Durwood Zaelke

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

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.

The importance of phasing down hydrofluorocarbons and other short-lived climate pollutants

While negotiations continue for a United Nations (UN) Framework Convention on Climate Change (FCCC) by December 2015 to take effect in 2020, a parallel effort to achieve fast climate mitigation is needed under the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol) to slow current impacts and reduce risks of passing tipping points that trigger self-amplifying feedback mechanisms that accelerate warming. Fast reductions of short-lived climate pollutants (SLCPs), including black carbon (BC), methane (CH4), tropospheric ozone (TO3), and hydrofluorocarbons (HFCs), can cut the rate of climate change in half by mid-century and by two thirds in the Arctic. The Montreal Protocol can be used to quickly phase down production and consumption of high global warming potential (GWP) HFCs, which can avoid 0.1xa0°C of warming by 2050, and 0.5xa0°C by 2100, while catalyzing improvements in appliance energy efficiency, which will provide further climate change mitigation by reducing energy use and carbon dioxide (CO2) emissions, particularly in fast-growing economies like India and China. The simultaneous global deployment of existing technologies can reduce emissions of BC, CH4, and TO3 by enough to avoid an additional 0.5xa0°C of warming by 2050, while providing immediate benefits for human health, agriculture, and sustainable development. Fast action to reduce the four SLCPs will reduce the risk of setting off irreversible feedback mechanisms and provide urgent optimism and momentum for a successful UN climate treaty in 2015.