3. 4. 5. C. d. Warming in the Northern Hemisphere. A greenhouse signal would include greater warming in the Northern Hemisphere by about 0.5°C. Observed temperatures, however, show no significant difference in temperature trends in the Northern and Southern hemispheres. (see Report pp. 6-7) Warming at high latitudes. Greenhouse calculations suggest that high latitudes should already have warmed 1oC more than low latitudes. Temperature records show no significant difference in trends between high and low latitudes. (see Report pp. 6, 8) Effect of pollution on the greenhouse signal. Some experts argue that the large greenhouse signal has been masked by pollution. However, pollution in the U.S. has decreased since 1970. Thus pollution cannot explain the absence of a greenhouse signal in the 1970s and 1980s. Pollution in other countries probably has increased in the last 20 years, but polluting particles only stay in the atmosphere for a few days, and disappear before the winds can carry them to the U.S. (see Report pp. 11-12) Climate change research contradicts apocalyptic predictions. With $1 billion spent yearly on climate change research, our knowledge is increasing rapidly, and some old predictions are falling to a better understanding of the facts. For example, a frequently predicted consequence of global warming is a melting of the polar ice caps and catastrophic flooding of low-lying areas. New research shows that sea levels would change very little if the earth continues to warm. (see Report pp. 22-24; attached Chart C) No cost if policy action is delayed. A five-year delay in action to restrict carbon dioxide emissions will produce at most an additional warming of a tenth of a degree spread over decades. (see Report pp. 27-28) 1. Satellite measurements of global temperature 1979-1991. The results do not show the large expected upward trend due to the greenhouse effect. Increases in some years are balanced by decreases in others. The average increase in the data is 0.06°C/decade. The 1992 Scientific Assessment report of the IPCC aives 0.3°C/decade as the consensus of theo. 16 3. Greenhouse calculations compared with observed temperature changes. The 0.5°C 2. Changing predictions of global flooding. Predictions of a rise in sea level resulting from the greenhouse effect have dropped markedly in recent years. Commonly quoted numbers for a greenhouse-induced sea level rise changed from 25 feet in 1979 to three feet in 1985, and decreased further to one foot in 1989. The trend in changing predictions, shown in the chart, suggests that in the early 1990s the predictions for sea level rise would decline to zero or negative values. In 1992, a report based on the study of 130,000 years of geological records confirmed this expectation, projecting a fall in sea level of about one foot in the next century as a result of the greenhouse effect. The episode suggests that apocalyptic forecasts in this area should be greeted with caution if not skepticism. Biographical Information on the Briefers William A. Nierenberg Professor William A. Nierenberg is Director Emeritus, Scripps Institution of Oceanography. He is a member of the Global Climate Subcommittee of the EPA, and member of the National Academy of Sciences Climate Research Board. Dr. Nierenberg is former Chairman of the NAS National Research Council's Carbon Dioxide Assessment Committee and the White House Office of Science and Technology Policy Acid Rain Peer Review Panel, whose reports, "Changing Climate" and "Acid Rain" were published in 1984. From 1982-87 he was chairman of JASON, the Department of Defense advisory panel. He is a member of the Board of Directors, George C. Marshall Institute. Frederick Seitz Frederick Seitz is President Emeritus of Rockefeller University and Past President of the National Academy of Sciences. Dr. Seitz is past President of the American Physical Society and recipient of the National Medal of Science. He is a member of the Defense Science Board, an organization he chaired, and Chairman of the Board of Directors, George C. Marshall Institute. |