UN says greenhouse gas concentrations hit record levels

GENEVA (BNO NEWS) — The World Meteorological Organization (WMO) on Monday warned in a new report that the amount of greenhouse gases in the atmosphere reached a new high in 2010, exceeding worst case scenarios set in 2001.

Between 1990 and 2010, the WMO recorded a 29 percent increase in radiative forcing – the warming effect on our climate system – from greenhouse gases. Carbon dioxide accounted for 80 percent of this increase, according to the WMO’s Greenhouse Gas Bulletin.

“The atmospheric burden of greenhouse gases due to human activities has yet again reached record levels since pre-industrial time,” said WMO Secretary-General Michel Jarraud. “Even if we managed to halt our greenhouse gas emissions today – and this is far from the case – they would continue to linger in the atmosphere for decades to come and so continue to affect the delicate balance of our living planet and our climate.”

According to the WMO, heat-trapping carbon dioxide concentrations are the single most important man-made greenhouse gas in the atmosphere and have reached 389 parts per million, which is the highest level since the start of the industrial era in 1750.

The high concentrations of carbon dioxide are primarily because of emissions from combustion of fossil fuels, deforestation and changes in land-use. Between 2009 and 2010, its atmospheric abundance increased by 2.3 parts per million.

Carbon dioxide currently contributes about 64 percent to the total increase in climate forcing by greenhouse gases. For about 10,000 years before the start of the industrial era in the mid-18th century, atmospheric carbon dioxide remained almost constant at around 280 parts per million.

In addition to water vapor and carbon dioxide, the most prevalent long-lived greenhouse gases are methane and nitrous oxide. Since 1750, the concentration of methane has increased 158 percent, mostly because of activities such as cattle-rearing, rice planting, fossil fuel exploitation and landfills. Human activities now account for 60 percent of methane emissions, with the remaining 40 percent being from natural sources such as wetlands.

Nitrous oxide contributes about six percent to the overall global increase in radiative forcing since 1750. It is emitted into the atmosphere from natural and man-made sources, including the oceans, biomass burning, fertilizer use and various industrial processes. It is now the third most important greenhouse gas, according to WMO.

The atmospheric burden of nitrous oxide in 2010 was 323.2 parts per billion – 20 percent higher than in the pre-industrial era. It has grown at an average of about 0.75 parts per billion over the past ten years, mainly as a result of the use of nitrogen containing fertilizers, including manure, which has profoundly affected the global nitrogen cycle.

Scientists say the impact of nitrous oxide on climate, over a 100 year period, is 298 times greater than equal emissions of carbon dioxide. It also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun.

“Now more than ever before, we need to understand the complex, and sometimes unexpected, interactions between greenhouse gases in the atmosphere, Earth’s biosphere and oceans,” said Jarraud. The WMO report released on Monday shows greenhouse gas concentrations have now exceeded the worst case scenarios of a United Nations expert climate panel in 2001.