Climate Change Litigation in Colorado

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Climate Change Litigation in Colorado

Colorado communities sue fossil fuel companies to pay the costs of climate change adaptation.


United States

Case Status:



Climate Justice, Extractive Industries


Climate Change Impacts, Adaptation to Climate Change


We joined the Colorado communities of Boulder County, San Miguel County, and the City of Boulder in filing a lawsuit against Exxon Mobil and Suncor Energy, two oil companies with significant responsibility for climate change. Both Exxon and Suncor have been particularly active in Colorado. Similar lawsuits are currently proceeding in California and New York, but this is the first such lawsuit in Colorado—or anywhere in the U.S. interior, to recover the costs associated with climate change impacts.

Colorado is one of the fastest warming states in the United States. Boulder County, San Miguel County and the City of Boulder continue to experience trends associated with rising temperatures. Over the next three decades, these communities are expected to face costs reaching hundreds of millions of dollars or more to adapt to and mitigate the impacts of climate change. Their local governments have done everything in their power to address climate change, while these companies have continued to act recklessly. Exxon and Suncor have made substantial contributions to the climate impacts that are now affecting these communities. These impacts are projected to grow worse over time:

  • More frequent and destructive wildfires
  • More frequent and severe droughts
  • Higher average temperatures that lead to more heat waves
  • Increasingly severe infestations of mountain pine beetles and other insects
  • Reduced snowpack
  • Earlier spring runoff from snow in the mountains
  • Changing precipitation patterns that place stress on agriculture
  • Greater intensity of short-term rainfalls, which could lead to flooding
  • Worse ground-level ozone concentrations, leading to respiratory problems

Climate change will affect fragile mountain ecosystems and hit at the heart of the local economy, damaging roads, forests, homes, the agricultural sector, the ski industry, open space, and much more. Adapting to such a wide range of impacts requires local governments to undertake unprecedented levels of planning and spending. Escalating costs have forced these Colorado communities to take legal action so that taxpayers are not stuck footing the bill.


The local governments of Boulder County, San Miguel County, and the City of Boulder brought this lawsuit to recover the costs of climate adaptation that would otherwise be borne by taxpayers. More than 330,000 residents call Boulder and San Miguel counties home. Due to the impacts of climate change, the health and safety of these residents are at risk. Since 1983, average temperatures in Colorado have risen more than 2℉ and are continuing to warm. Boulder County, San Miguel County, and the City of Boulder are already experiencing the impacts of climate change.


Fossil fuel combustion accounted for nearly 80 percent of all greenhouse gas emissions between 1970 and 2010. Exxon is one of the largest investor-owned fossil fuel producers in history. Suncor is one of the world’s largest independent energy companies and is particularly active in Colorado. Suncor’s U.S. operations are based in Denver, Colorado; the company supplies about 35 percent of the state’s gasoline and diesel fuel demand. The two companies work closely together in Colorado to market and sell fossil fuels. The two companies also jointly operate Syncrude Canada Ltd., the largest developer of Canada’s tar sands. Syncrude’s products are among the dirtiest in the world. Canadian tar sand operations produce higher concentrations of GHG emissions than almost any other fossil fuel.

Exxon Mobil and Suncor have long known about the risks that their products would cause to communities, especially in vulnerable coastal and mountain regions, but chose to continue business as usual. In 1968, industry scientists warned them that “significant temperature changes are almost certain to occur by the year 2000” due to rising greenhouse gases, and that “the potential damage to our environment could be severe.” By the 1970s, these two companies knew with high certainty that their products were dangerous and that inaction would cause dramatic, even catastrophic, changes to the climate. Exxon adapted its own facilities to protect from climate impacts, such as sea level rise. Yet Exxon Mobil and Suncor chose to conceal their knowledge, and continued promoting and selling fossil fuels. And worse, they actively spread doubt about climate change and sought to discredit the scientific voices that they knew were telling the truth.


David Bookbinder, Chief Legal Counsel, Niskanen Center
Kevin Hannon and The Hannon Law Firm LLC


An oil industry group, the American Petroleum Institute (API), began research on “gaseous compounds in the atmosphere to determine the amount of carbon of fossil fuel origin.”


 Stanford Research Institute completed a report commissioned by the oil industry titled “Sources, Abundance, and Fate of Gaseous Atmospheric Pollutants.” The report concluded that atmospheric CO2 was rising, and that fossil fuel combustion was by far the most likely source. The study warned that increased atmospheric concentrations of CO2 would increase global average temperatures, and that there was “no doubt” that the potential damage to the environment could be severe. This information was shared with managers of both Defendants.


The fossil fuel industry studied the impact of fossil fuel combustion on the earth’s atmosphere. The industry’s own scientists repeatedly informed company executives that there was growing consensus that fossil fuel use would result in likely catastrophic changes to the climate. The companies were told that one (if not the primary) cause for any “uncertainty” was the extent of future fossil fuel use and growth. Both Exxon and Suncor participated in these activities.


Public awareness of climate change started to grow with discussion about the “greenhouse effect.”


Exxon’s research team examined the positive and negative effects that a warming Arctic would have on oil operations.


