Re: Snowball Earth


"Carsten Troelsgaard" <carstenNOSPAM.troelsgaard@xxxxxxx> wrote in message
news:44038743$0$47076$edfadb0f@xxxxxxxxxxxxxxxxxxxxxxx

"Alastair McDonald" <alastair@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> skrev
i en meddelelse news:dtvki0$kh1$1@xxxxxxxxxxxxxxxxxxxxxxx

"Carsten Troelsgaard" <carstenNOSPAM.troelsgaard@xxxxxxx> wrote in message
news:44032b08$0$47077$edfadb0f@xxxxxxxxxxxxxxxxxxxxxxx

Thank you for the articles. If anything has made me move my opinion on
global changes, it's another branch of environmental science: The
population
of East-Greenland are the ones that suffers most (has acumulated the
highest
amounts) from the spread of PCB and the rest of "The dirty dozen". It's
staggering how the stuff concentrates in the most unlikely places.

http://www.mst.dk/udgiv/publications/2001/87-7944-977-8/html/kap09_eng.htm

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".
http://en.wikipedia.org/wiki/PT_extinction_event

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.
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.


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.

Must get on,

Cheers, Alastair.


.

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