“Not only is CO2 now at the highest level in millions of years, it is also rising faster than ever. Each year achieves a higher maximum due to fossil-fuel burning, which releases pollution in the form of carbon dioxide into the atmosphere,” said Ralph Keeling, director of the Scripps CO2 program that manages the institution’s 56-year-old measurement series. “Fossil fuel pollution just keeps building up, much like trash in a landfill.”

The record two-year growth rate observed from 2022 to 2024 is likely a result of sustained high fossil fuel emissions combined with El Niño conditions limiting the ability of global land ecosystems to absorb atmospheric CO2, said John Miller, a carbon cycle scientist with the Global Monitoring Laboratory.

The Mauna Loa data, together with measurements from sampling stations around the world, are incorporated into the Global Greenhouse Gas Reference Network, a foundational research dataset for international climate scientists and a benchmark for policymakers attempting to address the causes and impacts of climate change.