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30 juni 2009

Studie: biodiversiteit stort in elkaar bij 900 ppm CO2-concentratie



And extinction risk to plant biodiversity may occur at lower levels of atmospheric CO2 than previously considered
Physorg.com, June 29th, 2009

Scientists have traced a sudden collapse in plant biodiversity in ancient Greenland, some 200 million years ago, to a relatively small rise in atmospheric carbon dioxide which caused a rise in the Earth’s temperature.

According to the findings published in the leading journal Science, the current estimated levels of atmospheric carbon dioxide which are thought to lead to sudden biodiversity loss may have to be revised downwards.

Comment by Joe Romm on Climate Progress:
In 2007, the IPCC warned [see Climate Change 2007: Synthesis Report; Summary for Policymakers (PDF)] that "as global average temperature increase exceeds about 3.5°C [relative to 1980 to 1999], model projections suggest significant extinctions (40-70% of species assessed) around the globe". On our current emissions path, we will warm far more than that this century, which suggests we risk the high end of species loss.
A new study in Science study (subs. req’d) confirms this risk. It examines "the pace of diversity loss leading to the Triassic-Jurassic boundary (TJB)". It finds "the sudden diversity dropcoincided with a mere ~100 to ~350 ppmv rise in CO2-concentration", and "CO2-induced global warming was likely an important contributory factor to plant species turnover at the TJB".

A commenter on Climate Progress:
'It seems that not being able to account for sulfur dioxide emissions leaves this study with a great big question mark hanging over it, given how SO2 contributes to acid rain. Was it the heat or the acid rain or both that caused the mass extinction event? We don’t yet know. This study leaves me concerned, but not in a panic (yet).'

Also see:
Extinctions Linked to Hotter Temperatures

And:

Thanks to Our Fossil Fuel Addiction, We May Be Setting Ourselves Up for a Catastrophic Natural Event

By Scott Thill, AlterNet, July 3, 2009

Too much CO2 in the air and not enough oxygen in the oceans may release a toxic dose of hydrogen sulfide - an unheralded executioner.

(...) A growing scientific consensus explains that the death stroke [during the Triassic-Jurassic boundary] was probably delivered from Earth's anoxic oceans, whose resultant out-of-whack pH balance, once literally defined as the "power of hydrogen," released catastrophic stores of either methane hydrate or hydrogen sulfide into the atmosphere.

Whichever one it was, hydrogen had the power to bring Earth to its knees. And it could happen again.

Photo Scienceblogs.com: The long-necked plesiosaur Thalassiodracon from rocks spanning the Triassic-Jurassic boundary.

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