The WMO says that fossil fuel activities such as oil refining are driving atmospheric levels of CO2 to record highs. The levels of gases in the atmosphere that drive global warming increased to a record high in 2012. According to the World Meteorological Organization (WMO), atmospheric CO2 grew more rapidly last year than its average rise over the past decade. Concentrations of methane and nitrous oxide also broke previous records. Thanks to carbon dioxide and these other gases, the WMO says the warming effect on our climate has increased by almost a third since 1990. The WMO's annual greenhouse gas bulletin measures concentrations in the atmosphere, not emissions on the ground. Carbon dioxide is the most important of the gases that they track, but only about half of the CO2 that's emitted by human activities remains in the atmosphere, with the rest being absorbed by the plants, trees, the land and the oceans. Since the start of the industrial era in 1750, global average levels of CO2 in the atmosphere have increased by 141%. According to the WMO there were 393.1 parts per million (ppm) of carbon dioxide in the atmosphere in 2012, an increase of 2.2ppm over 2011. This was above the yearly average of 2.02ppm over the past decade. "The observations highlight yet again how heat-trapping gases from human activities have upset the natural balance of our atmosphere and are a major contribution to climate change," said WMO Secretary-General Michel Jarraud.