Scientists at Scripps Institution of Oceanography reported that carbon dioxide levels at the Mauna Loa Observatory reached 432.00 parts per million (ppm) in May 2026, a 1.8 ppm increase over the previous year. This continues a long-term trend of record-breaking annual peaks, with NOAA's independent measurements averaging 432.3 ppm. The data, part of the Keeling Curve record dating back to 1958, serves as a key benchmark for climate scientists and policymakers tracking the rise of the most important human-caused greenhouse gas. The steady increase in CO2 drives warming, extreme weather events, and ocean acidification. The Mauna Loa site was disrupted by a volcanic eruption in 2022 but has resumed measurements with solar power backup and limited road access. These readings are incorporated into NOAA's Global Greenhouse Gas Reference Network, providing foundational data for international climate research and emissions policy decisions.
