Climate change could become a “catastrophic” threat to global security, as people lose their livelihoods, fall ill and battle over scarce water and food, a host of U.S. security, military and intelligence experts warned on Monday.Pressures from global warming could intensify political tensions, unrest and conflict, fuel violent extremism and break down government security systems, the experts said in a report by the Center of Climate and Security, a nonpartisan policy institute.War-torn countries in Africa and the Middle East were cited as most at risk, but industrialized regions are vulnerable, it said.”Even at scenarios of low warming, each region of the world will face severe risks to national and global security in the next three decades,” the report said.”Higher levels of warming will pose catastrophic, and likely irreversible, global security risks over the course of the 21st century.”Concerns over the impact of climate change have led to calls to reduce …