Global CO2 levels continue to rise, and are now 50% higher than their level before the onset of the industrial era, US scientists announced.
Independent measurements taken by the US National Oceanic and Atmospheric Administration and the Scripps Institute of Oceanography from the Mauna Loa observatory in Hawaii indicated CO2 levels averaged 424 parts per million in May, the month in which CO2 peaks in the Northern Hemisphere.
This year, NOAA's measurements were obtained from a temporary sampling site at Mauna Kea because access to the observatory has been blocked since November 2022, when the Mauna Loa volcano erupted after 40 years or dormancy.
Scripps's measurements, though, were taken at Mauna Loa after the company's measuring device was repowered with a solar and battery system in March. The Mauna Loa observatory is situated at an elevation of 11,141 feet above sea level, while the Mauna Kea sampling location is situated at an elevation of 13,600 feet.
The 424 ppm number represents an increase of around 3 ppm over the May 2022 number at both institutes.
In a statement, geochemist Ralph Keeling, who runs the Scripps program, said the high levels of CO2 indicated how much more the world had to do in decarbonization. "What we'd like to see is the curve plateauing and even falling because carbon dioxide as high as 420 or 425 parts per million is not good," Keeling said.
The upward trend in global CO2 levels is known as the Keeling Curve, after Ralph's father David Keeling, who started measuring CO2 for Scripps at Mauna Loa in 1958.
The senior Keeling was the first to recognize that CO2 levels in the Northern Hemisphere declined during the growing season, but rose over autumn as plants died. His documentation of seasonal CO2 fluctuations allowed him to recognize that despite seasonal fluctuation, CO2 levels were rising every year.