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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. Completed RMCO reports detail projected future extremes in Boulder County and in Larimer County, and preliminary results are now available of a forthcoming similar analysis for the entire Denver metro area.

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 there would be on average more than a month's worth of days 95 degrees and hotter, and by late in the century more than a month's worth of days 100 degrees and 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 report. “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 projetions 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.”

The projections also address future precipitation extremes. Although projections for precipitation are more uncertain than for temperature, the models suggest that heavy storms may become more frequent.

“This shows why we need preparedness actions to address the impacts we could face, from more wildfires and possibly more floods to more heat waves that can threaten people’s health and even lives,” Saunders said.

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

For these three reports, RMCO analyzed 88 million individual projections for daily temperature and precipitation values for Boulder and vicinity, Boulder County mountains, Fort Collins and vicinity, Larimer County mountains, and the Denver metro area. 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 is being funded by the City and County of Denver's Department of Environmental Health, to provide information to that can help guide preparedness actions in Denver and beyond.

RMCO has previously reported on projected increases in extremes storms across the Midwest and in Michigan.

 

Figure Caption

The figure above shows how the number of days 95° or hotter in the Denver metro area could go from an average of 5 per year late in the last century to 77 per year late in this century. For future periods, the figure shows the range of the middle 80 percent of projections from multiple climate models (the checkered portions of the columns) and the medians (the numerals), for four possible levels of future heat-trapping emissions.

More information on projected climate extremes in the Denver metro area is available here.