LA Times: With Yosemite Falls in the background, President Obama told an audience Saturday that climate change is already impacting America`s national parks. "Make no mistake, climate change is no longer just a threat - it`s already a reality," he said from a lectern near Sentinel Bridge in Yosemite National Park. The first family`s trip to what, with about 4 million visitors a year, is the nation`s fourth most-visited park, comes as the National Park Service is approaching its 100th anniversary in August....