Super Pollutants

WHAT are  super pollutants?

Super pollutants are warming agents that are far more potent than carbon dioxide per tonne. They include methane, tropospheric ozone, fluorinated gases (F-gases; such as HFCs), nitrous oxide, and black carbon. 

Most super pollutants are greenhouse gases that trap Earth’s heat in the climate (methane, tropospheric ozone, F-gases, and nitrous oxide). Some also affect the climate by increasing the amounts of other greenhouse gases through atmospheric chemistry. Black carbon (also known as soot), is not a gas but an aerosol, warming the climate by absorbing sunlight.

Many super pollutants are also relatively short-lived in the atmosphere (methane, tropospheric ozone and its precursors, HFCs, BC), with lifetimes of days to decades. This is why super pollutants are known as a flow problem – controlling how fast the planet warms, whereas carbon dioxide is known as a stock problem – controlling the maximum extent of warming. Reducing emissions of both super pollutants and carbon dioxide is essential for establishing a safer climate both during our lifetimes and for generations to come. 

WHY are super pollutants important?

Super pollutants have several environmental consequences, with implications for climate change, public health, and food security. The flip side is that reducing emissions of super pollutants yields multiple benefits to society. Super pollutant mitigation is an important complement to drastically cutting carbon dioxide.

Climate change

Emissions of  super pollutants to date have caused half of today’s  warming [IPCC 2021], and emissions are increasing – some, like nitrous oxide, at alarming rates [Global Carbon Project 2024]. 

• This means that reducing super pollutants is essential for achieving global temperature targets – especially 1.5°C. Studies, when combined, suggest that we could avoid more than half a degree (C) of warming by midcentury [e.g. Shindell et al. 2012; Shoemaker et al. 2013] and more than a degree by end of century [e.g. Shoemaker et al. 2013; Xu et al. 2013; Ocko et al. 2021] by slashing emissions of all climate super pollutants.

Many super pollutants are short-lived in the atmosphere (methane, tropospheric ozone and its precursors, HFCs, BC), meaning that while they are potent, they only influence the climate for at most a decade on average.

• Reducing super pollutants is therefore the fastest way to slow down the rate of warming in the coming decades. The moment we slash emissions, we can almost immediately reduce their warming impact. A slower rate of warming is critical for people and the planet, including reducing the risks of ever increasingly extreme events, like heat waves, wildfires, and hurricanes [e.g. Fischer et al. 2021]. The sooner we act, the more benefits to the climate we will realize [e.g. Ocko et al. 2021; Sun et al. 2022].

Air pollution

Several super pollutants also affect air quality. Tropospheric ozone and its precursors, carbon monoxide and VOCs, and black carbon, are air pollutants. And methane also forms tropospheric ozone. Tropospheric ozone, also considered ground-level ozone, is the main component of smog.

• Reducing super pollutants will improve air quality, which has major public health benefits, such as preventing respiratory illnesses that will save millions of lives by midcentury [UNEP/CCAC GMA 2021].
• Improved air quality will also reduce crop damages and strengthen food security, saving tens of millions of tonnes of crops annually [UNEP/CCAC GMA 2021].

Ozone layer depletion

Nitrous oxide can destroy the ozone layer, allowing harmful UV radiation to penetrate to Earth’s surface.

• Reducing emissions of nitrous oxide will protect the ozone layer, benefiting human health such as through reduced rates of skin cancer, and food security through less crop damage.

WHERE do super pollutants come from?

Super pollutants are emitted from every economic sector and across the globe, including power generation, fossil fuel production and distribution, industrial processes, agriculture, transportation, buildings, and waste management. Decarbonization of the global economy, while essential to climate stability, will not reduce all emissions of super pollutants – such as those from agriculture and waste management.

HOW do we reduce super pollutants?

There are available and affordable measures to drastically and immediately cut emissions of  super pollutants from nearly all sources. These measures range from improved practices, to more efficient systems, to cleaner alternatives, to capture or destruction technologies. 

In addition to implementing and scaling up existing measures to reduce emissions of super pollutants, it is important to continue innovating new ways to reduce emissions and explore possibilities of removing them from the atmosphere. 
It is also crucial to raise awareness of the importance of super pollutants.

Especially as the world actively designs its next round of nationally determined contributions, which should include all greenhouse gases, as agreed to at COP28. This will be a powerful moment for countries to commit to serious action to reduce not just carbon dioxide emissions, but emissions of all climate warming agents.