Through Drought and Flood: the past, present and future of Climate Migration

This paper studies emigration pressures associated with climate change and sheds light on how they could evolve as climate degrades further. We start with a narrative approach focusing on four historical events. We document that severe climate disruption led to significant outward migration in the past, driven by social conflict, violence, and, in some cases, societal collapse. Then, we turn the analysis to the present. Using a regression panel approach for 154 countries between 1990 and 2020, we find a highly significant and nonlinear relationship between climate change and migration, with a U shape around a “temperature optimum.” The nonlinearity is stronger in poorer countries. Indeed, despite tropical climatic zones having experienced the smallest increase in temperature thus far, they exhibit the largest increase in outward migration due to their higher initial temperature and lower GDP per capita (limiting adaptation). Finally, we use the estimated model to project future migration under five IPCC scenarios and for a tipping point scenario (AMOC collapse). We find moderate effects on migration increase under moderate climate scenarios, but that migration would double for tropical areas in the most extreme scenario. In the AMOC collapse scenario, where regions close to the poles will freeze, we find much larger effects, with total outward migration being driven by cold and temperate climate countries. We conjecture that our results constitute a lower bound of the possible effects, given (i) the non-well-captured nonlinearities and (ii) the potential fall in income due to climate damages that limit adaptation.