5. Smoggier mountain skies
Rising temperatures could worsen air quality in New Hampshire’s White Mountains.
Nitrous oxides and hydrocarbons from car exhaust combine on warm, sunny days to produce ground-level ozone, an oxidant that irritates the mucus membranes in humans and animals, and that damages plants. In addition to blanketing major cities, this smog accumulates in alpine regions like the White Mountains. As a result, ozone readings atop Mt. Washington are generally 2 to 5 times higher than at lower elevations. Because higher temperatures increase ozone production, global warming will continue to degrade the air quality and the views on the Northeast’s high peaks.
6. Smaller glaciers
By mid-century, much of the permanent ice in America’s national parks will have vanished.
Nearly all of the world’s mountain glaciers have receded as average global temperatures have risen 1°F in the last century, according to the IPCC’s Climate Change 2007 report. In our backyard, 60 percent of Sierra Nevada glaciers and 40 percent of the perennial ice in North Cascades National Park has melted since the 1880s. Because carbon lingers in the atmosphere for decades after it’s produced, warming will continue even if emissions are cut. In the Pacific Northwest, the most glaciated region in the Lower 48, temperatures are predicted to rise another 1°F in the next 20 years, melting all but the high-elevation ice sheets, like those capping Mt. Rainier.
7. Soupier tundra
Melting permafrost could make Alaska hiking a nightmare and triple current atmospheric CO2 levels.
Eighty percent of Alaska’s interior, including most of Denali National Park, rests on permafrost, a layer of frozen soil. Scientists predict that rising temperatures will thaw the top 10 feet of half of the Northern Hemisphere’s permafrost acreage by 2050, aggravating existing damage to roads and buildings and turning solid tundra in prime hiking destinations into impassable bogs. Simulations run by the National Center for Atmospheric Research predict that 90 percent of the world’s permafrost could turn to slush by 2100. The real danger, however, is the resulting release of underground methane, a greenhouse gas that is 21 times more potent at trapping heat than CO2.
8. Less snowpack
Sierra snow levels are thinning, and they’re melting away three weeks earlier than they did 50 years ago.
Peak runoff for Yosemite’s waterfalls is shifting from early summer (when most hikers visit) to spring, when many trails remain inaccessible. The earlier melt will also cause some streams to dry up in July, a month early. Even if we reduce CO2 emissions, forecasters believe California temps will rise 3 to 5.5°F over the next few decades, causing the Sierra snowpack to decline by 30 percent. If we don’t, snowpack could shrink by 90 percent, ending most winter recreation and turning snow-fed streams into dry washes.