Violence has cast a long shadow over a climate summit opening in Paris on Monday, two weeks after 130 people were killed in a coordinated jihadist onslaught on the French capital.

As more than 150 world leaders prepared to meet under heightened security, analysts warned of an increasingly war-torn future facing humanity if they fail to limit global warming.

The Paris attacks on November 13 were claimed by the Islamic State group that has a brutal war in Syria -- a conflict rooted in part, experts say, on an historic drought from 2006 to 2010.

It drove some 1.5 million farmers and herders off their land and into cities and towns like Homs, Palmyra and Damascus.

"It's not a coincidence that, immediately prior to the civil war in Syria, the country experienced the worst drought on record," US Secretary of State John Kerry said in Milan last month.

According to Francesco Femia of The Center for Climate and Security in Washington DC, research has shown the Syrian drought "was made two-to-three times more likely because of climate change".

Many a report has suggested that water scarcity, exacerbated by global warming, has fuelled deadly conflicts in the Middle East and Africa, thus contributing to the flood of refugees seeking a better life in Europe and elsewhere.

Experts warn the situation is likely to worsen as climate conditions become more hostile to human survival -- and people become more desperate.

'Threat multiplier'

While climate change is not, on its own, a direct cause of conflict, competition for dwindling water and land resources can certainly fan flames in an already volatile situation, say analysts.

"Climate change is a 'threat multiplier'," Femia told AFP.

"If, in a certain place, you introduce climate stress to the kinds of natural resource deficiencies that can contribute to state failure or conflict, you increase the likelihood of a conflict occurring."

In July, an international team of scientists, policy analysts, financial and military risk experts, cautioned that food and water shortages would boost future conflicts over resources, mass migration and state failure.

Even sophisticated governments may be unable to deal with the combination of pressures, said the report entitled "Climate Change, a Risk Assessment".

"The expansion of ungoverned territories would in turn increase the risks of terrorism," with large numbers of marginalised and disenfranchised people to recruit from, said the report compiled for policymakers.

Negotiators from 195 nations will gather in Paris until December 11 to craft a pact to stave off worst-case-scenario climate change by limiting emissions of climate-altering greenhouse gases.

The goal is to limit warming to two degrees Celsius (3.6 degrees Fahrenheit) above mid-19th century levels, when industrial-scale emissions began.

Even a 2 C increase will mean a land-gobbling sea level rise, longer and more frequent droughts, and increasingly acute water shortages, scientists say. But the projected impacts worsen significantly beyond the two degree threshold.

A recent report by the Washington-based World Resources Institute warned that "high water stress" in Syria and its neighbours "will likely deteriorate in the coming decades."

"A well-documented path can connect water scarcity to food insecurity, social instability and potentially violent conflict," it said, adding that "climate change amplifies scarcity worries."

Earlier this month, Toby Lanzer, the UN's humanitarian coordinator for the Sahel, warned that Europe's migrant crisis will become worse if the Paris climate summit fails countries in the drought-stricken Lake Chad basin.

Some 2.5 million people in the region have been displaced by a toxic mix of drought, poverty and conflict.

An estimated 850,000 migrants have entered the European Union so far this year, mainly from the Middle East and North Africa.

'Increasing evidence'

"There is increasing evidence ... that there may be a statistically-significant correlation between climate change and conflict," Femia said.

This was borne out, he said, "in places like Kenya, where a changing climate has been linked to conflicts between pastoralists and farmers, and in Syria, where a mass internal displacement of people may be connected to political turmoil."

President Francois Hollande of climate summit host France, also linked climate and conflict in a magazine interview this week.

"Even if we solve the problem of Syria, we will still be confronted with the migration of millions of people forced to move because they can't cultivate their land," he told l'Express.

"This disorder can engender new conflicts."