Global climate patterns have changed over the last century, triggering more extreme weather events including hurricanes, heat waves, and droughts. Looking forward, the Intergovernmental Panel on Climate Change (IPCC) has projected that, at the current rate, global temperatures are likely to average 1.5°C above pre-industrial levels at some point between 2030 and 2052. Even this seemingly modest increase, which is well within the range of daily variability, will result in cascading impacts on ice sheets, ecosystems, and productive systems that will fundamentally alter habitability when spread over the entire land surface of the planet. The effects will not be spread evenly, and already high latitudes are warming at twice the rate of the rest of the world while drylands are expanding.

Climate can be seen as the envelope in which all economic activities take place, and these changes could spell significant disruptions for modern society, both in low- and high-income settings. Yet humans have the ability to adapt as well as free will, so one must be careful not to engage in a sort of environmental determinism that draws a direct line from projected climate changes to future migration. Instead, climatic circumstances exist as one of several factors that drive the decision by an individual or community to migrate, and may compound those other drivers or be mitigated through policy action or individual circumstance.

This article draws on a growing evidence base for contemporary environmentally induced migration that includes individual case studies, sophisticated statistical analysis, modeling work, and the UK government’s benchmark 2011 Foresight report, Migration and Global Environmental Change. It summarizes key lessons from the evidence and assesses the implications for future migration under climate change.

The question of how climate factors influence migration is fraught with so many contextual specificities that it is helpful to begin with a clarification of terms as well as some general observations. On the migration side, researchers for more than a century have uncovered a range of so-called “stylized facts” governing how, why, and under what circumstances people move. Push and pull factors in origin and destination areas produce migration streams and counter-streams; at the same time, intervening obstacles such as costs of travel and border controls inhibit migration. Human movement tends to increase over time, and migrants are more likely to move to places where relatives or friends have preceded them. Migration is selective, meaning that, depending on the context, some people—such as those who are younger or males—are more likely to move than others. Finally, economic motives tend to dominate. Environmental factors can influence all these elements.

Read the full article about climate migration by Alex de Sherbinin at Migration Policy Institute.