Methane Levels at an All-Time High

Methane Levels at an All-Time High
The methane cycle. (Encyclopaedia Britannica)

The National Oceanic and Atmospheric Administration’s (NOAA) analysis in Colorado has shown a frightening trend of increasing atmospheric methane (CH4). The NOAA is one of the world’s longest-running greenhouse gas monitoring programmes. These high levels were measured by sampling air in different parts of the world and creating a global average.

The analysis shows that in 2019, methane levels reached nearly 1875 parts per billion (ppb) — the highest level since record-keeping started in 1983.

This graph shows annual CH4 increase — the red line indicates the average monthly mean values, and the black line indicates the long-term trend with average seasonal cycles removed. (NOAA)

Atmospheric methane is a problematic greenhouse gas (GHG) because it is 30 times more potent as a heat-trapping gas than carbon dioxide (CO2) — the GHG we tend to care the most about. In fact, methane is responsible for a quarter of total atmospheric warming to date. However, methane also has a short atmospheric concentration with emissions breaking down after 10 years, whereas CO2 takes centuries.

Furthermore, another problem with this increase in methane levels is that it is really unexpected — so much so that it was “not considered in pathway models preparatory to the Paris Agreement” and as such has significant consequences for the Paris Agreement.

Methane emissions can come from natural processes like microbial decomposition of organic material in wetlands. However, methane emissions can also result from human activities. For instance, a significant source of anthropogenic methane emissions is fossil fuel production — it is a key by-product of the extraction and processing of natural gas. Other sources include landfills, which emit methane as waste decomposes, and ruminant livestock digestive processes.

A study in 2012 reported that agricultural methane emissions from livestock production and rice cultivation accounted for 44% of anthropogenic methane. However, another study considers that a constant rate of methane emissions will have one molecule replace a previously emitted one that has since broken down — considering methane breaks down after 10 years and enters a carbon cycle that sees the gas absorbed by plants and then eaten by livestock. This means that provided there is a constant number of cattle and no new animals — meaning that the methane is being released at a steady rate — then we would see the atmospheric methane levels stay the same, and not increase. As such, breeding fewer yet more productive livestock is a viable option. Furthermore, even changing ruminant feed to be more digestible with a better balance of carbohydrates and proteins can help emit fewer methane emissions in relation to their milk or meat output. However, these feeds should not use fertilisers which increase another GHG: nitrous oxide.

The main culprit of anthropogenic methane emissions is fossil fuel production and our reliance on fossil fuels. The best way to reduce methane pollution, in this case, would be to limit its release from oil and gas drilling sites, as natural gas is prone to leaking from wells. This can be minimised by plugging the leaks and also burning (otherwise known as flaring) the natural gas that escapes — turning the methane into CO2. For instance, in response to the Trump administration rolling back guidelines, Exxon Mobil has called for other oil and gas companies to continue reducing methane emissions. They have reduced their emissions by 20% since 2017 by detecting leaks, minimising venting (the release of unburned methane), and instead flaring it, as well as reporting their total methane emissions #MakeBrandsBeTransparent. (On a side note, it is worth mentioning that American oil and gas firms such as Exxon Mobil are much less ambitious than their European counterparts like BP which has made public net-zero ambitions). All of this can be done at a low cost, with one estimate claiming that oil and gas firms could cut methane pollution by 45% at no net cost.

These rising levels of methane are unprecedented and a cause for concern. However, there is hope considering methane’s atmospheric short-termism and the rising stakeholder pressure for oil and gas companies to reduce their emissions.