Fossil fuel combustion has already increased the concentration of carbon dioxide in the atmosphere by 36 percent over pre-industrial levels, from 280 ppm to 380 ppm. This contributes to global warming because CO2, despite its low concentration, effectively absorbs outgoing thermal infrared radiation. (Other greenhouse gases are water vapor, methane and ozone).

The correlation between CO2 and climate is evident in Antarctic ice cores extending back 400,000 years (160,000 years are shown in diagram). Regular variations in Earth's orbit orchestrate the transitions in and out of periodic ice ages. The warming trends are enhanced by CO2 (and methane) escaping from warmer seas and permafrost, and by shrinking ice caps that reflect less sunlight.

Politics cloud the issue, but the facts are inescapable: Humans are raising CO2 to unprecedented levels and thus causing the Earth to warm. By 2050 the Earth can expect an increase of about 2 degrees Celsius (3.6 Fahrenheit) and a rise in sea level of about 20 cm (8 inches). The total melting of ice caps would raise sea level by a catastrophic 80 meters, but that is not likely to occur during this millennium. These tentative estimates are from the USGS and NOAA.

Locally, the first significant impact of global warming may be increased food prices caused by declines in Sierran snowpacks and consequent water shortages. Warmer oceans evaporate more water, which will result in stormier weather, but our maritime climate should protect us from the oppressive heat that interior and southern states can expect. My prediction is that unbearable heat waves during the next century will induce millions of citizens to climb into their air-conditioned vehicles and move to Northwest coastal regions. Local pro-growth sentiments may finally be satisfied.

Don Garlick is a geology professor retired from HSU. He invites any questions relating to North Coast science, and if he cannot answer it he will find an expert who can. E-mail dorsgarlick@yahoo.com.