On May 9, instruments atop Hawaii’s Mauna Loa volcano pegged the atmospheric concentration of carbon dioxide (CO2) — the gas that contributes most to global warming — at slightly above 400 parts per ...

Scientists are warning the planet has now reached a grim climate milestone not seen for two or three million years. The National Oceanic and Atmospheric Administration says the amount of heat-trapping ...

Just over a year ago, atmospheric carbon dioxide (CO2) levels hit 410 parts per million (ppm) for the first time in millions of years. And we just hit another worrying threshold in April: levels ...

An instrument near the summit of Mauna Loa in Hawaii has recorded a long-awaited climate milestone: the amount of carbon dioxide in the atmosphere there has exceeded 400 parts per million (ppm) for ...