Methane emissions from Arctic-Boreal humid regions continue to grow

What is happening in the Arctic-Boreal regions is a manifestation of the climate feedback mechanism to global warming. The "anthropic" methane emission indirectly produces an increase in the "natural" methane emission, thus accelerating the global warming process.

Climate change.
Increases methane emission with consequent increase in the greenhouse effect and global warming.

A weak point in predicting the future evolution of climate change is represented by the natural climate feedback mechanisms, the so-called climate feedback. If on the one hand nature tends to counteract climate change, on the other hand it reacts by intensifying it.

A natural counteracting mechanism is, for example, the removal of excess carbon dioxide through absorption by plants or storage in the oceans in the form of carbonates. A reinforcing mechanism is instead the reduction of the albedo, whereby the Earth reflects less solar energy and absorbs more, or as we will see an increase in methane emission.

The role of methane in climate change

After carbon dioxide (CO2), methane (CH4) is the most abundant greenhouse gas produced by human activities (anthropogenic activities). Its production is estimated to represent approximately 20-30% of global greenhouse gas production. Although produced in smaller percentages, methane has a greenhouse effect up to 34 times greater than carbon dioxide, therefore much more powerful.

Greenhouse gases, such as carbon dioxide and methane, are characterised by the property of effectively absorbing the infrared radiation emitted by the Earth's surface, partially preventing it from escaping into space. The excess concentration of greenhouse gases in the atmosphere causes an excess of infrared radiation, therefore heat, to remain trapped in the Earth's climate system, leading to global warming.

Methane is produced both by human activities, agriculture and animal husbandry of ruminants, and in nature. The decomposition of organic substances in the absence of oxygen produces methane. This production process takes place underground, where oxygen is absent, and where methane deposits are consequently formed.

Greenhouse gases are and have been precious for the development and maintenance of life on Earth. They allowed the average temperature in the Earth's climate system to reach 15 C, whereas in their absence it would have been even below 0 C.
tundra
Typical image of tundra region with permafrost.

The problem is not the presence of greenhouse gases in the atmosphere, but an excess concentration, which is of anthropogenic origin.

What happens in the Arctic-Boreal humid regions

In the context of climate change, and specifically global warming, the excess of methane in the atmosphere is the result of human activity, but also the result of a climate feedback, i.e. a feedback mechanism. The natural production of methane is significantly linked to temperature.

As the temperature increases, production increases; in fact, as the temperature increases there are vast areas of the earth's surface in which the ongoing thawing reactivates the processes of organic decomposition. Climate change, we are rapidly losing the climate memory of the Arctic due to melting ice Climate change, we are rapidly losing the climate memory of the Arctic due to melting ice.

We are referring to the wetlands of the Arctic. For example, the northernmost regions of Siberia, but also Greenland, are characterised by the presence of permafrost, i.e. a superficial layer (up to 1500 metres deep) of frozen ground. Global warming is thawing the permafrost and, consequently, the organic material that was frozen in it is resuming the process of decomposition and therefore methane production.

Temperature anomaly.
The map shows the current increase in average temperature of the Arctic-Boreal region compared to the average of previous decades.

In very simple words, the excess of carbon dioxide and methane produced by man have led to an "anthropogenic" increase in temperature. The increase in temperature in turn is producing a "naturally occurring" increase in methane (but also in CO2).

This second process, i.e. the "natural origin" increase in greenhouse gases, is called a climate feedback mechanism. Its effect is to further accelerate global warming. If to some extent it is possible to measure and predict what the production of greenhouse gases by human activities will be in the coming years, and therefore the corresponding global warming, it is much more complicated to predict what the production of greenhouse gases will be in the coming years as a consequence of climate feedback.

There are models that allow us to predict how methane emissions will grow due to the feedback effect, but they are currently very approximate and generally tend to underestimate actual production. What we measure today is greater than what the models predicted.

A recent study

A recent study, presented in the journal Nature Climate Change, with first author Kunxiaojia Yuan of the Lawrence Berkeley National Laboratory (CA, USA), shows the results of monitoring methane emissions in humid Arctic/boreal regions.

Artic-Boreal region map.
On the left, the map of the Arctic-Boreal region with an indication of the methane emission measurement stations. On the right, the seasonal variation in methane emissions (blue line) plus a long-term increase (dotted line) due to global warming. Credit: Yuan, K. et al. Nat. Climate Chang. 14, 282–288 (2024).

The data analysis shows between 2002 and 2021 a seasonal variation in methane emission with peaks at the beginning of summer, due to the seasonal increase in temperature and the corresponding increase in ecosystem productivity. But to this seasonal variation, which we could define as natural and independent of climate change, is added a clear long-term increasing trend in methane emission levels.

This second long-term component is linked to the global increase in temperature. The negative note that emerges from their study is how current climate models are not capable of reproducing either seasonal or long-term variations in their correct amplitude, therefore underestimating the actual growth speed of emissions.