It is simply a scenario that we hope can help stimulate discussion about the nature of the actions required to yield only a modest climate forcing, instead of a large forcing. This is obtained by keeping the net increase of non-CO 2 forcings at 0 Watts and the increase of the CO 2 forcing at 1 Watt, as summarized in Figure 1. We note that there will be multiple benefits of a climate strategy that focuses on non-CO 2 forcings as well as on CO 2 . I will mention the three major non-CO 2 forcings. This is a major pollutant that has received inadequate attention.
Aerosols are tiny solid or liquid droplets in the air.
Coal and biomass burning are also major sources. Black carbon aerosols cause a positive climate forcing that is very uncertain in magnitude, but we estimate that it is probably of the order of 0.5 to 1 Watt per square meter on global average. Black carbon aerosols are a principal component of air pollution. In the words of Tony Hansen, microscopic soot aerosols are like tiny sponges that absorb other substances including toxic organic particles. Air pollution in developing countries, such as India and China, is even more severe.