Colorado’s Climate and Colorado’s Health

Rising Temperatures

Heat is one of the biggest climate-related public health threats, according to the Centers for Disease Control and Prevention (CDC).¹⁹

Colorado’s average temperature has varied over the past century. Scientists have established a baseline temperature based on a 30-year average. (See Figure 1.) They plotted the annual average temperature relative to that average from 1900 to 2012. The blue bars represent years when the average temperature was below the 30-year baseline. Red bars mark years when the average temperature rose above the baseline.

Colorado’s temperature spiked during the Dust Bowl in the 1930s and again in the 1950s. Temperatures began to be consistently higher than the average beginning in the mid-1990s.

Colorado’s average temperature has increased by two degrees Fahrenheit in the past 30 years. Looking ahead, climate models indicate a warmer future for Colorado. Projections say the state’s average temperature could be five degrees higher by 2050.^{20, 21} Such increases significantly outpace historical trends.

Currently, average summer temperatures in the Denver metro area are in the low- to mid-80s, but Denver has recorded several summers with 12 or more consecutive days above 90 degrees since 2008.²² Unusually hot temperatures — days above 90 degrees — can potentially harm health.²³

It’s possible that 90-plus degrees could become Colorado's average summer temperature by mid-century, according to the Western Water Assessment Team at CU-Boulder.²⁴

To put that in perspective, the National Oceanic and Atmospheric Administration (NOAA), a scientific agency within the U.S. Department of Commerce that studies climate, says that as time goes on Denver will begin to feel more like Pueblo in the summer, where average highs are in the low 90s.^{25, 26}

Health Implications

• Extreme heat affects cardiovascular, respiratory and nervous systems.²⁷ (See Figure 2.)
• Warmer temperatures also can cause heat stroke and dehydration.²⁸

Vulnerable Coloradans

• Almost six percent of Colorado’s adults have cardiovascular disease, putting them at an increased risk for heat exhaustion and heat stroke. A weakened heart has a harder time pumping blood throughout the body to normalize temperatures.
• The seven percent of Colorado’s adults with diabetes can have trouble cooling their bodies on hot days, a result of damage to blood vessels and nerves that impact sweat glands. Higher temperatures can also change how a person with diabetes uses insulin, requiring more frequent blood sugar tests and careful dietary choices.²⁹
• The state’s 1.2 million children are especially vulnerable. Children absorb more heat than adults because they have a greater ratio of skin surface to weight.³⁰
• The 711,000 seniors over age 65 are at increased risk because chronic illness and age can hinder the ability to regulate body temperature.

Air Quality

Changes in weather patterns — even slight modifications of wind, temperature, humidity or cloud level — increase pollutants such as ozone, carbon dioxide and particulate matter, which in turn impact overall air quality. (See Figure 3.)

Ozone can be good or bad for health depending on its location in the atmosphere. The Environmental Protection Agency (EPA) characterizes ozone as “good up high, but bad nearby.” The “good up high” ozone is six to 30 miles above the ground. This layer of ozone protects the Earth from harmful ultraviolet rays. ³¹

The “bad nearby” ozone is at ground level. It is created when chemicals and pollutants in the air are “cooked” in the heat and sunlight. Ground ozone is at its highest levels in the summer when temperatures reach into the upper 80s and mid-90s. ³²

In 2016, Metro Denver was ranked the eighth most ozone-polluted urban area in America by the American Lung Association. Fort Collins was 10th. Both cities saw a slight improvement in the 2017 rankings. Denver moved from eighth to 11th and Fort Collins from 10th to 15th. ^{33, 34}

High ozone days can be attributed to several factors, including motor vehicles, factories, gas stations and paint and chemical plants, according to the American Lung Association. ^{35, 36, 37}

Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas and Jefferson counties, along with parts of Larimer and Weld counties — an area designated as Denver Metro and Northern Front Range (DM/NFR) — have violated EPA ozone standards since they were set in the 1970s under the Clean Air Act. ³⁸

The DM/NFR area has until July 2018 to meet the 2008 standards of 75 parts per billion (ppb), a goal which will be difficult to achieve. ^{39, 40}

