Wednesday, April 11, 2012

An Alert - reposted from Climate Code Red

Just Incredible.

"We stand today at a crossroads: One path leads to despair and utter hopelessness. The other leads to total extinction. Let us hope we have the wisdom to make the right choice."

~ Woody Allen

Posted: 09 Apr 2012 03:42 PM PDT
  • Current levels of atmospheric carbon dioxide are probably sufficient to trigger large-scale permafrost carbon feedbacks and global warming that human effort would be unable to contain.
  • The time to slash emissions was a long time ago but now is still much, much better than later, which may, as new studies suggests, simply become too late.
Thawing permafrost
Two future climate impacts above all others will overwhelm human efforts to mitigate global warming should temperatures and carbon dioxide levels reach critical levels, which in the latter case we are already close to achieving.
       The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 3 to 6 degrees Celsius higher than they are today, the sea level was approximately 25 to 40 metres higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland.
     One impact is ocean acidification (increasing atmospheric carbon dioxide is well-mixed with the ocean, to form carbonic acid and thus increasing water acidity) and rising ocean temperatures.  Given that carbon dioxide emissions over the next two decades are being determined (more than we would wish!) by existing energy infrastructure, we are not far from disaster:
The second overwhelming impact would be the large-scale release of permafrost carbon. It is estimated that the amount of carbon stored in the polar north as soil permafrost or on the ocean bed as methane clathrates is around 1,670 billion tonnes, three times greater than the current quantity of atmospheric carbon.  Losing even a third of the Arctic carbon stores would double atmospheric carbon dioxide levels and usher in warming of 4 degrees Celsius or more.
     So the big question is how far we are from triggering large-scale permafrost release.
PIOMAS yearly minimum Arctic ice volume
(click to enlarge)
  • The first point to note is that the Arctic has already proved to be more sensitive to global warming that expected. It is now acknowledged that the Arctic has passed the tipping point for sea-ice-free summers. The lack of summer sea-ice will increase Arctic warming (already double the global average) as heat-reflecting ice is replaced by dark, heat-absorbing open seas. There may well be a summer sea-ice-free Arctic by around 2015 (see chart).
  • Those circumstances will increase the rate of melting of the Greenland ice sheet, which is already accelerating. And now the tipping point for Greenland's ice sheet (eventual sea level rise of 7 metres) has been revised down from around 3 degrees C to just 1.6C (uncertainty range of 0.8C-3.2C). At the current temperature rise of 0.8C we may have already reached Greenland's tipping point, and with temperature rises in the pipeline (global emissions still rising, no reasonable agreement to reduce them), we are very likely to hit 1.6C in two to three decades. 
  • Global average temperatures have warmed just less than 1ºC since the Industrial Revolution, but average temperatures in Siberia, Alaska and western Canada are now 3ºC to 4ºC warmer than 50 years ago. In parts of northern Canada, Greenland and the surrounding ocean during the 2010-2011 northern winter, temperatures were more than 6 degrees Celsius warmer than the baseline temperature average for the period of 1951-1980, and 7 to 9 degrees Celsius above average over the Chukchi Sea. So by mid-century the regional increase increase could easily be 4ºC to 6ºC.
  • Predictions in 2011 suggested that as soon as 2020 carbon emissions from melting permafrost could be close to a billion tonnes a year. Researchers said that this positive permafrost carbon feedback will “will change the Arctic from a carbon sink to a source after the mid-2020s and is strong enough to cancel 42–88% of the total global land sink.”
  • Work by Celia BitzPhilippe Ciais and others suggests that the tipping point for the large-scale loss of permafrost carbon is around 8–10C regional temperature increase. As temperatures rise, it is projected that Arctic amplification (the multiple by with the Arctic warms compared to the global average) would be approximately times three, so around a 3C increase in global temperature is probably more than enough to detonate the permafrost timebomb. This feedback in the carbon cycle would drive temperatures significantly higher. Caias told the March 2009 Copenhagen science conference that: “A global average increase in air temperatures of 2C and a few unusually hot years could see permafrost soil temperatures reach the 8C threshold for releasing billions of tonnes of carbon dioxide and methane”.
And now former UN climate chief Yves de Boer thinks that limiting warming to "two degrees is out of reach", which makes Caias's statement more than ominous.  Of course, permafrost tipping points is not the only reason to view 2 degrees Celsius as a crazy outcome and to be avoided at all costs. NASA climate chief James Hansen concludes that at the current temperature, no “cushion” is left to avoid dangerous climate change, and that the Australian government target goals  “… of limiting human-made warming to 2 degrees Celsius and CO2 to 450 ppm are prescriptions for disaster”.
RELATED POSTS
 On 19 March this year, a study published in Geology found that temperatures were 2 degrees warmer climate in late Pliocene (3–4 million years ago) and this meant 12-32 meters higher sea levels. Yet at that time CO2 levels were around 365–410 parts per million, similar to today's level of 390 parts per million, and Arctic temperatures were 11 to 16°C warmer. Other studies over this period estimated global temperature to be 3 to 4°C warmer than pre-industrial temperatures.  
     The take-home message is that current levels of atmospheric carbon dioxide are probably sufficient to trigger large-scale permafrost carbon feedbacks and global warming that human effort would be unable to contain.

In the Pliocene 3 million years ago conditions were 11-16 degrees Celsius warmer, at atmospheric carbon dioxide levels similar to today.

And now comes a new study which shows a sudden and extreme global warming events 55 million years ago known as the Palaeocene–Eocene Thermal Maximum (PETM) is characterized by a massive input of Antarctic permafrost carbon, ocean acidification and an increase in global temperature of about 2 degrees Celsius within a few thousand years.  The study's author, Rob DeConto, says the implications of the study appear dire for the long-term future as polar permafrost carbon deposits have begun to thaw due to burning fossil-fuels: 
Similar dynamics are at play today. Global warming is degrading permafrost in the north polar regions, thawing frozen organic matter, which will decay to release CO2 and methane into the atmosphere. This will only exacerbate future warming in a positive feedback loop.

2 comments:

  1. We have to do something to stop this, it is an emergency situation. Why do so few people here this message? Thanks for posting this article, I'm going to share it.

    ReplyDelete
  2. Thanks Desert Dreamer! I usually try to stay away from climate and stick to trees - there are so many climate blogs out there. But I thought that, even though there is nothing actually new in this article, it is really well put together to convey the severity of the feedbacks.

    And the feedbacks are what is going to get us. The initial forcing - greenhouse gases - is nothing in comparison.

    Yeah, I'm scared. It IS an emergency and anyone who doesn't think so is a cretin, I don't mind saying.

    ReplyDelete

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