Mega cities like Mumbai and New York will face serious impacts from rising sea levels, UN Secretary General Antonio Guterres warned on Tuesday, as he exhorted the global community to address climate crisis, which he said is the "root cause of rising seas." "Rising seas are sinking futures. Sea-level rise is not only a threat in itself. It is a threat-multiplier. For the hundreds of millions of people living in small island developing states and other low-lying coastal areas around the world, sea-level rise is a torrent of trouble," Guterres said at the UN Security Council debate on 'Sea-Level Rise- Implications for International Peace and Security.' He asserted that rising seas threaten the very existence of some low-lying communities and even countries.