Climate change often evokes images of powerful hurricanes and rising sea levels, which is perfectly understandable. What often falls by the wayside, though, is the fact that this anthropogenic phenomenon could trigger an entirely new refugee crisis, one that may see up to 2 billion people escape its ravages by the end of the century.

Now, a new study in Science has attempted to estimate the number of climate refugees that will seek asylum in the European Union (EU). By 2100, under a fast-warming scenario wherein emissions continue to rise – a “business-as-usual” future – the EU will see a 188 percent rise in applications.

That’s 660,000 additional applications per year, a not insignificant number. From the turn of the millennium until now, about 351,000 people per year from 103 countries sought asylum in the EU. This means that if nothing is done to stop climate change, then a tripling of asylum seekers could occur, which may spark a refugee crisis of unprecedented proportions.

Even under a slower warming scenario, in which emissions begin to decline across the world, those seeking asylum from climate change-linked extreme weather events will increase by around 28 percent – which equates to around 98,000 extra asylum seekers per year.

This study, penned by a pair of researchers from the School of International and Public Affairs at Columbia University, is based on a relatively simple calculation. Their efforts largely focus on nations whose economies are still fairly agrarian in nature.

Although this fluctuates from country to country, the authors suggest that – based on pre-existing data – a moderate optimum temperature of 20°C (68°F) is required for agriculture to thrive. Any higher (or lower) and this begins to falter; crops cannot adjust or keep up.

An analysis of past asylum seeker information revealed that a correlation existed between deviations from this optimum and the number of people seeking asylum to the EU. Significantly, the team found that as the mercury rose beyond this optimum, the number of asylum seekers from these countries didn't just increase; they also accelerated.

Assuming that no other factors play a role in this regard, the researchers simply extrapolated this trend to 2100 based on various global warming scenarios.

“Our findings support the assessment that climate change, especially continued warming, will add another 'threat multiplier' that induces people to seek refuge abroad,” the team conclude in their paper.

This research, although jarring in its conclusions, isn’t unique in its endeavor. The link between climate change and human behavior has been looked into before, most notably when it came to the conflict in Syria.

Although a key 2015 study didn’t state that revolution, war, and a mass exodus broke out simply because of a regional, climate change-linked drought, it did suggest that the phenomenon was an exacerbating factor. Another study published last year found a surprisingly linear correlation between rising temperatures and the levels of violent crime and conflict in various parts of the world.

Still, it’s important to point out that human behavior isn’t driven by climate change alone. Yes, climate change makes everything – not just agriculture – worse or more extreme, but economics, socio-political factors, education, and war all play major roles. You cannot simply reduce such a complex issue down to a simple correlation.

Some researchers have been somewhat critical of the study. They have pointed out that the specific link between climate change and refugee numbers is still somewhat tenuous, and because of this, such estimates cannot be accurately made. Others, however, have rushed to its defence, pointing to a robust analysis.

Either way, this study will provoke a much-needed discussion about the potential effect that climate change could have on an already daunting refugee crisis facing the EU, something that few policymakers have previously taken into account. It’s an important if flawed attempt to look into the near future, one that could still be scarred by recent surges in nationalism and isolationism.