The satellite images viewed by President Obama before a meeting with eight Western governors were stark, showing how snowpack in California’s mountains had shrunk by 86 percent in a single year. “It was a ‘Houston, we have a problem’ moment,” recalled White House counselor John D. Podesta, one of two aides who briefed the president that February day. Obama mentioned the images several times as he warned the governors that political leaders had no choice but to cope with global warming’s impact.