The levels of carbon dioxide, methane and other greenhouse gases in the atmosphere reached record levels in 2011, according to a report issued today by the World Meteorological Organization (WMO), a Geneva-based agency of the United Nations.


The WMO, which represents 189 member nations, collected information from around the world for this, its eighth annual report on greenhouse gases. "WMO's Global Atmosphere Watch network, spanning more than 50 countries, provides accurate measurements which form the basis of our understanding of greenhouse gas concentrations, including their many sources, sinks and chemical transformations in the atmosphere," WMO Secretary-General Michel Jarraud said in a prepared release.


According to the report, levels of carbon dioxide in the atmosphere reached 390.9 parts per million (ppm) in 2011, 40% above pre-industrial levels. CO2 is the most prevalent of the greenhouse gases, which trap radiation within the Earth's atmosphere, causing global warming. According to the report, CO2 has increased by 2 ppm each year during the past decade. Environmental groups such as and climate scientists argue that CO2 levels must be lowered to 350 ppm in order to avoid the worst future effects of global warming.


CO2 alone does not tell the whole story. While less prevalent than CO2, other gases such as methane can have a much greater warming effect. According to the WMO report, methane (CH4) levels have reached a new high of 1813 parts per billion, which is 259% above pre-industrial levels. Another gas, nitrous oxide (N2O), reached 324.2 parts per billion in 2011. The WMO says that N2O has an impact on climate 298 times that of CO2.


The report also found that levels of sulphur hexafluoride (SF6), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are also increasing.


Jarraud said the billions of tonnes of carbon dioxide that have already been added to the atmosphere by human activities will take centuries to break down. Meanwhile, emissions have exceeded the point at which the Earth's natural systems are able to absorb them. "Until now, carbon sinks have absorbed nearly half of the carbon dioxide humans emitted in the atmosphere, but this will not necessarily continue in the future," Jarraud said. "We have already seen that the oceans are becoming more acidic as a result of the carbon dioxide uptake, with potential repercussions for the underwater food chain and coral reefs. There are many additional interactions between greenhouse gases, Earth's biosphere and oceans." He is calling for increased monitoring capability and a growth of scientific knowledge in order to better understand the future effects of these greenhouse gases.


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