Experts: Climate change driving additional, more intense rain in Minnesota - Duluth News Tribune

Climate change means more intense rain in Minnesota - Duluth News Tribune | News, weather, and sports from Duluth, Minnesota

Experts: Climate change driving additional, more intense rain in Minnesota

Heavy rain is already more common and intense in the state, and that trend is expected to persist as emissions continue to rise.

DULUTH — Since the June 18 storms dumped up to 5-8 inches of rain in some areas of Northeastern Minnesota, the flood in Cook has receded, the rushing rivers along the North Shore of Lake Superior have calmed and the washed-out roads throughout the region are beginning to reopen.

But the effects of climate change on Minnesota continue.

“We’ve had this predominant tendency for our years to be warmer than they used to be, and also to produce more precipitation than they used to. … And one thing we know we are seeing is a higher frequency of what you would call ‘heavy precipitation events,’” said Kenny Blumenfeld, a senior climatologist at the Minnesota State Climatology Office.

The number of precipitation events of 2 or more inches has increased, according to the National Oceanic and Atmospheric Administration. And since 1916 the amount of rain during the largest annual storm in the state has increased by an inch, according to the University of Minnesota’s Climate Adaptation Partnership

“So, essentially, each year the strongest rainstorm brings more than an inch of rain more than it used to,” said Suzi Clark, a climate adaptation and resilience extension educator at the Climate Adaptation Partnership.

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The why

As air temperature increases, so does the amount of moisture it can hold.

When Minnesota experiences wet weather, it’s generally because moist air comes up from the Gulf of Mexico via the Mississippi River valley.

Add in the effects of climate change, and a passing weather system will have access to more water, giving it the potential to produce precipitation with more volume, greater intensity or larger aerial coverage, Blumenfeld said.

“As you increase those global temperatures, you are increasing the rate of evaporation off of the oceans. You’re also increasing the temperature of the oceans, which further increases their rate of evaporation,” Blumenfeld said.

The future

Clark said swings of extreme dry and wet periods — similar to what was seen in this year’s dry winter but wet spring and early summer — will be more common.

“We expect the state will continue to get wetter in the future, but that’s the annual average,” Clark said, adding that increased precipitation is expected in the spring and fall while summer will actually see less precipitation.

“If you expect there to be more rain overall, but that rain is expected to happen in a shorter period of time, it’s going to be more intense,” Clark said.

The Climate Adaptation Partnership recently launched the Minnesota Climate Mapping and Analysis Tool, which visualizes climate change projections for the state's temperature, precipitation and other factors under intermediate, high, and very high emissions scenarios.

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Clark said she hopes future infrastructure projects will consider projected climate scenarios in their design instead of historical records.

Blumenfeld echoed Clark’s outlook on the possibility of swings between wet and dry periods and an increase in the average annual precipitation.

“It almost certainly doesn’t mean that every year will be wet, but instead it could be that you actually have years with really nasty drought in them — just like we’ve had — but then are counterbalanced, or really overcompensated, by these extremely wet years with even greater departures than the dry years,” Blumenfeld said.

What about 50- and 100-year rainfall events?

“These are still rare events,” Blumenfeld said. “They are becoming more common, but they’re also still rare.”

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