Chart of Montanas

The chart above shows the different levels of warming Montana could see by mid-century and the end of the century under a stabilization emissions scenario (RCP 4.5) and business-as-usual (RCP 8.5).

Montana has already gotten nearly 3 degrees warmer in the last 70 years because of climate change.

If nothing is done to halt the current rate of global warming, by the middle of this century Montana could be 6 degrees Fahrenheit warmer than last century.

And by the end of this century, the state will be nearly 10 degrees warmer.

That might sound appealing in a state once known for nine months of winter and three months of hard sledding.

But a climate that much warmer would have far-reaching impacts. Snowpack that skiers, farmers and fishermen depend upon will melt away faster. Forest fires will be more frequent and severe. Wheat farmers and cattle ranchers will have to make big adjustments. Summers will get hotter. Droughts will happen more often.

Those are some conclusions that can be drawn from the 2017 Montana Climate Assessment, the most comprehensive report to date on Montana’s changing climate.

It was produced by the Montana Institute on Ecosystems and written by top scientists from Montana State University and the University of Montana, working with the state Climate Office, Montana Water Center and MSU Extension.

MSU scientists Cathy Whitlock and Bruce Maxwell, past and current co-directors of the Montana Institute on Ecosystems, worked on the report with a 30-member team over two years. They collected mountains of data to document changes that have already happened and show the future trends.

One thing is clear. Montana in coming decades will be even warmer.

5 to 10 degrees hotter

The Montana climate report, 269 pages long, focused on three key areas — water, farming and forests.

Those topics were chosen after team members traveled around the state to ask Montanans what they’d like to know about the changing climate.

Temperatures here have been rising faster than global or national averages, and that trend will continue, the assessment predicts.

That’s true under both the best-case scenario — if the world finds a way to cap the amount of carbon in the atmosphere — and the worst-case scenario — if it’s business as usual and carbon levels keep rising.

By the middle of this century, Montana’s average daily maximum temperatures will increase by 4.5 degrees Fahrenheit (best case) to 6 degrees (worst case).

By the end of this century, the state will warm between 5.6 degrees and 9.8 degrees.

By mid-century, Montana will have 24 to 44 more frost-free days. Montanans will experience five to 35 additional summer days of 90 degrees or hotter.

The report found the fastest warming region of the state is along the Hi-Line. North-central Montana has warmed by half of 1 degree every decade since 1950. Southwestern Montana, including Bozeman, had the slowest increase, warming by about a third of 1 degree each decade from 1950 to 2015.

Here are impacts predicted in Montana Climate Assessment:

Water: In the future, rain and snow will be less predictable, with more year-to-year variability. There is potential for more frequent and longer drought.

Precipitation will increase in winter, spring and fall. Summers will get less rain.

“We’ll probably get snow in winter, but it will change to rain sooner,” Whitlock said. “That will be hard on industries that depend on snow.”

Montana’s snowpack has already declined since the 1930s in the mountains west and east of the Continental Divide. As Montana gets warmer, there will be less snowpack at middle and lower elevations.

Snowpack is melting sooner, and that trend will continue. With earlier spring runoff, there will be less water available in late summer.

There will likely be more stress on Montana’s water supply. People will use more groundwater.

Forests: Warming may be good for forests in cool moist areas, but warming and changing snow and rain patterns will hurt forests in drier areas. Wildfires and bark beetle outbreaks will cause greater harm.

Wildfire risk will get worse. The size, frequency and severity of fires will likely increase. Fire seasons will be longer. And fires will release more carbon into the atmosphere.

Whitlock, an Earth sciences professor, got her start studying fires historic fire patterns during the Yellowstone National Park fires of 1988. She found from investigating thousands of years of evidence that major fires didn’t just happen cyclically, as people assumed, but directly followed changes in the climate.

“Whenever climate is warming,” she said, “we have more fires.”

Large forest fires in the West have steadily increased, Maxwell said. In the 1980s, there were 140 large fires. In the 1990s, that increased to 160.

From 2000 to 2012, the West recorded 250 major fires.

Agriculture: Montana’s farmers and ranchers have always faced volatility, extreme weather, pests and changes in markets, prices and government policies. Climate change will add more uncertainty and stress.

Decreasing snowpack will mean less reliable irrigation water in the late season. That will have the greatest impact on hay, sugar beets, malt barley, market gardens and potato production.

Weeds like cheatgrass, pests and diseases will increase and hurt crop yields.

Farmers and ranchers will have to adapt. That could mean diversifying crops, rotating lentils and pulse crops, innovative tilling methods and using cover crops.

Farmers are already adapting, Maxwell said, by planting more winter wheat, because it’s surviving the warmer winters better, and farmers are finding it harder to successfully grow spring wheat.

With more carbon dioxide in the air, plants can grow faster. But fast growth can hurt crop quality. With hotter summers, some wheat crops show evidence that pollen has dried up, leaving few kernels of grain on each head of wheat.

Ranchers will also be affected.

“Cows and livestock can only withstand major heat during the day if they cool off at night,” Maxwell said. “Unfortunately, the nights are staying warmer. Livestock require more water.

“I was in central Montana talking to ranchers. Their primary effort is distributing more water — unfortunately pulling down the aquifer.”

Skeptics and pragmatists

Climate skeptics acknowledge that the world is getting warmer. What they challenge are the ideas that humans are causing it and that action is needed to keep things from getting warmer.

Maxwell said there are always problems with science and lots of things scientists don’t know. We don’t know, for example, what will happen if the sea ice disappears and Arctic permafrost melts.

Still, Maxwell argued that the pragmatic thing is to adopt the “precautionary principle.”

That means if there’s a strong suspicion something will cause harm to the environment, it is better to take precautions now, rather than waiting for ironclad scientific proof, when it could be too late to prevent the harm.

On the MSU campus, Maxwell said, he sees successful efforts to cut down on greenhouse gases and save energy — by using geothermal heat in new buildings, installing solar panels and replacing big campus pickup trucks with small trucks.

It’s “really impressive,” he said. And it saves money.

“Even if we’re wrong,” Maxwell said, “would it be so bad to become more efficient?”

Gail Schontzler can be reached at gails@dailychronicle.com or 406-582-2633. Follow her on Twitter @gailnews.

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