More heatwaves, wildfires and water shortages in the outlook
FRISCO — By the middle of this century, Denver’s average temperature could be 6 degrees Fahrenheit warmer than today — on par with Albuquerque, according to a new climate report released by the Colorado Water Conservation Board in early August.
Even with deep cuts in greenhouse gas emissions, Colorado will continue to get warmer. An increase of at least 2 degrees Fahrenheit by mid-century is all but certain, and that will have a big impact on the state’s water supplies, state officials said, reinforcing the results of a series of studies all showing that rising temperatures will reduce the amount of water in many of Colorado’s streams and rivers, melt mountain snowpack earlier in the spring, and increase the water needed by thirsty crops and cities.
The state’s future precipitation regime is less clear. Climate models haven’t yet been able to pinpoint a clear trend in rainfall and snow because Colorado is located between an area likely to dry further (the U.S. Southwest) and one likely to get wetter (Northern Great Plains).
“Despite some uncertainties around precipitation, it’s clear that as temperatures rise in Colorado, there will be impacts on our water resources,” said Jeff Lukas, lead author of the new report and a researcher at the Western Water Assessment, a program of the University of Colorado Boulder funded by the National Oceanic and Atmospheric Administration.
“Already, snowmelt and runoff are shifting earlier, our soils are becoming drier, and the growing season has lengthened,” Lukas said. “Wildfires and heat waves have become more common, too. Climate projections suggest those trends—all of which can affect water supply and demand—will continue.”
Even if the future brings more precipitation, the report notes, skiers, farmers and cities may not benefit because a warmer atmosphere will pull more moisture out of the state’s snowpack, soils, crops and other plants.
“This report will help to inform critical products like the Statewide Water Supply Initiative and Colorado’s Water Plan,” said James Eklund, Colorado Water Conservation Board director.
Among the findings presented in the new report:
- Colorado has warmed: Statewide average annual temperatures are 2 degrees Fahrenheit higher than they were three decades ago.
- Climate models indicate that the state’s average annual temperature will continue to increase, by 2.5 to 6.5 degrees by 2050.
- A 2-degree increase would make Denver’s temperatures in 2050 more like Pueblo’s today.
- Colorado has seen no long-term increase or decrease in total precipitation or heavy rainfall events. Climate models are split about Colorado’s future precipitation, showing a range of possible outcomes from a 5 percent decrease in precipitation to an 8 percent increase by midcentury.
- Climate models tend to show a shift toward higher midwinter precipitation across the state.
- Hydrology models show a wide range of outcomes for annual streamflow in Colorado’s river basins, but an overall tendency towards lower streamflow by 2050, especially in the southwestern part of the state.
The Western Water Assessment (WWA) is part of the Cooperative Institute for Research in Environmental Sciences (CIRES), a joint institute of CU- Boulder and the National Oceanic and Atmospheric Administration (NOAA). The Colorado Water Conservation Board (CWCB) is a division of the Colorado Department of Natural Resources and spearheads the state’s climate change adaptation efforts.