Greenhouse gases hit new high - earth - 19 February 2007 - New Scientist Environment

Greenhouse gases hit new high -

Greenhouse gases widely blamed for causing global warming have climbed to record highs in the atmosphere, an Arctic researcher has revealed.

"Levels are at a new high," said Kim Holmen, research director of the Norwegian Polar Institute, which oversees the Zeppelin measuring station on the Arctic archipelago of Svalbard, about 1200 kilometres (750 miles) from the North Pole.

He said that concentrations of carbon dioxide, the main greenhouse gas, emitted largely by burning fossil fuels in power plants, factories and cars, had risen to 390 parts per million from 388 ppm a year ago.

Levels have hit peaks almost every year in recent decades and are far above 270 ppm level seen before the Industrial Revolution of the 18^th century.

Holmen said the increase of 2 ppm from 2006 reflected an accelerating rise in recent years. "When I was young, scientists were talking about 1 ppm rises" every year, he said. "Since 2000, it has been a very rapid rate."

Coal fired

Holmen suggests that the growth of Asian economies, led by China, may be responsible for this steeper rise. By some estimates, China is opening coal-fired power plants at the rate of almost one per week.

Carbon dioxide concentrations peak just before spring in the northern hemisphere, when plants start soaking up the gas as they grow. Southern hemisphere seasons have less effect as there are fewer land masses and plants south of the equator.

The Zeppelin station is run in cooperation with Stockholm University and is one of the main measuring points, along with a station in Hawaii. Scientists say the concentration of CO₂ in the atmosphere is at its highest in at least 650,000 years.

90% chance

In a report published on 2 February, the world's top climate scientists said they were more than 90% certain that human activities, led by burning fossil fuels, were to blame for global warming. That was up from 66% certainty in a previous report published in 2001.

The UN's Intergovernmental Panel on Climate Change said that temperature rises were set to accelerate and could increase by between 1.1°C and 6.4°C 2100, bringing floods to some regions, droughts to others, and rising sea levels.

Apart from emissions caused by burning fossil fuels, scientists say other factors could affect CO₂ levels in future. On one hand, plants may grow more in a warmer world, soaking up more CO₂. But if the soil gets warmer, dead plants and leaves may rot more in winter, releasing more carbon.

Any heating of the oceans may mean less absorption of CO₂, partly because the greater buoyancy of warmer water prevents it from mixing with deeper levels.