(CNN) Ken Isaacs, the Trump administration's nominee to lead the United Nations migration agency, told reporters Friday that he believes in climate change and said a tweet questioning it was taken out of context.

However, a CNN KFile review of his tweets shows that Isaacs repeatedly and forcefully cast doubt on climate science in the past.

In a news conference at the United Nations Friday, Isaacs, when asked about climate denial in his tweets said, "The context that I made that -- this is the last time I'm going to comment on the tweets, you know, y'all can ask me questions all day long, but I've done deep in-depth interviews on this. The context of the tweet was a conference that was held in Paris about climate change and terrorism. And I said this will be a joke at the dinner table of ISIS," Isaacs said, adding that as head of the Samaritan's Purse relief organization, he had responded to disasters caused by climate change.

Isaacs' comments were in reference to one Facebook post uncovered by the Washington Post in which he referred to the connection between national security and climate change as "a joke."

"The meeting in Paris next week is not going to be a rebuke to ISIS. It is going to be a dinner joke, a laughing stock, and a diversion of all the real issues," Isaacs wrote.