The United Nations created the Intergovernmental Panel on Climate Change, a scientific and intergovernmental body dedicated to providing an objective view on climate science and the impacts of climate change. The IPCC becomes the leading and most credible authority on climate science. Since that time, the IPCC has published five assessment reports (1990, 1995, 2001, 2007, and 2014) reviewing the latest in climate science. The first report concluded that there was scientific certainty that human-caused emissions were substantially increasing greenhouse gas concentrations in the atmosphere, leading to rising average temperatures. By the fourth report in 2007, the IPCC emphasized that “warming of the climate system is unequivocal,” that there was a greater than 90% probability that the warming was due to human activities, and that the impacts were already evident.

Late 1980s – 2000s

The fossil fuel industry, led in large part by the American Petroleum Institute, created several entities whose mission is to cast doubt on climate science. Examples include the Global Climate Coalition created in late 1980s and the Global Climate Science Communications Team created in late 1990s. The industry also commissioned a number of scientists to publish papers casting doubt on climate science and attack the IPCC, such as Fred Seitz and Fred Singer.


World leaders came together to create the UN Framework Convention on Climate Change. Over 130 countries will sign onto this treaty.


Exxon, Suncor, and other members of the fossil fuel industry spent millions of dollars and participate in initiatives to cast doubt on climate science. A fossil fuel industry lobbying group, the American Petroleum Institute (API), leads many of the to cast doubt on climate science. Exxon and Suncor are active members of API.


While building offshore exploration facilities in Canada, Mobil Oil (now Exxon) made structural adaptations to account for rising temperatures and sea level rise.


Several polls found that a significant percentage of the American population doubted climate change, despite the scientific consensus at the IPCC. Time Magazine found that only 56% of Americans thought global temperatures had risen; ABC found that 80% believed global warming was “probably happening,” but 64% did not believe the science was settled, perceiving “a lot of disagreement among scientists”; Pew Research Center found that only 41% believed human activity caused global warming.


A Pew Research Center poll found that only 44% of Americans believed there was solid evidence that global temperatures are rising. Only 47% said that temperatures are rising as a result of human activity, such as burning fossil fuels.


In a sharp decrease from the previous year, a Pew Research Center poll found that only 35% of Americans believed there was solid evidence that global temperatures are rising. Only 36% said temperatures are rising as a result of human activity, such as burning fossil fuels.


It came to light that a leading climate denial voice, aerospace engineer Wei-Hock (Willie) Soon at Harvard-Smithsonian Center for Astrophysics had received, but not disclosed, over $1.2 million from Exxon, API, and other fossil fuel interests in 2001-2012. His funders were given the right to review his work before it was published.

In August, “Our Children’s Trust” youth plaintiffs filed a lawsuit asserting that the federal government is failing to protect them from climate change.

In September, a series of investigative reports by InsideClimateNews and the Los Angeles Times reviewed internal Exxon documents that disclosed that the company had known for decades about the dangers of climate change and then spent millions of dollars to create doubt and spread misinformation about climate science.

In November, the Attorney General of New York launched an investigation into Exxon to see if the company lied to the public about the risks of climate change and to investors about the implications of climate change on the oil business.


In April, the Attorneys General of Massachusetts and the U.S. Virgin Islands began similar investigations into Exxon.


In July, three communities in California–San Mateo County, Marin County, and Imperial Beach–filed separate lawsuits against 37 fossil fuel companies seeking compensation for the costs of adapting to sea level rise and other climate impacts.

In September, the California cities of San Francisco and Oakland filed lawsuits against five fossil fuel companies seeking compensation for the costs of adapting to sea level rise and other climate impacts.

In December, the California communities of Santa Cruz and Santa Cruz County filed a lawsuit against 29 fossil fuel companies seeking compensation for the costs of adapting to sea level rise and other climate impacts.


In January, New York City filed a lawsuit against five fossil fuel companies seeking compensation for the costs of adapting to sea level rise and other climate impacts. The City of Richmond in California also files a similar lawsuit against 29 fossil fuel companies.

In April, Boulder County, San Miguel County, the City of Boulder and EarthRights International filed a lawsuit against fossil fuel companies Exxon Mobil and Suncor.

In June, Plaintiffs filed an amended complaint. Later that month, Suncor and Exxon filed a motion to remove to federal court.

In August, the plaintiffs filed a remand brief.


In September, federal judge William J. Martinez ruled that the case should proceed in Boulder County District Court. The defendants asked for a stay of this ruling while they appealed.

In October, Judge Martinez denied their request.

Legal Issues

The plaintiffs are seeking compensation under nuisance and trespass claims: Exxon and Suncor have acted knowingly and recklessly and should pay their fair share of the damage. Taxpayers should not be expected to pick up the tab. In this case, because climate impacts are already inevitable, the plaintiffs are being forced to spend significant amounts of taxpayer dollars to adapt to the changing climate.

Evidence demonstrates that these two companies knowingly and substantially contributed to the climate crisis by producing, developing, promoting and selling a substantial portion of the fossil fuels that are causing and exacerbating climate change, while concealing and misrepresenting the dangers associated with their intended use.The plaintiffs have asked the court for compensation for the costs of adaptation measures needed to protect local residents and property. The communities have not asked the court to stop or regulate the future production of fossil fuels in Colorado.