Despite the coronavirus pandemic, the rate of carbon dioxide (CO2) in the atmosphere reached its highest level in May since it began to be measured 63 years ago, scientists said Monday.

In May 2021 the bar of 419 parts per million (ppm), the unit used to measure air pollution, was exceeded, according to the United States National Oceanic and Atmospheric Administration (NOOA).

Measurements have been made since 1958 by the Mauna Loa Observatory in Hawaii.

Every year, May is the month with the highest CO2 rate. That of May 2020 was 417 ppm.

"No discernible sign of the disruption in the world economy caused by the coronavirus pandemic was found in the data," the agency said.

The atmospheric CO2 load is now comparable to what it was between 4.1 and 4.5 million years ago. At that time the rate was close to or greater than 400 ppm, according to the NOAA report.

At that time the sea level was a score of meters higher and the Arctic region was occupied by large forests, according to studies.

"If we want to avoid catastrophic climate change, the highest priority must be to reduce CO2 pollution to zero as soon as possible said Pieter Tans, a NOAA scientist.

Carbon dioxide is generated by the combustion of fossil fuels used in transportation or electricity, but also by other practices, such as the manufacture of cement or deforestation, among others.

This gas retains heat in the atmosphere and consequently contributes to global warming. It persists in the oceans and atmosphere for thousands of years, stresses NOAA.

"Despite decades of negotiations, the world community was unable to significantly slow down, let alone reverse, annual increases in atmospheric CO2 levels," the agency said.