He is chairing a virtual meeting of the 15-member council on climate-related risks to international peace and security.
"Think of a young man forced onto the road when his home becomes a desert... He goes to some camp, he becomes prey for violent extremists, people who radicalize him, and the effects of that radicalization are felt around the world," Johnson said.
With the world struggling to cut planet-warming emissions fast enough to avoid catastrophic warming, the United Nations will stage a climate summit in November in Glasgow, Scotland.
It will be the most important gathering since the 2015 event that yielded the Paris Agreement, when nearly 200 countries committed to halt rising temperatures quickly enough to avoid catastrophic change.
The November summit serves as a deadline for countries to commit to deeper emissions cuts.
BORIS JOHNSON: Very, very important contribution, and one I think everybody-- climate change is a threat to our collective security and the security of our nations. And I know that there are people around the world who will say that this is all kind of green stuff from a bunch of tree-hugging tofu munchers and not suited to international diplomacy and international politics. I couldn't disagree more profoundly.
The causes of climate change, we've got to address, but the effects as you've heard from Nasrin, you've heard from Antonio in those speeches just now, are absolutely clear. I think of a young man forced onto the road when his home becomes a desert. One of 16 million people displaced every year as a result of weather related disasters, and weather related disasters that are associated with climate change.
He goes to some camp. He becomes prey for a violent extremists, people who radicalize him. And the effects of that radicalization are felt around the world.