“I don’t deny that consensus that the climate is changing,” he said. “In fact, I fully believe and know that the climate is changing. I also know that we humans beings are contributing to it in a major way. Carbon dioxide is a greenhouse gas. We’re putting it into the atmosphere in volumes that we haven’t seen, and that greenhouse gas is warming the planet. That is absolutely happening, and we are responsible for it.”
Bridenstine did not say that humans are the main drivers of climate change. But his assertion that people are contributing to climate change “in a major way” marks his strongest support to date for the scientific consensus behind warming temperatures. And he went further than perhaps any other Trump-picked leader has.
Bridenstine went further on Thursday than he has in the past—even in the very recent past, like at his Senate confirmation hearing in November, which was convened a month after President Trump picked Bridenstine as his choice to lead NASA. When Brian Schatz, a Democratic senator from Hawaii, questioned Bridenstine about his views on climate change, Bridenstine said, “I believe carbon dioxide is a greenhouse gas. I believe that humans are contributing to carbon dioxide in the atmosphere.”
“To what extent?” Schatz asked.
“That is a question I do not have an answer to, but I do know that humans have absolutely contributed to global warming,” Bridenstine replied.
“Are they the primary cause?” Schatz said.
“It’s going to depend on a whole lot of factors, and we’re still learning more about that every day,” Bridenstine said. “In some years, you could say absolutely. In other years, during sun cycles and other things, there are other contributing factors that would have more of an impact.”
Bridenstine said something similar in June 2013, six months after he took office in the House of Representatives, and soon after a tornado killed 24 people in Oklahoma. During a floor speech, Bridenstine asked former President Barack Obama to apologize to Oklahomans for spending more money on global-warming research than on weather forecasting and warnings (a claim that PolitiFact, a fact-checking website run by reporters, rated as “mostly false.”)
“Global temperature changes, when they exist, correlate with sun output and ocean cycles,” Bridenstine said back then. “During the Medieval Warm Period from 800 to 1300 A.D., long before cars, power plants, and the industrial revolution, temperatures were warmer than today. During the Little Ice Age from 1300 to 1900 A.D., temperatures were cooler. Neither of these were caused by any human activity.” (Scientists have found that volcanic eruptions also play a large role in these natural changes in climate, and they note that recent temperature changes dwarf any of these historic anomalies.)
Bridenstine’s appearance at Thursday’s town hall signaled a shift in the way he talks about climate change—and it was fairly reassuring for some on the other side.