Oklahoma Republican James Inhofe threw a snowball on the Senate floor last winter as proof that it was "very, very cold out," which must mean climate change is a hoax. Now, President Barack Obama is using a glacier to make the opposite case. On his historic trip to Alaska, Obama hiked to Exit Glacier in the Kenai Fjords, which he said "is as good of a signpost of what we’re dealing with when it comes to climate change as just about anything." He added, “We want to make sure that our grandkids can see this.” 

Every presidential warning about climate change, of course, draws a mocking and inaccurate retort from conservatives. This week's right-wing meme: Ice melts in summer! It's gained traction on Drudge Report and among some conservative commenters, like Dinesh D’Souza

A screenshot from Drudge Report.

Science 101: Glaciers advance and retreat all the time. This occurs naturally, but human activity is driving ice loss at an alarming pace. Alaska is warming at twice the rate of the rest of the world—by 3.4 degrees Fahrenheit in the past 50 years, which isn't far off from the worldwide 4.7 degrees Fahrenheit future we are trying to avert. And so glaciers in Alaska and worldwide are in retreat, with tourist attraction Exit Glacier serving as a stark visual example—in geological terms, its retreat is happening in a blink of an eye. While the amount of melt year-to-year can vary—it loses more than 30 feet on average a year since 1973, 187 feet last year, and 800 feet since 2008—the longer-term trend is clear, illustrated by this aerial map: 

National Park Service
A 2015 Geophysical Reserach Letters paper from Alaskan scientists found that the state's glaciers lost 75 billion metric tons of ice per year between 1994 and 2013, which translates into at least several millimeters of sea level rise. As the world warms, Alaska's hotter and longer summers will accelerate this ice loss. If a future president visits Exit Glacier, too, he or she will have to walk hundreds of feet further to reach it.