Global warming in the twenty-first century: An alternative scenario

A common view is that the current global warming rate will continue or accelerate. But we argue that rapid warming in recent decades has been driven mainly by non-CO 2 greenhouse gases (GHGs), such as chlorofluorocarbons, CH 4 , and N 2 O, not by the products of fossil fuel burning, CO 2 and aerosols, the positive and negative climate forcings of which are partially offsetting. The growth rate of non-CO 2 GHGs has declined in the past decade. If sources of CH 4 and O 3 precursors were reduced in the future, the change in climate forcing by non-CO 2 GHGs in the next 50 years could be near zero. Combined with a reduction of black carbon emissions and plausible success in slowing CO 2 emissions, this reduction of non-CO 2 GHGs could lead to a decline in the rate of global warming, reducing the danger of dramatic climate change. Such a focus on air pollution has practical benefits that unite the interests of developed and developing countries. However, assessment of ongoing and future climate change requires composition-specific long-term global monitoring of aerosol properties.