Jürgen Scheffran, a professor of geography at the University of Hamburg, has been investigating whether climate change makes armed conflict more likely for more than a decade. In 2012, he worked on a team that analyzed all 27 empirical studies investigating the link between war and climate change.
“Sixteen found a significant link between climate and conflict, six did not find a link, and five found an ambiguous relationship,” he told me. He described these numbers as inconclusive. Trying to prove that climate change is linked to war, he said, would be like trying to prove that smoking causes cancer with only one available case study.