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Cutting Short-Lived Climate Pollutants Best for Reducing Near-Term Warming, Impacts


Only dual strategy with CO2 can avoid breaching 2°C barrier

Washington, DC, 28 May 2015 – A new study released by Oxford University today reaffirms that cutting short-lived climate pollutants may “be a more cost-effective way to limit the rate of climate change over the coming decades to ensure that ecosystems, food production and the economy can adapt, which also has a role in avoiding dangerous climate change” in the long-term.

The study, which focuses on emissions metrics for comparing different climate pollutants, also concludes that immediate and simultaneous reductions of both short-lived climate pollutants (SLCPs) and CO2 is the best method for keeping the climate safe.

The paper, by Professor Myles Allen, explains that the dual CO2 + SLCP strategy is needed to meet the objectives of the current UN climate treaty, which states in Article 2:

“The ultimate objective of this Convention [is] stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.”

“We don’t need to choose between cutting CO2 and cutting short-lived climate pollutants.  We can and must do both,” said Durwood Zaelke, President of the Institute for Governance & Sustainable Development.  “The bottom line is that aggressive reductions in both CO2 and short-lived climate pollutants are necessary to avoid dangerous climate impacts in the near and long-term.”

According to Zaelke, cutting SLCPs to slow near-term warming has several benefits.  “First it reduces immediate climate damage, often suffered most by poorer countries, including sea level rise and more powerful storm surges and other extreme weather events.  According to research led by V. Ramanathan, cutting short-lived climate pollutants could avoid up to 0.6°C of warming by mid-century, compared to 0.1°C for CO2, and up to 1.5°C of warming by end of century, compared to 1.1°C for CO2.  The cuts to SLCPs could slow the annual rate of sea-level rise by up to 50% by end of century. Second, reducing near term warming reduces the risk of setting off more powerful feedback mechanisms such as the melting of permafrost and the release of methane, which then accelerates global warming.”

The study notes that “Many measures required to reduce short-lived climate pollutant emissions, such as reducing soot emissions from biomass burning and coal-fired power plants, would also have significant co-benefits for human health and welfare, making them much easier to achieve politically.” Zaelke explains that, “Many of these actions to cut short-lived climate pollutants will simultaneously cut CO2.  According to the Lawrence Berkeley National Lab, embracing super-efficient air conditioners while phasing down hydrofluorocarbons refrigerants, as India recently proposed doing under the Montreal Protocol, could effectively double the climate mitigation from avoiding HFC refrigerants and could save enough electricity to avoid building up to 120 medium sized power plants in India in the next 15 years.”

The Allen study raises the question whether some governments may feel they need to make a choice between CO2 mitigation or cutting short-lived climate pollutants.  Zaelke states that, “the empirical evidence is to the contrary, as many governments are already taking action to cut their air pollution while also increasing efforts to reduce CO2 by protecting forest protection, expanding renewables, and improving the efficiency of products and equipment that use fossil fuels.  China, for example, has a new air pollution law and announced plans to invest nearly $300 billion to clean the air, largely to protect public health and cut the air pollution death rate, which now exceeds two million citizens every year.”

Parties to the Montreal Protocol will meet later this year to continue negotiations on phasing down HFCs, the powerful greenhouse gas that is one of four short-lived climate pollutants, along with black carbon soot, methane, and tropospheric ozone, the main component of urban smog.  Support for the HFC amendment is growing, as India, the U.S., Canada and Mexico, the EU, and eight pacific Island states, have all submitted formal amendment proposals this year.  An agreement Montreal Protocol Meeting of Parties this November to phasedown HFCs would avoid the equivalent of up to 100 billion tonnes of carbon dioxide by mid-century, and avoid up to 0.5°C by end of the century, along with significant energy efficiency and further CO2 mitigation from improvements in energy efficiency of air conditioners and other appliances.  Additionally, concluding the HFC amendment would build political momentum for the UN climate negotiations in Paris this December, where a new climate deal may be concluded, to take effect in 2020.

Myles Allen, Short-Lived Promise? The Science and Policy of Cumulative Short-Lived Climate Pollutants

IGSD’s  Primer on SLCPs

IGSD’s  Primer on HFCs