Insurers’ most immediate climate peril is water. More heat means more moisture held in the atmosphere and greater precipitation. Melting ice is pushing up sea levels. A 2013 study in the journal Nature projected average flood losses for the world’s 136 biggest coastal cities could rise from $6 billion a year in 2005 to $52 billion a year by 2050 due to increased population and development. When taking climate change and a sea-level rise into account, flood losses could exceed $1 trillion a year by 2050, the study concluded, unless the cities invested about $50 billion annually in adapting.