A Phased‐in approach to greenhouse‐gas‐induced climatic change

To address this concern, it will be helpful to describe the motivation, objective, approach, and scope of our Nature study. One of us, Schlesinger, was an invited participant at the White House Conference on Science and Economics Research Related to Global Change, held in Washington, D.C., April 17–18, 1990. At this conference two opposing policy positions were espoused, neither of which appeared to have been based on a scientific evaluation of the global warming issue. This motivated our study to assess the urgency of this issue. Our approach was to use our simplified climate/ocean model, which we employed in projections for the IPCC report on global warming to the year 2100 [Houghton et al., 1990], to determine how much of the potential reduction in future global warming would be lost if the initiation of a 20‐year transition from the emission rate of the IPCC “business‐as‐usual” scenario A to the emission rate of any other IPCC scenario (B, C, D) was deferred by 10 years. Our findings were that 5% of the potential reduction, at most, would be lost by such a 10‐year deferral, regardless of the temperature sensitivity of the climate system to a CO₂ doubling (ΔT_2x) , within the 0.5–4.5° range we considered. This result indicates to us that the urgency of the global warming issue is not as great as some have thought, and suggests that we have some time to improve our understanding of the issue to enhance our ability to respond appropriately