Photo: AP

The civil war in Syria and unrest in Iraq and other parts of the world has spawned a huge humanitarian crisis. It’s the largest mass migration in history, and the shock waves will reverberate for decades to come. Climate change may even have played a role, particularly in destabilizing Syria.

New research published on Thursday in Science suggests that climate change will only put more stress on vulnerable populations. If carbon pollution continues unchecked, asylum seekers looking for refuge in the European Union could increase nearly 200 percent by century’s end. The findings are highly provocative—and as with all cutting edge research, come with multiple caveats—but are an early attempt to understand how rising temperatures can destabilize regions and force future migrations.

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Because the findings are on the frontier, more work is needed to tease out just how climate change could mix with other factors that force people to flee their homes.

“I think this is an excellent paper on a very important, much hypothesized, and still poorly understood topic,” Marshall Burke, a climate and conflict researcher at Stanford not involved with the study, told Earther. “Overall it’s a much needed piece of evidence on a very important topic, and is going to be very useful for both researchers and policymakers.”

The research, performed by two Columbia economists, looks at the relationship between climate and asylum seekers using 2000-2014 data on asylum seekers coming to the European Union, and growing season temperature and precipitation fluctuations in their home country. The idea is that in developing countries that rely heavily on small-scale agriculture, any shifts in weather could trigger people to leave.

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Previous studies have shown that Syria’s descent into civil war was preceded by its worst drought in at least 900 years, and that climate change almost certainly played a role. First-time asylum seekers from Syria have accounted for more than a quarter of the 2.46 million applications to the European Union over the past two years.

The researchers don’t include those years, though, instead focusing on 2000-2014. The European Union received 351,000 asylum applications over that period from 103 countries included in the study. Those applications account from roughly a tenth of all refugees attempting to enter the European Union.

They then compared those applications with maize growing season temperature, showing that there are fewer asylum applicants when the average temperature is around 68°F. That’s right around the ideal growing temperature for maize to maximize yields. Applications increase if it gets hotter or colder because yields decrease, the researchers posit. Three times more applications were accepted in the two years following a temperature or rainfall shock, according to the new study.

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Using this relationship, they modeled what would happen as the world gets hotter and all other factors, such as geopolitics and gross domestic product, remain the same. Under a moderate warming scenario where we start to get a handle on carbon pollution by mid-century, asylum applications would still increase by 28 percent, to 98,000 per year at the end of the century. If we let carbon pollution continue on its current trend, though, really bad things could happen. Their findings show asylum seekers could skyrocket by 660,000 applicants annually, a 188 percent increase compared to 2000-2014.

That’s a recipe for widespread instability and could reshape how open (or closed) borders. But it also comes with caveats.

Burke said he found the the assumption of a relationship between crop yields and acceptance rates “a little surprising given that the EU pointedly does not want to take economic migrants, and rather wants to take people fleeing war or persecution.”

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Beyond the acceptance rates, there’s also oversimplification going on, according to Justin Ginnetti, the head of data analysis for the Internal Displacement Monitoring Centre.

Migration is an intensely personal issue, and people leave by force or by choice for reasons beyond crop yields. Larger geopolitical forces are often at work, which is in part why boiling an analysis down to just temperature is problematic. Ginnetti said there are more than 1,500 development indicators the World Bank uses that could play a role in migration.

The other big issue underpinning the study is assuming all things remain equal out to 2100 aside from climate change’s influence on temperature. The world is going to drastically change, including continuing the growth of urban areas. More people living in cities means fewer people will be directly impacted by changes in agricultural temperatures.

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Crop yields may decrease in hot years in, say, Kenya. That will directly impact farmers, but if there’s fewer of them, there will be fewer overall migrants. Heat waves or droughts could drive up food prices in cities, but maybe there will be more interconnected markets in 2100 to help blunt some of the price upticks. Or for countries with a lot of land, people might just move internally to where growing conditions and food prices are lower. Or if a brutal civil war breaks out, migrations could spike even more dramatically. Case in point: the 2.46 million asylum seekers to the European Union over the past two years, which is more than seven time the number of applicants over the preceding 14 years.

There are so many complexities here it makes it hard to hang a hat on the relationship between growing season temperatures and migration, let alone asylum seekers.

“Let’s say you created this model just after the Dust Bowl and calibrated it to fit the data for farmers in the Midwest,” Ginnetti told Earther in an email. “Then let’s say you projected from the 1930s to 2000 and based the migration outcomes on the changes in temperature (had the analyst in question known about the warming to come). Well, they’d be pretty surprised that the migration patterns of 2000. (‘I mean, hell, people migrating to Arizona and Nevada?!’)”

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Despite the shortcomings, this isn’t a study to dismiss out of hand. We know climate change is a threat multiplier, and we’re still figuring out just how much chaos it adds to already messy system.

We really need to know what rising temperatures, shifting rainfall patterns and more severe storms mean for society, particularly its most vulnerable members. We need to know who will suffer and why to avert catastrophe. This type of boundary-pushing research gets us closer to understanding those impacts and (one would hope) closer to doing something about them.