The concentration of carbon dioxide (CO₂) in Earth’s air has reached a new milestone, hitting 430.2 parts per million (ppm) in May 2025, according to data released by the Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration (NOAA).
This is the highest level recorded in millions of years, and scientists warn it poses a growing threat to human health and the planet’s stability.
The measurement, taken at NOAA’s Mauna Loa Observatory in Hawaii, shows an increase of 3.5 ppm over the past year. Experts say the relentless rise is driven by continued fossil fuel use, with global emissions showing no sign of slowing down. “This problem is not going away, and we’re moving further and further into uncharted—and almost certainly, very dangerous—territory,” said Ralph Keeling, director of the Scripps CO₂ Program.
The health risks associated with rising CO₂ are both direct and indirect. Higher concentrations of CO₂ in Earth’s air contribute to more frequent and severe heatwaves, droughts, floods, and wildfires, all of which threaten food security, water supplies, and public health.
In addition, elevated CO₂ levels can worsen air quality, aggravate respiratory conditions, and, at much higher concentrations, cause cognitive impairment and other health issues.
Rising CO₂ is also driving ocean acidification, which harms marine life and disrupts food chains. Scientists warn that unless immediate action is taken to reduce emissions and transition to cleaner energy, the world will face even greater instability and health risks in the years ahead.
