U.S. President Donald Trump's new environmental chief said Thursday that carbon dioxide emissions are not a chief contributor to global warming.
"I would not agree that it's a primary contributor to the global warming that we see," Environmental Protection Agency ( EPA) Administrator Scott Pruitt said on CNBC's 'Squawk Box.' "But we don't know that yet ... We need to continue to the debate and continue the review and the analyses," Pruitt added.
Pruitt's position on carbon dioxide is contrary to the official positions formulated by scientists at the National Oceanic and Atmospheric Administration and at the federal space agency NASA.
"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," the two agencies said in January.
The Union of Concerned Scientists, a non-profit, science advocacy group, said carbon-dioxide emitting vehicles, such as cars, trucks, trains and planes, are a "major cause of global warming." The transportation sector, it says, "produces nearly 30 percent of all U.S. global warming, more than almost any other sector."
Since Pruitt's Senate confirmation in February, he has begun staffing many top positions at the environmental agency with skeptics of climate change. Pruitt is moving to appoint former staffers of Senator James Inhofe, a fellow Oklahoma Republican who is known as the most influential climate change skeptic in Congress.
Former Inhofe chief of staff Ryan Jackson will be Pruitt's chief of staff. Ryan Brown, another former Inhofe staffer, will serve as Jackson's deputy.
Before week's end, President Trump is expected to sign an executive order authorizing Pruitt to begin repealing former President Barack Obama's environmental regulations that were designed to reduce heat-trapping emissions from coal-fired power plants.
Pruitt also is expected to soon begin weakening Obama's regulations requiring higher vehicle fuel-economy standards, raising the ire of congressional Democrats.
Senate Democratic leader Charles Schumer and 11 other Democrats said on Tuesday it was "critical" for the Trump administration to preserve the rules, saying the higher standards were achievable.
"These automobile emissions standards are economically feasible and technologically achievable for the auto industry," the Democratic senators, including former presidential candidate Bernard Sanders, wrote in a letter to Pruitt. "It is critical they remain in place," the letter added.
Automakers contend the higher fuel standards would raise the fleet-average fuel efficiency from 44.2 kilometers per gallon of gasoline in 2010 to more than 80.5 kilometers per gallon in 2025.
Representatives of automakers General Motors, Ford Motor Company and Toyota Motor Corporation, have asked the EPA to repeal the higher standards. Separately, the chief executives of Toyota, Volkswagen, Honda, Hyundai Motor Company and others have called on President Trump to revisit them.
Pruitt, who previously served as attorney general of Oklahoma, gained national recognition as a leader in a campaign by Republican attorneys general to challenge Obama's regulatory program. Prior to leading the EPA, Pruitt sued or collaborated 14 times in legal actions against the agency.