Each GHG stays in the atmosphere for periods of time that differ depending on multiple factors and interdependencies. Methane has a lifetime in the atmosphere of about a decade (+/- 2 years) before being broken down through oxidation, compared to carbon dioxide’s much longer atmospheric lifetime of hundreds of years.

To understand the impact of each GHG, we consider its Global Warming Potential (GWP). GWP is a measure of how effectively a GHG traps heat in the atmosphere over time, enabling us to compare the radiative impacts of two or more gases to that of carbon dioxide—hence, “carbon dioxide equivalent”, or “CO2-e”.

Under the GWP 100 comparison, methane is 28 times more potent than carbon dioxide over a 100-year period. A shorter-term comparison paints a more disturbing picture. According to the IPCC’s 2021 report, the 20-year GWP of methane is over 80 times greater than that of carbon dioxide. Because methane breaks down after about a decade, it does its damage in the short term, a fact that is not readily apparent if we use only GWP 100. (Note that the newer GWP*, while mentioned in the IPCC’s 2021 report, is not widely used at this time and has been criticized as being inadequate as an emissions metric.)

INGER ANDERSEN, EXECUTIVE DIRECTOR OF THE UNITED NATIONS ENVIRONMENT PROGRAMME, CONCLUDES:

“Cutting methane is the strongest lever we have to slow climate change over the next 25 years and complements necessary efforts to reduce carbon dioxide.”

Both GWP 100 and GWP 20 are needed, because each measure reflects a different but key aspect of climate impact. Including both measures enables us to focus appropriately on both short-lived climate pollutants (SLCPs) like methane, as well as long-lived GHGs like carbon dioxide. The Global Methane Pledge, launched in 2021 at COP26 and now with more than 150 participating states, indicates that methane reduction has been recognized as a global priority.

GWP measures are in flux

In an earlier IPCC report, the 20-year GWP of methane was estimated to be 84 times, not 80 times, that of carbon dioxide. Why the difference?

GWPs are updated periodically to reflect changes in the estimated atmospheric lifetimes of GHGs and atmospheric concentrations that impact the behavior of other GHGs. These updates are just one illustration of the fact that climate is a complex and dynamic system.

New research suggests that as rising global temperatures lead to increased methane emissions, the atmosphere’s ability to rid itself of methane is hampered by increased wildfires.

The methane situation today

Atmospheric methane concentrations were at about 720 parts per billion (ppb) in the pre-industrial era but have risen sharply since then, with a marked acceleration between 2007 and 2021, when atmospheric methane exceeded 1,900 ppb.

About 40% of global methane emissions are due to natural sources and processes, while 60% are from human activities (anthropogenic). The precise nature of the relationship between man-made warming and natural emissions is not fully understood, but there is growing concern in the scientific community that warming is feeding warming.

Agriculture is the largest single source of man-made methane emissions, producing about 150 million tonnes per year. In a 2020 study, methane from manure management and enteric methane was estimated to be one third of total global anthropogenic emissions.

Enteric methane is produced by ruminant animals like cattle, sheep, and goats, as a natural part of their digestion, and they emit it mainly through belching.

Because global demand for meat and dairy products (critical sources of protein) is projected to grow significantly over the next decade, agricultural methane, and specifically enteric methane, will also grow unless effective solutions are implemented rapidly.

Reducing enteric methane

Proven solutions to radically reduce enteric methane already exist in the market.

Large-scale food producers and processors have begun to adopt CH4 Global’s natural supplement (feedstock additive). Our solution is based on Asparagopsis seaweed, a material that has been shown in numerous scientific studies to reduce enteric methane by up to 90%. Other options exist to reduce enteric methane, and while not nearly as effective, they have a role to play in the producer’s tool set.

Our enteric methane-reduction roadmap includes a 5-year target of reaching 150 million cattle on all six habitable continents, which will prevent the emission of more than 1 gigatonne of carbon dioxide equivalent. As a point of reference, it will deliver more climate benefit annually than decommissioning 50 - 100 million fossil-fueled cars (depending on whether measuring GWP 100 or 20).

By achieving our mission, we and our partners will help buy valuable time for other climate innovations to be developed and implemented while there’s still time.

References