On Jan 8, 12:42*pm, delboy wrote:
As the Earth has maintained reasonably stable temperatures (with
relatively minor variations) for billions of years, it must have
pretty good natural control and feedback mechanisms. Otherwise life on
it would have already died out.

Um, which planet earth do you live on? There have
been multiple "extinction events" which take all of 5
seconds to find on wackypedia.

In particular, the "clathrate gun hypothesis" is particularly
relevant.

A snippet to whet your appetite...

The clathrate gun hypothesis is the popular name given
to the hypothesis that rises in sea temperatures (and/or
falls in sea level) can trigger the sudden release of
methane from methane clathrate compounds buried in
seabeds and permafrost which, because the methane
itself is a powerful greenhouse gas, leads to further
temperature rise and further methane clathrate
destabilization – in effect initiating a runaway process,
as irreversible once started as the firing of a gun
...
However there is stronger evidence that runaway methane
clathrate breakdown may have caused drastic alteration of
the ocean environment and the atmosphere of earth on a
number of occasions in the past, over timescales of tens
of thousands of years; most notably in connection with the
Permian extinction event, when 96% of all marine species
became extinct 251 million years ago.

Sounds pretty drastic to me!