California–battered by population growth, landslides, and water shortages–is already taking action on flood-control projects and considering how to protect, for example, fresh-water intakes in the Sacramento River delta, which is expected to become more brackish. Now it’s trying to respond specifically to climate change as well, but progress is slow. Coastal real-estate development policy, for example, hasn’t changed. “How well prepared is coastal California to deal with the impact of climate change?” asked Susanne Moser, a coastal-zone expert at NCAR who is advising the state. “The bottom line is, there are very, very few counties and municipalities that are doing anything about this topic so far.”
On a wall-size screen inside the darkened Visualization Laboratory at NCAR, the display of global temperatures across two centuries gets rolling. The animation, which uses a middle-range estimate of future greenhouse-gas emissions, starts in 1870; small splotches of blue and yellow–minor temperature deviations from historical averages–flash over a slowly spinning earth. In the mid-1880s, more blues appear; the planet cooled for a time, thanks to atmospheric dust kicked up by the massive Krakatoa volcanic eruption in August 1883. Things level out at the turn of the century and remain steady through World Wars I and II.
But from the 1950s through the 1980s, yellow blotches proliferate. In the 1990s, the jaundice spreads; by 2005, the earth looks disturbingly like a glowing yellow tennis ball. By the 2050s, the top of the planet appears red. And by 2099, much of the world has been painted orange and red by global warming.
Another model shows the projected changes in seasonal expansion and contraction of Arctic sea ice as the years roll by. It’s like a slowly diminishing heartbeat, with summer ice gradually vanishing.
Caspar Ammann, an NCAR scientist, offers some perspective on the disturbing show. A temperature increase at the upper end of the IPCC’s projections–5 ºC by the end of the century–is about the same size as the increase that’s occurred since the depths of the last ice age. In other words, during the ice age, it was 5 ºC cooler than it is today. If global temperatures rise 3 ºC above recent averages, they will be in the vicinity of temperatures last seen three million years ago, when sea levels were at least 15 meters higher–though it could take centuries for ice sheets to melt and raise the oceans that much. “This is the magnitude of the [temperature] change that is possible in 100 years,” says Ammann. “We need to see that perspective clearly.”
Two days after I saw the NCAR simulations, I visited Ted Scambos, lead scientist at the University of Colorado’s National Snow and Ice Data Center (NSIDC) in Boulder. Scambos studies ice dynamics to understand the rate at which the ice sheets of Antarctica and Greenland are responding to climate change. He and other scientists at NSIDC spend their days poring over satellite data, studying how glaciers slide down ancient hidden fjords and how warmer ocean water and the glaciers’ own meltwater lubricate their progress. “We are warming so fast that the earth is still staggering backwards from the warming,” Scambos said. “We may have already crossed the threshold of the last warm period, a time when people were growing grain in Iceland and raising dairy cattle in southeastern Greenland. And even if you flattened out greenhouse emissions right now, my hunch is that all the arctic sea ice in summer will eventually disappear.
Vanishing Yosemite Snowpack
These images–which show details of the one on page 65–reveal snowpack changes in a 100-kilometer swath of California’s Yosemite National Park. The top image shows current spring conditions, with snowpack depth depicted by colors (greener indicates less snow, whiter indicates more). The bottom image is a visualization of snowpack between 2050 and 2070. Contour lines depict percentages of snowpack lost, which range from 80 percent (light blue contour) near today’s snow line to 20 percent (red contour) near peaks. This level of topographic precision is critical to helping communities plan for changes in the amount of annual snowpack and the timing of melting, on which millions of people depend for their water supplies.