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11 maart 2009

Hansen: aarde kan tweede Venus worden

Ter herinnering: de NASA-klimatoloog Jim Hansen houdt serieus rekening met de huiveringwekkende of beter: helse mogelijkheid dat de aarde zo sterk zal opwarmen, dat de oceanen aan de kook raken en de aarde een Venus-achtige planeet wordt. In zijn 'Bjerknes Lecture'-presentatie (Powerpoint hier) voor de American Geophysical Union op 17 december 2008 zei hij:

'The Earth’s climate becomes more sensitive as it becomes very cold, when an amplifying feedback, the surface albedo, can cause a runaway snowball Earth, with ice and snow forming all the way to the equator.
If the planet gets too warm, the water vapor feedback can cause a runaway greenhouse effect. The ocean boils into the atmosphere and life is extinguished.
The Earth has fell off the wagon several times in the cold direction, ice and snow reaching all the way to the equator. Earth can escape from snowball conditions because weathering slows down, and CO2 accumulates in the air until there is enough to melt the ice and snow rapidly, as the feedbacks work in the opposite direction. The last snowball Earth occurred about 640 million years ago.
Now the danger that we face is the Venus syndrome. There is no escape from the Venus Syndrome. Venus will never have oceans again.
Given the solar constant that we have today, how large a forcing must be maintained to cause runaway global warming? Our model blows up before the oceans boil, but it suggests that perhaps runaway conditions could occur with added forcing as small as 10-20 W/m2.
(...) In my opinion, if we burn all the coal, there is a good chance that we will initiate the runaway greenhouse effect. If we also burn the tar sands and tar shale (a.k.a. oil shale), I think it is a dead certainty...'

De lezing van Jim Hansen:

Zie ook:
Is Venus a Model for Earth's Future Climate?

Stephen Hawking op bezoek in China op 21 juni 2006:
Asked about the environment, Hawking (..) said he was "very worried about global warming." He said he was afraid that Earth "might end up like Venus, at 250 degrees centigrade and raining sulfuric acid."

Hawking denkt overigens sci-fi-achtig dat de mens andere planeten moet koloniseren om te overleven. Hier staat een kritisch stukje over een en ander. [Update: is weggehaald, wel nog gearchiveerd hier.]

Zie verder mijn blognotities:
'Netherlands face catastrophic flooding' (9 maart 2009)
Zeespiegel van ijsvrije aarde (maart 2007)


Stabilize at 350 ppm or risk ice-free planet, warn NASA, Yale, Sheffield, Versailles, Boston et al
Climate Progress, November 9th, 2008

Veel minder alarmerende cijfers staan in deze studie:

New York Seas to Rise Twice as Much as Rest of U.S.
National Geographic News, March 15, 2009

In tegenstelling tot:

Are We Breeding Ourselves to Extinction?
By Chris Hedges, Truthdig, March 11, 2009

[...] Oxygen and nitrogen would disappear if the biosphere was destroyed. The result would be a greenhouse atmosphere similar to that of Venus, a planet that is consequently hundreds of degrees hotter than Earth.

[...] [In] 'The Vanishing Face of Gaia', his latest book, which has for its subtitle 'A Final Warning', (...) Lovelock says a continued population boom will make the reduction of fossil fuel use impossible.

The Vanishing Face of Gaia:
'Celebrities drive hybrids, Al Gore won the Nobel Peace Prize, and supermarkets carry no end of so-called “green” products. And yet the environmental crisis is only getting worse. In Surviving Gaia’s Revenge, the eminent scientist James Lovelock argues that the earth is lurching ever closer to a permanent “hot state”—and much more quickly than most specialists think. There is nothing humans can do to reverse the process; the planet is simply too overpopulated to halt its own destruction by greenhouse gases.
In order to survive, mankind must start preparing now for life on a radically changed planet. The meliorist approach outlined in the Kyoto Treaty must be abandoned in favor of nuclear energy and aggressive agricultural development on the small areas of earth that will remain arable.
A reluctant jeremiad from one of the environmental movement’s elder statesmen, Surviving Gaia’s Revenge offers an essential wake-up call for the human race.'

Toegevoegd 16 maart: Kritische reactie op bovenstaand stuk:

Rebuttal to Chris Hedges: Stop the Tired Overpopulation Hysteria
Raising alarms about overpopulation distracts us from the real environmental tasks at hand and legitimizes top-down punitive policies that hurt women.

Zie ook m'n blognotitie:
De aarde kan te heet worden voor mensen

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