Secretary of State John Kerry this week acknowledged twice that the Islamic State and the threat of terrorism around the world is a bigger threat than climate change, even though he has insisted in past years that climate is the bigger threat.

Kerry revealed his subtle change of thinking during his trip to Europe, where he twice indicated that when it comes to global threats, terrorism is first, and climate change is a very close second.

"[L]et me just say that one of the greatest challenges of our times besides the fight against extremism is to deal with the enormous battle of climate change," he said in Denmark Thursday. The phrase "besides the fight against extremism" indicates he sees terrorism as the top threat.

He made a similar comment in Norway on Wednesday, when at first seemed prepared to say climate is the bigger issue, but then conceded that terrorism ranks at the top.

"The threat of climate change is, without question, one of the defining if not the defining challenge — I'd probably give violent extremism — have to say one of — the defining threat of a generation," he said. "And it is a challenge that everybody has to approach with urgency."

While subtle, the shift was noticeably present in his overseas remarks that were delivered just days after an Islamic State-inspired gunman killed 49 people in Orlando before he was killed by police. Just a few years ago, Kerry was routinely saying that climate was the top issue.

In 2014, for example, Kerry indicated that he saw climate change as " the greatest challenge of our generation."

He also called it the world's " largest weapon of mass destruction."

And near the end of 2014, Kerry indicated the two issues were tied for first place, when he said climate change needs to be addressed with as much "immediacy" as the Islamic State.

While Kerry seems to now say terrorism is the top threat, that didn't stop him relaying all the dangers humans face due to climate change.

In Denmark, he said he was traveling to Greenland to see what he could do there to stop the melt of ice sheets there.

"That's why I'm going to Greenland tomorrow, because if we were to lose the ice sheet of Greenland, we would see a sea level rise of some 22 feet over the course of this century," he said.

And in Norway on Wednesday, he said climate change still poses an existential threat to humans.

"[T]his thing called climate change is looming out there, a decidedly different challenge but, let me tell you, one that is existential and already impacting our lives, giving us a preview of the planet-wide catastrophe that we would face if we don't change course," he said. "And with it, the kinds of catastrophic movements of people."

"If we think we see refuges today, imagine what would happen when whole rivers dry up and food shifts and production is limited and people are fighting over those limitations," he added.