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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
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
This paper reviews MLF accomplishments, summarizes TEAP assessment of funding required to replenish MLF, and offers analyses of the benefits that could be achieved with more funding.
Super pollutants
In an effort to provide insight into six Southeast Asian (SEA) markets at risk of environmental dumping, CLASP and IGSD assessed the RAC markets for Indonesia, Malaysia, the Philippines, Singapore, Thailand, and Vietnam. The six countries represent 90% of the regional SEA market. Currently energy efficiency policies in Southeast Asia lag behind the innovation in […]
Super pollutants
There are well-established international standards for GHG monitoring and reporting, notably those under the UN Framework Convention on Climate Change (UNFCCC). This study examines: (i) GHG data monitoring and reporting for mandatory carbon markets based on China’s sector-based reporting standards; (ii) methods and practices related to carbon sequestration measurement; (iii) metrics and measurement standards for […]
Super pollutants
The transition away from the production and consumption of high global warming potential (GWP) hydrofluorocarbons (HFCs) under the 2016 Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer has prompted air conditioning, refrigeration, and heat pump equipment manufacturers to seek alternative refrigerants with lower direct climate impacts. Additional factors affecting alternative […]
Super pollutants
Each year, one-third of the total food for human consumption is either lost or wasted even as millions worldwide experience food insecurity. Similarly, over 25 percent of vaccines are wasted each year while millions die from vaccine-preventable illnesses Sustainable cold chain infrastructure can significantly reduce post-harvest food loss and vaccine wastage and deliver social and […]
Super pollutants Other efforts
Multilateral approaches to nitrogen pollution are generating synergies between climate change and food security and presenting opportunities to reduce nitrous oxide (N2O) globally. N2O is the most abundant ozone-depleting substance not yet regulated by the Montreal Protocol and a powerful greenhouse gas. Failure to reduce emissions will delay ozone layer recovery and worsen the climate […]
Super pollutants Other efforts
Heating and cooling demand for space conditioning and refrigeration accounts for around a fifth of global final energy consumption. Climate change, urbanization, and economic development have tripled electricity demand for cooling alone since the 1990s, with the majority coming from the use of inefficient cooling equipment, which burdens electricity grids, especially during peak hours. It […]
Super pollutants Other efforts
Cities are responsible for over 70 percent of global greenhouse gas emissions and 75 percent of primary energy consumption. By 2050, over two-thirds of the world population will live in cities, resulting in even greater infrastructure needs and increased carbon emissions. Yet, cities largely remain on the sidelines in the design of national and international […]
Super pollutants Other efforts
This paper recalls and documents the military leadership under the Montreal Protocol, presents indicative case studies of how technical performance of military systems was maintained or improved by adopting newer technologies and summarizes key lessons from military leadership in protecting the ozone layer. In addition to collaboration on technology development and demonstration, between 1991 and […]
Super pollutants