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Reducing CO2 emissions is essential to limit long-term warming but it cannot slow warming quickly enough to stay below 1.5°C or even 2.0°C by the 2050s.
While carbon dioxide (CO2) is the largest single contributor to current warming, responsible for about half of the warming, the non-CO2 climate pollutants are responsible for the other half.
Reducing CO2 emissions is essential to limit long-term warming but it cannot slow warming quickly enough to stay below 1.5°C or even 2.0°C by the 2050s. This is because when fossil fuels are burned, short-lived cooling aerosols are co-emitted as byproducts. A realistically paced phase-out of fossil fuels, or even a rapid one under aggressive decarbonization, is likely to have minimal net impacts on near-term temperatures because the removal of co-emitted aerosols will unmask the true magnitude of warming the planet is experiencing today.
The non-CO2 climate pollutants include the four short-lived climate pollutants (SLCPs or “super climate pollutants”)—methane (CH4), black carbon soot, tropospheric ozone (O3), and hydrofluorocarbons (HFCs)—as well as the longer-lived nitrous oxide (N2O). Because short-lived super climate pollutants only last in the atmosphere from days to 15 years, reducing them will prevent 90 percent of their predicted warming within a decade.
Reducing non-CO2 climate pollutants is the fastest way to reduce near-term warming over the next two decades and the only currently known way to slow the rate of warming in the near term, limit self-amplifying climate feedbacks, and avoid or at least slow irreversible tipping points.
Fast Mitigation
Mitigation strategies targeting non-CO2 climate pollutants can cut the rate of global warming in half
A fast phasedown of HFCs can avoid nearly 0.1°C of warming by 2050 and up to 0.5°C by the end of the century, according to the Quadrennial Scientific Assessment of Ozone Depletion (2018). The Assessment also calculated that the initial schedule of the Kigali Amendment to the Montreal Protocol will capture 90% of the potential (0.44°C; range 0.4-0.5°C) and that an accelerated schedule or leapfrog strategy can capture the rest. Promoting the energy efficiency of cooling technology during the switch to climate-friendly refrigerants would double these climate benefits.
Cutting anthropogenic methane emissions by 45% by 2030 can avoid additional warming of nearly 0.3°C by the 2040s, with the potential for significantly more avoided warming from emerging technologies to remove atmospheric methane faster than the natural cycle—with the potential of avoiding up to 0.6°C by mid-century.
Reducing anthropogenic N2O emissions by 50-75% by 2030 can avoid up to 0.05°C of warming by 2050.
These non-CO2 mitigation strategies comprise a fast mitigation sprint that can avoid four times more warming by 2050 than targeting CO2 alone, which is a longer-term marathon.
The good news is we have shovel-ready technologies and policy proposals at hand. Some of the quickest actions we can take include:
- Require climate-friendly refrigerants and cooling equipment that are super energy-efficient. Cutting HFCs under the Kigali Amendment to the Montreal Protocol can avoid up to 0.5°C of future warming.
- Deploy soot-free diesel. Retrofit diesel vehicles fueled by ultra-low sulfur diesel with diesel particulate filters, on the way to electric vehicles and perhaps hydrogen for trucking.
- Ban food waste from landfills. One-third of food waste is dumped in landfills. Along with other organic waste, it is one of the largest sources of methane, equivalent to the emissions of 37 million cars. The edible part of the food should be used to feed the hungry while the non-edible can be processed through biodigesters to produce renewable fuels.
- Manage manure on farms. Reduce methane and other climate pollutants produced by cattle and other farm animals through feed additives and manure management including biodigesters that can produce renewable fuel as we shift our diet to depend less on farm-raised animals.
- Fix pipeline leaks. Replace leaky equipment and ramp up monitoring and detection to reduce fugitive methane from transmission and distribution of natural, or fossil, gas.
Winning the super pollutant sprint is critical for staying within the limits of adaptation and for building resilience.
