Moderate warming tipped to produce flood of refugees into Europe

Over the past two decades, the global population of forcibly displaced people has grown substantially, from 33.9 million in 1997 to 65.6 million in 2016, and it remains at a record high, according to the United Nations High Commissioner for Refugees. 

Most of these people have been forced to leave their homes and seek asylum elsewhere because of regional conflicts, but the crisis will be greatly exacerbated by climate change, according to a new study by Wolfram Schlenker and Anouch Missirian, researchers from Columbia University in the United States, and published in the journal Science.

By the end of the century, say the authors, even under a slow-warming scenario in which future greenhouse gas emissions decline, applications into the EU could increase by 28%. They could increase by 188% under a fast-warming scenario where future emissions continue to increase.

As part of this relationship between fluctuations in asylum applications and weather anomalies, they identified a trend that begins to affect countries that have average temperatures around 20 degrees Celsius and is more pronounced in countries with higher baseline temperatures. 

Previous studies have found links between weather variations and migration, but Missirian and Schlenker examined the relationship on a global scale. They analysed EU asylum applications filed from 103 countries between 2000 and 2014 (giving an average of 351,000 applications a year), comparing these numbers with environmental data across those countries during the corresponding time, and adjusting for other factors such as conflict. 

Their research indicates that a global temperature increase of 2.6 to 4.8 degrees may result in 660,000 additional applications into the EU per year by the end of this century. 

They note that weather fluctuations are known to affect agriculture and gross domestic product, even in developed and industrialised countries that do not have a large agricultural sector. This may help explain the trends observed in this study, they say.

The report cites a 2015 study in which unrest in Syria was found to be preceded by a record drought that led to lower agricultural yields and forced farmers to migrate to urban areas. Although that study does not attribute the Syrian conflict to the drought, the authors argue that it added another stress factor.

The report also notes that the US Pentagon calls climate change a “threat multiplier”. 

However, lead author Schlenker says, “Instead of looking at individual countries, we take a step back and investigate the role of weather shocks in global distress-driven migration to the EU in 2000–2014, preceding the recent crisis. 

“Asylum applications to the EU from the 103 source countries in our sample totaled 1.5 million in 2015; that is, more than four times the average in our sample. Previous studies had found a relationship between weather variations and migration, but ours is the first to focus on distress-driven migration (as measured by asylum applications) on a global scale.”

Schlenker says their research focused on the EU “because it receives the largest share of asylum applications and, despite having a high rejection rate, remains a major provider of international protection”. Also, colder countries in Europe outside the EU are predicted to account for fewer asylum applications in a warming world, whereas hotter countries, especially in Asia and Africa, are expected to see sizable increases.

In sampling the 103 non-OECD source countries that reported asylum applications to the EU in each year between 2000 and 2014, the researchers found that the majority of asylum applications per year, about 140,000, came from the 31 Asian countries, including Afghanistan and Iraq, each of which supplied about 25,000 applicants. The 46 African and 11 non-EU countries in Europe accounted for about 100,000 applicants each, and 16 countries in the Americas accounted for the rest. For example, 55,943 people from Serbia applied for asylum in the EU in 2000. The research sample covered 93% of all applications.

Schlenker says they found a statistically significant relationship between fluctuations in asylum applications and weather anomalies: applications are lowest for average temperatures around 20 and increase if the weather is too cold or too hot. 

Total precipitation, on the other hand, is not an important predictor of migration, the report says, consistent with previous research that indicates that temperature, as opposed to precipitation, is a stronger predictor of conflict. 

Moreover, it says, the relative changes in temperature under future climate change scenarios will affect crop yields more than do precipitation changes.

The report finds a “strong nonlinear relationship” between agricultural yields and temperature. 

“Moderate temperatures (i.e., in the lower 20 degrees range) over the growing season are ideal, with both hot and cold temperatures reducing yields. Second, gross domestic product (GDP) growth rates have been found to be very sensitive to temperature, even on the nonagricultural components of the GDP and even in industrialised countries,” the researchers write.

“For both yields and GDP, being too hot is worse than being too cold.”

A further factor noted in the report is the relationship between weather and aggressive behaviour, which increases with temperatures that reduce agricultural output. 

“Our findings support the assessment that climate change, especially continued warming, will add another ‘threat multiplier’ that induces people to seek refuge abroad,” Schlenker says. “Weather impacts in low-income source countries will not be confined to those countries or regions but will instead likely spill over into developed countries through increased refugee flows.”