Temperature affects human migration, new research shows

Living on Earth

If global warming gas emissions continue at the present pace, the number of asylum-seekers to Europe could increase by nearly 200 percent, according to a new study.

Unrest, war and terrorism have boosted the number of desperate people fleeing parts of the Middle East and Africa, but new research from Columbia University economist Wolfram Schlenker shows a warming planet may also be a culprit.

The research, which appears in the journal, Science, links higher temperatures in agricultural regions with the flood of people seeking asylum in the European Union. If current temperature trends continue, the EU can expect an additional 600,000 or more refugees begging to enter each year — nearly twice as many as those who currently seek asylum.

The researchers examined the immigration numbers to EU destination countries and looked at 103 source countries for which they had both immigration and temperature data, Schlenker explains. They used satellite scans to identify agricultural areas and found that these areas are responsible for 93 percent of all asylum applications to the EU.

The paper, Schlenker says, is in two parts. The first links year-to-year changes in weather to changes in asylum applications over a period of 15 years, starting with 2000. It asks a straightforward question: Was it hotter than average or colder than average and, as a result, did asylum applications to the European Union from that country increase or decrease?

“Around 20 degrees Celsius, which is 68 degrees Fahrenheit, we see that asylum applications seem to be lowest. If you're hotter or colder, they tend to increase,” Schlenker explains. "This implies that if you're a country which currently has a temperature that is higher than this optimal 20 degree Celsius level, you would see an increase with warming. If you are in a country that currently has a temperature that is lower than the 20 degrees Celsius optimum, you would actually see a decrease from warming."

The second part of the paper uses this statistical relationship to predict what could happen to asylum applications by the end of this century. Under a "business-as-usual" scenario — continued use of fossil fuels and high population growth — asylum applications to the EU are predicted to increase by 188 percent.

While in scientific research there’s a big difference between correlation and causation, Schlenker feels confident that the first part of the paper reveals a causal relationship. “Those weather shocks, whether you're hotter than normal or colder than normal, are random and exogenous,” he explains. “So, that's not just a correlation. I'm pretty sure this is a causal relationship."

The second part, which uses the observed statistical relationship and fast-forwards 80 years into the future, makes an assumption that events essentially remain constant, but “you might argue that in 80 years things might change,” Schlenker says. But they could change in either direction.

“On the one hand, people might adapt [and] become better at withstanding higher temperatures,” he explains. “Therefore, we might expect that in the future you see less sensitivity to temperature than we observe now. On the other hand, you might argue that right now we're basically measuring the effect of [an occasional] bad outcome … while in the future, with climate change, we would observe [these outcomes] years in a row, [which] might lead to further unraveling.”

Despite the potentially tragic outcomes his research predicts, Schlenker remains optimistic.

“There are myriad impacts from climate change in various countries,” he says. “I also really believe in human ingenuity. I really believe that humans have ways to combat climate change, and so far, I feel like the best estimate is that it's not that costly, considering what the potential benefits might be. So, I personally feel that with human action, with human engineering and new developments, it might very well still be feasible to achieve something, but what we need is the political willingness to engage in that.”

This article is based on an interview that aired on PRI’s Living on Earth with Steve Curwood. 

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