Atmospheric C02 hits 424 ppm in May

Measurements taken atop Hawaiian volcanoes show an increase of 3 parts per million of carbon dioxide compared to 2022. The world is now more than double pre-industrial revolution levels.

Not a surprise here, but to be noted nonetheless: Atmospheric concentrations of carbon dioxide as measured atop volcanoes in Hawaii peaked at 424 parts per million in May, an increase of 3 ppm compared to the prior May.

This represents the fourth-largest annual increase in the peak of the Keeling Curve in the records of the National Oceanic and Atmospheric Administration.

Scientists at the Scripps Institute of Oceanography at the University of California San Diego, who maintain an independent record, calculated a May monthly average of 423.78 ppm, almost a 3 ppm increase compared to the May 2022 average.

Carbon dioxide levels are now more than 50% higher than they were before the onset of the industrial era.

This pollution is generated by burning fossil fuels for transportation and electrical generation, by cement manufacturing, deforestation, agriculture and many other practices. Like other greenhouse gases, CO2 traps heat radiating from the planet’s surface that would otherwise escape into space, amplifying extreme weather events, such as heat waves, drought, and wildfires, as well as precipitation and flooding.

“Every year we see carbon dioxide levels in our atmosphere increase as a direct result of human activity,” said Rick Spinrad, administrator of NOAA. “Every year, we see the impacts of climate change in the heat waves, droughts, flooding, wildfires and storms happening all around us. While we will have to adapt to the climate impacts we cannot avoid, we must expend every effort to slash carbon pollution and safeguard this planet and the life that calls it home.”

Rising CO2 levels also pose a threat to the world’s ocean, which absorbs both CO2 gas and excess heat from the atmosphere. Impacts include increasing surface and subsurface ocean temperatures and the disruption of marine ecosystems, rising sea levels and ocean acidification, which changes the chemistry of seawater, leading to lower dissolved oxygen, and interferes with the growth of some marine organisms.

This year, NOAA’s measurements were obtained from a temporary sampling site atop the nearby Mauna Kea volcano, which was established after lava flows cut off access to the Mauna Loa observatory in November 2022. Scripps’s May measurements were taken at Mauna Loa, after NOAA staff successfully repowered a Scripps instrument with a solar and battery system in March.

This graph shows the full record of monthly mean carbon dioxide measured at Mauna Loa Observatory, Hawaii. The carbon dioxide data on Mauna Loa constitute the longest record of direct measurements of CO2 in the atmosphere. Measurements were begun by C. David Keeling of the Scripps Institution of Oceanography in March of 1958 at the NOAA Weather Station on Mauna Loa volcano.

NOAA started its own CO2 measurements in May of 1974, and they have run in parallel with those made by Scripps since then. (Credit: NOAA Global Monitoring Laboratory)