Atmospheric carbon dioxide measured at NOAA’s Mauna Loa Atmospheric Baseline Observatory peaked in May 2024 at a monthly average of 426.9 parts per million, establishing another high mark in the 66-year record of observations on the Hawaiian volcano, according to scientists from NOAA and Scripps Institution of Oceanography at the University of California San Diego. (2019 photo of observatory grounds on the Big Island of Hawaii.). Credit: Susan Cobb/NOAA Research