Straw man alert.
It seems to be a bit of a myth that a "tipping point" always involves
irreversibility or "unable to
return to given state by any circuitous route whatever".
It may. Or it may not.
The usual usages do not -- simply that one stable state is changed to
another stable state, usually
"suddenly".
Even "irreversibility" in the classic reductionist sense doesn't
dictate that a state becomes forever unreachable --
just that if A -> B is irreversible then we can't have B -> A.
Another thing to watch out for is 1d thinking. When it comes to the
"environment" it just doesn't do to imagine (loosest possible sense of
the technical term, given the context) a "state" consists of a single
variable -- e.g. temperature.
Finally, there is little that a mass extinction or other planet-
killing event can't reset the clock to zero.
Of course they are the things some of us are trying to avoid and
others deny are possible.
--
[Feel the meta-evidence, Luke:]
The great thing about science is that once you understand it you tend
to defend it, especially against pretenders to science like the agw
activists here and at various institutions like the CRU, GISS, Penn
State and against political activists at the IPCC and Greenpeace.
-- Tunderbar <
tdco...@gmail.com>, 8 Jul 2011 11:05 -0700 (PDT)