Atmospheric carbon dioxide nears a troubling milestone

Nature : In 1958, an atmospheric carbon dioxide monitoring station was established on the summit of Mauna Kea in Hawaii. It is now the longest-running such monitoring station. Initial measurements put the concentration of CO ₂ at 316 parts per million (ppm), not significantly higher than the 280 ppm observed before the Industrial Revolution. Within the next month, if the current upward trend continues, the facility is expected to record a daily concentration of 400 ppm, a level not seen in that area for millions of years. According to Corinne Le Quéré of the University of East Anglia in the UK, the 400-ppm level is considered the tipping point at which it will become very difficult to keep global warming in check. Although the global average daily CO ₂ concentration is still several years away from reaching that mark, there are no signs that the increasing concentrations are slowing down.