Climate change mitigation is about more than just carbon dioxide. The so-called “short-lived climate pollutants” such as soot, methane, and tropospheric ozone all have harmful effects. Climate policy must be guided by a clearer understanding of its disparate impacts.
It is a common practice in climate policy to group together the pollutants of global warming and express their overall impacts in terms of “CO2 equivalence”. This “parity” is based on a comparison of climate impacts on a 100-year timescale. This approach poses a problem, as IASS scientist Kathleen Maar explains in a new paper: “The truth is that climate influencing factors are simply not“ equivalent ”- their impacts on climate and ecosystems are distinct. Short-lived climate factors have the greatest impact on climate in the near term, While carbon dioxide has the largest impact on the climate in the long term. Using a 100-year time horizon as a primary basis for assessing climate impacts reduces the impacts of short-lived climate-impacting pollutants (SLCPs) and thus reduces the value of the near-term positive impacts that can be achieved by reducing SLCP emissions.
Reducing SLCP emissions benefits climate, human health and food security
One of the most harmful qualities of carbon dioxide is that it accumulates in the atmosphere – once it is emitted, it takes a long time to remove it. On the other hand, persistent organic pollutants remain in the atmosphere for much shorter periods. The atmosphere and climate system are reacting more quickly to the decreases in emissions of these pollutants. Marr argues that this should be a boon for policymakers: “Reducing SLCP emissions would slow climate warming in the near term, reduce air pollution, and improve crop yields – all the positive benefits that citizens can experience today and in the near future.” Studies show that a rapid reduction in emissions of persistent organic pollutants can slow the rate of climate change, reduce the risk of causing dangerous and irreversible climate tipping points, and allow more time for climate adaptation.
Measures to reduce emissions of persistent organic pollutants can be implemented using current technologies and practices, such as collecting landfill gas for power generation. Changes in other sectors will be needed to achieve further cuts. Methane and soot emissions from the agricultural and waste management sectors, for example, have important climate impacts as well as health impacts. Likewise, hydrofluorocarbons (HFCs), which are more powerful climate forcing agents than carbon dioxide, are still widely used as refrigerants.
Designing Effective Climate Change Mitigation: Don’t Overlook Persistent Organic Pollutants
Marr argues that clear communication on different time horizons related to mitigating CO2 emissions and short-lived climate pollutants will help steer climate policy discussions toward more effective outcomes: “To mitigate the more damaging consequences of climate change as a whole, we need to reduce both the short-term and the impacts. Long-term climate – this means reducing persistent organic pollutants in parallel with carbon dioxide. However, the positive benefits of mitigating the effects of persistent organic pollutants simply are not captured when the 100-year time horizon is used as the sole criterion for assessing climate impacts.
Realizing the broader benefits of reductions in persistent organic pollutants, many countries have stepped up and made mitigation of the impact of persistent organic pollutants a core component of their national climate strategies. Chile, Mexico and Nigeria include persistent organic pollutants in their national obligations under the Paris Agreement. If this kind of holistic approach can be scaled up and translated into on-the-ground emissions reductions on a global scale, it would certainly be a win not just for climate, but for air quality, health and sustainable development.
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