John Kerry, a key figure in environmental diplomacy in recent decades, leaves the front line of the fight against warming. John Kerry: goodbye to the climate 'czar' as fear grows of Donald Trump's return.

Kerry's departure coincides with Trump's overwhelming victory on the Super-called Super Tuesday, which boosts him in the race to return to the White House. And many environmentalists and environmentally concerned politicians are holding their breath again, warns Alice Hill, a member of the Council on Foreign Relations.