Is it already too late?

Climate change is now being recognised as the major issue it is. Governments are scrambling
to put schemes and policies into affect - but there is a question that is looming large in
the minds of some scientists, most notably James Lovelock (creator of the Gaia hypothesis):
Is it already too late to do anything about climate change?

This can either be interpreted as 'it is already too late to prevent climate change of some
magnitude; all we can do now is reduce the amount of change' or 'it is too late to prevent
catastrophic change'. The former is widely assumed to be an accurate statement. The earth-
atmosphere system has a built in time lag, whereby it takes some length of time for the
effect of any changes to be felt and responded to. The time lag of the atmosphere is of the
order of about a day to up to several years, depending on the processes involved. The ocean,
a major factor in the earth system, has a much longer timescale, and this is why we would
still not feel the full impact of climate change (even if all greenhouse gas emissions were
stopped instantaneously) until decades into the future. Considering the sudden huge increase
of greenhouse gases in the last 100 years or so, our climate will most definitely be altered
in some way in the coming years.

And so it is the latter form of the 'is it too late' question which becomes important. At
what point does climate change become 'catastrophic', and at what point do we pass the point
of no return, where nothing we can do can stop a climate catastrophe from occuring?

It may be that an increase of only a couple of degrees is enough to cause catastrophic
effects: an alteration in atmospheric systems could mean drought in some places, floods and
violent storms in others. At what point, at what amount of loss of life would climate change
be seen to be disatrous?
Alternatively, we could see few effects until temperatures rise greatly, causing such
alterations in climate across the world that entire habitats and ecosystems die out.

James Lovelock, in his book 'Revenge of Gaia', revelas his fears that we are already doomed,
and advises that we should stash survival manuals in the arctic where the few human
survivors of the upcoming climate disaster can find them.
However he admits that his gloomy prediction is based on nothing more than a gut feeling:
most climate models do not reveal a doomsday result. However the world is an extremely
complex system, which computer models can only approximate - the world may have some
previously undiscovered interaction which could change everything.

A example of a relatively unknown but potentially catastrophic climate feedback is that from
methane clathrates.
Methane clathrates occur when water ice forms under certain conditions, with a crystal
structure that can readily absorb and contain gases. It is known that there may be
potentially vast deposits of methane clathrates at the bottom of the oceans. Clathrates are
not very stable, and can hold less methane at higher temperatures. It is not hard to see how
warming climates could cause the release of methane from the ocean floor. Methane is a very
strong greenhouse gas (stronger than carbon dioxide, but less abundant), and so the feedback
effect of increased warming means more methane release from the clathrates.
Is is unknown how fast this will occur, but it is hypothesised that a sudden release of
methane into the atmosphere could have huge, potentially catastrophic effects.

A lot of research is now based on finding the hypothetical tipping point; the point of no
return for our climate, where no changes in emissions can alter our climate destiny.
I wonder if this will be seen as discovering just how far we can push it?