Former ExxonMobil CEO Rex Tillerson refused to answer questions on Wednesday about the oil giant’s long history of denying the science of climate change, telling senators that scientific literature on global warming is “inconclusive.” The comments came during a Senate Foreign Relations Committee hearing into Tillerson’s nomination for secretary of state. Exposés by InsideClimate News and the Los Angeles Times have revealed Exxon knew that fossil fuels cause global warming as early as the 1970s, but hid that information from the public and instead poured millions of dollars into PR efforts aimed at sowing doubt over the science of climate change. Tillerson was asked about those reports by Virginia Democrat Tim Kaine.

Sen. Tim Kaine: “Are these conclusions about ExxonMobil’s history of promoting and funding climate science denial, despite its internal awareness of the reality of climate change, during your tenure with the company true or false?”

Rex Tillerson: “Senator, since I’m no longer with ExxonMobil, I’m in no position to speak on their behalf. The question would have to be put to them.”

Sen. Tim Kaine: “And let me ask you: Do you lack the knowledge to answer my question, or are you refusing to answer my question?”

Rex Tillerson: “A little of both.”

Sen. Tim Kaine: “Um, I have a hard time believing you lack the knowledge to answer my question.”

Tillerson worked at Exxon for 41 years. During Wednesday’s hearing, Tillerson refused to label Saudi Arabia a human rights violator and avoided condemning Philippines President Rodrigo Duterte over thousands of extrajudicial killings carried out under Duterte’s “war on drugs.” Tillerson said he would advise President Trump to veto any attempt to end the U.S. embargo on Cuba, and said the U.S. should challenge China over its territorial claims in the South China Sea. Tillerson also denied knowledge of ExxonMobil’s efforts to prevent U.S. sanctions against Russia, testifying that he never personally lobbied against sanctions. That prompted Senate Foreign Relations Committee Chair Bob Corker to respond, “I think you called me at the time.” During the hearing, Tillerson was repeatedly interrupted by protesters from Greenpeace opposed to naming an oil company executive as secretary of state. Outside the hearings, about 200 people rallied holding signs reading #EXXONKNEW. We’ll have more on Rex Tillerson’s nomination—and ExxonMobil’s history of climate denial—after headlines, with oil and energy analyst Antonia Juhasz.