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 0.1 °C of warming by 2050, and 0.5 °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 0.5 °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.