Dr. Ben Carson, a retired neurosurgeon who is consistently polling just behind Donald Trump in the race for the Republican nomination, responded to a letter from California Gov. Jerry Brown, who sent the frontrunner a flash drive including the latest U.N. report on climate change.

“It doesn’t change my opinion,” Carson told a reporter from the Sacramento Bee who asked about the letter and report from Brown. “My opinion being that, as responsible human beings, we should look out for the environment. And I don’t think we have to make it into a big political issue.”

Carson added, “”already quite familiar with the data.”

In August, Brown also took on former Hewlett-Packard CEO Carly Fiorina, who has blamed the ongoing drought in California on aggressive environmental policies.