PNNL

Abstract

The upcoming sixth meeting of the Conference of the Parties to the Framework Convention on Climate Change (FCCC) has refocused attention on climate change policy. Recently, debate has been stimulated by the publication of a paper by Hansen et al who have suggested an "alternative scenario" for mitigating climate change that focuses primarily on non-CO2 greenhouse gases and local air pollutants. Their proposal is to limit CO2 forcing limited over the next 50 years to an additional 1 W/m2, with no net increase from the combination of non-CO2 greenhouse gases, aerosols, and tropospheric ozone.Reducing the emissions that lead to local air pollution may, indeed, help contribute to reducing climate forcing, particularly if concentrations of methane or tropospheric ozone can be decreased ? although the science here is complex and net forcing reductions might not materialize. Clean-up of soot emissions will also tend to reduce climate forcing and non-CO2 greenhouse gases would have an important role to play. But the overall gains of such reductions are not enough to remove the primary focus from carbon dioxide emissions.