Vermont Sen. Bernie Sanders still believes global warming is the greatest threat to America’s national security, rehashing the stance taken by Democratic politicians in recent years that carbon dioxide emissions are more dangerous than terrorists.

“If we are going to see an increase in drought, in flood, and extreme weather disturbances as a result of climate change, what that means is that people all over the world are going to be fighting over limited natural resources,” Sanders told CBS’ “Face the Nation” Sunday, doubling-down on remarks he made during the Democratic presidential debate Saturday night. (RELATED: Sanders: Climate Change Still Greatest Threat To National Security [Video])

“If there is not enough water, if there is not enough land to grow your crops, then you’re going to see migrations of people fighting over land that will sustain them. And that will lead to international conflict,” Sanders said.

Sanders, who’s in the running for the Democratic nomination, isn’t the only liberal politician to make the connection between conflict and climate. Sanders’ primary opponents former Secretary of State Hillary Clinton and former Maryland Gov. Martin O’Malley has repeatedly claimed global warming contributed the Syrian Civil War, and therefore the rise of the Islamic State.

President Barack Obama himself has also said global warming is the U.S.’s greatest national security threat.

“It is not a coincidence that immediately prior to the civil war in Syria, the country experienced the worst drought on record,” Secretary of State John Kerry said in an October speech.

Sanders and other politicians acknowledge “terrorism is a major issue that we’ve got to address today,” but still name rising carbon dioxide emissions from fossil fuels represent the greatest long-term threat to Americans — an increasingly popular claim as United Nations climate summit approaches.

“In fact, climate change is directly related to the growth of terrorism,” Sanders said during Saturday’s debate. “And if we do not get our act together and listen to what the scientists say you’re gonna see countries all over the world– this is what the C.I.A. says, they’re gonna be struggling over limited amounts of water, limited amounts of land to grow their crops. And you’re gonna see all kinds of international conflict.”

The U.N. global warming summit will be held in Paris, which suffered a massive terrorist attack Friday. A group of ISIS gunmen killed more than 120 people in a series of attacks launched across the French capital. (RELATED: French Authorities Secure Concert Hall: 12 Freed, 118+ Dead)

The attack has cast a cloud over the summit, but environmentalists say the terror attacks have only made it more likely countries will back an international agreement to cut carbon dioxide emissions. Even French officials want a climate treaty to be signed, despite the attacks.

“Nations will be more likely to work closely with France to produce a constructive outcome,” former U.S. diplomat Nigel Purvis told Politico, agreeing with claims that the Paris attacks have only bolstered support for a treaty.

Is Global Warming Driving Terrorism?

Simply bolstering support for a U.N. climate treaty misses the point of whether global warming is a driver of violent conflict.

The news magazine Time came to Sanders’ defense Sunday, arguing that “many academics and national security experts agree that climate change contributes to an uncertain world where terrorism can thrive.” Time’s Justin Worland pointed to a 2014 Defense Department report and another study published in the Proceedings of the National Academy of Sciences earlier this year to bolster such claims.

“The worst drought on record in the Middle Eastern country has created instability for farmers and threatened the food supply,” he wrote. “At the same time, the government has struggled to hold on to power across the country in the face of militant groups and millions of Syrians have fled their homeland.”

But it’s unclear if global warming actually had an detectable impact on Syria’s climate in the run-up to the start of the civil war in 2011.

Syria has a long history of droughts, and poor government agricultural policies encouraged farmers to grow cotton and other water-intensive cash crops — despite the country’s drought-ridden past.

“It is not until you dig pretty deep into the technical scientific literature, that you find out that the anthropogenic climate change impact on drought conditions in the Fertile Crescent is extremely minimal and tenuous—so much so that it is debatable as to whether it is detectable at all,” Chip Knappenberger and Patrick Michaels, climate scientists at the libertarian Cato Institute, wrote in March.

Drought “conditions which are part and parcel of the region climate and the intensity and frequency of which remain dominated by natural variability, even in this era of increasing greenhouse gas emissions  from human activities,” the scientists wrote.

While a drought no doubt made things worse for Syrians, contributing to rising tensions, the cause of conflicts almost always stem from politics and not environmental causes. National security expert Jeff Kueter with the George C. Marshall Institute wrote in a 2014 paper that “[p]olitical and economic factors prove to be much better and more compelling explanations for men to fight other men.”

Claims that global warming will drive more violent conflict also hinges on the argument that warming will cause extreme weather events, like droughts, to become more frequent and intense. But that doesn’t seem to be occurring like climate models predicted.

The Intergovernmental Panel on Climate Change (IPCC) found in its latest major report there’s no strong evidence extreme weather is getting more frequent or extreme. The IPCC said “there is not enough evidence at present to suggest more than low confidence in a global-scale observed trend in drought or dryness since the middle of the 20th century due to lack of direct observations, geographical inconsistencies in the trends, and dependencies of inferred trends on the index choice.”

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