May exceeds 430ppm monthly average, second highest peak to peak increase in history

Scripps Oceanography scientists calculated a May monthly average of 430.2 ppm for 2025, an increase of 3.5 ppm over May 2024’s measurement of 426.7 ppm. Scientists with NOAA’s Global Monitoring Laboratory reported an average of 430.5 ppm, an increase of 3.6 ppm over last year.

“Another year, another record,” said Ralph Keeling, director of the Scripps CO2 Program. “It’s sad.”