UNEP’s 2017 Emissions Gap report says reduction of short-lived climate pollutants, including HFCs, is an important part of mitigation efforts to meet Paris Agreement’s 2ᵒC target.
The 8th Emissions Gap Report, published this month by the United Nation Environment Programme (UNEP), for the first time acknowledges the potential contribution short-lived climate pollutants (SLCPs) such as HFCs, methane, and black carbon (soot), can play in the global effort to keep the planet’s warming gain above pre-industrialized levels below 2ᵒC.
An online post by the Climate & Clean Air Coalition (CCAC) Secretariat, citing the UNEP report, noted that over the period 2018-2050, “stringent SLCP reductions based on existing, demonstrated technical measures could reduce warming by between 0.3ᵒC and 0.9 ᵒC relative to current emissions projections.” Roughly half of the mitigation potential is associated with methane, one-third with black carbon, and the remainder (about 17%) with HFCs.
“Reductions of SLCPs limit the rate of short-term warming and when sustained and combined with carbon dioxide (CO2) also help limit long-term warming,” the UNEP report says.
An example of the potential of SLCP-reduction is the Kigali Amendment to phase down hydrofluorocarbons (HFCs) under the Montreal Protocol, “Agreed to in October, 2016, the Amendment has the potential to decrease HFC emissions by 61% and prevent up to 0.09˚C of warming by 2050,” noted the CCAC Secretariat. “Technology alternatives to HFC cooling and refrigeration systems are also often much more energy efficient than the systems they replace, which provides additional CO2 and air quality benefits by reducing energy consumption.”
By the turn of the century, the Kigali Amendment is structured to avoid 0.5ᵒC of warming.
“Reductions of SLCPs limit the rate of short-term warming and when sustained and combined with carbon dioxide (CO2) also help limit long-term warming.”
– UNEP's 2017 Emissions Gap Report
The UNEP report looks at the gap between emissions reductions needed to hold global warming to well below 2ᵒC (preferably no more than 1.5ᵒC) and the likely emissions reductions from full implementation of the Paris Agreement. The report concludes that “there is an urgent need for accelerated short-term action and enhanced longer-term national ambition if the goals of the Paris Agreement are to remain achievable – and that practical and cost-effective options are available to make this possible.”
Fast action to reduce SLCPs would also help “reduce climate change impacts caused by cumulative heat uptake (for example, sea-level rise, and glacier and ice sheet melting) and reduce the likelihood of passing irreversible temperature thresholds and triggering large positive feedbacks,” said the CCAC Secretariat.
The lead authors of the section of the UNEP report on SLCPs (chapter six, “Bridging the gap - The role of short-lived climate pollutants”) are Zbigniew Kilmont, Research Scholar at the International Institute for Applied Systems Analysis (IIASA) and Drew Shindell, Professor of Climate Science at Duke University and Chair of the Climate and Clean Air Coalition Scientific Advisory Panel.