Global Warming Research Still Rife with Uncertainties

A May 24 hearing reviewing the status of U.S. research on global climate change revealed a field still beset with scientific uncertainty, conflicting opinions, and many complex factors on which more research is needed. Senate Energy and Natural Resources Committee chairman J. Bennett Johnston (D-Louisiana) opened the hearing with the hope that it might help clarify “lingering uncertainties.” He questioned whether the U.S. could meet its commitment to greenhouse gas reductions without harsher measures than those called for in President Clinton’s plan.

Ranking minority member Malcolm Wallop (R-Wyoming) argued that “mankind can afford to take the time necessary to fully understand the scientific factors” before taking drastic action. He said that “actions beyond Clinton’s plan are not supported by scientific evidence and will be accompanied by high social and economic consequences.” Wallop charged that some of the documents produced by the International Panel on Climate Change (IPCC), upon which the Administration policy is based, were politically rather than scientifically motivated.

While the witnesses agreed that significant uncertainties still exist, they disagreed on other areas. Robert Watson, the Office of Science and Technology Policy’s Associate Director for Environment, defended the IPCC assessments, saying they “represented strong, concise statements from the majority of the international scientific community.” He admitted that while the IPCC predicts that increased greenhouse gases will lead to warming, “substantial reduction of key uncertainties needs decades or more.” He reported that the Clinton Administration recognized the need for an expanded research program, which was largely reflected in the fiscal year 1995 budget request for the NSF portion of the multi-agency U.S. Global Climate Change Research Program.

Jerry Mahlman, Director of NOAA’s Geophysical Fluid Dynamics Laboratory, warned that “none of the uncertainties can make the problem of global warming go away.” However, Richard Lindzen, Sloan professor of meteorology at MIT, argued that the main concerns and predictions of global warming “appear to be without legitimate basis.” Watson’s response: “How risk-averse do [policy-makers] want to be?”

Stephen Schwartz, a senior chemist at Brookhaven National Lab, discussed evidence that the increase in anthropogenic aerosols might be causing a cooling effect comparable in magnitude to, and possibly masking, the warming influence of greenhouse gases. Noting the much shorter-term effect of aerosols, he warned vehemently against any consideration of using them to offset the effects of greenhouse gases. Doing so, he said, would only “exacerbate the problem.”

Several other witnesses discussed the role of changes in the Sun’s activity on global climate change. Watson stated that while solar activity fluctuations can affect the Earth’s climate, they were unlikely to dominate in the long term.

The Committee has no plans to introduce a new bill on the subject. Johnston concluded the hearing by saying the issue “needs to be very seriously addressed, even if we don’t understand it fully.”