Secretary of State John Kerry speaks at the Milan Expo 2015 in Milan, Italy, on Saturday, October 17, 2015. (Photo: State Department)

(CNSNews.com) – Secretary of State John Kerry said Saturday that climate change was a contributing factor in the Syrian civil war, alluding to a study last spring that linked drought-driven urbanization to the conflict that began in 2011.

“It is not a coincidence that immediately prior to the civil war in Syria, the country experienced the worst drought on record,” he said in a speech at the Milan Expo 2015 in Italy.

“As many as 1.5 million people migrated from Syria’s farms into Syria’s cities, and that intensified the political unrest that was beginning to brew,” he continued.

“Now, I’m not telling you that the crisis in Syria was caused by climate change. No, obviously, it wasn’t. It was caused by a brutal dictator who barrel-bombed, starved, tortured, and gassed his own people,” Kerry said.

“But the devastating drought clearly made a bad situation a lot worse.”

Unrest in Syria erupted in March 2011, when demonstrators, evidently inspired by protest movements in Tunisia, Egypt, Libya and Yemen, began calling for political reforms, an end to five decades of emergency law, and freedom for political prisoners – at the time estimated to number around 4,000.

In the southern town of Dara'a, 60 miles from Damascus, security forces opened fire on protesters demanding reforms – and the release of more than a dozen school students arrested for writing anti-regime slogans on walls. Four people were killed.

Protests against the Assad regime quickly spread, and over the ensuing month more than 170 people were killed, the majority by live ammunition fired by security forces. By early August the death toll had reached 1,600.

The unrest degenerated into a full-blown civil war, complicated by the proliferation of extremist groups and foreign support for various parties in the conflict. The U.N. estimates that more than 250,000 Syrians have died, and millions have sought refuge in neighboring countries while others seek new lives in Europe.

The notion of climate change as a factor in the conflict began making headlines last March, when a study published in the Proceedings of the National Academy of Sciences highlighted a severe drought in Syria and surrounding parts of the Middle East in 2007-2010 that triggered a mass migration from farms to urban centers.

The authors, from the University of California Santa Barbara, Columbia University and Columbia’s Lamont–Doherty Earth Observatory, referred to the figure of 1.5 million, as cited by Kerry. (A footnote in the study links to a 2009 news report in which an official from the regime’s State by Planning Commission is quoted as saying the drought had forced between 1.25 and 1.5 million people to leave their villages for the suburbs of Syrian cities.)

“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,” the authors wrote.

They said that the drought – which they attributed in part to “human influences on the climate system” – exacerbated other factors that contributed to the Syrian unrest, including corruption, unemployment and inequality.

In his speech in Milan, Kerry pointed to the refugee and migrant crisis besetting Europe, and said that without action on climate change, future refugee flows could be even worse.

“Here in Europe, you’re in the middle of one of the worst refugee crises in decades,” he said. “And I would underscore, unless the world meets the urgency of this moment, the horrific refugee situation that we’re facing today will pale in comparison to the mass migrations that intense droughts, sea-level rise, and other impacts of climate change are likely to bring about.”

He linked his appeal to the forthcoming U.N. climate conference in Paris, France, which governments and activists hope will deliver a far-reaching new global climate agreement.

“We need every country on the same page, all pushing for an ambitious, durable, and inclusive agreement that will finally put us on the path towards a global clean-energy future,” Kerry said.