Rafael Reif, President of MIT: Global warming is not a distant problem — not distant in time or space. Communities across the United States and around the world are already experiencing the impacts. Without immediate and concerted action, the damaging consequences will grow worse. As the Pentagon describes it, climate change is a “threat multiplier,” because its direct effects intensify other challenges, including mass migrations and zero-sum conflicts over existential resources like water and food. In short, global warming and its consequences present risks too grave to gamble with.