Scott Pruitt, the new director of the Environmental Protection Agency, challenged the scientific consensus on the causes of climate change.

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 global scientific consensus on climate change.

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

“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 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.”

Dr. 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 is preparing the way for a rollback of environmental regulations that limit carbon dioxide emissions.