They're not saying it will cause violence, but will be an added factor making things even more dangerous. Fights over resources, like water and energy, hunger and extreme weather will all go into the mix to destabilise the world a bit more, says the report by the Nobel Peace Prize-winning Intergovernmental Panel on Climate Change.
Climate change will not directly cause conflict but it will exacerbate issues of poor governance, resource inequality and social unrest, retired US Navy admiral David Titley, now a Pennsylvania State University professor of meteorology, wrote in an email. The Arab Spring and Syria are two recent examples.
But Titley, who wasn't part of the IPCC report, says if you are already living in a place affected by violent conflict I suspect climate change becomes the least of your worries.
That illustrates the tricky calculus of climate and conflict, experts say. It's hard to point at violence and draw a direct climate link to say how much blame goes to warming and how much is from more traditional factors like poverty and ethnic differences. Then looking into future is even more difficult.
If you think it's hard to predict rainfall in one spot 100 years from now, it's even harder to predict social stability, said Jeff Severinghaus, a climate scientist at the Scripps Institution for Oceanography who isn't part of this climate panel. Obviously that's going to be controversial. The most important thing is that it's going to be talked about.
Severinghaus and other scientists say this will be one of the more contentious issues as the panel representing more than 100 nations meets here and edits word-by-word a 30-page summary of the multi-volume report for political leaders. Observers said the closed door meeting went through the security and climate section Sunday, in the hurried last hours of editing.
There's an entire 63-page chapter on security problems, but most leaders will read the handful of paragraphs summarising that and that's where there may be some issues, he says.
The chapter on national security says there is robust evidence that human security will be progressively threatened as climate changes. It says it can destabilize the world in multiple ways by making it harder for people to make a living, increasing mass migrations, and making it harder for countries to keep control of their populations.
The migration issue is big because as refugees flee storms and other climate problems, that adds to security issues, the report and scientists say.
Poverty is the issue when it comes to security problems and policies to fight climate change increase poverty, says David Kreutzer at the conservative Heritage Foundation in Washington. But environmental groups such as the Environmental Justice Foundation are issuing reports that dovetail with what the IPCC is saying.
Titley holds out hope that if nations deal with climate change jointly, it can bring peace instead of war.
A woman writes on a wall dedicated to the passengers of the missing Malaysia Airlines flight MH370 during the the Malaysian F1 Grand Prix at Sepang outside Kuala Lumpur. (Reuters)