Carbon dioxide concentrations remain at record levels despite lockdown measures due to COVID-19

According to the World Meteorological Organization (WMO), the industrial slowdown due to the COVID-19 pandemic has not offset the unprecedented levels of heat-trapping greenhouse gases in the atmosphere, driving temperatures soaring and exacerbating extreme weather conditions, melting ice, rising sea levels and ocean acidification.

Lockdown measures have reduced emissions of many pollutants and greenhouse gases such as carbon dioxide (_CO2). All in all, any change in _CO2 concentrations —which are the sum of past and current emissions—is no greater than that caused by the normal fluctuations in the carbon cycle that occur from year to year and by the marked natural variability to which carbon sinks such as vegetation are subjected.

Once again, _CO2 concentrations experienced a sudden increase in 2019, and as noted in the WMO Greenhouse Gas Bulletin, the annual global average exceeded a significant threshold: 410 parts per million (ppm). In 2020 the increase has continued. Since 1990, total radiative forcing– which has a climate-warming effect – has increased by 45% because of long-lived greenhouse gases. Four-fifths of that increase is due to _CO2.

“Carbon dioxide remains 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. The temperature was then 2 to 3 °C warmer and the sea level between 10 and 20 meters higher than today, but there were not 7.7 billion inhabitants,” said WMO Secretary-General Professor Petteri Taalas.

“In 2015 we exceeded the global threshold of 400 ppm. And just four years later, we surpassed 410 ppm. That rate of increase is unprecedented in our historical records. The reduction in emissions due to the lockdown measures is nothing more than a minuscule irregularity in the long-term graph. We have to flatten the curve continuously,” said Professor Taalas.

“The COVID-19 pandemic is not a solution to climate change. However, it provides us with an opportunity to adopt more sustained and ambitious climate action aimed at reducing emissions to net zero through a comprehensive metamorphosis of our industrial, energy and transport systems. The changes that need to be implemented are technically possible and economically feasible, and their impact on our daily lives would only be marginal. It is to be appreciated that an increasing number of countries and companies have committed to achieving carbon neutrality,” he said. “There is no time to waste.”

Trends in 2020

The Global Carbon Project has estimated that, during the period with the strictest restrictions on activity, daily _CO2 emissions may have been reduced by up to 17% on a global scale due to the confinement of the population. As the duration and degree of the lockdown measures and their degree of rigour are still unclear, any prediction of the total reduction in annual emissions over the course of 2020 is highly uncertain.

Preliminary estimates indicate a decrease in global annual emissions of between 4.2 and 7.5%. On a global scale, a reduction in emissions of this magnitude will not reduce the concentration of atmospheric _CO2 . Thus, the concentration of this gas will continue to increase, although at a slightly slower rate (reduction in annual growth of between 0.08 and 0.23 ppm). These are values compatible with the natural interannual variability of 1 ppm. This means that, in the short term, the impact of the confinement measures applied in the wake of COVID-19 cannot be differentiated from natural variability, as noted in the Bulletin.

New records in 2019

The WMO Greenhouse Gas Bulletin — one of the Organization’s most prominent reports — provides detailed information on the atmospheric abundance of the main long-lived greenhouse gases: carbon dioxide, methane and nitrous oxide.

The Bulletin is based on observations and measurements from the WMO Global Atmosphere Watch and associated networks, which include atmospheric monitoring stations in remote polar regions, high mountain areas and tropical islands. These stations have continued to operate despite the fact that restrictions imposed in the wake of COVID-19 hamper replenishment operations and staff turnover in places that are often isolated and subject to difficult conditions.

Carbon dioxide

Of all the long-lived greenhouse gases resulting from human activities, _CO2 has the most important presence in the atmosphere, and is responsible for about two-thirds of radiative forcing. The average annual concentration of _CO2 globally was approximately 410.5 ppm in 2019, up from 407.9 ppm in 2018, having passed the 400 ppm threshold in 2015. The increase in the concentration of _CO2 recorded between 2018 and 2019 was higher than that observed between 2017 and 2018 and also the average of the last decade.

In 2019, emissions from fossil fuel burning and cement production, deforestation and other land-use changes triggered CO concentrations.₂ atmospheric up to a value equivalent to 148% of the pre-industrial level of 278 ppm, which represents the equilibrium point of flows between the atmosphere, the oceans and the terrestrial biosphere. Over the past decade, about 44% of _CO2 has remained in the atmosphere, while 23% has been absorbed by the oceans, 29% by land and the remaining 4% has not been attributed.

The WMO Greenhouse Gas Bulletin is based on the global average figures for 2019. Data from individual stations show that the upward trend continues in 2020. The average monthly _CO2 concentration at the Mauna Loa reference station in Hawaii was 411.29 ppm in September 2020, up from 408.54 ppm in September 2019. At Cape Grim station in Tasmania, Australia, the figures were 410.8 ppm in September 2020, up from 408.58 ppm in 2019.

The concentration of methane, a potent greenhouse gas whose permanence in the atmosphere is less than a decade, increased by 260% compared to pre-industrial levels to stand at 1 877 ppmm in 2019. The increase between 2018 and 2019 was slightly lower than that observed between 2017 and 2018, but remained higher than the average of the last decade.

Methane is responsible for approximately 16% of radiative forcing due to long-lived greenhouse gases. About 40% of this gas emitted into the atmosphere comes from natural sources (e.g. wetlands and termites), while approximately 60% comes from anthropogenic sources (e.g. ruminant farming, rice cultivation, fossil fuel exploitation, landfills and biomass combustion).

Nitrous oxide, which is both a greenhouse gas and an ozone-depleting chemical, reached 332.0 ppmm in 2019, a 123% increase from pre-industrial levels. The increase in the concentration of that gas between 2018 and 2019 was also lower than that observed between 2017 and 2018, and practically equal to the average rate of increase of the last ten years.

The Bulletin also provides data on other gases, including ozone-depleting substances regulated under the Montreal Protocol.

Source: World Meteorological Organization