M. Molina et al., PNAS, Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions

Proceedings of the National Academy of Sciences, published online before print October 12, 2009; doi: 10.1073/pnas.0902568106

Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO₂ emissions

Mario Molina, Durwood Zaelke*, K. Madhava Sarma, Stephen O. Andersen, Veerabhadran Ramanathan and Donald Kaniaru

Edited by Hans Joachim Schellnhuber, Environmental Change Institute, Oxford, U.K., and approved August 31, 2009 (received for review March 9, 2009).

Abstract

Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of “dangerous anthropogenic interference” (DAI). Scientific and policy literature refers to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to help avoid DAI and abrupt climate changes. We define “fast-action” to include regulatory measures that can begin within 2–3 years, be substantially implemented in 5–10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO₂ GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO₂ emissions. 

*Correspondence; e-mail: dzaelke@igsd.org or zaelke@inece.org

Link to abstract:  http://www.pnas.org/content/early/2009/10/09/0902568106.abstract