Distinctly Montana Magazine

D I S T I N C T L Y M O N T A N A M A G A Z I N E • S U M M E R 2 0 1 9 32 M O N TA N A i n Y E L L O W S T O N E P H O T O FROM A SCIENTIFIC STANDPOINT, WHAT DO YOU BELIEVE WILL BE THE SIGNIFI- CANT CHANGES IN YELLOWSTONE BY THE YEAR 2049? e following climate trends are already happening and well docu- mented using climate data from the last 30-70 years. I believe that these trends will continue into the future and that the rate of change is likely to increase. HOTTER AND DRIER: e minimum temperatures (coldest temperatures in a 24-hour period, usually the temperatures at night) are warming faster than the maximum or daytime temperatures. We aren't getting the multi- day stretches of extremely cold temperatures that used to occur during cold winters. By mid-century it will be much warmer at all elevations across the park, with temperatures estimated to increase at a rate of 4.8 oF/century. At mid-elevations, we've lost many of the nights that used to go below freezing during the summer. By 2049 we estimate that the park will lose about half of the days that still go below freezing in a year. LOWER SNOWPACK (LESS TOTAL SNOW), SHORTER WINTERS: We've looked at long-term (> 35 years) records of snow accumulation, and the snow- pack levels are trending lower in Yellowstone and throughout the Greater Yellowstone Ecosystem. We will still get winters with lots of snow, but the long-term trend is clearly for less snow in the future. One analysis found that by mid-century, snow levels across the Northern Range will decrease by 68% to 90%. We won't be using snowmobiles to get to Old Faithful in the winter of 2049. By April, 2049 the mid and lower eleva- tion areas of the park will be mostly snow free. EARLIER RUNOFF, LOWER FLOWS, WARMER WATER: Warmer temperatures in the spring already trigger earlier melting of the snowpack and earlier peak flows in the rivers. Low snowpack years result in low flows in the rivers dur- ing the summer and fall. When the low flows correspond with high summer air temperatures, the water temperature is elevated above normal and there are negative impacts to the native fish that require cold water to survive. A re- cent study predicted that mean August stream temperatures in Yellowstone's Northern Range will increase by 1.5 oF by mid-century. Conversely, during high snow years, warmer temperatures in the spring cause a lot of the snow to melt quickly, leading to downstream flooding events. LONGER GROWING SEASON: e growing season in the park is get- ting longer. Winter is shorter, spring happens earlier, and the nighttime temperatures don't get as cold as they used to. After analyzing data from across the park's Northern Range, we concluded that the growing season is approximately 30 days longer than it was 50 years ago. irty years from now it might be a month longer than it is now. is means that the onset of spring green-up, which drives ungulate migrations, the timing of insect emergence, and the weather conditions when migratory birds arrive are all changing. MORE FREQUENT, LARGE WILDFIRES: A longer growing season means a lon- ger fire season. Warmer summer temperatures drive more evapotranspiration (loss of water from plants and soil) leading to drier conditions. As unusu- ally hot and dry conditions become more common, the potential for large wildfires increases. If we start to get 1988-like conditions every 5 to 10 years (as some scientists are predicting) instead of every 150 years, it will clearly in- crease the chances that big fires will occur more frequently than they do now. yea rs 3 "BY MID-CENTURY IT WILL BE MUCH WARMER AT ALL ELEVATIONS ACROSS THE

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