One more year, the concentrations of greenhouse gases broke all records again

Geneva, 25 October 2021 (WMO) — The abundance of heat-trapping greenhouse gases in the atmosphere reached a new record last year, with the annual rate of increase recorded above the average for the period 2011 -2020. This trend has continued in 2021, according to the Bulletin of the World Meteorological Organization (WMO) on greenhouse gases.

The concentration of carbon dioxide (CO ₂ ), the most abundant of the greenhouse gases, reached 413.2 parts per million (ppm) in 2020, standing at 149% of pre-industrial levels. As for methane (CH ₄ ) and nitrous oxide (N ₂ O), their concentrations were, respectively, 262% and 123% of the levels of 1750, the year chosen to represent the moment when human activity began. to alter the natural balance of the Earth. The economic slowdown caused by COVID-19 had no apparent effect on atmospheric levels of greenhouse gases or their rates of increase, although there was a temporary decline in new emissions.

If emissions are not stopped, global temperatures will continue to rise. CO ₂ is a gas characterized by its long life and, therefore, the temperature level currently observed will persist for several decades even if the emissions are reduced rapidly until reaching the level of net zero. If this is coupled with global warming, the result will be the proliferation of extreme weather events (such as intense heat events, heavy rains, melting ice masses, sea level rise and ocean acidification), which will have far-reaching socioeconomic

About half of the CO ₂ currently emitted from human activities remains in the atmosphere, while oceans and terrestrial ecosystems absorb the other half. The bulletin warns about the possibility that, in the future, oceans and terrestrial ecosystems will lose effectiveness as “sinks”, and this will reduce their ability to absorb CO ₂ and act as regulators that prevent increases in temperature even greater.

The bulletin shows that between 1990 and 2020, the radiative forcing exerted by long-lived greenhouse gases (an effect that warms our climate) increased by 47%, and about 80% of that increase was due to CO ₂ . These percentages have been calculated thanks to the monitoring carried out by the WMO Global Atmosphere Monitoring Program (GAW) network.

“The WMO Greenhouse Gas Bulletin sends a strong scientific message to climate change negotiators who will participate in the 26th Session of the Conference of the Parties (COP26) to the United Nations Framework Convention on Climate Change (UNFCCC) If the current rate of increase in greenhouse gas concentrations continues, the increase in temperature by the end of this century will far exceed the goal set under the Paris Agreement to limit the global warming to 1.5-2°C above pre-industrial levels,” said WMO Secretary-General Professor Petteri Taalas. “We are very far from the marked path.”

“The amount of _CO2 in the atmosphere passed the 400 ppm milestone in 2015. And just five years later, we surpassed 413 ppm. This is not a mere chemical formula and a few figures on a graph. It carries major negative repercussions for our daily lives and well-being, for the state of our planet and for the future of our children and grandchildren,” said Professor Taalas.

“Carbon dioxide stays in the atmosphere for centuries and even longer in the oceans. The last time a comparable concentration of CO ₂ was recorded on Earth was between three and five million years ago. At that time the temperature was 2-3°C warmer, and the sea level 10-20 meters higher than it is today, but there weren’t 7.8 billion people on the planet then,” Professor Taalas explained.

“Many countries are setting targets to achieve carbon neutrality and COP26 is expected to see a dramatic increase in commitments made in that regard. that drive climate change. We must transform our industrial, energy and transport systems and our entire way of life. The necessary changes are economically affordable and technically feasible. There is no time to lose,” said the Professor Taalas.

Highlights from the Greenhouse Gas Bulletin

carbon sinks

About half of the CO ₂ currently emitted from human activities remains in the atmosphere, while oceans and terrestrial ecosystems absorb the other half. The part of CO ₂ that remains in the atmosphere is an important indicator of the balance between sources and sinks. Its concentration changes from year to year due to natural variability.

