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May 12th, 2013:

Sharp rise in carbon dioxide levels poses major global-warming threat

Sunday, 12 May, 2013, 12:00am



The New York Times[1]

The level of the most important heat-trapping gas in the atmosphere, carbon dioxide, has passed a long-feared milestone, scientists reported, reaching a concentration not seen on the earth for millions of years.

Scientific instruments showed that the gas had reached an average daily level above 400 parts per million – a sobering reminder that decades of efforts to bring human-produced emissions under control are faltering.

The best available evidence suggests that the amount of the gas in the air has not been this high for at least three million years, before humans evolved, and scientists believe the rise portends large changes in the climate and the level of the sea.

“It symbolises that so far we have failed miserably in tackling this problem,” said Pieter Tans, who runs the monitoring programme at the National Oceanic and Atmospheric Administration that reported the new reading.

Virtually every car ride, plane trip, and in most places flip of a light switch adds carbon dioxide to the air, and relatively little money is being spent to find and deploy alternative technologies.

China is now the largest emitter, but Americans have been consuming fossil fuels extensively for far longer, and experts say the United States is more responsible than any other nation for the high level.

The new measurement came from analysers atop Mauna Loa, the volcano on the big island of Hawaii that has long been ground zero for monitoring the worldwide trend on carbon dioxide. Devices there sample clean, crisp air that has blown thousands of kilometres across the Pacific Ocean, producing a record of rising carbon dioxide levels that has been closely tracked for half a century.

Carbon dioxide above 400ppm was first seen in the Arctic last year and had also risen above that level in hourly readings at Mauna Loa. But the average reading for an entire day surpassed that level at Mauna Loa for the first time.

“It feels like the inevitable march towards disaster,” Maureen Raymo, a scientist at the Lamont-Doherty Earth Observatory of Columbia University, said.

From studying air bubbles trapped in Antarctic ice, scientists know that, going back 800,000 years, the carbon dioxide level oscillated in a tight band, from about 180ppm in the depths of ice ages to about 280ppm during the warm periods between. The evidence shows that global temperatures and carbon-dioxide levels are tightly linked.

For the entire period of human civilisation, roughly 8,000 years, the carbon-dioxide level was relatively stable near that upper bound. But the burning of fossil fuels has caused a 41 per cent increase in the heat-trapping gas since the Industrial Revolution, and scientists say the climate is beginning to react, though they expect far larger changes in the future.

Indirect measurements suggest that the last time the carbon-dioxide level was this high was at least three million years ago, during an epoch called the Pliocene. Geological research shows that the climate then was far warmer than today, the ice caps were smaller and the sea might have been up to 25 metres higher.


Global Warming

Carbon Dioxide

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