At the 18th UN-Climate Change Conference, the findings of an innovative comparative study confirm that rainfall variability and food insecurity are key drivers for human mobility. The empirical research – carried out by CARE International and the United Nations University in eight countries in Asia (Bangladesh, India, Thailand, Viet Nam), Africa (Ghana, Tanzania) and Latin America (Guatemala, Peru) – revealed that migration is an important risk management strategy for vulnerable households. Land scarce households trying to cope with food insecurity send migrants during the hunger season to find food or money to buy food. Migration is often temporary and seasonal, if migrants are successful, but can be permanent if options cannot be found to deal with rainfall variability and rural food insecurity. The research is based on a 1,300 household survey and participatory research sessions involving 2,000 individuals. It further models future migration in Tanzania under different rainfall scenarios from 2014–2040.