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

TLDR

Global warming is widely expected to continue or accelerate, yet accurate assessment requires composition‑specific long‑term monitoring of aerosol properties. The study proposes that reducing methane and ozone precursor emissions could bring non‑CO₂ greenhouse‑gas forcing to near zero over the next 50 years. The authors find that recent rapid warming is largely driven by non‑CO₂ greenhouse gases, whose growth rate has slowed, and that curbing these gases along with black carbon and CO₂ emissions could reduce the warming rate and lessen climate‑change risks, offering shared benefits for developed and developing nations.

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-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.