WASHINGTON — Scott Pruitt, the head of the Environmental Protection Agency, said on Thursday that carbon dioxide was not a primary contributor to global warming, a statement at odds with the established scientific consensus on climate change.
Asked his views on the role of carbon dioxide, the heat-trapping gas produced by burning fossil fuels, in increasing global warming, Mr. Pruitt said on CNBC’s “Squawk Box” that “I think that measuring with precision human activity on the climate is something very challenging to do and there’s tremendous disagreement about the degree of impact, so, no, I would not agree that it’s a primary contributor to the global warming that we see.”
“But we don’t know that yet,” he added. “We need to continue the debate and continue the review and the analysis.”
Mr. Pruitt’s statement contradicts decades of research and analysis by international scientific institutions and federal agencies, including the E.P.A. His remarks on Thursday, which were more categorical than similar testimony before the Senate, may also put him in conflict with laws and regulations that the E.P.A. is charged with enforcing.
His statements appear to signal that the Trump administration intends not only to roll back President Barack Obama’s climate change policies, but also to wage a vigorous attack on their underlying legal and scientific basis.
A report in 2013 by the Intergovernmental Panel on Climate Change, a group of about 2,000 international scientists that reviews and summarizes climate science, found it to be “extremely likely” that more than half the global warming that occurred from 1951 to 2010 was a consequence of human emissions of carbon dioxide and other greenhouse gases.
A January report by NASA and the National Oceanic and Atmospheric Administration concluded, “The planet’s average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere.”
Benjamin D. Santer, a climate researcher at the Energy Department’s Lawrence Livermore National Laboratory, said, “Mr. Pruitt has claimed that carbon dioxide caused by human activity is not ‘the primary contributor to the global warming that we see.’ Mr. Pruitt is wrong.”
“The scientific community has studied this issue for decades,” Dr. Santer added. “The consensus message from many national and international assessments of the science is pretty simple: Natural factors can’t explain the size or patterns of observed warming. A large human influence on global climate is the best explanation for the warming we’ve measured and monitored.”
The basic science showing that carbon dioxide traps heat at the Earth’s surface dates to the 19th century, and has been confirmed in many thousands of experiments and observations since.
Mr. Pruitt has faced frequent criticism for his close ties to fossil fuel companies. In his previous job as the attorney general of Oklahoma, he sought to use legal tools to fight environmental regulations on the oil and gas companies that are a major part of the state’s economy. A 2014 investigation by The New York Times found that energy lobbyists had drafted letters for Mr. Pruitt to send, on state stationery, to the E.P.A., the Interior Department, the Office of Management and Budget and even Mr. Obama, outlining the economic hardship caused by the environmental rules.
But in a sign of how far outside mainstream views Mr. Pruitt’s remarks on Thursday have placed him, even executives of some of the nation’s largest fossil fuel producers said they were surprised by his comments. Interviewed at CERAweek, an annual conference of major energy producers this week in Houston, Wael Sawan, an executive vice president at Shell Energy Resources, said he was “absolutely convinced CO2 can cause serious damage to not only this generation but future generations.”
Mr. Pruitt spoke at the Houston energy conference on Thursday afternoon in a session moderated by Daniel Yergin, a prominent energy economist and a member of a White House advisory panel. Mr. Yergin did not ask Mr. Pruitt any questions about his remarks from Thursday morning, saying later that he had been unaware of the comments when interviewing him.
Mr. Pruitt did not clarify his comments or respond to reporters who sought to question him.
He said at the energy conference that the Obama administration had gone too far with some environmental rules and that he intended to work more closely with industry and individual states to address pollution issue
“The future ain’t what it used to be at the E.P.A.,” he said.
Mr. Pruitt’s remarks come as the Trump administration prepares to roll back Mr. Obama’s two signature policies to address global warming: a pair of sweeping regulations intended to curb carbon dioxide emissions from vehicles and power plant smokestacks.
At the same time, the White House is considering a 17 percent cut to the budget of NOAA, one of the nation’s premier agencies of climate science research, according to a memo obtained by The Washington Post.
Mr. Pruitt’s remarks on Thursday were consistent with his past public statements questioning the established science of human-caused climate change, but in denying the role played by carbon dioxide, they go a step further.
In addition to putting him at odds with the consensus of climate scientists, Mr. Pruitt’s remarks also raise the possibility that, as the Trump administration moves forward with unwinding Mr. Obama’s climate change regulations, it could put the administration in violation of federal law.
In 2009, the E.P.A. released a legal opinion known as an endangerment finding concluding that, because of its contribution to global warming, carbon dioxide in large amounts met the Clean Air Act’s definition of a pollutant that harms human health. Under the terms of the Clean Air Act, one of the nation’s most powerful environmental laws, all such pollutants must be regulated by the E.P.A. A federal court upheld the finding, and the Supreme Court declined to hear a challenge to it.
Thus the E.P.A. remains obligated to regulate carbon dioxide.
In his Senate hearing, Mr. Pruitt said that as administrator of the E.P.A. he would not revisit that 2009 legal finding. “It is there, and it needs to be enforced and respected,” Mr. Pruitt said. But energy lobbyists close to the Trump administration have since urged the new administration to consider building a legal case against the endangerment finding.
Advisers to Mr. Trump’s transition team said they read Mr. Pruitt’s remarks as a signal that he intends to do just that.
“President Trump’s campaign commitment was to undo President Obama’s entire climate edifice,” said Myron Ebell, who worked on Mr. Trump’s E.P.A. transition team but has no role in policy making. “They’re thinking through the whole thing, and based on what Scott Pruitt said this morning, I do think they are looking at reopening the endangerment finding.”
Mr. Trump is expected to announce an executive order next week directing Mr. Pruitt to begin the legal process of unwinding the climate change regulations on emissions from power plants.