Why Compare Methane to CO2 Over 100 Years?

Written By Teacher: Teresa Pettitt-Kenney

Hi there! My name is Teresa and I just finished my Bachelor's degree in Environmental Science and am excited to pursue environmental education in the future! I am extremely passionate about climate change, equitable climate action, and how education can work to address these issues. 

When we talk about climate change and greenhouse gases, the focus usually centers around CO2. As our students’ understanding of climate change grows, we can start to dive into greenhouse gases further and better grasp why certain industries contribute the most to climate change. Explore the greenhouse effect of methane through lesson plans, like Methane and Climate Change or dive into the chemistry of carbon dioxide versus methane through games, such as Carbon Crush. Read on for key insights into methane and carbon dioxide that will help you bring these important concepts to life in your classroom.

Written By: MIT Environmental Solutions Initiative

The MIT Climate Change Engagement Program, a part of MIT Climate HQ, provides the public with nonpartisan, easy-to-understand, and scientifically-grounded information on climate change and its solutions.

Methane is a colorless, odorless gas that’s produced both by nature (such as in wetlands when plants decompose underwater) and in industry (for example, natural gas is mostly made of methane). It is widely regarded as the second most important greenhouse gas, after carbon dioxide (CO2). However, methane is about 200 times less abundant in the atmosphere and lasts there for only about a decade on average—while CO2 can last for centuries. To put it another way: methane does its damage quickly but soon fades away, while CO2 traps a smaller amount of heat consistently, decade after decade.

Jessika Trancik, an MIT associate professor at the Institute for Data, Systems, and Society, says this interplay of different factors makes it hard to compare these two gases directly. Climate scientists often think about the issue like this: Exactly how many tons of CO2 would it take to warm the Earth as much as one ton of methane?

The trouble is that the answer changes depending on how far in the future you look. Let’s say a factory releases a ton of methane and a ton of CO2 into the atmosphere today. The methane immediately begins to trap a lot of heat—at least 100 times as much as the CO2. But the methane starts to break down and leave the atmosphere relatively quickly. As more time goes by, and as more of that original ton of methane disappears, the steady warming effect of the CO2 slowly closes the gap. Over 20 years, the methane would trap about 80 times as much heat as the CO2. Over 100 years, that original ton of methane would trap about 28 times as much heat as the ton of CO2.