Land and ocean sinks of CO ₂ have increased proportionally to the increase in emissions registered in the last 60 years. But these catchment processes are sensitive to the evolution of the climate and changes in land use. The loss of effectiveness of the carbon sinks would entail serious implications for the achievement of the objectives of the 2015 Paris Agreement and would require the application of adjustments in the magnitude of the emission reductions determined and in the calendar foreseen for their fulfillment.

Ongoing climate change and related feedbacks, such as the increase in the frequency of droughts and the consequent increase in the number and intensity of wildfires, could reduce the capacity of terrestrial ecosystems to absorb CO ₂ . These changes are already taking place, and the bulletin shows the transition of part of the Amazon from a carbon sink to a carbon source. Ocean uptake could also be reduced due to increased sea surface temperatures, lower pH caused by CO ₂ uptake, and slower meridional ocean circulation due to increased sea ice melting.

To anticipate future changes in the balance between sources and sinks, it is essential to have timely and accurate information on these types of changes, which is why they are monitored by the GAW networks.

Carbon dioxide (CO ₂ ) is the most abundant greenhouse gas in the atmosphere, contributing about 66% of the warming effect of the climate, mainly from the burning of fossil fuels and the production of cement.

Global average concentrations of CO2 reached a new high of _413.2 ppm in 2020. The increase in CO ₂ concentration from 2019 to 2020 was slightly lower than that observed between 2018 and 2019, but higher than the average annual increase rate of the last decade. And this occurred despite the fact that in 2020 the restrictions imposed in the wake of COVID-19 caused a decrease of approximately 5.6% in CO ₂ emissions from the burning of fossil fuels.

Data from monitoring stations clearly show that CO2 _levels continued to rise in 2021.

In July 2021, concentrations of CO₂ observed at Mauna Loa (on the US island of Hawaii) and Cape Grim (on the Australian island of Tasmania) reached, respectively, 416.96 ppm and 412.1 ppm, compared to 414.62 ppm and 410.03 ppm recorded in July 2020.

Methane (CH4) is a powerful greenhouse gas that remains in the atmosphere for about a decade.

It is responsible for about 16% of the warming effect of long-lived greenhouse gases, according to the US National Oceanic and Atmospheric Administration (NOAA). About 40% of the CH ₄ emitted into the atmosphere comes from natural sources (for example, wetlands and termites), while about 60% comes from anthropogenic sources (for example, ruminant farming, rice cultivation, exploitation of fossil fuels, landfills and biomass burning).

The increase in the concentration of this gas from 2019 to 2020 was higher than that observed between 2018 and 2019, and was also higher than the average annual increase rate of the last decade.

Short-term reduction of atmospheric CH4 could help achieve the goals of the Paris Agreement and could contribute to achieving many Sustainable Development Goals (SDGs) because mitigating methane emissions would have multiple spin-off benefits. However, this does not diminish the importance of the need to drastically, rapidly and sustainably reduce CO ₂ emissions.

Nitrous oxide (N ₂ O) is a powerful greenhouse gas and, at the same time, an ozone-depleting chemical. It is responsible for approximately 7% of the radiative forcing caused by long-lived greenhouse gases.

Emissions of N ₂ O to the atmosphere come from natural sources (about 60%) and anthropogenic sources (about 40%), such as the oceans, soils, biomass burning, fertilizer use, and various industrial processes.

In 2020, the global average of the mole fraction of that gas reached 333.2 parts per billion (ppb), which represents an increase of 1.2 ppm compared to 2019. The annual increase from 2019 to 2020 was higher than that recorded between 2018 and 2019, and was also higher than the average rate of increase of the last ten years (0.99 ppb per year).

Global N ₂ O emissions from human activities, predominantly nitrogen fertilization of cropland, have increased by 30% over the last four decades. Thus, agriculture is the cause of 70% of all anthropogenic emissions of this gas due to the use of nitrogenous fertilizers and manure. This increase was the main cause of the increase in the atmospheric load of N ₂ O.

Source: WMO