From the 1980s to the mid 2000s, the American multinational oil and gas corporation ExxonMobil was a leader in climate change denial, opposing regulations to curtail global warming. For example, ExxonMobil was a significant influence in preventing ratification of the Kyoto Protocol by the United States. ExxonMobil funded organizations critical of the Kyoto Protocol and seeking to undermine public opinion about the scientific consensus that global warming is caused by the burning of fossil fuels. Of the major oil corporations, ExxonMobil has been the most active in the debate surrounding climate change. According to a 2007 analysis by the Union of Concerned Scientists, the company used many of the same strategies, tactics, organizations, and personnel the tobacco industry used in its denials of the link between lung cancer and smoking.
ExxonMobil has funded, among other groups, the Competitive Enterprise Institute, George C. Marshall Institute, Heartland Institute, the American Legislative Exchange Council and the International Policy Network. Between 1998 and 2004, ExxonMobil granted $16 million to advocacy organizations which disputed the impact of global warming.Weart, S. (2025) The public and climate change. In: The Discovery of Global Warming From 1989 until April 2010, ExxonMobil and its predecessor Mobil purchased regular Thursday advertorials in The New York Times, The Washington Post, and The Wall Street Journal claiming that the science of climate change was unsettled.
An analysis conducted by The Carbon Brief in 2011 found that 9 out of 10 of the most prolific authors who cast doubt on climate change or speak against it had ties to ExxonMobil. Greenpeace have said that Koch industries invested more than US$50 million in the past 50 years on spreading doubts about climate change.
Since the 1970s, ExxonMobil and its predecessors had engaged in climate research focusing on global warming. From the late 1970s and through the 1980s, Exxon funded internal and university collaborations, broadly in line with the developing public scientific approach. A review in 2023 found that the global warming projections documented by and the models created by ExxonMobil's own scientists between 1977 and 2003 had "accurately" projected and "skillfully" modeled global warming due to fossil fuel burning, and had reasonably estimated how much would lead to dangerous warming. The authors of the paper concluded: "Yet, whereas academic and government scientists worked to communicate what they knew to the public, ExxonMobil worked to deny it."
In April 2014, ExxonMobil released a report publicly acknowledging climate change risk for the first time. ExxonMobil predicted that a rising global population, increasing living standards and increasing energy access would result in lower greenhouse gas emissions. In 2015, it expressed support for a carbon tax.
In 2015, the Attorney General of New York launched an investigation whether ExxonMobil's statements to investors were consistent with the company's decades of extensive scientific research. In October 2018, based on this investigation, ExxonMobil was sued by the State of New York, which claimed the company defrauded shareholders by downplaying the risks of climate change for its businesses.
Own research From the late 1970s and through the 1980s, Exxon, one of predecessors of ExxonMobil, had a public reputation as a pioneer in climate change research. Exxon funded internal and university collaborations, broadly in line with the developing public scientific approach, and developed a reputation for expertise in atmospheric carbon dioxide ().: Since the late 1970s and into the 1980s, Exxon had been at the forefront of climate change research, funding its own internal science as well as research from outside experts at Columbia University and MIT. Between the 1970s and 2015, Exxon and ExxonMobil researchers and academic collaborators published dozens of research papers.: From the time the scientific community first began worrying about the climate issue in the 1970s, the company financed research on the topic, with its scientists generally supporting an emerging consensus that fossil fuel emissions could pose risks for society. Company scientists have contributed to dozens of scientific papers that supported this view and explored the extent of the risks. ExxonMobil provided a list of over 50 article citations from that period.: "ExxonMobil scientists have been involved in climate research and related policy analysis for more than 30 years, yielding more than 50 papers in peer-reviewed publications."
