The most comprehensive study done to assess the link between climate change, war and migration has confirmed that the warming planet is fueling conflicts that lead to more refugees.

The conclusions published Jan. 23 in a scientific journal underscore the rising levels of anxiety that global warming has among leaders. Attendees at this year’s World Economic Forum in Davos, Switzerland, said the inability to adapt to higher temperatures is the biggest global risk. A Pentagon report published Jan. 22 in Washington warned that rising seas and more frequent wild fires threaten U.S. security.

The peer-reviewed study, Climate, Conflict and Forced...