The DM/NFR region will be further challenged in meeting even stricter national standards adopted in 2015. These changes called for a reduction in ozone emissions from the 2008 standard of 75 ppb to 70 ppb. The EPA will reevaluate the region in late 2023 for compliance with these new 2015 standards. ^{41, 42, 43}

Health Implications

• Ozone is a lung irritant, meaning that high levels can cause breathing problems.
• Pollutants such as particulate matter and carbon dioxide (CO²) can cause or exacerbate allergies.
• Warmer temperatures and an increased presence of CO² promote growth of plants that release airborne allergens. ⁴⁴ This seasonal shift could extend the allergy season.

Vulnerable Coloradans

• Seniors with bronchitis or emphysema.
• The 107,000 children with asthma. ⁴⁵
• The approximately 380,000 adults with asthma.
• The 180,000 Colorado adults with respiratory ailments such as Chronic Obstructive Pulmonary Disease (COPD).
• Coloradans who are prone to pollen and mold allergies.⁴⁶

Wildfires

Climate and weather strongly influence the health of forests and the intensity and size of wildfires.⁴⁷    

Rising temperatures are shifting the timing of Colorado’s snow melt to earlier in the spring — anywhere from 15 to 30 days sooner over the past 30 years — leaving forests water-starved in the late summer and autumn and creating conditions ripe for fire.⁴⁸ (See Figure 4.)

Thirsty forests are a welcome environment for the invasive bark beetle, which has destroyed 3.4 million acres in Colorado since 1996.⁴⁹ Those dead trees, in turn, are volatile fuel for wildfires.

Colorado has seen changes in wildfire trends.⁵⁰ There were 78 large wildfires (>1,000 acres burned) between 1970 and 2012. But 19 of those wildfires – nearly 25 percent – occurred during the drought years between 2010 and 2012.⁵¹ 

Smoke from wildfires increases ozone and particulate matter in the air. Pollutants can travel, affecting communities far from the flames. Smoke from the Pacific Northwest fires in August 2015 travelled up to 600 miles.⁵² The smoke was so dense in some distant states that residents felt certain that the fires were nearby.⁵³   

Wildfires cause soil erosion, which threatens the quality and quantity of the water supply. Hot fire can result in a waxy, water-repellent layer on the soil.⁵⁴ This leads to water runoff, which can destroy watersheds and contaminate water supplies hundreds of miles from burn sites. After Colorado’s Hayman Fire in 2002, water sources in the surrounding areas had elevated levels of nitrates and particles, causing cloudiness for five years after the blaze.⁵⁵ 

Health Implications

• Immediate harm takes the form of death, burns, smoke inhalation, traumatic injury and the potential for post-traumatic stress for residents living in fire-prone areas and firefighters.⁵⁶  
• Secondary impacts such as induced asthma attacks, coughing, chest pain, eye and nose irritation may be felt by residents living farther away because of smoke’s ability to travel long distances.  
• Smoke carries pollutants such as particulate matter (PM2.5) in the air, increasing the risk of lung cancer, cardiovascular disease, asthma and COPD.⁵⁷ 

Vulnerable Coloradans

• Coloradans who live in the wildland-urban interface areas. This population has increased from about 980,000 in 2000 to more than 2 million in 2012.⁵⁸  
• Coloradans with COPD, asthma, and lung cancer.⁵⁹
• People with cardiovascular disease.

At the Intersection of Climate Change and Health: What’s Being Done

Many climate change policies, research and programs originate at the federal level.   

The United States Department of Agriculture, the Department of Health and Human Services and the Department of Energy are among the federal organizations that develop or enforce climate change-related policies, studies and programs.   

The EPA is the primary organization that creates and implements most of the nation’s climate-related policies, including the Clean Power Plan, the National Environmental Policy Act, the Clean Water Act and the Clean Air Act. 

The overarching goal is to protect the environment by limiting pollutants and emissions, setting standards and requiring environmental assessments and impact statements before building new infrastructure. 

