The relationship between climate change and human migration is not homogenous and depends critically on the differential vulnerability of population and places. If places and populations are not vulnerable, or susceptible, to climate change, then the climate–migration relationship may not materialize. The key to understanding and, from a policy perspective, planning for whether and how climate change will impact future migration patterns is therefore knowledge of the link between climate vulnerability and migration. However, beyond specific case studies, little is known about this association in global perspective. We therefore provide a descriptive, country-level portrait of this relationship. We show that the negative association between climate vulnerability and international migration holds only for countries least vulnerable to climate change, which suggests the potential for trapped populations in more vulnerable countries. However, when analyzed separately by life supporting sector (food, water, health, ecosystem services, human habitat, and infrastructure) and vulnerability dimension (exposure, sensitivity, and adaptive capacity), we detect evidence of a relationship among more, but not the most, vulnerable countries. The bilateral (i.e., country-to-country) migration show that, on average, people move from countries of higher vulnerability to lower vulnerability, reducing global risk by 15%. This finding is consistent with the idea that migration is a climate adaptation strategy. Still, ~6% of bilateral migration is maladaptive with respect to climate change, with some movement toward countries with greater climate change vulnerability.

Mitigation of greenhouse gas (GHG) emissions and adaptation to climate risk are two essential ingredients of climate change policy. Both are needed and co-benefits may exist. Yet, mitigation and adaptation are not usually pursued together. Part of remedying this shortcoming is understanding the relationship between GHG emissions and climate vulnerability reduction and recognizing when and where they trend together. Here, we compare changes in fossil fuel CO2 emissions per capita and in climate vulnerability scores over the past two decades in 179 countries. We use climate vulnerability scores from the well-established ND-GAIN Country Index, a composite metric constructed from thirty-six indicators covering three components of vulnerability (exposure, sensitivity and adaptive capacity). We find that 69% of the countries decreased climate vulnerability, while increasing their per capita fossil fuel CO2 emissions. These countries are successfully reducing climate vulnerability but are increasing their GHG emissions and thus failing in mitigation efforts. In contrast, 23% of the countries have been successful in simultaneously reducing per capita CO2 emissions and climate vulnerability. Furthermore, in highly vulnerable countries, increasing CO2 emissions are not correlated with decreasing climate vulnerability. These findings underscore that climate vulnerability reduction may be due only partly to economic development. This finding also changes our prevailing view that increases in CO2 emissions are associated with vulnerability reduction. Finally, examining mitigation and climate-vulnerability reduction by sector, we show that a majority of countries are able to reduce vulnerability in ecosystem services. Those countries and sectors with positive trends provide examples for others to follow, as solutions at the mitigation-climate vulnerability reduction interface are essential for sustainable economic development.