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The concentration of greenhouse gases in the atmosphere reaches a new record

According to the World Meteorological Organization (WMO), levels of heat-trapping greenhouse gases in the atmosphere have reached a new record high. This continuing long-term trend means that future generations will face increasingly severe effects of climate change, such as rising temperatures, more extreme weather events, increased water stress, rising sea levels and disruption of marine and terrestrial ecosystems.

The WMO Greenhouse Gas Bulletin has shown that the global average concentration of carbon dioxide (CO2) reached 407.8 parts per million (ppm) in 2018, after being 405.5 ppm in 2017.

The increase in CO2 that occurred from 2017 to 2018 was very similar to that observed from 2016 to 2017 and was just above the average of the last decade. Global CO2 levels surpassed the symbolic and important threshold of 400 parts per million in 2015.

CO2 remains in the atmosphere for centuries and even longer in the oceans.

Meanwhile, methane and nitrous oxide concentrations soared and rose in greater quantities than during the last ten years, according to observations by the Global Atmosphere Watch network, which has stations in remote regions of the Arctic, in mountainous areas and on tropical islands.

Since 1990 there has been a 43% increase in total radiative forcing – which has a climate-warming effect – caused by long-lived greenhouse gases. According to figures provided by the National Oceanic and Atmospheric Administration (NOAA) of the United States of America cited in the WMO Bulletin, CO2 contributed almost 80% to this increase.

“There is no indication that there will be a slowdown, let alone a decrease, in the concentration of greenhouse gases in the atmosphere despite all the commitments made under the Paris Agreement on climate change,” said WMO Secretary-General Petteri Taalas. “We need to translate commitments into action and increase the level of ambition for the future well-being of humanity,” he said.

“It should be remembered that the last time a comparable concentration of CO2 occurred on Earth was between 3 and 5 million years ago. Back then, the temperature was 2 to 3 °C higher.

warm and the sea level between 10 and 20 meters higher than the current one,” explained Mr. Taalas.

Disparity in emissions

The WMO Greenhouse Gas Bulletin reports on atmospheric concentrations of greenhouse gases. Emission is understood as the amount of gas that is released into the atmosphere and by concentration the amount that remains in the atmosphere after the complex interactions that take place between the atmosphere, the biosphere, the cryosphere and the oceans. About a quarter of total emissions are absorbed by the oceans and another quarter by the biosphere.

Global emissions are not expected to peak by 2030, let alone in 2020, if the current climate policies and ambition levels of Nationally Determined Contributions (NDCs) are maintained. The preliminary findings of the 2019 Emissions Gap Report show that greenhouse gas emissions continued to rise in 2018 and, more specifically, according to a preliminary chapter of that Report, published as part of the United in Science Synthesis Report for the UN Secretary-General’s Climate Action Summit in September.

The United in Science Report, produced through the work of leading partner organizations in the field of global climate change research, highlighted the glaring and widening disparity between the agreed goals to solve the problem of global warming and reality.

The United Nations Environment Programme will issue a separate and complementary report on the emissions gap on 26 November. In this tenth edition, the Report evaluates the latest scientific studies on current and projected greenhouse gas emissions, which are compared with the levels of emissions eligible for the world to progress on a trajectory based on the lowest cost for the achievement of the objectives of the Paris Agreement. This difference between “what the likely situation will be in the future and what it should be” is known as the disparity in emissions.

United Nations Secretary-General António Guterres stated that the Summit had given new impetus and renewed cooperation and ambition, but that there was still a long way to go.

Now the United Nations Climate Change Conference will take over, which will be held from December 2 to 15 in Madrid (Spain) under the presidency of Chile.

Main conclusions of the Greenhouse Gas Bulletin

Among the topics covered in the Bulletin, special attention is paid to how isotopes confirm the predominant role of fossil fuel burning in increasing atmospheric carbon dioxide.

There are multiple indications that the increase in atmospheric CO2 levels is related to the burning of fossil fuels. These fuels were formed millions of years ago from plant matter and do not contain radiocarbon. Thus, with the burning of these fuels, CO2 is released into the atmosphere without radiocarbon, which increases CO2 levels and decreases its radiocarbon content. And that’s exactly what the measurements show.

Carbon dioxide

Carbon dioxide is the main long-lived greenhouse gas in the atmosphere related to human activities. Its concentration reached a new maximum value in 2018, namely 407.8 ppm or, in other words, 147% of the pre-industrial level in 1750.

The increase in CO2 that occurred from 2017 to 2018 exceeded the average growth of the last ten years. The average CO2 rate of increase for three consecutive decades (1985–1995, 1995–2005 and 2005–2015) increased from 1.42 ppm/year to 1.86 ppm/year and 2.06 ppm/year, with the highest growth rates observed during El Niño episodes.

The annual greenhouse gas index of the National Oceanic and Atmospheric Administration (NOAA) of the United States of America shows that between 1990 and 2018 radiative forcing caused by long-lived greenhouse gases increased by 43%, with CO contributing2 to that increase by almost 80%.

Methane

Methane (CH4) is the second most important long-acting greenhouse gas and contributes approximately 17% to radiative forcing. About 40% of the CH4 emitted into the atmosphere comes from natural sources (e.g. wetlands and termites), while approximately 60% comes from anthropogenic sources (e.g. livestock farming, rice cultivation, fossil fuel exploitation, landfills and biomass combustion).

Atmospheric CH4 reached a new peak value in 2018, namely 1,869 parts per billion (ppb), making it 259% of the pre-industrial era level. Its increase from 2017 to 2018 was greater than that observed from 2016 to 2017 and the average of the last decade.

Nitrous oxide

Nitrous oxide (N2O) emissions into the atmosphere come from natural sources (around 60%) and from anthropogenic sources (40%), such as oceans, soils, biomass burning, fertilizers and various industrial processes.

In 2018 the atmospheric concentration of N2O was 331.1 parts per billion, equivalent to 123% of pre-industrial levels. Its increase from 2017 to 2018 was also greater than that observed from 2016 to 2017 and the average of the last decade.

This gas also contributes significantly to the destruction of the stratospheric ozone layer, which protects us from the Sun’s harmful ultraviolet rays. It is responsible for 6% of the radiative forcing caused by long-lived greenhouse gases.

Source: UNFCCC