A United Nations climate panel for the first time is connecting hotter global temperatures to hotter global tempers.
Top scientists are saying climate change will complicate and worsen global security problems, such as civil wars, strife between nations and refugees.
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. The summary of the report was being finalised at the weekend by the panel in Yokohama.
Report lead author Chris Field, of the Carnegie Institution of Science in California, said the summary of 2007 didn't mention security issues.
"There's enough smoke there that we really need to pay attention to this," said Ohio University security and environment professor Geoff Dabelko, one of the lead authors of the report's chapter on security and climate change.
For the past seven years, research in social science has found more links between climate and conflict, with the full report referencing hundreds of studies on climate change and conflict.
The US Defence Department earlier this month, in its four-yearly strategic review, called climate change a "threat multiplier" to go with poverty, political instability and social tensions worldwide. Warming would trigger new problems but also provide new opportunities for resources and shipping routes in places such as the melting Arctic.
After the climate panel's 2007 report, UN Secretary General Ban Ki-moon wrote that along with other causes, the conflict in the Darfur region of western Sudan "began as an ecological crisis, arising at least in part from climate change".
While the IPCC report this year downplays global warming's role in that particular strife, saying other issues were far more influential, the report's drafts do add that there is "justifiable common concern" that climate change increases the risk of fighting in similar circumstances.
"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 professor of meteorology, said. "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. Looking into the 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 and edits a 30-page summary of the multi-volume report for political leaders. Observers said the meeting went through the security and climate section yesterday, in the hurried last hours of editing.
There's a 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 destabilise 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.