“But we don’t know that yet,” he added. “We need to continue the debate and continue the review and the analysis.”

Speaking of carbon dioxide, the heat-trapping gas produced by burning fossil fuels, Pruitt told 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.”

WASHINGTON — Scott Pruitt, the head of the Environmental Protection Agency, said Thursday that carbon dioxide was not a primary contributor to global warming, a statement at odds with the global scientific consensus on climate change.


Pruitt’s statement is not consistent with scientific research on climate change, including decades of research by federal agencies. His remarks may also put him in conflict with laws and regulations his agency is charged with enforcing.

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.”


Santer added, “The scientific community has studied this issue for decades. 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.”

Pruitt’s remarks come as the Trump administration prepares to roll back President Barack Obama’s two signature global warming policies: 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 premiere agencies of climate science research, according to a memo obtained by The Washington Post.

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 his Senate confirmation hearing in January, he said, “Science tells us that the climate is changing and human activity in some manner impacts that change. The human ability to measure with precision the extent of that impact is subject to continuing debate and dialogue, as well they should be.” That statement, while inaccurate, did not specifically mention carbon dioxide.

In addition to putting him at odds with established scientific consensus, Pruitt’s remarks also suggest that, as the Trump administration moves forward with unwinding Obama’s climate change regulations aimed at reining in carbon dioxide pollution, it may not issue replacement regulations, which could put the administration in violation of federal law.


In 2009, the EPA released a legal opinion known as an endangerment finding that, because of its contribution to global warming, carbon dioxide in large amounts met the Clean Air Act’s definition of a pollutant that harmed 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 EPA. A federal court then upheld the finding and the Supreme Court declined to hear a challenge to it.

Thus the EPA remains legally obligated to regulate carbon dioxide.

In his January Senate hearing, Pruitt said as head of the EPA he would not revisit that 2009 legal finding. “It is there, and it needs to be enforced and respected,” Pruitt said. “There is nothing that I know that would cause it to be reviewed.”

However, energy lobbyists close to the Trump administration have since urged Pruitt, President Donald Trump and their staffs to consider building a legal case against the endangerment finding.

Trump is expected next week to announce an executive order directing Pruitt to begin the legal process of unwinding the climate change regulations on emissions from power plants.