Do We Need to Act Now on CO2 Emission Limits?
October 28, 1997
In anticipation of the Kyoto meeting in December, the United States is under in-creasing pressure to deal with the problem of global warming by making reductions in its CO2 emissions. Does the science support the need for these reductions? What would be the penalty for waiting to obtain better information, and to let new energy technologies develop, before we decide on CO2 emission limits?
A recent study (Wigley, Richels, and Edmonds, Nature 379, p. 240, 1996) finds that if we wait more than twenty years before taking action to limit worldwide CO2 emis-sions, the additional temperature rise caused by the delay will be at most 0.2°C spread over a 100-year period.
An incremental warming of a few tenths of a degree spread over a century would be indistinguishable from natural fluctuations in climate.
The authors of the study take the goal of CO2 limits to be a stabilization of CO2 concentrations in the atmosphere at approximately twice the pre-industrial level. They find that there is little difference between a policy of immediate cuts and the alternative of no cuts now and heavy cuts starting in 2020. Both scenarios lead to the same stabi-lized CO2 concentrations by 2100. And the policy of immediate cuts saves only 0.2°C in long-term warming, as noted above.
Thus far the climate data have not shown the large temperature increases predicted by the climate models as a result of human-made CO2. Either the climate models are ex-aggerating the warming effect of the added CO2, or the warming is being masked by some other factor. Still, even if fears of a harmful human-caused global warming turn out to be justified ? a possibility which finds no support in the scientific data to date ? there is no significant penalty for waiting more than twenty years to obtain better infor-mation before cutting CO2 emissions. Since CO2 emission cuts are expected to have a destructive impact on the U.S. economy, waiting until more information is in hand would seem to be the prudent policy.