Future Climate Extremes in Colorado

Reports by the Rocky Mountain Climate Organization project large increases in the frequency and extent of extremely hot days in Colorado’s Front Range urban corridor, with the extent depending on whether global heat-trapping emissions continue on a high trajectory or are reduced. Our reports detail projected future extremes in Boulder County, Larimer County, the Denver metro area, and, most recently, Eagle County and Summit County.

For the Denver metro area, the median projections from 20 climate models are that with continued high increases in heat-trapping emissions:

By mid-century (2040-2059), a typical year would have seven days 100 degrees or hotter. This means that the typical year in mid-century would have more extreme heat than the Denver area has yet experienced, as the record so far is six days 100 degrees or hotter, set in 2012.
By late in the century (2080-2099), a typical year would have more than a month’s worth of 100-degree days — 34 per year.

The above totals are averages for typical years. The hottest year in each 20-year period would have far more extremely hot days. Again with continued high increases in heat-trapping emissions, the average projections from multiple climate models are that:

The hottest year in the middle of the century would have 25 days 100 degrees or hotter.
The hottest year late in the century would have 72 days 100 degrees or hotter.

“These analyses are the most detailed and comprehensive yet done anywhere in the nation of how climate change will drive local extreme conditions. And the changes really could be extreme,” said Stephen Saunders, president of RMCO and lead author of the reports. “This would be fundamentally different from the climate we have known in Colorado.

“But we do not have to get this hot,” Saunders said. “These projections powerfully illustrate how different our future will be depending on whether we limit heat-trapping emissions or not. If we bring emissions down to a very low level, we can avoid any further increases in extreme heat beyond the relatively modest increases we face in the next couple decades.

“This shows why we need preparedness actions to address the impacts we could face, from more heat waves that can threaten people’s health and lives. And this kinds of increases in extreme heat can have many other impacts across our state and region, beginning with more wildfires,” Saunders said.

For the detailed projections for the different local areas, see the separate pages on the reports for Boulder County, Larimer County, the Denver metro area, Eagle County, and Summit County.

For each of these reports, RMCO analyzed tens of millions of individual projections for daily temperature and precipitation values. A projection for an individual day does not have any particular value, but enough of them over a sufficient period of time enables analysis of how often particular conditions are projected to occur in that period. The projections are from the latest generation of downscaled global climate models, and RMCO’s detailed analyses of the projections provides the most detailed, comprehensive look yet at what the latest climate models say about how climate change will drive increases in local temperature and precipitation extremes.

The Boulder and Larimer county reports were funded by the Colorado Department of Local Affairs, using Community Development Block Grant—Disaster Recovery funding through the Resilience Planning Program. Boulder and Larimer counties were heavily affected by the High Park wildfire in 2012 and the September 2013 flooding that led to federal disaster designations. The purpose of the reports is to help local governments in these two counties better understand and prepare for the increased risks of wildfire and flooding expected to come with further climate change. The Denver metro area analysis was funded by the City and County of Denver’s Department of Environmental Health, to provide information to support Denver’s climate protection efforts and to help guide preparedness actions across the metro area. The Eagle County report was funded by the Eagle County government and the Northwest Colorado Council of Governments’s Water Quality/Quantity Committee. The Summit County report was funded by the Summit County government, the towns of Breckenridge and Frisco, and the Northwest Colorado COG Q/Q Committee.

RMCO has previously reported on projected increases in extremes storms across the Midwest and in Michigan. We also previously prepared for the City of Fort Collins a less detailed analysis of projected future temperature extremes in that city. More comprehensive information is in the newer report on Larimer County, which includes Fort Collins.