It is ironic, I think, that the places where we can actually "see" dramatic climate change occurring are at the North Pole, in the Arctic and Antarctic, at Greenland - even Siberia. These are places we are most unlikely to visit or "see," which is unfortunate since, for most people, seeing is believing.
We do know, however, that since 1979, more than 20 percent of the polar ice cap has melted away; that the Larsen B ice shelf in the Antarctic Peninsula continues to break up; that the Greenland ice sheet has been shrinking by 12 cubic miles (in terms of volume, not square miles) per year since the 1990s.
Melting snow and ice seems reasonable in a world that is getting warmer, but the earth itself, the dirt, the soil, the permafrost is melting as well. Most of the land in the Arctic, and nearly one quarter of all the land in the Northern Hemisphere (that's 5.5 billion acres) is underlaid by zones of permafrost. Permafrost by definition is any piece of ground that has remained frozen for at least two years. In some places, such as Siberia, the permafrost is almost a mile deep. In Alaska, it varies from a couple of hundred feet to a depth of several thousand feet.
In Fairbanks, Alaska, after their warmest summer on record in 2004, their third lowest year of rainfall, and forest fires that began early in June and were still burning in late August, the area around Fairbanks was pockmarked with holes (called thermokarsts) that had opened up in patches of permafrost. Wherever permafrost is disturbed or thawing, houses, lawns or roads no longer have a solid foundation and everything from trees to houses end up listing at odd angles.
The Alaska pipeline that runs along the Dalton Highway runs mostly above ground, on pilings that contain ammonia which keeps them cool, because of the permafrost In Siberia, Russians build all houses, buildings, pipelines - everything - on stilts to avoid warming the permafrost.
Permafrost, very much like a peat bog or a coal deposit, acts as a storage unit for accumulated carbon. So, one of the risks of rising temperatures is that the organic material that has been frozen for millennia in the permafrost will begin to break down, giving off carbon dioxide and methane - both greenhouse gases.
Whereas trends in air temperature can vary greatly (and so make us doubt if global warming truly exists), permafrost works as a low-pass filter. The warming of the permafrost is more "seeable," if you will. Alaska's permafrost has warmed by nearly six degrees already in some parts of the state.
• Ursula Carlson, Ph.D., teaches writing and literature at Western Nevada College and is currently reading studies on climate change.