Danger in Degrees: Whether man-made or not, the climate is changing | AspenTimes.com

Danger in Degrees: Whether man-made or not, the climate is changing

Allen Best

Hiking along the Continental Divide north of Georgetown during late summer three years ago, Ed Knapp noticed something awry. Several feet below the lip of a withering field of ice and snow was a skull with down-turning horns. It was, he quickly concluded, the skull of a bison.Bison skulls in the mountains are by no means rare, even if none had ever been found quite so high, at nearly 13,000 feet above sea level. The surprise was the rapid retreat of ice, from which the bison skull emerged. When Knapp, a 60-year-old building contractor from metropolitan Denver, began hiking the Continental Divide near Jones Pass in the 1970s, the permanent snowfield was 200 yards long. A year after it yielded the skull, it vanished altogether.Make no mistake – the climate is shifting across North America and the world. The 10 warmest years since record-taking began have occurred since 1983. Mountain glaciers have been reduced by about half. Sea levels are up 6 to 10 inches. Severe heat waves have become more frequent.In the mountains, evidence of warming is found at every turn. Winter nights are less frigid. Spring runoff comes earlier. The frost-free season has expanded – in Aspen by more than three weeks, according to records kept since 1949 at the town’s water plant.

Do not make too much of local or even regional weather, says Susan Salomon, a scientist from Boulder renowned for her pivotal role in research about the ozone hole over Antarctica. “Climate varies in your back yard much more than it does in the global mean,” she says. “We have to be very careful in trying to attribute local variations to global warming.” That said, there’s no question the globe is warming. Some change may well be due to natural climate change, but the broader evidence of climatic change is beginning to add up. Nearly all scientists now agree that people – primarily through the burning of coal, petroleum and other fossil fuels that create greenhouse gases – are the main reason.Unlike pure oxygen, greenhouse gases trap a portion of the solar energy that warms the Earth every day, similar to the way your windows trap heat in your car. Too little of these greenhouse gases, and the Earth becomes a snowball. Too much of them and our planet becomes an oven.New consensusThose questions about the critical role of greenhouse gases 15 years ago were at the core of a lively debate. There was no strong consensus among scientists, much less the public. But the huge body of research conducted since then has left few scientists as doubters.

Global atmospheric concentrations of carbon dioxide, the most common greenhouse gas, rose 20 percent during the 20th century. As the century closed, temperatures spiked dramatically in what many researchers think was a direct result of those gases.”It’s almost impossible to find a scientific researcher who doubts the connection between people and greenhouse warming, and that we’re in for an unprecedented warming during the next 100 years,” says John Harte, a professor at the University of California at Berkeley who spends his summers conducting global warming-related experiments near Crested Butte.Yes, you can find Web sites that dismiss the human fingerprints on global warming as bad or at least unproven science. But Harte points out that until recently, there were scientists and spokesmen for the tobacco companies who questioned any link between cigarettes and cancer. “That’s exactly what’s going on in the global warming debate,” says Harte.That’s not to say that scientists know exactly where the climate is headed. They do not. Climate change is enormously complicated. The slight wobble in the Earth’s orbit around the sun causes shifts from swamps to glaciers. Drifting continents also provoke climatic shifts. The mechanics of these climate changes are only poorly understood. Particularly puzzling is the role of carbon, which is continually being redistributed among the plants, the ocean and the atmosphere. Clouds are another major mystery.

All of this means that scientists are far from figuring out how climates shift naturally. With this sinister Joker of growing greenhouse gases in the playing deck, the game is even more difficult to figure out. But what is disquieting is that, in the absence of action to reduce the burning of fossil fuels, carbon concentrations at the end of this century will be higher than they have been in 20 million years – long before people were on the planet.Century’s top issueThat makes climate change, as many observers have noted, the paramount issue for the 21st century. It is an environmental problem unlike any other ever faced.Most environmental problems have local causes and local solutions. But local becomes global very quickly in the atmosphere. The air circumnavigates the globe in about two weeks at the same latitude. In other words, the pollution from Denver – or the emissions from your car on Interstate 70 – hit Washington, D.C., in a few days, Athens in about a week, and Beijing and Tokyo a few days later before returning home.But over time the air mixes. It takes one year for the air on one hemisphere to thoroughly mix. Within two years, the global atmosphere becomes one big punch bowl.

A second way that the accumulating greenhouse gases are unlike more conventional environmental problems is the cumulative effect and lag time. Once sent into the atmosphere, carbon dioxide stays there for 100 years or more.Hence, the heating in the year 2030 will be the result of pollution from that year, but also this year – and from the year you were born, the year your mother was born, even the year that Beethoven was born. It takes probably thousands of years for the gases to dissipate.”The problem we are creating has a 10,000-year effect,” says Duane R. Kitzis, a scientist with the National Oceanic and Atmospheric Administration in Boulder.Scientists, as weathermen have begun doing, always carefully couch predictions about the effects of global warming in terms of probability. A prediction issued last December by two Boulder-based scientists, Thomas Karl and Kevin Trenbert, has the sort of odds you’d like in Las Vegas.There is, they said, a 90 percent probability that between the years 1990 and 2100, global temperatures will rise by 3.1 to 8.9 degrees Fahrenheit.