In an impassioned Senate floor speech in August, Kerry compared the potential peril from climate change to the threat of war. “I believe that the situation we face [with climate change] is as dangerous as any of the sort of real crises that we talk about” in Iran, Syria, and other trouble spots, he said.

He has taken plenty of heat for that view from Republicans, many of whom question the science of human-caused climate change, scoff at any link to national security, and say that solving global warming is the wrong priority for the nation’s chief diplomat. But defense and intelligence officials say the link between climate change and national security is clear, dangerous, and urgent—and a raft of national security experts say it’s high time the nation’s top foreign policy official treated it as such. ….

Around the globe, climate change contributes to rising sea levels, more-intense drought, and food and water scarcity. Already, swaths of land in Africa and the Middle East have become too barren to support crops, and scientists warn far worse is to come as the globe continues to heat up in the coming century. …

The question, however, is what the chief U.S. diplomat can actually do about climate change. Although no single official, or nation, can solve the problem alone, Kerry will be uniquely positioned to broker action through diplomacy. In France in 2015, the world’s nations are set to sign a global treaty that would legally bind them to cut their global-warming pollution. Much of the world views the success of the treaty as largely resting in American hands. If the United States acts to cut its carbon emissions—either through legislation or, as seems far more likely, through Obama’s use of executive authority and regulations issued by the Environmental Protection Agency—the country will be well positioned to broker a global climate deal.