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

Abstract

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-CO₂ greenhouse gases (GHGs), such as chlorofluorocarbons, CH₄, and N₂O, not by the products of fossil fuel burning, CO₂ and aerosols, the positive and negative climate forcings of which are partially offsetting. The growth rate of non-CO₂ GHGs has declined in the past decade. If sources of CH₄ and O₃ precursors were reduced in the future, the change in climate forcing by non-CO₂ GHGs in the next 50 years could be near zero. Combined with a reduction of black carbon emissions and plausible success in slowing CO₂ emissions, this reduction of non-CO₂ 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.