Carbon Dioxide Rate is at Highest Level for 650,000 Years

[marmar]

from the Independent UK, via CommonDreams:


Published on Saturday, February 3, 2007 by the lndependent/UK
Global Warming: The Final Warning
Carbon Dioxide Rate is at Highest Level for 650,000 Years
by Steve Connor

Concentrations of carbon dioxide in the atmosphere are at their highest levels for at least 650,000 years and this rise began with the birth of the Industrial Revolution 250 years ago, according to the Intergovernmental Panel on Climate Change (IPCC).

Carbon dioxide is the principal greenhouse gas responsible for global warming and, in 2005, concentrations stood at 379 parts per million (ppm). This compares to a pre-industrial level of 278 ppm, and a range over the previous 650,000 years of between 180 and 300 ppm, the report says.

Present levels of carbon dioxide - which continue to rise inexorably each year - are unprecedented for the long period of geological history that scientists are able to analyse from gas samples trapped in the frozen bubbles of deep ice cores.

However, the IPCC points to a potentially more sinister development: the rate of increase of carbon dioxide in the atmosphere is beginning to accelerate. Between 1960 and 2005 the average rate at which carbon dioxide concentrations increased was 1.4 ppm per year. But when the figures are analysed more closely, it becomes apparent that there has been a recent rise in this rate of increase to 1.9 ppm per year between 1995 and 2005.

It is too early to explain this accelerating increase but one fear is that it may indicate a change in the way the Earth is responding to global warming. In other words, climate feedbacks that accelerate the rate of change may have kicked in.

The IPPC's report points out that, as the planet gets warmer, the natural ability of the land and the oceans to absorb carbon dioxide from the atmosphere begins to get weaker. .....(more)

The complete piece is at: http://www.commondreams.org/headlines07/0203-03.htm

[kestrel91316]

1. I wish they would phrase that differently - I think they mean

highest level IN (the past) 650,000 years.

"Highest level FOR 650,000 years" has an entirely diffenent meaning, that the CO2 HAS BEEB this high for a hell of a long time, and that certainly wouldn't be newsworthy.

The Brits have a funny way of saying things sometimes.

(That bit about waiting ON line rather than IN line always ticked me off, too)

[meow mix]

2. why 650,000?

just wondering about that time frame. why not a million?
because co2 was higher at that point, or because they cant go further back due to some contraints on the methods?

[Odin2005]

3. That's as far back as the ice core data goes.

I'm sure the CO2 levels haven't been this high since at least before the Modern Ice Age began 3 million years ago, but scientists officially stick with the "650,000 years" phrase in order not to allow the denialists an opportunity to scream "unsubstantiated assertion."

[Dead_Parrot]

4. Limits of accuracy

The IPCC like to be pretty certain of things before they include them in their considerations: 650 kya was (until recently) the longest ice-core that had been tested for CO₂ with a high level of confidence in the results, so that's what they are using.

There was a longer one sampled last last year that confirmed the highest levels for 800,000 years (see http://news.bbc.co.uk/2/hi/science/nature/5314592.stm) but that will take a while to sink through the IPCC process.

We have an idea of concentrations going back much further, like this chart from wiki:


But the errors bars are too big for definitive statements like this one. Squinting at some of the charts, I'd say it looks like CO₂ is the highest it's been for about 3 million years, but I haven't got a reputation to stake on it. :silly:

Edit: Re-reading the Beeb's story, it's actually the same core as the 650 kya figure - they just hadn't finished the testing. They've now been through the whole lot.

[meow mix]

5. ahhh ty, nice chart :D

the purple and green lines are interesting around 800ppm in the jurassic/triassic age? eep

[kestrel91316]

6. Things are only now as bad as they were 650,000 years ago.

So how much farther back they can go isn't the point of it.

There IS a limit to how far back they can figure these things out, I think. The ice cores in Antarctica only go back so far..........

There is a way to figure CO2 levels in alluvial sediments in the ocean, IIRC, that goes back way beyond the oldest ice.