Colorado is slated for a future with less water, shrinking snowpack, more disastrous wildfires and an unpredictable agricultural economy as climate change continues to drive warming and aridification across the state and region, according to a massive new federal climate report.
The Fifth National Climate Assessment — released by the White House on Tuesday — combines thousands of studies and spells out the risks a warming world poses to American society. The last such assessment was released in 2018.
Climate change is “harming physical, mental, spiritual and community health and well-being through the increasing frequency and intensity of extreme events, increasing cases of infectious and vector-borne diseases, and declines in food and water quality and security,” the assessment said.
The lower 48 states since 1970 have warmed by 2.5 degrees compared to the global average of 1.7 degrees, according to the report. The warming has created rising sea levels, increased weather disasters, shrinking water supplies and increased disasters like floods, extreme drought, heatwaves and wildfires.
The impacts of climate change become more devastating with every fraction of a degree that temperatures rise. Since 2018, the Southwest — which includes Colorado — has weathered 31 large climate-related disasters resulting in 700 deaths and more than $67 billion in damage, the assessment states. The disasters in Colorado include the 2021 Marshall fire in Boulder County, ongoing severe drought and dangerous hail storms, like the one that injured concertgoers at Red Rocks Amphitheatre in June.
“Every tenth of a degree of warming that we avoid matters,” Allison Crimmins, director of the assessment, said Wednesday in a call with reporters.
The assessment examines climate change impacts in each of 10 regions. The Southwest faces a future with less water, more difficult agricultural production and more severe fire.
Climate impacts can also make energy production designed to reduce emissions more difficult. More wildfire smoke makes solar energy less reliable. Less reliable water means less reliable hydropower.
The report states that the U.S. has made significant strides in reducing greenhouse gas emissions but must do more — and quickly — to avert more damage and death.
“One of the first and most important things people can do about climate change is to talk about it,” said David White, lead author of the chapter on the Southwest and the director of the Global Institute of Sustainability and Innovation at Arizona State University.
These are four major impacts of climate change expected in Colorado, according to the report.
Persistent years of low snow are expected over the next 50 years if climate change continues at its current speed, the assessment states. Snow will be less common at lower elevations and melt earlier in the spring than in the past.
Rocky Mountain snowpack has been declining over the past century but the shrink has accelerated in recent years due to warming trends, White said.
“That water is essential,” White said.
Water from mountain snowpack flows through city faucets, irrigates farmlands and — before it melts — fuels a multi-billion-dollar winter sports industry.
As the snowpack shrinks, the landscape absorbs more of the sun’s heat instead of reflecting it, which further speeds melt.
Less snow means less runoff in the rivers Colorado relies upon for its water. Less snow, combined with higher temperatures that speed evaporation and drier soils that soak up more moisture, will lead to difficult decisions about how to use and conserve water. Underground aquifers will also refill more slowly with less rainfall and runoff.
The Colorado River — one of the major water sources for the region — continues to dry. Between 1913 and 2017, the river’s annual flow decreased by 9% for every degree Celsius average temperatures rose, the assessment states.
“We had a lot of conversations about the Colorado River but also similar issues that are happening in other river basins in the southwest,” said Elizabeth Koebele, one of the authors of the assessment and an associate professor at the University of Nevada, Reno.
Long-term aridification — punctuated with serious weather events — will make water supplies more unpredictable. The unpredictability may threaten the region’s ability to consistently use dams to create electricity, disrupting a typically reliable and low-carbon source of energy, the report states.
More difficult farming
Warmer winters will be detrimental to orchard crops, false springs will increase vulnerability to late-season freezes and heatwaves will threaten production. Raising cattle on rangeland will also become more unsustainable as the region becomes more arid.
“Continuing drought and water scarcity will make it more difficult to raise food and fiber in the Southwest without major shifts to new strategies and technologies,” the report states. “Extreme heat events will increase animal stress and reduce crop quality and yield, thereby resulting in widespread economic impacts.”
If the rate of climate change is not slowed, increased temperatures and less water could lead to lower food availability, higher prices and fewer options.
“That’s determined by how we respond to these risks,” White said.
Increased heat will also threaten the health of people who work outside, especially migrant workers who are marginalized from health care and social services. Extreme heat can lead to dehydration and kidney illness while dust storms — which are expected to increase — can impact lung health.
Indigenous communities that have resided for centuries in the Southwest have successfully changed agricultural practices in times of drought, flood and fire, Koebele said.
“We can learn a lot from working with communities that have adapted in the past,” she said.
More severe wildfires
Wildfires in Colorado and across the region have become larger and hotter as the world warms, creating a string of unprecedented blazes.
“High-severity wildfires are expected to continue in coming years, placing the people, economies, ecosystems and water resources of the region at considerable risk,” the report states.
The three largest wildfires in Colorado’s history occurred in 2020. California’s seven largest wildfires all occurred since 2018. The largest fires in Nevada, Arizona, New Mexico and Utah have all occurred since 2007.
The number of large fires on grassland — like the Marshall fire, which killed two people and destroyed $2 billion in property — has increased fivefold since 1984.
Earlier spring runoff from the mountains due to warming will increase plant growth in the spring, creating more fire fuel during warmer summers. Wildfire smoke poses risks to human health and can make solar energy less productive, as it did in Southern California in 2020.