Methane Vs CO2: Which Is the Most Potent Greenhouse Gas As White House Unveils New Pledge

President Joe Biden has announced a fight against methane emissions at the crucial COP26 climate change meeting this week.

Encouraging every nation to join in with the efforts, Biden said the U.S. was launching a "Global Methane Pledge" alongside the European Union with the aim of slashing methane emissions by 30 percent by 2030, and that 70 countries had signed up.

It comes as scientists are warning more urgently than ever that world leaders need to keep global temperatures from increasing by 1.5 degrees Celsius compared to pre-industrial levels.

The number is seen as a critical threshold for preventing some of the worst effects of climate change.

Carbon Dioxide is perhaps the most vilified greenhouse gas, and for good reason. It accounted for 80 percent of all U.S. greenhouse gas emissions in 2019, according to the Environmental Protection Agency (EPA).

Methane, by comparison, accounted for 10 percent.

On a global scale, CO2 accounted for 77 percent of all greenhouse gas emissions and methane for 16 percent according to a 2014 study by the Intergovernmental Panel on Climate Change.

But there are other factors to consider when deciding the severity of a greenhouse gas, and the Global Warming Potential (GWP) measurement is a good starting point.

GWP of Methane Versus CO2

The GWP was invented to allow direct comparisons between different gases implicated in global warming. It measures how much energy one ton of a gas will absorb over a given period of time compared to one ton of CO2.

If a gas has a higher GWP than CO2, it means it will warm the Earth more over that period than CO2 would.

Since CO2 is being used as the reference, it has a GWP of one. Methane has a GWP of between 28 and 36 over 100 years, according to the EPA, meaning it is significantly more potent as a greenhouse gas than CO2.

It gets worse. The GWP of methane gets even higher over shorter periods of time due to the gas' shorter life span. Over a period of 20 years, methane has a GWP of between 84 and 87.

According to the Environmental Defense Fund, while CO2 lasts for longer than methane, methane "sets the pace for warming" in the short term.

CO2 is Hard To Shake

On the other hand, CO2 has proven tough to tackle. It is easy to emit due to human activity, and once it's in the atmosphere it can linger for not just hundreds but thousands of years, depending on how it's transferred back into the environment.

Methane, by comparison, has a lifetime in the atmosphere of just 12 years, the EPA notes.

Combustion of fossil fuels such as gasoline and diesel for transport, electricity production and industrial processes all churn huge amounts of CO2 into the atmosphere, and a growing population and increased demand for travel mean that (despite urgent cries to cut CO2 over the past several years) U.S. CO2 emissions were actually higher in 2019 than they were in 1990, despite a reduction in the mid-2000s according to the EPA.

Methane emissions decreased by 15 percent over the same time period.

To tackle methane emissions further, the Global Methane Pledge will put restrictions on emissions from methane sources, such as oil and gas well sites.

According to a White House statement, these restrictions could cut methane emissions from covered operations by around 75 percent.

It will also seek to boost methane capture efforts from landfill sites—key methane contributors—and work with farmers to slash methane emissions from agriculture.

The agriculture sector, including the farming of animals for food, is the largest source of methane emissions in the U.S., according to the EPA, though the White House said today that the oil and gas industry was the worst.

Power plant
A photo shows a California power plant in December, 2008. Emissions of CO2 stay in the air longer than methane, but methane is more potent in the short term. David McNew/Getty