UN: Carbon dioxide pollution levels hit record high in 2012

World carbon dioxide pollution levels in the atmosphere are accelerating and reached a record high in 2012, the United Nations weather agency said Wednesday.

The heat-trapping gas, pumped into the air by cars and smokestacks, was measured at 393.1 parts per million (ppm) last year, up 2.2 ppm from the previous year, the Geneva-based World Meteorological Organization said in its annual greenhouse gas inventory.

That figure is far above the 350 ppm that some scientists and environmental groups promote as the upper limit for a safe level for carbon dioxide, which is the main gas blamed for global warming by many researchers and activists. The rise in levels in 2012 outpaced the past decade's average annual increase of 2.02 ppm.

Based on that rate, the organization says the world's carbon dioxide pollution level is expected to cross the 400 ppm threshold by 2016. That mark was already reached at some individual measurement stations in 2012 and 2013.

Scientists say the earth probably last had this much carbon dioxide in the atmosphere at least a few million years ago, when sea levels were higher. Carbon dioxide levels are believed to have been around 280 ppm before the Industrial Revolution.

Carbon dioxide traps heat as if in a greenhouse and accounts for three-quarters of the planet's heat-trapping gases that many scientists say are causing sea levels to rise, glaciers to melt and some weather patterns to change. Other gases, like methane, trap heat much more efficiently but have a shorter life span.

Carbon dioxide remains in the air for a century, some of it far longer, which means that a lot of future warming could already be locked in.

The rising amount of greenhouse gases in the atmosphere shows how people have "upset the natural balance of our atmosphere and are a major contribution to climate change," said Michel Jarraud, the secretary-general of the World Meteorological Organization.

The Associated Press