Republican Jeb Bush said on Wednesday that the Earth's climate is changing but that scientific research does not clearly show how much of the change is due to humans and how much is from natural causes.
Bush delved into climate politics during a campaign-style house party in New Hampshire at which he took questions from voters on his viewpoints as he considers whether to seek the Republican presidential nomination in 2016.
While President Barack Obama and many scientists believe humans are largely to blame for climate change, Bush said the degree of human responsibility is uncertain.
"Look, first of all, the climate is changing. I don’t think the science is clear what percentage is man-made and what percentage is natural. It’s convoluted. And for the people to say the science is decided on, this is just really arrogant, to be honest with you," he said.
"It's this intellectual arrogance that now you can’t even have a conversation about it. The climate is changing, and we need to adapt to that reality," he said.
The former Florida governor challenged Obama's determination earlier in the day that climate change is now a threat to U.S. national security.
"As a small part of U.S. foreign policy," Bush said, the United States should encourage states that have had an increase in carbon emissions to take on the challenge.
But the overall country has had a reduction in carbon emissions due to new technologies, conservation measures, higher gas mileage in vehicles and a shift toward natural gas, he said.
"If the president thinks this is the gravest threat to our national security, it seems like he would say, ‘let’s expand LNG (liquefied natural gas) as fast as we can to get it into the hands of higher carbon-intense economies like China and other places. Let’s figure out ways to use compressed natural gas for replacing importing diesel fuel, which has a higher carbon footprint,’” Bush said.
He said that although he does not believe climate change is the "highest priority," the United States should not ignore it.