The Clean Power Plan (CPP), finalized in 2015, aims to reduce carbon pollution from power plants. But its fate is uncertain. West Virginia, 27 other states — including Colorado — and hundreds of organizations sued the EPA, claiming the requirements of the CPP are unconstitutional. President Trump in March signed an executive order calling for EPA Director Scott Pruitt to begin dismantling the regulations.

Colorado, meanwhile, is creating climate change policies, ordering studies of the effects of a changing climate and developing evidence-based recommendations and guidelines. 

Colorado voters approved the Renewable Energy Standard in 2004 requiring investor-owned electricity providers — such as Xcel Energy — to obtain 30 percent of their energy from renewable resources by 2020. 

The state legislature updated the standard in 2013 to require cooperative utilities, such as Grand Valley Rural Power Lines, to obtain 20 percent of their electricity from renewable resources by 2020.^{60, 61}     

Renewable resources may be solar, the result of anaerobic digestion, recycled energy, landfill gas, wind, hydropower, geothermal, pyrolysis, coal mine methane or woody biomass.

Colorado has been a leader in clean energy, in large part because of the standard. The state avoided 5.5 million tons of CO2  (carbon dioxide) emissions from utilities in 2012.⁶²  

Former Gov. Ritter released Colorado’s first climate action plan in 2007. The plan called for a 20 percent reduction in greenhouse gas emissions by 2020  and an 80 percent reduction by 2050.⁶³ 

Ritter’s plan called on state agencies, private utility companies, businesses and individuals to engage in initiatives such as recommending efficient energy use in households, setting recycling goals, changing farming practices and increasing clean transportation. 

At the local level, Denver became one of the first large American cities to develop its own climate action plan in 2007, setting a goal of reducing greenhouse gas emissions by 10 percent per capita below 1990 levels. Since then, the city has released three updated plans, including one in 2015 which calls for reducing emissions by 80 percent by 2050. 

Denver conducts an annual “GHG inventory” to evaluate emissions levels and progress in reduction efforts. The plan calls for Denver’s building and energy sector to change how structures are built and identify energy efficiency strategies. 

Other Colorado cities taking steps to address climate change include Aspen, Fort Collins and Boulder. Each has created a climate action plans similar to Denver’s.

Aspen followed in the footsteps of Burlington, Vermont, and Greensburg, Kansas, to supply 100 percent of its electricity from renewable energy resources.⁶⁴ Boulder was the nation’s first city to pass a climate action plan tax, which funds initiatives to reduce emissions. Fort Collins created a ClimateWise voluntary program, which provides residents and local businesses with resources to become more sustainable.⁶⁵ In 2015, the program helped reduce CO2 emissions by 16,444 metric tons. That’s equivalent to 280,000 roundtrips between Fort Collins and Denver International Airport.⁶⁶ 

Conclusion

Higher temperatures, worsening air quality and more wildfires place the health of all Coloradans at risk.

This report highlights the adverse health effects of climate change – from aggravated asthma and allergies to dehydration and heat stroke. Colorado’s 1.2 million children and 711,000 seniors are especially vulnerable, as are people with chronic conditions such as diabetes and cardiovascular disease.

The good news is that Colorado, in many ways, is leading the way when it comes to health and climate change.

Coloradans have set standards for using renewable energy resources. Initiatives to reduce emissions are being implemented at the state and local level. Communities are preparing for extreme weather, adopting emergency response plans. Strategies from the Colorado Climate Change Plan have set the stage for government agencies, researchers, and organizations to collaborate on addressing this threat to human health.

This work to address climate change has an important goal: helping to improve the health of all Coloradans.

About This Report

This paper marks the first research done by the Colorado Health Institute into the impact of climate change on health. It was prompted by the growing body of scientific research connecting the two. The Colorado Health Institute is an independent, nonpartisan health policy research institute with a mission to provide evidence-based insight and analysis to support sound health policy decision-making.

Recent CHI reports about the impacts of climate change on health include Think Globally, Adapt Locally: Colorado Counties Health and Climate Index (2022) and Colorado's Health and Climate Policy Agenda: A Call to Action to Protect Our Communities from Climate Change (2023).