Carbon dioxide (CO2) levels in the atmosphere hit a new record of 410.5 parts per million in 2019 and will likely rise this year despite a minor cut in emissions due to COVID-19 lockdowns, the World Meteorological Organization (WMO) said Monday.
CO2 is a key greenhouse gas that traps heat in the atmosphere and contribute to climate change, and it has risen by nearly 50% since pre-industrial times, said the WMO in its annual Greenhouse Gas Bulletin.
"The CO2 which we have now in the atmosphere is accumulated since 1750," Oksana Tarasova, WMO’s head of Atmospheric and Environment Research Division, said at a news conference in Geneva.
"So, it's every single bit which we put in the atmosphere since that time actually forms the current concentration. It's not what happened today or yesterday; it's the whole history of the human economic and human development, which lead us to this global level of 410."
Due to the pandemic, the industrial slowdown has not curbed record levels of greenhouse gases trapping heat in the atmosphere, increasing temperatures, and driving more extreme weather, ice melt, sea-level rise, and ocean acidification, according to the WMO report.
Lockdowns have cut emissions of many pollutants and greenhouse gases such as carbon dioxide.
But any impact on CO2 concentrations from the cumulative past and current emissions is no more significant than the typical year to year fluctuations in the carbon cycle and the high natural variability in carbon sinks like vegetation.
The rise in carbon dioxide levels has continued in 2020.
"Since 1990, there has been a 45% increase in total radiative forcing – the warming effect on the climate - by long-lived greenhouse gases, with CO2 accounting for four-fifths of this," said the report.
WMO Secretary-General Petteri Taalas said: "Carbon dioxide remains in the atmosphere for centuries and in the ocean for even longer."
The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago when the temperature was 2-3°C warmer, and sea level was 10-20 meters higher than now. But there were not 7.7 billion inhabitants.
Preliminary estimates indicate a reduction in the annual global emission between 4.2% and 7.5%.
Globally, an emissions reduction on this scale will not cause atmospheric CO2 to go down, said the report.
CO2 will continue to go up at a slightly reduced pace (0.08-0.23 ppm per year lower).
The increase in CO2 from 2018 to 2019 was more extensive than that observed from 2017 to 2018 and also larger than the average over the last decade.
The figure represented a balance of fluxes in the atmosphere, the oceans, and the land biosphere said the WMO.
By Peter Kenny in Geneva