Is there a link between climate change and terrorism?

Barack Obama has spent considerable time in recent months publicly explaining his positions on both climate change and violent extremism.

But in a Coast Guard commencement address last week, the U.S. president deliberately combined the two, saying that climate change "constitutes a serious threat to global security."

• Jeb Bush criticizes Obama for overstating climate change issue
• ISIS poses bigger threat after nearly a year of coalition bombing: Nahlah Ayed
• Iraq lacks 'will to fight' ISIS, U.S. says

Security analysts say the idea has been percolating in Western military circles for the past few years, but there is still skepticism about a direct link.

Francesca de Chtel, an Amsterdam-based researcher with an expertise in water issues in the Arab world, says that while issues such as climate change and terrorism are real, "bundling them all together" is problematic.

"Climate change implies a lot of unknowns, and then if you add to that conflict, which also implies unknown outcomes, it just creates an air of uncertainty and fear," she says.

Stage-setting for climate talks

Still, for Obama, "climate change constitutes a serious threat to global security, an immediate risk to our national security, and, make no mistake, it will impact how our military defends our country," he told over 200 graduating Coast Guard cadets in Connecticut.

The same day as Obama's speech, the White House released a paper called "The National Security Implications of a Changing Climate."

It concludes that climate change "will change the nature of U.S. military missions, demand more resources in the Arctic and other coastal regions vulnerable to rising sea levels and other impacts, and require a multilateral response to the growing humanitarian crises that climate change is predicted to bring."

Since the mid-term elections, the president has emphasized environmental degradation as one of the world's most pressing issues. The Obama administration is onside with the majority of scientists who believe that man-made greenhouse gases are largely responsible for climate change.

Jeffrey Mazo, a consulting senior fellow on environmental issues at the International Institute for Strategic Studies in London, feels the speech reflects Obama's belief in the importance of tackling the environment and was a way to "mobilize support" in anticipation of the Paris climate talks this fall.

Origins in the '80s

Mazo says U.S. research into the connection between climate change and global conflicts dates back to the early 1980s, and that the security establishment has been looking at the relationship seriously for more than a decade.

Last year, the U.K.-based International Institute for Strategic Studies released a report that said environmental factors, such as water availability, soil degradation and severe weather events, "have been implicated in at least 73 conflicts since 1980."

One of the effects of climate change is that it disrupts rain patterns and can lead to drought, which in turn wreaks havoc on farm yields and causes famines or raises the price of food for consumers.

With this in mind, there has been significant research into whether a severe drought in the Levant between 2006 and 2010 laid the foundations for the Syrian civil war, a conflict that has not only led to widespread violence and displacement but facilitated the rise of ISIS and other radical groups.

A water researcher, deChtel says "a direct link is very hard to make, because there were so many other factors."

She also notes that drought has long been part of the Syrian climate and that this particular dry spell coincided with a cut in government farming and fuel subsidies and mismanagement of the water supply, which were also factors in the popular unrest.

So was the general mood of dissent that swept through North Africa and the Middle East in 2010 and 2011.

"Without the Arab Spring, I don't think anything would have happened in Syria," says de Chtel.

For his part, Mazo says one of the best examples of the influence of climate change on national security can be found in Darfur, Sudan.

The UN has acknowledged that the long-running drought there increased tension between black farmers and Arab nomads over water supplies, and eventually caused rebel groups to wage war against the government over the perceived oppression of non-Arab citizens.

"If you want to say, 'What was the main cause of the outbreak of violence in Darfur?', I couldn't pin it down," says Mazo. "But if you said, 'Was climate change a factor?' I would say, definitely yes."

'Threat multiplier'

Obama's May 20th speech was pilloried by many Republicans, who were incredulous that the president would use climate change to explain the rise of violent movements such as the Islamic State in Iraq and Syria, which a U.S.-led coalition is currently struggling to contain.

There is some misunderstanding on the issue, says Francesco Femia, founding director of the Centre for Climate and Security, an independent Washington think tank.

"I don't think the president is claiming that climate change in any way directly or exclusively causes conflicts," says Femia.

Rather, the government is just acknowledging that "we have to factor in what climate is doing to certain situations on the ground," he says.

Last fall, then-U.S. defence secretary Chuck Hagel called climate change "a threat multiplier," saying that it has "the potential to exacerbate many of the challenges we already confront today."

Climate change is not necessarily a more significant threat multiplier than population growth or the rise of Islamic fundamentalism, says Mazo.

What makes it unique, however, "is that it's a global phenomenon, and that it's new."