The data is available: Carbon dioxide levels in the atmosphere reached 419 parts per million in May. Levels have now reached the dangerous threshold of being 50% higher than at the start of the industrial age – and the average rate of increase is faster than ever.

This figure is the highest measurement of crucial greenhouse gas in the 63 years that data has been recorded at the Mauna Loa Basic Atmospheric Observatory in Hawaii – despite slowing air travel and industry. during a global pandemic last year.

The 10-year average rate of increase also set a record, now reaching 2.4 parts per million per year.

According to The National Oceanic and Atmospheric Administration, the reason is complex. Global emissions fell 6.4% in 2020, but given seasonal and natural variability, modest reductions would not have a large impact on the global carbon emissions count. And even as emissions faded, forest fires were burning through the trees carbon dioxide released – perhaps even at a pace similar to the modest decline in emissions due to the slowing impact of the pandemic on the global economy.

The ultimate control knob on atmospheric CO2 it’s fossil fuel emissions, ”geochemist Ralph Keeling, whose father began collecting data at the Mauna Loa site, tell NOAA. “But we still have a long way to go to stop the rise, because every year more CO2 accumulates in the atmosphere. We ultimately need cuts that are much larger and sustained longer than the Covid-related closures of 2020. “

In order to achieve the objectives of the Paris climate agreements – keep the temperature rise at 1.5 ° C – the Report of the United Nations Environment Program notes that countries need to reduce their global emissions by 7.6% each year over the next decade.

“Reaching 50% more carbon dioxide than the pre-industrial era really sets a new benchmark and not in a good way,” said Cornell University climatologist Natalie Mahowald, who was not with the research.

“If we are to avoid the worst consequences of climate change, we have to work much harder to reduce carbon dioxide emissions and now. “

Mauna Loa’s laboratory, located on a volcano in the middle of the Pacific Ocean, combines two complementary observations to arrive at the primordial value of carbon dioxide. The current level has not existed on Earth since the Pliocene Era, between 4.1 and 4.5 million years ago – and the world’s seas were 78 feet higher than current levels.

The annual increase of 1.8 parts per million in May was slightly lower than in previous years, although monthly measurements for 2021 show that this year may be closer to the average increase of 2.3 parts per million.

Scientists are focusing on the month of May with the highest carbon dioxide levels of the year, as it occurs before plants and trees in the northern hemisphere begin to absorb carbon dioxide during their season. of summer growth. Then, in the fall and winter, plants and soils release carbon dioxide into the atmosphere.

The Associated Press contributed to this report