President Trump’s nominee for the top White House environmental post changed her tune on the Renewable Fuel Standard at her confirmation hearing Wednesday morning.

Kathleen Hartnett White, Trump’s pick to lead the Council on Environmental Quality, told the Senate Environment and Public Works Committee that she supports the Environmental Protection Agency's Renewable Fuel Standard, which requires increasing amounts of ethanol and other biofuels be blended into the nation’s fuel supply. She once wanted to repeal the regulation, referring to it as “counterproductive and ethically dubious.”

In her confirmation hearing, White said she “solidly” supports the program and would “uphold” it. The Trump administration had considered weakening the standard, but recently vowed to maintain it after Midwestern senators complained.

“I salute the [ethanol] industry,” White said. “An industry like ethanol has contributed to giving new life to families in once-vibrant small towns.”

Her views on the RFS will be crucial in determining whether she can advance through the committee. Republican Sens. Deb Fischer and Joni Ernst have said they are wary of White’s stance on the biofuel mandate, and just one GOP defection would block her nomination in committee.

“I worry about your lack of understanding of the purpose of the [RFS] law,” Fischer said at the hearing. “I worry about your extremist views.”

The Council on Environmental Quality coordinates environmental policy at the White House. White would be in charge of implementing Trump executive orders on energy and the environment.

She is former chairwoman of the Texas Commission on Environmental Quality who works at the Texas Public Policy Foundation, a conservative think tank that has received funding from Koch Industries, Exxon Mobil, Chevron and other energy companies.

Lawmakers also prodded White for controversial statements she has made about climate change.

She has said that "carbon dioxide is not a pollutant" and once referred to former President Barack Obama's climate change policies as "deluded and illegitimate."

She also has said that those who believe in climate change follow a "kind of paganism" for "secular elites.”

Those are disqualifying comments, said Sen. Tom Carper of Delaware, the top Democrat on the committee.

“Ms. White has shown a disdain for science, disregard for laws and regulations already on books, and a staggering disrespect for people who have views with which she disagrees,” Carper said, calling her a “science denier.”

White countered Wednesday morning that her comments were “taken out of context.”

But she continued to express doubt about the extent that human activity contributes to climate change.

She said she believes human activity contributes to climate change, but that she does not believe the extent of is known with precision, a position held by other Trump administration officials.

She said emissions of carbon dioxide have increased from preindustrial levels, but not "drastically."

“It’s likely that CO2 emissions from human activity have some influence on the climate, but ... CO2 in the atmosphere has none of the characteristics of a pollutant that contaminates and fouls... that can have direct impact on human health. As an atmospheric gas, it’s a plant nutrient,” White said.

White refused to back the findings of a major climate change report released last week by Trump administration scientists that found it is “extremely likely” that human activities are the “dominant cause” of global warming.

“For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence,” the report says.

The comprehensive study of climate science by U.S. government researchers across 13 federal agencies, known as the Climate Science Special Report, is part of a larger scientific review called the fourth National Climate Assessment. It is mandated by Congress to be released every four years.

"I view this report as a product of the past administration, not of this one,” White said. The report began under the Obama administration in 2015 and is done by career staff members.

White said her top priority as the White House’s top environmental adviser would be reducing permit delays for infrastructure projects.

“I would welcome the challenge to make significant changes to environmental reviews to reduce costs and uncertainty,” she said. “That would be historically important.”

Combating climate change would be among her top three priorities, she said.