Carbon dioxide levels in the atmosphere hit a new record in May, as the accumulation of the warming gas increased despite the brief environmental respite caused by coronavirus and the global recession.
Atmospheric carbon dioxide reached more than 417 parts per million on average during May at the Mauna Loa Observatory in Hawaii, suggesting that even though lockdowns around the world have caused emissions to drop temporarily, warming trends are set to continue.
The new record, based on separate measurements taken by US National Oceanic and Atmospheric Administration, and the Scripps Institution of Oceanography, is the highest level of carbon dioxide in the atmosphere for millions of years.
“People may be surprised to hear that the response to the coronavirus outbreak has not done more to influence CO2 levels,” said Professor Ralph Keeling, a geochemist and head of the CO2 programme at the Scripps Institution.
“The build-up of CO2 is a bit like trash in a landfill — as we keep emitting, it keeps piling up,” Prof Keeling said. “The crisis has slowed emissions, but not enough to show up perceptibly at Mauna Loa. What will matter much more is the trajectory we take coming out of this situation.”
Levels of atmospheric carbon dioxide typically peak each year in May, just before the growing season begins in the northern hemisphere. Atmospheric carbon dioxide fluctuates on an annual cycle, as the gas gets absorbed by the ocean and by growing plants, and released by decaying organic matter.
Carbon dioxide emissions linked to human activities hit a record high last year, but fell in the spring due to the effect of the virus crisis. Global daily emissions in April were 17 per cent lower than normal levels, according to a recent paper in the journal Nature Climate Change.
Total emissions from fossil fuels are expected to be about 8 per cent lower this year than in 2019 as a result of the pandemic, according to research from the International Energy Agency.
The use of renewable energy has also risen during lockdowns, particularly in Europe. The continent set a new record by drawing 55 per cent of its power from clean energy sources on May 24, according to data from Wartsila Energy Transition Lab.
However, the ongoing emissions this year, even at lower levels, still contribute to the accumulation of carbon dioxide, which can remain in the atmosphere for more than a hundred years.
Pieter Tans, scientist at NOAA, said the new figures for atmospheric carbon dioxide did not show any “progress” as they were still going up.
“If humans were to suddenly stop emitting CO2, it would take thousands of years for our CO2 emissions so far to be absorbed into the deep ocean, and atmospheric CO2 to return to pre-industrial levels,” he said.
“We continue to commit our planet, for centuries or longer, to more global heating, sea-level rise, and extreme weather events every year,” he added.
The measurements taken at Mauna Loa are the longest continuous record of atmospheric carbon dioxide — they began in 1958 — and helped establish the link between fossil fuel emissions and global warming.