Britain’s Prince Charles on a visit to the Biodiversity Conservation Center in Perth, Australia, on Nov. 15. (Richard Wainwright/Agence France-Presse via Getty Images)

Britain’s Prince Charles has blamed climate change in part for the Syrian war and warned that global warming could exacerbate similar conflicts worldwide.

Charles’s comments — in an interview broadcast Monday — came exactly one week before the start of a United Nations climate change conference in Paris, where he plans to deliver a keynote address. Unless world leaders take action to slow the impact of climate change, “it’s going to get so much worse,” Charles warned in the interview with Sky News, which was recorded before the Nov. 13 terrorist attacks in Paris.

“Some of us were saying 20 something years ago that if we didn’t tackle these issues you would see ever greater conflict over scarce resources and ever greater difficulties over drought, and the accumulating effect of climate change, which means that people have to move,” he said. “And, in fact, there’s very good evidence indeed that one of the major reasons for this horror in Syria, funnily enough, was a drought that lasted for about five or six years, which meant that huge numbers of people in the end had to leave the land.”

Charles, a longtime environmentalist, is the latest person to blame the Syrian conflict on climate change. Various leading politicians, academics and military officials have made similar claims in recent years.

“It’s not a coincidence that immediately prior to the civil war in Syria, the country experienced its worst drought on record,” Secretary of State John F. Kerry said in a speech at Virginia’s Old Dominion University on Nov. 10. “As many as 1.5 million people migrated from Syria’s farms to its cities, intensifying the political unrest that was just beginning to roil and boil in the region.”

Climate change was “obviously” not the main reason for the crisis, Kerry added, but the drought “exacerbated instability on the ground.”

[There’s a surprisingly strong link between climate change and violence]

Democratic presidential candidates Martin O’Malley and Bernie Sanders have made similar claims. And although the fact-checker PolitiFact found thatSanders overstated a direct link between climate change and terrorism, it rated O’Malley’s description of the “cascading effects” of climate change on instability as “mostly true.”

O’Malley based his claim on a substantial March study published in the Proceedings of the National Academy of Sciences. The study found that the drought “had a catalytic effect with dire consequences for Syrians” — and that there is “strong evidence” that the drought was connected to climate change, lead author Colin P. Kelley wrote in a related article for the International Peace Institute at the time.

The drought drove an “unprecedented rise” in Syrian food prices, leading to a “dramatic increase” in nutrition-related diseases among children in Syria’s northeastern provinces, the authors found. That led to the internal displacement of as many as 1.5 million Syrians, swelling the country’s urban centers.

“The rapidly growing urban peripheries of Syria, marked by illegal settlements, overcrowding, poor infrastructure, unemployment, and crime, were neglected by the Assad government and became the heart of the developing unrest,” they contend.

Models they developed suggest that severe droughts such as the one in Syria were two to three times more likely “to occur under the effects of climate change than in its absence,” Kelley wrote.

Other researchers have predicted increased armed conflict in Africa driven by climate change.

And a 2013 academic review of the literature found “that there is more agreement across studies regarding the influence of climate on human conflict than has been recognized previously.”

[Is it too late to solve the mess in the Middle East?]

But these concerns aren’t limited to academics or politicians. In its 2014 Quadrennial Defense Review, the Defense Department described the effects of climate change as “threat multipliers” that could worsen the conditions that facilitate terrorism.

Here’s how the report describes the chain of events (emphasis added):

Climate change poses another significant challenge for the United States and the world at large. As greenhouse gas emissions increase, sea levels are rising, average global temperatures are increasing, and severe weather patterns are accelerating. These changes, coupled with other global dynamics, including growing, urbanizing, more affluent populations, and substantial economic growth in India, China, Brazil, and other nations, will devastate homes, land, and infrastructure. Climate change may exacerbate water scarcity and lead to sharp increases in food costs. The pressures caused by climate change will influence resource competition while placing additional burdens on economies, societies, and governance institutions around the world. These effects are threat multipliers that will aggravate stressors abroad such as poverty, environmental degradation, political instability, and social tensions — conditions that can enable terrorist activity and other forms of violence. 

Then-Defense Secretary Chuck Hagel used the same phrase — “threat multiplier” — in a speech last year, warning that the glacial melt could set off a chain of events wreaking havoc worldwide.

“Destruction and devastation from hurricanes can sow the seeds for instability,” he said at the Conference of Defense Ministers of the Americas. “Droughts and crop failures can leave millions of people without any lifeline and trigger waves of mass migration.”

A year earlier, Navy Adm. Samuel J. Locklear III — who was the top military official monitoring threats from the likes of North Korea, along with conflicts between China and Japan — called climate change the biggest long-term security threat in the Pacific region.

Climate change “is probably the most likely thing that is going to happen … that will cripple the security environment, probably more likely than the other scenarios we all often talk about,” he told the Boston Globe.

Related stories:

Drought helped cause Syria’s war. Will climate change bring more like it?

What the ruins of Kobane tell us about the destruction of Syria

How climate change makes the world more violent

Whether or not global warming leads to more war, it hurts vulnerable people