Last year global concentrations of carbon dioxide (CO2), methane and nitrous oxide -- the main long-lived greenhouse gases (GHG) in the atmosphere -- reached the highest levels recorded since pre-industrial times, according to the World Meteorological Organization (WMO), an agency of the United Nations (UN).

Since 1990 the increase in radiative forcing caused by all long-lived greenhouse gases is 26%. The increase was 1.3% from 2007 to 2008, WMO said last Monday. (An increase in radiative forcing indicates that more energy is entering the atmosphere.) The figures, published in WMO's 2008 Greenhouse Gas Bulletin, "confirm the continued trend of rising atmospheric burdens of greenhouse gases since 1750," WMO said.

WMO, through its Global Atmosphere Watch Programme, coordinates the observations of GHG in the atmosphere via a network of stations in more than 50 countries. Its latest GHG observations come on the eve of climate talks next month in Copenhagen, Denmark (see related story). In advance of the event scientists in the United Kingdom last Tuesday renewed a call to fight global warming. And last Monday the provincial government of Quebec said it would target a 20% reduction in GHG emissions below 1990 levels by 2020.

The globally averaged mixing ratio of CO2 in 2008 was 385.2 parts per million (ppm), with an increase of 2 ppm from the previous year, continuing the tendency of exponential increase, WMO said. CO2 is the most important human-emitted greenhouse gas in the atmosphere, contributing 63.5% to the increase in overall radiative forcing since 1750. Its atmospheric abundance was nearly constant at about 280 ppm before industrialization. During the 1979-1984 period CO2 contributed 56% of the increase in radiative forcing caused by long-lived greenhouse gases. Since then CO2 has gained importance and during the five-year period from 2003 to 2008 CO2 was responsible for 86% of the increase in radiative forcing, which is more than four times that of all other long-lived GHG emissions combined. Since 1750 atmospheric CO2 has increased by 38%, primarily because of emissions from combustion of fossil fuels, deforestation and land use change, WMO said.

The current Greenhouse Gas Bulletin is the fifth in the series, reporting data since 2004. Its release precedes the 15th session of the UN Framework Convention on Climate Change to be held in Copenhagen Dec. 7-18.

Three UK scientific organizations involving most of the country's scientists working on climate change emphasized the need to address emissions of GHG.

"[W]e cannot emphasize enough the body of scientific evidence that underpins the call for action now, and we reinforce our commitment to ensuring that world leaders continue to have access to the best possible science. We believe this will be essential to inform sound decision-making on policies to mitigate and adapt to climate change up to Copenhagen and beyond," said a statement from the Natural Environment Research Council, the UK's Meteorological Office and The Royal Society of London for the Improvement of Natural Knowledge.

Citing a 2007 report by the UN's Intergovernmental Panel on Climate Change (IPCC), the groups said there is "unequivocal evidence for a warming climate and a high degree of certainty that human activities are largely responsible for global warming since the middle of the 20th century." Beyond that report, though, the scientists said evidence of climate change has grown. They noted that:

"We expect some of the most significant impacts of climate change to occur when natural variability is exacerbated by long-term global warming, so that even small changes in global temperatures can produce damaging local and regional effects," the groups said. "Year-on-year the evidence is growing that damaging climate and weather events -- potentially intensified by global warming -- are already happening and beginning to affect society and ecosystems."

In Quebec the government noted that it has set a GHG reduction goal of 20% below 1990 levels by 2020, which it said is similar to the target established by the European Union.

"It is a very ambitious target for the government, given that 48% of Quebec's total energy currently comes from renewable energy sources," said Quebec Premier Jean Charest. "We currently hold the best GHG emissions record in Canada, which is approximately 11 tons per capita, half of the Canadian average. With a minus 20% target by 2020, Quebec will have the smallest level of emissions per capita in North America."

Quebec is relying on the introduction of a GHG cap-and-trade scheme in 2012, which it said will be the largest in North America and is being developed in partnership with the Western Climate Initiative.

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