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"Alastair McDonald" <alastair@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> skrev
i en meddelelse news:du1eu0$btf$1@xxxxxxxxxxxxxxxxxxxxxx
>> >> You know my take as a geologist on global climate changes - it happens
>> >> through time. ...
>> >
>> > And so do mass extinctions!
>>
>> We do a pretty good job at that allready, so if climate returned to
>> 'normal'
>> even now, we can be sure to have left our 'extinction-event' in the
>> annals
>
> The megafauna extinction was carried out by prehistoric man. Now that we
> are more advanced we are much more powerful, and so our destructive
> potential
> has greatly increased.
>
> Our predecessors destroyed the megafauna, leaving the maxifauna such as
> elephants, tigers, buffalos, and rhinos for us to exterminate by removing
> their habitats. When that is complete, the largest animals left will be
> us, and the composition of the atmosphere that made the Holocene and
> civilisation possible will have been destroyed.
>
>> > The warming from increased
>> > carbon dioxide could well cause a release of methane hydrates such as
>> > happened during the Palaeocene-Eocene Thermal Maximum.
>>
>> Have you got a source for the methane hydrate thing?
>
> Try PETM in Google. Adding extinction should limit your hits.
> http://en.wikipedia.org/wiki/Paleocene-Eocene_Thermal_Maximum
> Also try "PT extinction methane".
> en.wikipedia.org/wiki/PT_extinction_event">http://en.wikipedia.org/wiki/PT_extinction_event
I thought that you had some clues as to how these events relates to the
current situation. I'm aware what's happened through geological history, why
and the uncertainties involved. You've picked the worst extremes and sort of
put yourself outside a rational approach. If anything, you've highlighted
the fact that climatic turmoil happens, with or without the help of man.
>> I've had a look at a giant landslide 'Storeggan', taking off on the
>> Norwegian shelf and slushing up on the shores of the British Isls. It's
>> thought to have come by a methane hydrate release. The only way I can
>> figure
>> out how, is as a result of pressure-release from overburden water
>> disappearing onto the continent as ice (low sealevel) and perhaps
>> lithospheric lifinng as a peripheral bulge. And I always looked at it as
>> a
>> possible reason for an abrupt end to an ice-age ... not a consequence of
>> a
>> warm climate.
>
> IMHO the Storegga tsunami was caused by an earthquake due to isostatic
> readjustment after the last glaciation.
> en.wikipedia.org/wiki/Storegga">http://en.wikipedia.org/wiki/Storegga
> There was also a release of methane but nothing like as large as that
> at the Paleo-Eocene and Permian-Triassic boundaries.
You surprise me.
www.searchanddiscovery.com/documents/2004/jung/index.htm">http://www.searchanddiscovery.com/documents/2004/jung/index.htm
These guys suggests a post-glacial clathrate release - in response to
pressure/temperature changes in a shallow reservoire. This differs from my
suggestion of an early release from a deep reservoire.
>> Sorry Alastair, there's something you've got wrong. The ice-cores shows
>> an
>> abrupt end to ice-ages. You tend to forget that we'r not currently in an
>> ice-age, so whatever the feed-back of a quick ice-melt as it's seen in
>> the
>> cores, it's not working now. Or would you prefer that I write probably
>> not
>> working now. The loss of sea-ice has an influence on albedo .. I wonder
>> weather anyone has been calculating on this part.
>
> The sea-ice is the clue to rapid climate change, because no only does
> it change the albedo it also alters the water vapour concentration, which
> is the major greenhouse gas. Temperatures still have not reached those
> during the Eemian interglacial, and when the Arctic sea ice melts there
> will be a rapid warming in the NH, which will melt the Greenland ice,
> further altering albedo and atmospheric water vapour.
We'll se what happens. The public is not deaf to the question, but I oppose
a notion that a sudden catastrophy is on the verge of happening as is how I
read your initial post.
Carsten
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