THEY are just lines on a page, lines that point steadily upwards, ever climbing towards the right. But they are lines that all of us should take a look at from time to time, as a reminder that we need to try harder. This week it’s the methane graph, as the National Oceanic and Atmospheric Administration (NOAA), which monitors concentration of the gas, has announced that its levels had jumped by 17 parts per billion (ppb) in 2021, the largest annual increase recorded since modern measurements began in 1983.

Methane has been regarded in recent years as the “low-hanging fruit” with regard to climate mitigation, a potent greenhouse gas that we could reduce through strategies that would involve reduction of leakage from the oil and gas industry. At COP26 last year, 100 countries came together to make a Global Methane Pledge, to reduce worldwide emissions of methane by 30 per cent by 2030.

This focus on methane has come partly because of the nature of its impact as a greenhouse gas. It’s 25 times as potent as carbon dioxide but has the virtue of being more short-lived: the atmospheric residence time of methane is less than a decade, whereas some of the carbon dioxide emitted today will continue to warm the planet for thousands of years. It’s said that around 40% of the Ford Model T carbon dioxide emissions from 1911 are still in the air today.

This rising methane graph mirrors the graph we see for carbon dioxide, the Keeling Curve, whose rise shows no sign of slowing. It is almost certain that this month it will be announced that CO2 levels have hit or even exceeded 420 parts per million, according to readings at the Mauna Loa Observatory in Hawaii. The curve, in other words, is not yet flattening or even bending.

Because of methane’s potency, when it comes to hacking away fast at greenhouse gases, it is seen as a good target, though not a replacement for CO2 emissions reduction. The problem is that, though we know fairly well why carbon dioxide levels continue to increase – chiefly, our burning of fossil fuels – the reasons behind rising methane are less clear. Methane in the atmosphere, the NOAA notes, is generated by many different sources, such as fossil fuel production, transport and use, from the decay of organic matter in wetlands, and, of course, those infamous cow burps. The NOAA statement says that “determining which specific sources are responsible for variations in annual increases of methane is complex, but scientists estimate that fossil fuel production and use contributes roughly 30% of the total methane emissions”.

The emissions from fossil fuel production are what people refer to when they talk about the low-hanging fruit. The International Energy Agency earlier this year published a Global Methane Tracker, which shows where emissions are happening – and, in fact, the UK is shown as having only 11% of its methane emissions coming from the energy sector (our biggest source of methane being waste). Russia, however, sees 75% of methane emissions coming from the energy sector, the United States 54%, Oman 86%, Turkmenistan 93%. Those that would advocate fracking as the solution to our problems should note that a 2019 paper by Cornell University linked the US fracking boom to a global methane spike.

What is the picture like in Scotland? Again, we only have pieces of the picture, but SEPA recently released data from 2020, which shows methane emissions from its registered industrial sites, and which noted that “carbon dioxide, methane and nitrous oxide emissions continue to follow a downward trend, although less pronounced than in the period from 2007 to 2016.” The data, of course, only covers methane emissions from registered industrial sites, but it does tell a little bit of the story – and one of the things it shows us is that while the waste industry is on a trajectory of reduction, the energy sector saw an increase between 2019 and 2020.

The NOAA’s latest announcement is a reminder that we must keep cutting away at methane as well as carbon dioxide. It’s also a reminder of what we don’t yet know. What is worrying is that, the NOAA notes that biological sources of methane such as “wetlands or ruminant agriculture” are a primary driver. “NOAA scientists,” it says, “are concerned that the increase in biological methane may be the first signal of a feedback loop caused in part by more rain over tropical wetlands that would largely be beyond humans’ ability to control.”

It’s a note of warning. The possibility of such feedback loops should provide all the more reason to cut harder and faster – both methane and carbon dioxide. Before we really do run out of time.