Climate change, combined with economic instability, is creating a prime recruiting ground for Islamic radicals, said a national security adviser to former Republican President George W. Bush on Thursday.

"Climate change and a lot of other economic dislocations have put a lot of people out of work," said Stephen Hadley, citing the refugee crisis in Europe as a prime example. Hadley served as Bush's national security adviser from 2001 to 2009.

"They are on the move and they have no place to go, and it means they are recruiting grounds for terrorists and extremists and potential refugee flows that will tax Europe even more," he said while speaking at a forum hosted by Politico on Thursday.

President Obama and his Secretary of State John Kerry have been prime targets by Republicans who have derided them for calling climate a threat to national security, and an issue equal to the threat faced by the Islamic State.