The concentration of heat-trapping gases in the atmosphere climbed to a record high in 2011, according to the latest analysis of observations from the World Meteorological Organization’s (WMO) Global Atmosphere Watch programme.
The atmospheric concentration of carbon dioxide (CO2) — the single most important greenhouse gas — reached 390.9 parts per million (p.p.m.) in 2011 and is now 40% above the pre-industrial level of 280 p.p.m., the WMO reports today in its Greenhouse Gas Bulletin. Methane (1,813 parts per billion) and nitrous oxide (324 parts per billion) — both potent greenhouse gases — also reached new highs last year.
From 1990 to 2011, radiative forcing by long-lived greenhouse gases has increased by almost one-third, with CO2 alone accounting for about 80% of this increase. Since the start of the industrial era in 1750, about 1,377 billion tonnes of CO2 have been released into the atmosphere, according to the report.
About one half of that amount may have been absorbed by the ocean and by soils and plants on land. The other half lingers in the atmosphere, causing temperatures near the surface to warm.
The WMO bulletin reports on atmospheric concentrations — not emissions — of greenhouse gases. Emissions of CO2 from fossil-fuel burning and cement production increased by 3% in 2011, reaching an all-time high of around 34 billion tonnes.
Concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, terrestrial biosphere and the oceans.
If the ocean’s capacity for taking up CO2 and sequestering carbon were to decline, which scientists fear might happen, the global carbon sink could become substantially less efficient in the future.
With unstopped emission growth, the world is now on a dangerous path towards 4 °C global warming by the end of this century, the World Bank warned in a report released yesterday.
United Nations climate talks will resume next week in Doha, Qatar, where nations will negotiate the future of the 1997 Kyoto Protocol on Climate Change.