Carbon levels hit high despite pandemic
Carbon dioxide levels in the northern hemisphere were on average 50 per cent higher than before the industrial revolution last month and are expected to set a new peak of 419.5 parts per million this year.
The level of atmospheric CO2 has continued to rise despite a slowdown in industrial activity because of the COVID-19 pandemic. Average CO2 concentrations for March 2021 at the Mauna Loa Observatory in Hawaii was 417.14 parts per million, 50 per cent higher than the average for the period 1750-1800.
The average CO2 concentration for the pre-industrial period was 278 parts per million.
Britain’s Met Office said the milestone of 50 per cent above pre-industrial levels was significant because it was halfway towards “doubled-CO2”, which has long been a benchmark for quantifying future global warming.
The rate of warming for a doubling of CO2 is hotly debated but the Met Office said recent research suggested it was likely to be between 2.6C and 4.1C.
The rate of build-up of CO2 in the atmosphere is accelerating. According to the Met Office, it took more than 200 years for levels to increase by 25 per cent but only another 30 years to increase to 50 per cent above.
The Met Office said if the current trend continued, doubled-CO2 would be reached in about 55 years. It said reversing this trend and slowing the atmospheric CO2 rise would need global emissions to reduce.
The Met Office said the human-caused 50 per cent increase in CO2 had been a major driver of the observed global temperature rise of more than 1C.
Daily measurements of CO2 in the atmosphere can vary from local wind conditions. On April 3, the National Oceanographic and Atmospheric Association reported a record concentration of 421.21 parts per million.
In the Southern Hemisphere, the CSIRO’s Cape Grim site in Tasmania reported a February average of 410.6 parts per million.
CSIRO climate scientist Pep Canadell said humans were emitting globally in the vicinity of 40 billion tonnes of CO2 every year.
“The impacts of COVID-19 on the economy have resulted in a reduction in emissions of 2.5 billion tonnes in 2020”, Dr Canadell said.
However, “CO2 will continue to accumulate in the atmosphere and break new records until the day we no longer produce emissions”.
Steven Sherwood from the University of NSW said it would not be possible for an economic contraction to significantly affect the trajectory of CO2. “The only practical way to do so is to shift to newer, clean energy sources”, Professor Sherwood said. “This shift must eventually include nearly all of our energy.”