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The volume of heat-trapping gases in the Earth's atmosphere reached a new record high in 2020, with an annual growth rate higher than the average for the 2011-2020 period, warns the World Meteorological Organization (WMO) in its most recent bulletin. The WMO warns that the trend continues in 2021 and that we are far off the path of the Paris Agreement.
The concentration of carbon dioxide (CO2), the most important greenhouse gas, reached 413.2 parts per million (ppm) in 2020 and was 149% above pre-industrial levels.
"The amount of CO2 in the atmosphere surpassed the 400 ppm milestone in 2015. And just five years later, we exceeded 413 ppm. This is not just a chemical formula and a few figures on a graph. It carries major negative implications for our daily lives and well-being, for the state of our planet and for the future of our children and grandchildren," said WMO Secretary-General Professor Petteri Taalas.
The organization warns that if emissions are not curbed, global temperatures will continue to rise. Carbon dioxide is a long-lived gas and, therefore, the temperature level we are currently observing will persist for several decades, even if emissions are rapidly reduced to net zero.
Suppose we add global warming to this situation. In that case, the end result will be a proliferation of extreme weather events such as heatwaves, heavy rainfall, melting ice masses, rising sea levels and ocean acidification, which will have far-reaching socio-economic repercussions.
Approximately half of the CO2 currently emitted by human activities remains in the atmosphere, while the oceans and terrestrial ecosystems absorb the other half.
The bulletin warns of the possibility that, in the future, the oceans and terrestrial ecosystems could lose their effectiveness as CO2 sinks, their capacity to absorb the gas and to act as regulators that prevent further temperature increases.
At the same time, the WMO pointed out, concentrations of other gases such as methane (CH4) and nitrous oxide (N2O) were equivalent in 2020, respectively, to 262% and 123% of the levels in 1750, the year chosen to represent the moment when human activity began to alter the Earth's natural balance.
The economic slowdown caused by COVID-19 had no apparent effect on atmospheric levels of greenhouse gases or their rates of increase. However, there was a transient decline in new emissions, according to the WMO.
Taalas stressed that the bulletin sends a strong scientific message to negotiators attending the 26th session of the Conference of the Parties (COP26) to the United Nations Framework Convention on Climate Change.
"If the current rate of increase in greenhouse gas concentrations continues, the temperature increase at the end of this century will far exceed the target set under the Paris Agreement to limit global warming to 1.5 to 2 °C above pre-industrial levels. We are way off track," he said.
"The last time the Earth recorded a comparable concentration of CO2 was between three and five million years ago. At that time, the temperature was 2 to 3 °C higher, and the sea level was 10 to 20 meters higher than it is today, but there were not 7.8 billion people on the planet then," he added.
The scientist said that, although many countries are setting their goals to achieve carbon neutrality and that major commitments in this regard are expected during COP26, it is necessary to transform these ambitions into actions that have an impact on the gases that cause climate change.
"We must transform our industrial, energy and transport systems and our entire way of life. The changes needed are affordable economically and technically feasible. There is no time to lose," he emphasized.