In July 1977, a senior scientist of Exxon, James Black, reported to the company's executives that there was a general scientific agreement at that time that the burning of fossil fuels was the most likely manner in which mankind was influencing global climate change.: "By 1977... he made a presentation to the company's leading executives warning that carbon dioxide accumulating in the upper atmosphere would warm the planet and if the concentration continued to rise, it could harm the environment and humankind." What is considered the best presently available climate model for treating the Greenhouse Effect predicts that a doubling of the concentration in the atmosphere would produce a mean temperature increase of about 2°C to 3°C over most of the earth.: ...the company's knowledge of climate change dates back to July 1977, when its senior scientist James Black delivered a sobering message on the topic. "In the first place, there is general scientific agreement that the most likely manner in which mankind is influencing the global climate is through carbon dioxide release from the burning of fossil fuels," Black told Exxon's management committee. A year later he warned Exxon that doubling gases in the atmosphere would increase average global temperatures by two or three degrees—a number that is consistent with the scientific consensus today. He continued to warn that "present thinking holds that man has a time window of five to 10 years before the need for hard decisions regarding changes in energy strategies might become critical." In 1979–1982, Exxon conducted a research program of climate change and climate modeling, including a research project of equipping their largest supertanker Esso Atlantic with a laboratory and sensors to measure the absorption of carbon dioxide by the oceans.: Exxon budgeted more than $1 million over three years for the tanker project to measure how quickly the oceans were taking in . In 1980, Exxon noted that synthetic fuels increase emissions over their petroleum equivalents. Exxon also studied ways of avoiding emissions if the East Natuna gas field (Natuna D-Alpha block) off Indonesia was to be developed.
In 1981, Exxon shifted its research focus to climate modelling. In 1982, Exxon's environmental affairs office circulated an internal report to Exxon's management which said that the consequences of climate change could be catastrophic, and that a significant reduction in fossil fuel consumption would be necessary to curtail future climate change. It also said that "there is concern among some scientific groups that once the effects are measurable, they might not be reversible."
In 1992, the senior ice researcher, leading a research team in Exxon's Canadian subsidiary Imperial Oil, assessed how global warming could affect Exxon's Arctic operations, and reported that exploration and development costs in the Beaufort Sea might be lower, while higher sea levels and rougher seas could threaten the company's coastal and offshore infrastructure.: An extended open water season, Croasdale said in 1992, could potentially reduce exploratory drilling and construction costs by 30% to 50%...he advised the company to consider and incorporate potential "negative outcomes," including a rise in the sea level, which could threaten onshore infrastructure; bigger waves, which could damage offshore drilling structures; and thawing permafrost, which could make the earth buckle and slide under buildings and pipelines.: Croasdale said global warming could lower the costs but increase the length of time it would be possible to explore for oil in the Beaufort Sea, north of Alaska and Canada's Yukon Territory. He and his team of researchers had developed models that showed with climate change, drilling in the Beaufort Sea could grow from two months per year to as many as five, with costs cut by as much as half. At the same time, rising sea level due to climate change could hurt infrastructure Imperial included these forecasts into its facility planning in the Mackenzie River Delta in the Northwest Territories. In 1996, Mobil, another predecessor of ExxonMobil, calculated the climate changes effect to the Sable gas field project. An ExxonMobil spokesperson said that standard practice in major project planning is to consider a range of factors, and that ExxonMobil's consideration of environmental risks was not inconsistent with their public policy advocacy.
In 2016, the Center for International Environmental Law, a public interest, not-for-profit environmental law firm, claimed that from 1957 onward Humble Oil, one of predecessors of nowadays ExxonMobil, was aware of rising in the atmosphere and the prospect that it was likely to cause global warming. ExxonMobil responded to this claim that "to suggest that we had definitive knowledge about human-induced climate change before the world's scientists is not a credible thesis."
Denial tactics despite own research results In 1989, shortly after the presentation by the Exxon's manager of science and strategy development Duane LeVine to the board of directors which reiterated that introducing public policy to combat climate change "can lead to irreversible and costly Draconian steps," the company shifted its position on the climate change to publicly questioning it.: "After a decade of frank internal discussions on global warming and conducting unbiased studies on it, Exxon changed direction in 1989 and spent more than 20 years discrediting the research its own scientists had once confirmed." This shift was caused by concerns about the potential impact of the climate policy measures to the oil industry.
In the fall of 2015, InsideClimate News published a series of reports on an eight-month investigation based on decades of internal Exxon Mobil files and interviews with former Exxon employees, which stated "Exxon conducted cutting-edge climate research decades ago and then, without revealing all that it had learned, worked at the forefront of climate denial, manufacturing doubt about the scientific consensus that its own scientists had confirmed." Exxon responded to the article by saying the allegations were based on cherry-picked statements from ExxonMobil employees and noting the ongoing climate research the company engaged in during the time in question.
The company also denied claims made by InsideClimate News that it had curtailed carbon dioxide research in favor of climate denial. Exxon's statement said the drop in oil prices hurt oil companies in the 1980s and caused research cutbacks. The statement also claimed that it was uncertain if increases in greenhouse gas emissions caused significant warming, or if immediate action on climate change was necessary.