COLORADO — The legal filing comes as agricultural producers face challenges from shifting weather patterns and water scarcity. Deirdre Macnab is a rancher in northwestern Colorado who enlisted six other ranchers to join the legal brief after reading that leaders of Rio Blanco County would back the oil companies. The group seeks to demonstrate how climate change directly impacts rural livelihoods and regional economies.

Caleb Valdez is a rancher in Cortez, Colo., who owns about 200 cattle. He buys water and hauls it with a tanker truck to fill troughs for his cattle because his irrigation system no longer provides water. Jay Fetcher is a rancher who also joined the effort to support the local governments' claims. These individuals represent a sector that the Boulder lawsuit complaint states is valued at $41 billion in Colorado.

The ranchers' amicus brief states that average temperatures in Colorado have climbed 2.3 degrees since 1980. It further notes that since 2000, the Southwest has been plagued by a megadrought that has dramatically shrunk the flow of the Colorado River. The brief adds that the Colorado River’s reservoirs have declined to their lowest levels on record. These environmental shifts threaten the source of the Colorado River in the Rocky Mountains, which is drying up and threatening a critical water lifeline for about 35 million people and 5 million acres of farmland across the Southwest.

The city and county of Boulder, Colo., filed a lawsuit against Suncor Energy and Exxon Mobil in 2018. The Boulder lawsuit argues that oil companies concealed and misrepresented the dangers of fossil fuels and should help pay for costs linked to climate change, including wildfires, drought, and heat waves. The complaint also states that Colorado’s ski industry is valued at $5 billion.

Suncor and Exxon Mobil stated in a recent brief that nearly 60 other local governments and states have brought similar suits. They also stated in a recent brief that damages in any single case could reach into the billions. Suncor Energy is a Canadian energy company with operations in the region. The outcome of this case will determine whether state courts can adjudicate claims related to global greenhouse-gas emissions.

Timeline

Last year, the Colorado Supreme Court ruled in Boulder’s favor, finding the case can proceed under state law. The Rocky Mountains had the least snow on record this year. The U.S. Supreme Court is scheduled to hear arguments in Suncor Energy vs. County Commissioners of Boulder County on Oct. 5, 2026.

What's New

The U.S. Supreme Court granted the defendants’ petition to review an earlier Colorado Supreme Court decision allowing Boulder’s case to move forward, and the Supreme Court will decide whether federal law precludes state law claims seeking relief for injuries allegedly caused by the effects of interstate and international greenhouse-gas emissions on the global climate. Research titled "Colorado Communities Sue ExxonMobil and Suncor for Climate Damages" appears in the Climate Change and Law Collection. Research titled "Four. The Historical Context of Porcupine Cave: American Indians, Spaniards, Government Surveyors, Prospectors, Ranchers, Cavers, and Paleontologists in South Park, Colorado" was published in 2019 in Biodiversity Response to Climate Change in the Middle Pleistocene.

Boulder County stated in August that it must eliminate a further $13.2 million from its 2027 budget after making an equal reduction for 2026. Boulder County has eliminated roughly 90 positions while projecting that it must find $30 million to $40 million in savings over three years. The Colorado Supreme Court is the highest court in the U.S. state of Colorado.

Boulder County is a county in Colorado, United States. The city of Boulder’s recommended 2027 budget closes a separate $6.3 million gap in part by laying off 13 employees.

Why It Matters

This case represents a test of whether state courts can hear claims against major energy companies for contributions to global climate change. The U.S. Supreme Court will decide whether federal law precludes state law claims seeking relief for injuries allegedly caused by the effects of interstate and international greenhouse-gas emissions. A ruling in favor of the oil companies could block similar suits from nearly 60 other local governments and states that have brought comparable cases.

The financial implications are substantial, with Suncor and Exxon Mobil stating that damages in any single case could reach into the billions. For local governments like Boulder County, which faces budget shortfalls and staff reductions, the outcome could affect their ability to fund climate adaptation measures. The ranchers' involvement shows the direct impact of climate trends on agriculture, a $41 billion industry in Colorado, and water resources that support millions of people across the Southwest.