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Dr. James Hansen — the same scientist who alarmed Americans in 1988 with claims that global warming would bring catastrophic temperature increases — has declared before the scientific community in a prestigious journal of the National Academy of Sciences that predicting global temperature with climate models is all but impossible.1 Hansen’s pronouncement shakes the foundation of the climate policy debate, because without reliable climate model projections and almost no evidence of a warming trend, there is little reason to anticipate catastrophic global warming.
Dr. James Hansen — the same scientist who alarmed Americans in 1988 with claims that global warming would bring catastrophic temperature increases — has declared before the scientific community in a prestigious journal of the National Academy of Sciences that predicting global temperature with climate models is all but impossible.1 Hansen’s pronouncement shakes the foundation of the climate policy debate, because without reliable climate model projections and almost no evidence of a warming trend, there is little reason to anticipate catastrophic global warming. The Clinton administration and Congress must now completely reexamine the U.S. policy on climate change in light of Hansen’s landmark scientific paper.
What did Hansen say? Dr. Hansen’s statement that "the forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change," is profound.2 In layman’s terms, long-term temperature prediction is, at least for now, completely impossible. We cannot say with any confidence what direction temperature trends will follow given today’s science. What remains to be seen, however, is whether or not the Clinton administration will abandon the economically lethal emission reductions required under the Kyoto Protocol — the international "global warming" treaty that the Energy Information Administration maintains will cost Americans $397 billion, annually.3
Ultimately, Dr. Hansen’s new research renders invalid the widely cited prediction by the United Nations Intergovernmental Panel on Climate Change (IPCC) that global average temperature could rise by up to 3.5 degrees Celsius by 2100,4 a prediction that forms the basis of the Clinton administration’s climate change policy.
Climate models were never designed to be policy tools. Scientists have long used models to investigate the various atmospheric mechanisms driving long-term changes in average temperature and weather. Successfully predicting future climate — an objective that many scientists believe is theoretically impossible — would require a complete mathematical understanding of the atmospheric phenomena that affect climate. Among these phenomena are "climate forcings," or changes in the climate’s energy balance from extraneous factors. Although not completely understood by climate scientists, these factors could include changes in levels of water vapor, carbon dioxide, methane, ozone, as well solar activity and cosmic ray influx. Forcings can either raise or lower global average temperature; however, the level of forcing from such factors remains hypothetical.
Heeding the data. In the absence of reliable climate model projections of future temperature, we must turn to the past to determine climate change policy. Climate data over the past century suggests a much different and much less expensive policy. In fact, the same IPCC publication cited by the Clinton administration in support of radical reductions in emissions of greenhouse gases says the following about the occurrence of extreme weather events during the 0.5 degree Celsius warming over the last century: " . . . Overall, there is no evidence that extreme weather events, or climate variability, has increased in a global sense, through the 20th century, although data and analyses are poor and not comprehensive."5
Sea levels have risen over the past century according to the IPCC. However, this rise cannot be necessarily associated with the 0.5 degree Celsius warming that occurred over the past century, because the dearth of data produces a range of uncertainty greater than the observed increase in sea level.6 Additionally, the U.N. body notes that hurricanes have not increased over the past century, and global precipitation has declined.7 These findings are not consistent with the theory of catastrophic — anthropogenic or otherwise — global warming.
1998: Record warmth or El NiÃ±o anomaly? Despite the calm and warm climate of the past century, and the inaccuracy of climate models, Dr. Hansen still maintains that the global warming trend continues and is cause for concern. Dr. John Christy, also of NASA, agrees that global temperatures rose according to satellite measurements. However, as Dr. Christy states: "In contrast to the gradual warming of the surface over the past 20 years, the tropospheric measurement from MSU [microwave sound unit] showed no trend until the major warm El NiÃ±o event of ‘98." Many scientists maintain 1998 to be an anomalous event due to El NiÃ±o and not a sign of a continuing warming trend.8
Will the president see the light? Hansen’s proclamation is truly an historical event in the policy debate over climate change. In light of Hansen’s new findings, President Clinton and the administration must take a step back and reassess the prudence of attempting to reduce greenhouse gas emissions. Over a century of weather data suggests no reason for hasty policies that will cost American consumers hundreds of billions of dollars.
1James E. Hansen, Makiko Sato, et al., "Climate Forcings in the Industrial era," Proceedings of the National Academy of Science, vol. 95, pp. 12753-12758, October 1998.
2Ibid., p. 1.
3Energy Information Administration, "What Does the Kyoto Protocol Mean to U.S. Energy Markets and the U.S. Economy?" October 1998, pp. xii-xiii.
4Intergovernmental Panel on Climate Change, Climate Change 1995, The Science of Climate Change, p. 6.
5Ibid., p. 173.
6B.D. Santer, et al., "Climate Models — Projections of Future Climate," Climate Change 1995: The Science of Climate Change, Cambridge University Press, 1996, p. 339.
7Landsea, C.W., et al., "Downward Trends in the Frequency of Intense Atlantic Hurricanes During the Past Five Decades," Geophysical Research Letters, vol. 23(13), pp. 1697-1700.
8John Christy, "Scientists Present 1998 Earth-Temperature Trends," National Aeronautics and Space Administration Press Release, January 12, 1999.