Climate change threatens natural carbon dioxide sinks

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The recently released first volume of FLUXES, the European Greenhouse Gas Bulletin, a new publication from the Integrated Carbon Observation System (ICOS), focuses on spatial and temporal changes in European carbon sinks such as oceans and forests. The latest data show that natural carbon dioxide sinks are not at all stable, and climate change makes them even more vulnerable. As a result, in some cases they may even become carbon dioxide emitters. The changing behavior of natural sinks makes it clear that further reductions in emissions are required in order to achieve carbon neutrality. The global greenhouse gas monitoring system proposed by experts provides a scientific basis for decisions, which can help in the development of future climate protection measures. Hungary has been a full member of the European ICOS consortium since January 1, 2022. At the Hegyhátsál TV Tower, the ELKH Institute for Nuclear Research (ATOMKI) operates currently the only measuring station in Hungary that belongs to the ICOS measuring network. ATOMKI is also responsible for coordinating the Hungarian consortium, ICOS Hungary.

The goal of ICOS's annual new publication is to present the latest scientific results in a comprehensible manner. The scientific information it contains will help the planning of action against climate change, which means that it could be extremely useful for decision-makers.

Front page of FLUXES – the European Greenhouse Gas Bulletin. Are carbon sinks in danger?

"Imagine the atmosphere as a reservoir containing a powerful greenhouse gas, carbon dioxide (CO2). Its presence has a serious impact on our climate. What determines this level? Fluxes! Fluxes of CO sources into the atmosphere and fluxes from the atmosphere into other reservoirs, the so-called carbon sinks, like the ecosystems on land and in the ocean. These include the ecosystems on land and in the ocean. These fluxes give the European Greenhouse Gas Bulletin, FLUXES, its name," writes ICOS Director General Dr. Werner L. Kutsch in his introductory text. "To understand what drives the concentration of CO2 in the atmosphere, it is crucial to understand the complexity of the underlying CO2 fluxes. This first volume of FLUXES will inform you about this."

The climate crisis accompanying the increase in the average temperature on Earth is a result of the increase in the concentration of atmospheric greenhouse gases. The most important greenhouse gas, carbon dioxide, is affected by three major fluxes: emissions and uptake by terrestrial ecosystems, emissions and uptake by the oceans, and emissions from the burning of fossil fuels. Terrestrial ecosystems and oceans – such as natural sinks – have absorbed half of the emissions from fossil fuels to date. However, it is far from certain that this will remain the case in either the near or more distant future.

Ecological systems capture atmospheric carbon dioxide and store it in plants and soil. At the same time, they themselves emit carbon dioxide through plant respiration and soil respiration, and as a result of fires. If the capture of CO2 is greater than the release, the ecosystem as a whole acts as a sink. This delicate balance is easily disturbed by human activity, such as cutting down forests, clearing green areas for construction or road construction, and agricultural processes that deplete the soil's carbon content. However, this balance is also extremely sensitive to changes in the climate. ICOS data show how ecological systems respond to changes in climate and land use. The weakening of terrestrial carbon dioxide sinks and even the possibility of them becoming emitters could raise a serious obstacle to society's efforts to achieve carbon neutrality.

The oceans are huge sinks of carbon dioxide. They mitigate global warming by sequestering a quarter of the amount from fossil fuels. However, experts do not know how long this absorption capacity will remain if the climate warms. They only have a clouded understanding of how the oceans absorb and release carbon dioxide, and they don't know how global warming affects this process. Due to rising temperatures and the changing climate, the amount of carbon dioxide stored in dissolved form in the oceans is changing. In order to understand the carbon cycle taking place in the oceans and to make predictions of the future, there is no question that it will be necessary to construct a significant monitoring system.

Climate change due to excess carbon dioxide is caused by humans burning fossil fuels, which are needed for the production of electricity, industrial activity, transport and heating. In Europe, emissions from fossil sources have fallen in recent years thanks to the spread of renewable energy and an increase in energy efficiency. However, in order to correctly interpret the results of efforts to curb emissions, all causes must be taken into account, including the behavior and changes of natural sinks, as well as weather-influenced fuel consumption to meet heating or cooling needs. In addition, unexpected events such as a pandemic may occur where emissions from transportation are reduced due to closures.

Natural land and ocean carbon sinks are strongly affected by climate change, making them increasingly vulnerable. To solve this problem, we need to dramatically reduce emissions from fossil fuels.

The increase in atmospheric carbon dioxide concentration is not linear: the measured values display seasonal changes and deviations depending on the site of measurement. The carbon dioxide curve peaks each spring and declines each summer. The fall is due to the high carbon dioxide sequestration capacity of the European terrestrial ecosystem, i.e. natural plants and organisms that live in the spring and are green in the summer. In addition, the typical weather in a given location also results in significant differences between the curves seen each year. Emissions from fossil fuel use also vary with time and place, and there is continuous mixing in the atmosphere. In light of the above, it is necessary to establish a wide-scale global greenhouse gas monitoring system as soon as possible. The infrastructure operated by the European ICOS can serve as a good example.

In the current global climate crisis, the growth rate of atmospheric carbon dioxide will be the measure of success. Swift action is needed to keep temperature increases below 1.5 degrees Celsius, as required by the Paris Agreement. Decision-makers must take bold and effective steps to encourage self-restraint in society in order to reduce the amount of greenhouse gases resulting from human activity. The global greenhouse gas monitoring system helps climate protection measures by providing a scientific basis for decisions.