Kathleen Hartnett White testified before a Senate committee weighing her confirmation as chair of the Council on Environmental Quality at the White House. White, who is from Texas, reiterated her view that carbon dioxide is a "plant nutrient," not a pollutant.
Pressed by Democrats about the specific evidence linking carbon emissions to global warming, White grew visibly flustered.
"I am not a scientist, but in my personal capacity I have many questions that remain unanswered by current climate policy," said White, who holds academic degrees in East Asian studies and comparative literature. "We need to have a more precise explanation of the human role and the natural role."
The climate assessment released Friday as the consensus view of 13 federal agencies concluded that more than 92 percent of the observed rise in global average temperatures since 1950 is the direct result of human activity. Since 1900, Earth has warmed by 1.8 degrees (1 degree Celsius) and seas have risen by 8 inches. Heat waves, downpours and wildfires have become frequent.
White served under former Texas Gov. Rick Perry, now Trump's energy secretary, for six years on a commission overseeing that state's environmental agency. White was fiercely critical of what she called the Obama administration's "imperial EPA" and pushed back against stricter limits on air and water pollution.
She is a senior fellow at the Texas Public Policy Foundation, a conservative think tank that has received funding from fossil-fuel companies that include Koch Industries, ExxonMobil and Chevron. White is also a member of the CO2 Coalition, a group that seeks to educate "thought leaders, policy makers, and the public about the important contribution made by carbon dioxide."
Also appearing before the Senate Environment and Public Works committee on Wednesday was Andrew Wheeler, Trump's nominee to serve as the second-highest ranking official at the Environmental Protection Agency. Until recently, Wheeler worked as a lobbyist whose clients included Murray Energy, one of the nation's largest coal mining companies.
Wheeler said he had not read about the new climate report and could not comment on it. He expressed general agreement that human activities play a role in climate change, though he said there is uncertainty about how much - repeating the view often cited by EPA Administrator Scott Pruitt.
Bob Murray, the CEO of Murray Energy, said in a media interview published earlier this week that he had given Trump a three-page plan to revive the nation's struggling coal industry, and that about a third of that plan had already been implemented by the administration.
Asked about Murray's plan, Wheeler said he had seen it but denied having a copy. He said he couldn't remember the details of the plan, though he acknowledged attending meetings where it was discussed with members of the administration and Congress.
But it was White, with voluminous past writings and speeches denying climate science and advocating the continued burning of fossil fuels, who received the most aggressive questioning by both Republicans and Democrats on the committee.
White stood by her past statements saying particulate pollution released by burning fuels is not harmful unless one were to suck on a car tailpipe. Asked by Democratic Sen. Cory Booker of New Jersey about a Harvard University study linking ozone and particulate pollution to premature deaths, especially in urban communities, White said she had not read the study but found it "confusing" that would qualify as a crisis when much of the country meets federal air quality standards.
Republicans peppered White with questions about her past opposition to federal biofuels mandates, which she said would cause food shortages and widespread hunger. Though opposed by the petroleum industry, the federal requirements requiring ethanol to be blended into fuel has broad support from members of Congress from states economically dependent on farming.
White on Wednesday disavowed her past opposition to the program, saying her writings on the subject relied on flawed, out-of-date data.
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