Carbon dioxide passes symbolic mark - Noaa atmospheric lab - The measurements are made at a station on the Mauna Loa volcano The level of carbon dioxide in the atmosphere has risen above 400 parts per million for the first time in human history, US researchers say. The "Keeling Lab" in Hawaii has the longest continuous measurement of the greenhouse gas, which is a key driver of climate change. Thursday's measurement, made atop the Mauna Loa volcano, registered 400.03. The last time CO2 was regularly above 400ppm was about 3-5 million years ago - before modern humans existed. The climate back then was also considerably warmer than it is today, according to scientists. The usual trend seen at the volcano is for the CO2 concentration to rise in winter months and then to fall back as the northern hemisphere growing season kicks in and pulls some of the gas out of the atmosphere. This means the number can be expected to decline by a few ppm in the coming weeks. But the long-term trend is upwards. When the late Charles Keeling began recording CO2 concentrations at the volcano in 1958, they were around 315 ppm (parts per million by volume - that is 315 molecules of CO2 for every one million molecules in the air). Every year since then, the curve has squiggled resolutely higher.

Antarctic may host methane stores

Large volumes of methane - a potent greenhouse gas - could be locked beneath the ice-covered regions of Antarctica, according to a new study.