BBC: Greenhouse gases in the atmosphere hit a new record high in 2011, the World Meteorological Organization reports. In an annual report released Tuesday, the organization said carbon dioxide levels reached 391 parts per million in 2011.
The organization estimates that 375 billion tons of carbon have been released into the atmosphere since 1750; half of that amount is believed to remain present in the atmosphere.
Photo: WMO and NOAA operate monitoring stations around the world. (SPL)