How climate change contributes to the atmospheric rivers slamming the West Coast

(NEW YORK) — The California coast is currently getting pummeled with heavy rain from atmospheric rivers, essentially rivers in the sky that collect moisture from tropical areas and redistribute the water to higher latitudes. The current El Niño pattern is also favoring multiple rounds of heavy rain and an overall period of unsettled, rainy weather, forecasts show.

The relentless moisture is causing life-threatening flooding in some of the most populous cities in Southern California, including Los Angeles and San Diego, which were already soaked from a previous round of torrential rain late last week.

Climate change and a strong El Niño event could both play a role in the intensity of impacts that atmospheric rivers bring when they hit the West Coast, according to scientists.

While it is not possible to say that a specific weather event is due to climate change as it unfolds, research shows that climate change is making the impacts from naturally occurring events, like atmospheric rivers, more intense.

There are many variables involved when linking atmospheric river events to climate change, and this year another major variable is El Niño. Some experts caution that more research is needed before the link between climate change and atmospheric rivers can be more specific and with higher certainty.

Julie Kalansky, a climate scientist and deputy director of operations at the Center for Western Weather and Water Extremes at the University of California, San Diego’s Scripps Institution of Oceanography, told ABC News that while there is still a lot to learn about the potential links between atmospheric rivers, climate change, and El Niño, broader connections can be made to the extreme impacts that certain events bring.

“More of [California’s] precipitation, so rain and snowfall, will be coming from atmospheric rivers, according to the model projections,” Kalansky said.

In a warming climate, more winter precipitation will fall as rain instead of snow, and the winter season will experience larger increases in extreme precipitation events since winter is the season experiencing the greatest overall warming, according to the Fifth National Climate Assessment, released in November.

The report found that the effects of climate change were worsening in every part of the U.S.

Experts say that this shift in precipitation type could be accompanied by more frequent and intense extreme rainfall events, adding that atmospheric rivers have the potential to cause more extreme precipitation events in the future.

As global temperatures continue to warm, it allows the atmosphere to hold more moisture, causing rainfall events to become more frequent and extreme, according to recent research by the National Oceanic and Atmospheric Administration

More intense extreme rain events also increase the frequency and scale of flash flooding, as the influx of water is more than current infrastructure was built to handle.

In the continental U.S., California already experiences the most year-to-year variability wet and dry conditions, Kalansky told ABC News. Southern California has an even more variable climate than Northern California, even without the current El Niño event in place, which is also contributing heavily to the excessive moisture in recent weeks.

“Climate projections show that the variability between wet and dry is projected to become even more variable in the future,” said Kalansky.

In states like California, the latest research shows that human-amplified climate change could produce less frequent, but more intense precipitation events. Wild swings, for example, from a devastating drought to record-breaking precipitation will become more common and extreme in the coming years, which could also lead to more destructive impacts, according to the California Climate Adaptation Strategy.

The El Niño pattern currently in place is favoring multiple rounds of heavy rain and an overall period of unsettled, rainy weather, according to NOAA. During the winter months, El Niño typically leads to wetter-than-average conditions across much of the southern U.S, including a large swath of California.

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