Got questions? Ask the Green Geek

Hi Green Geek,

I’m starting to hear conversations about methane being called a "super-pollutant." What does that mean? I thought CO2 was what we are trying to reduce. 

Cassandragreen geek logo

Hi Cassandra,

This is indeed a very important question and I’m happy to tell you all about it. This response is going to be a little bit longer than usual, as I will take this opportunity to incorporate some Climate Change 101 information just so you can see how methane plays into the bigger picture. It’s the bigger picture — the impacts of climate change we already see and will face in the near future — that fuels the fire of any environmental advocate, including myself. Even if this is information that you know, it’s always good to get a refresher course. 

So what’s the story with methane and why do we care about it? Methane is one of the main greenhouse gases (GHGs) found in the atmosphere. It is absolutely correct to identify CO2 as a GHG, but it’s not the only one. For the U.S., the greenhouse gases that contributed to our total 2019 emissions were (according to the Environmental Protection Agency):
  • Carbon Dioxide (80%)
  • Methane (10%)
  • Nitrous Oxide (7%)
  • Fluorinated gases (3%) 
Each of these GHGs has a different impact on the earth’s warming. If you haven’t been given this imagery before, think about a blanket covering the earth’s atmosphere. The more GHGs we emit, the thicker the blanket, and, as a result, the warmer the earth. It’s like the difference between wrapping yourself in a thin, single-layer fleece blanket versus a thick, feather-stuffed, down comforter. 

In this atmospheric "blanket," there are different concentrations of each GHG, as seen by the percentages provided above. Additionally, each GHG has a different "warming" impact dependent on its lifespan in the atmosphere and its energy absorption capacity (i.e. radiative efficiency). For the latter, there are values given to each GHG that express its radiative effect compared with CO2. This is called the Global Warming Potential (GWP). Below are the lifespans and GWPs of each GHG:
  • Carbon Dioxide: 100 years; GWP of 1 
  • Methane: 12 years; GWP of 25
  • Nitrous Oxide: 121 years; GWP of 265
  • Fluorinated gases: 10,000+ years; GWP of 100-3,000+
To go back to your comment about CO2, yes, we are quite focused on reducing how much of it we emit because of its alarming increase in our atmosphere since pre-industrial times, with a most recent peak in 2012.

Methane, however, has started to increase as well. It’s called a super-pollutant because of the heavy punch it packs as related to its GWP. Though methane only accounts for 10% of U.S. emissions, it traps up to 100 times more heat in the atmosphere than CO2 within a five-year period. Its impact is intense but short-lived since it has a lifespan of only 12 years compared with CO2's 100 years.

Reducing CO2 is only part of the battle, especially since it stays in the atmosphere longer. Since we already have an alarming concentration of CO2 in our atmosphere — our legacy carbon — reducing emissions now will, of course, help mitigate impacts in the future. However, we have devastating impacts in the pipeline already.

This is why methane is starting to come to the mitigation forefront. If we could reduce methane, it can help avoid 0.3 degrees Celsius of warming by the early 2040s. 

Now that number does not seem like a lot, right? In fact, the Paris Agreement international goal to limit global warming temps to 1.5 degrees Celsius and not have it go past 2.0 degrees Celsius above pre-industrial levels still seems insignificant if you are just looking at the face value of the numbers. 

Well, I encourage you to watch this animation of how our planet has warmed from 1880 to 2020. Even if you don’t understand the exact impacts of this warming, it still doesn’t look right. Frighteningly so, we are already seeing a temperature anomaly from 1951-1980 temperatures of 1.02 degrees Celsius. We are only 0.48 degrees Celsius away from reaching that Paris Agreement limit! 

With this perspective, reducing methane will do us some good. Without it, well, we can expect to experience devastating impacts of global warming much sooner than we would like.

Already in the pipeline is an increase of massive flooding events, the severity of droughts, extreme precipitation events and much more. Human health and our economies are at risk as well. Check out this NASA article that gives us a good breakdown of the stark realities when we reach that limit of 1.5 degrees Celsius and cross into the threshold of 2.0 degrees Celsius. 

Again, our efforts to reduce methane emissions (from fossil fuel production, agriculture and landfills) can and will make a big difference. Our reduction of fluorinated gases, more commonly hydrofluorocarbons (HFCs), can make an even greater impact. If the EPA is successful in phasing down HFCs with the support of legislation, long-term strategies and innovative technologies such as solar-powered refrigeration systems, we could help avoid 0.5 degrees Celsius of warming by 2100.

I know that sometimes all of these issues can seem larger than life, but each and every one of our efforts to educate ourselves and transition to more sustainable lifestyles makes a significant difference in the race to save our planet and learn how to live with its changes. Take a look at my past articles and look forward to the ones to come to learn more ways we can do our part together. 

Green Geek
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