"Dan" wrote:

The jury's out on the cause-effect relationship. We see a correlation
-- that does not necessarily imply causation, and the IPCC waffles on
this point as well.

You can call it waffling if you like. I call it caution.

So the first Big Question is -- is CO2 increase anthropogenic?

The resounding IPCC answer -- maybe.

They sound pretty sure, to me:
=========================
The increase in CO2 mixing ratios continues to yield the largest sustained RF
of any forcing agent. The RF of CO2 is a function of the change in CO2 in the
atmosphere over the time period under consideration. Hence, a key question is
'How is the CO2 released from fossil fuel combustion, cement production and
land cover change distributed amongst the atmosphere, oceans and terrestrial
biosphere?'. This partitioning has been investigated using a variety of
techniques. Among the most powerful of these are measurements of the carbon
isotopes in CO2 as well as high-precision measurements of atmospheric oxygen
(O2) content. The carbon contained in CO2 has two naturally occurring stable
isotopes denoted 12C and 13C. The first of these, 12C, is the most abundant
isotope at about 99%, followed by 13C at about 1%. Emissions of CO2 from coal,
gas and oil combustion and land clearing have 13C/12C isotopic ratios that are
less than those in atmospheric CO2, and each carries a signature related to
its source. Thus, as shown in Prentice et al. (2001), when CO2 from fossil
fuel combustion enters the atmosphere, the 13C/12C isotopic ratio in
atmospheric CO2 decreases at a predictable rate consistent with emissions of
CO2 from fossil origin. Note that changes in the 13C/12C ratio of atmospheric
CO2 are also caused by other sources and sinks, but the changing isotopic
signal due to CO2 from fossil fuel combustion can be resolved from the other
components (Francey et al., 1995). These changes can easily be measured using
modern isotope ratio mass spectrometry, which has the capability of measuring
13C/12C in atmospheric CO2 to better than 1 part in 105 (Ferretti et al.,
2000). Data presented in Figure 2.3 for the 13C/12C ratio of atmospheric CO2
at Mauna Loa show a decreasing ratio, consistent with trends in both fossil
fuel CO2 emissions and atmospheric CO2 mixing ratios (Andres et al., 2000;
Keeling et al., 2005).

-4AR WG1, 2
========================


Nevertheless, for argument's sake, IF we accept the hypothesis that
the earth is warming at a steady rate that will result in measurable
change to global and regional climates, there is no model that
adequately predicts the impact of these changes, long or short term.
They may in fact be benign or even salutary.

I disagree that the hypothesis predicts a steady rate. There are too many
other things going on to say that.


Thee time span for all these cataclysmic results is also in great
doubt -- 100 - 400 - 1,00 years?

Here it comes:

It Depends.

What do you mean by "cataclysmic?" Which result? What level of GHGs at what
time?

Hardly a hurdle for humans, given our remarkable ability to adapt.

One foot sea level rise in 400 years? Not too tough.

One meter in 100 years? Colossally expensive and disrupting.

And that's only one thing. What about the death of coral reefs, disruption of
the Gulf Stream, burning of the Amazon forests?

The scariest thing about this to me is the grumbling from some scientists that
the IPCC is way too conservative in what it puts in the reports because of
over-sensitivity to "alarmist" charges. These folks are saying the there's a
chance the **** is *really* going to hit the fan, and sooner than we think.
Are they right? I don't know. Hell, *they* don't know. They're just saying,
"You better think about this." (Not that any of the pol's at the Bali
Conference paid much attention; they were at a cocktail party or something.)

So, it depends.

As an aside:

It's amazing how much more coherent and convincing your arguments
appear when you're not sniping.

I'm not signing up for the cause, just making an observation.

I have a history with this subject. I'm used to being attacked by shrieking
political zealots and talk radio zombies in such discussions .

You don't fit those categories, but it takes a while to realize that
sometimes. Thanks for your patience.