, these events have increased in area by 6 to 9%, frequency by 2 to 6%, and have become slightly wetter. 

Scientists have long predicted that as climate change from the burning of coal, oil and gas makes the air warmer, it holds more moisture, which means bigger, nastier atmospheric rivers are coming in the future. This week’s study shows that this future is already unfolding.

The backstory:

Atmospheric rivers have historically caused significant damage, including mudslides and flooding. 

In the 1860s, California had to relocate its capital due to flooding from an atmospheric river. 

These events are not limited to California; they occur globally, sometimes without being recognized as atmospheric rivers. 

For instance, New England experienced a foot of rain and 50 mph winds in 2023, while Alaska saw 99 inches of snow in 2020.

What they're saying:

"This doesn’t mean that it’s necessarily all because of climate change. We didn’t study that, but it does line up, broadly speaking, with some expectations of how (atmospheric rivers) will change in a warming atmosphere," study lead author Lexi Henny, an atmospheric scientist at the University of North Carolina who did her research while at NASA.

What’s happened already "is still small relative to the changes that we think are going to happen" in a future warmer world, Henny said.

Why you should care:

Understanding atmospheric rivers is crucial as they can bring necessary rain to drought-stricken areas but also pose significant dangers when strong and prolonged. 

The increasing frequency and intensity of these events highlight the urgent need for preparedness and adaptation strategies in affected regions.

What's next:

Researchers will continue to study atmospheric rivers to better predict their future behavior and impacts. 

The data from this study will help scientists develop models to anticipate intense rain and snow events, aiding in disaster preparedness and mitigation efforts.