Super Pollutants Resources
Long-term success requires that NDCs be aggressive in terms of ambition and comprehensive in terms of gasses and sectors covered. We call upon nations to include all GHGs in the next NDCs and specify additional ambitious quantitative contributions from methane and other non-CO₂ gasses; this is a critically important opportunity to increase overall mitigation ambition, […]
Super pollutants
Nitrous oxide (N2O) is a potent greenhouse gas and an ozone-depleting substance (ODS). Its global warming potential over 100 years is 273 times greater than that of carbon dioxide (CO2). To slow self-amplifying feedbacks and avoid irreversible climate tipping points, the world must quickly cut global human-caused N2O emissions as part of any fast climate […]
Super pollutants
The IGSD Resource Guide on Preventing the Dumping of Inefficient Cooling Equipment provides information and resources for government representatives and their advisors, researchers, academics, non-profit, philanthropic and other nongovernmental organizations, and other citizens to understand the practice of environmentally harmful dumping of new but energy-inefficient cooling equipment that uses high global-warming-potential refrigerants. The Resource Guide also provides insights for those working […]
Super pollutants
PxD and IGSD are partnering on an initiative to collaboratively identify opportunities for innovation in climate change mitigation, particularly for the greenhouse gases most problematic in agricultural production, methane, and nitrous oxide, as well as carbon dioxide. This initiative includes four analytical pieces on the opportunities for climate change mitigation by smallholder farmers. Methane is […]
Super pollutants
The remaining carbon budget framework tracks progress towards the Paris Agreement’s goal to limit longer-term warming to well below 2 °C, but no analogous framework exists for constraining mid-century warming. Established single-basket methods of combining gases into CO2-equivalents using Global Warming Potentials (GWPs) lead to ambiguity over what combination of short- and long-lived emissions reductions […]
Super pollutants
Anthropogenic methane (CH4) emissions increases from the period 1850–1900 until 2019 are responsible for around 65% as much warming as carbon dioxide (CO2) has caused to date, and large reductions in methane emissions are required to limit global warming to 1.5°C or 2°C. However, methane emissions have been increasing rapidly since ~2006. This study shows […]
Super pollutants
This IGSD Background Note summarizes the science supporting the need for fast climate mitigation to slow warming in the near term (2022–2041). It also describes the importance of cutting short-lived climate pollutants and protecting sinks in order to slow self-reinforcing feedbacks and avoid tipping points. It explains why winning a fast mitigation sprint to 2030 […]
Super pollutants
Climate change poses an existential threat to humankind. The intertwined nature of climate change and human rights becomes apparent as we witness the adverse effects on various dimensions of human life. To address the climate emergency, we must slow down the rate of warming as much as possible as quickly as possible. Only a dual […]
Super pollutants
Cutting methane emissions is the fastest way to slow warming in the near term and keep the goal of limiting global warming to 1.5°C within reach. Methane plays an increasingly important role in China’s responses to climate change. This paper reviews a number of measures aimed at reducing its methane emissions China has adopted over […]
Super pollutants
By phasing out production and consumption of most ozone-depleting substances (ODSs), the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol) has avoided consequences of increased ultraviolet (UV) radiation and will restore stratospheric ozone to pre-1980 conditions by mid-century, assuming compliance with the phaseout. However, several studies have documented an unexpected increase in […]
Super pollutants
Fast action to mitigate non-CO2 climate pollutants, such as methane, including through implementing methane intensity requirements (such as via procurement specifications) for domestic and imported oil and gas, can have a significant role in reducing the likelihood of triggering catastrophic climate impacts as countries pursue carbon-neutrality goals. Without robust monitoring, reporting, and verification (MRV) of methane emissions, we will not be […]
Super pollutants
The Global Cooling Watch report, Keeping it Chill: How to meet cooling demands while cutting emissions – by the UN Environment Programme-led Cool Coalition – lays out sustainable cooling measures in three areas: passive cooling, higher-energy efficiency standards, and a faster phase down of climate-warming refrigerants. The report is released in support of the Global Cooling Pledge, a […]
Super pollutants