A new publication from the Population Reference Bureau examines migration due to climate change.
From the summary:
Throughout human history, people have been on the move—exploring new places; pursuing work opportunities; fleeing conflict; or involuntarily migrating due to changing political, social, or environmental conditions.
Today there are an estimated 230 million international migrants, a number that is projected to double to over 400 million by 2050. Beyond the people who cross international borders, probably more than two to three times as many are internal migrants, people who have moved within their own countries.
The reasons for moving are complex, but over the past decade, as the evidence of global climate change has accumulated, academics, policymakers, and the media have given more attention to migration as a result of environmental change.