Here is a look back at the Valley’s summer of storms.

Arizona could experience heavier monsoon rains in the coming decades, according to the author of a new study examining rainfall changes around the world.  

The study, published in the journal Science Advances, does not detail specific rainfall changes in Arizona.

But Aaron Putnam, its lead author and a geologist at the Climate Change Institute at the University of Maine, speculates that while there could be an “invigoration of the North American monsoon,” a warmer planet might also lead to a drop in precipitation during the wintertime, potentially reducing the snowfall that helps replenish water-storage reservoirs. 

MORE: Climate change could foul up precipitation worldwide


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“The input of CO2 in the atmosphere is a bit of a sledgehammer on to the system,” he said. “It might respond in non-linear, more unpredictable ways.” 

A heavier monsoon in the summer might be “flashy,” Putnam said, but less precipitation in the winter would diminish water levels in aquifers and reservoirs critical to the state’s water supply.

MORE: Parched: Arizona’s shrinking aquifers

Monsoon rains typically fall fast, while melting snow offers “a more sustained flow.”

Arizona’s Extreme Weather

The National Weather Service marks the start of the monsoon season Thursday, though summer storms typically don’t begin to develop until late June or early July. 

Putnam and his colleagues used geological archives to determine how precipitation patterns will change with a warmer climate. From their research, they concluded that “wet areas will get wetter and dry regions will become drier.”

“The geologic record is trying to tell us something about how the system behaves,” he said. 

MONSOON NEWS:  Read the latest on the season, check out videos and photos


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In the study, the researchers also note that moisture will be directed north, away from the Sierra Nevada and the Great Basin, which spans much of the Intermountain West.

Last year’s monsoon season in Phoenix saw 2.49 inches of rain, but more critical to long-term water supplies is the snow that accumulates during the winter months and produces runoff for reservoirs come spring. The National Weather Service has recorded 96.7 inches of snowfall in Flagstaff since July 1 of last year. Normal snowfall is 101.8 inches. The year before, snowfall was 78.3 inches.

READ:  Newcomer’s guide to your first Phoenix-area summer 

Putnam thinks the state’s main challenge will be managing water as its accessibility shifts.

“It’s really trying to come to grips with how water availability changes,” he said. 

Environmental coverage on and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow the azcentral and Arizona Republic environmental reporting team at OurGrandAZ on Facebook, Twitter and Instagram.


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