Is methane a greenhouse gas?

Methane is a more powerful greenhouse gas than carbon dioxide, but there is far less of it in the atmosphere and it does not stay there as long. Methane is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere over the course of a century, but it has an 'atmospheric lifetime' of around 12 years, whereas carbon dioxide molecules hang around for hundreds of years.

This means that if humans stopped adding any methane to the atmosphere tomorrow, within several decades all trace of the extra methane and its climate influence would be gone, whereas the same is not true for carbon dioxide. However, methane is still an important greenhouse gas because there are many human-caused sources of it. Methane today is responsible for about 0.5°C of total warming.

Methane is released during the extraction and transport of fossil fuels including coal, oil and natural gas. It is also released by rice fields, the decay of food waste in rubbish dumps, and even cows - meaning the rise in beef consumption worldwide has increased methane emissions.

There are also natural sources of methane that are being released faster due to global warming itself. These include the melting of permafrost, the layer of previously permanently frozen ice within soil in polar and sub-polar regions. These methane emissions could in turn accelerate warming, leading to the release of more methane, and so on.

Dr Joeri Rogelj, Director of Research at the Grantham Institute, Imperial College London, says, 'Methane does not persist for long in the atmosphere but is nevertheless a powerful greenhouse gas. If we make rapid cuts to methane emissions now, together with efforts to drastically reduce our carbon dioxide emissions, it will ensure that we limit global warming as much as possible.'

At the COP26 climate summit, more than 90 nations agreed to cut their methane emissions by 30% by 2030 compared to 2020.

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