It is one of the largest annual May-to-May increases in carbon dioxide levels on record, behind only 2016 and 2019, which had jumps of 3.7 and 3.4 parts per million.
“The relentless rise in atmospheric CO2 is incredibly worrying if not wholly predictable,” said Brown University climate scientist Kim Cobb, who was not part of the research. Carbon dioxide levels rise more during El Nino climate cycles because it is drier in the northern hemisphere. An El Nino is brewing. That 3.0 increase may be a sign of an El Nino bump, she said.
The other way is to measure how much carbon dioxide is in the air. NOAA and partner agencies measure all around the world. Hawaii has the longest history of direct measurements and is the home of the Scripps Institution of Oceanography’s which has kept track of carbon in the air since 1958 when the May reading peaked at 317.5. Emissions have gone up about 33% since then.