The earth's climate is getting warmer because of a buildup of carbon dioxide in the atmosphere that will continue well into the next century, according to a report released October 20 by the National Research Council (NRC), the research arm of the National Academy of Sciences. As the result of a 2-year study commissioned by Congress, the NRC's Carbon Dioxide Assessment Committee predicts a global temperature rise of as much as 4.5°C by the year 2100, enough to shift weather patterns, raise sea levels, and eliminate agriculture in some parts of the world. What's more, the trend seems inevitable— even drastic changes in our energy use would not prevent the warmup, according to the committee's findings.
CO2, the major contributor to a thermal “greenhouse effect” that traps re-radiated heat in the atmosphere, has risen from a concentration of 315 parts per million (ppm) to 340 ppm in one generation, largely as a result of the use of fossil fuels. Sometime in the third quarter of the next century, the report predicts, the concentration will probably be double the current level. The result will be a global warming of surface air of between 1.5° and 4.5°C, with temperature rises relatively greater at the poles.