Methane is not given enough consideration as a climate killer

When people talk about climate change, they quickly think of carbon dioxide. But experts are also concerned about another greenhouse gas. The concentration of methane in the atmosphere has been rising rapidly in recent years and no one can yet explain why.

The concentration of methane in the atmosphere in 2022 was more than 2.5 times higher than before the industrial revolution, as reported by the World Meteorological Organization (WMO) - for the main greenhouse gas carbon dioxide, it is 1.5 times higher. Researchers have evidence that this is not only due to energy consumption and agriculture, but that global warming is causing more methane to rise from wetlands. Methane (CH4) has around 85 times more impact on the climate than carbon dioxide (CO2) over a 20-year period.

The WMO cites two probable causes for the sharp rise in methane since 2007. Measurement data "indicate that increasing CH4 emissions from wetlands in the tropics and from anthropogenic sources in the mid-latitudes of the northern hemisphere are the likely causes of this recent increase." In the case of man-made CO2, the WMO mentions energy production from coal, oil and gas as well as agriculture.

Is climate change itself a methane driver?

"There are many indications that climate change is the main reason for the increase in methane in recent years," says Thomas Kleinen from the Max Planck Institute for Meteorology, referring to emissions from natural sources. "Most chemical processes run faster when it's warm," and this also applies to microorganisms that produce methane. "Therefore, even a slight increase in temperature can lead to a sharp rise in methane production." At the same time, however, there is a higher uptake of the greenhouse gas CO2 by plants.

It is also very likely that the increase in methane since the mid-2000s has mainly come from tropical wetlands. "But it's difficult to measure," says Kleinen. "Rainforests are often difficult to access."

Methane from thawing permafrost

Many experts fear that the permafrost region could also release large quantities of methane one day. Whether this has already begun is unclear. Huge amounts of plant remains are frozen in the permafrost and therefore a lot of carbon. If it thaws, the greenhouse gases carbon dioxide (CO2) or methane (CH4) can be produced from the carbon (C) in the plants. The latter is formed by bacteria in the absence of air. This also happens in the stomachs of cattle and sheep, on landfill sites or in rice fields.

As the Arctic warms, the permafrost soil is increasingly thawing in many places and becoming warmer, says Guido Grosse, Head of the Permafrost Research Section at the Alfred Wegener Institute for Polar and Marine Research in Potsdam. "We've been seeing this for some time."

However, there is now also selective data on increased methane emissions. "We have measured more methane during various and more frequent dew processes in the Arctic." The soil is influenced by many events, such as sea growth, forest fires, landslides, the collapse of permafrost moors and coastal erosion. Studies have shown that they occur more frequently and lead to faster permafrost thawing. "In all of these processes, old carbon is mobilized from permafrost soils and thawed," says Grosse. For a large proportion of such events, it has been proven that increased methane is formed and emitted, particularly in the first years and decades.

No one can say how much methane will be released

However, the future scale of methane release is still uncertain, says Grosse. Methane is mainly produced in the Arctic when the soil is moist, carbon dioxide when it is drier. "It is still unclear what the thawing permafrost soils of the Arctic will be like in the future and depends on many factors that are currently difficult to predict."

The permafrost region covers around a quarter of the land surface in the northern hemisphere. Kleinen from the MPI for Meteorology emphasizes that a lot of methane has always come out of the ground naturally, especially in damp areas of the tundra. An increase in methane emissions can currently be measured in the Arctic. However, there are only a few such measurements and the emissions depend heavily on local conditions. "It is difficult to draw conclusions about the entire Arctic from the few measurements we have. The question is how representative the measuring points are," says Kleinen.

"I am not aware of any study that proves that methane emissions have already increased in the permafrost region as a result of climate change," emphasizes Torsten Sachs from the Potsdam Geo Research Centre. So far, there have been very few measurement series spanning more than ten years.

Sachs and his colleagues analyzed methane emissions in the Siberian tundra between 2002 and 2019 at the Lena River delta. It had become warmer there and methane emissions had increased by 1.9 percent per year for June and July. "To our knowledge, we provide the first observational evidence for an increasing trend in early summer methane emissions from tundra wetlands associated with atmospheric warming," the team writes in the journal Nature Climate Change in 2022.

Russia's war of aggression interrupts investigation

However, Sachs does not want to see the study as proof of the onset of increasing methane emissions in the permafrost region. "We show increased emissions in June and July. Nothing changes in August, in September it is statistically unclear and possibly decreasing. We lack sufficient data for the rest of the year." The fact that something shifts in early summer does not mean that more is being emitted over the course of the year. It is currently not possible to continue the measurements as his team is unable to travel to Russia and is no longer receiving any data.

Sachs refers to another long series of measurements from a station in Alaska. There, it had become 1.2 degrees warmer between 1986 and 2015, but there had been no additional methane emissions.

According to Grosse, permafrost is the largest store of carbon on land. "We have to put the brakes on man-made greenhouse gases. With everything we emit, we ensure that more permafrost thaws and more of the previously frozen carbon is released."

According to the World Weather Organization, around 40 percent of methane emissions currently come from natural sources. Around 60 percent is caused by humans with cattle, rice cultivation, the extraction of fossil fuels, landfills and biomass combustion.

Reducing methane emissions by 2050

At the initiative of the EU and the USA, numerous countries decided at the 2021 Glasgow Climate Conference to reduce methane emissions by 30 percent between 2020 and 2030. The project aims to reduce global warming by at least 0.2 degrees by 2050. According to the International Energy Agency, around 150 countries that emit more than half of man-made methane have signed up to this agreement, the Global Methane Pledge (GMP ), by the beginning of 2023. However, the world's largest methane emitter China, India and Russia are among those missing.

China presented its own 14-page methane reduction plan at the beginning of November 2023. However, it is very vague. In mid-November, the EU Parliament and countries agreed to tighten the rules for the oil, gas and coal industries - with a fixed timetable.

"Overall, the Global Methane Pledge has managed to draw attention to the issue," says Thea Uhlich, climate spokesperson for the organization Germanwatch. In fact, the USA and the EU refer to many new international initiatives and funding in a joint letter. New GMP initiatives are expected at the climate conference in Dubai, which runs until December 12.

"Ultimately, of course, what counts is whether the GMP leads to actual methane reductions that would not have occurred without it," says Uhlich. It is still too early for an assessment. Bill Hare, head of the "Climate Analytics" organization, points out that the GMP target is not enough to limit global warming to 1.5 degrees, as envisaged in the Paris Agreement. This would require a global reduction of 34 percent by 2030.

Germany with good results

According to the Federal Environment Agency (UBA), Germany has already reduced its methane emissions by 66% between 1990 and 2022. This is mainly due to a drastic reduction in the energy and waste sector, such as the cessation of hard coal mining. Mine gas is being extracted and used, and less gas is also escaping from landfill sites. Waste separation and the use of biogas were important factors here.

At almost 76 percent, agriculture is currently the largest source of methane in Germany, with cattle farming accounting for the majority. This is also where Ann-Sophie Katte from the Federal Environment Agency sees the greatest leverage for citizens: a plant-based diet with fewer products from cattle and other ruminants. "Other levers can be the purchase of organically produced products and the avoidance of food waste."

Wet rice cultivation accounts for eight percent of global man-made methane emissions. "As methane emissions from rice cultivation are lower than those from meat and milk production and the amount of rice consumed per capita in Germany is quite low, no recommendations are currently being made on the consumption of rice," says Katte.