John Dann wrote:
On Fri, 10 Feb 2006 21:52:58 -0000, "Richard Orrell"
wrote:

It is fair to say that we have now arrived at an almost
unprecedented situation when a totally overwhelming majority of scientists
the world over agree that the recent warming trend is significantly due to
anthropogenic affects. Are you really suggesting that all of these people
are incorrect?

Comments like this always worry me a little. I think it's true that
most scientists can agree on the accuracy and validity of a paritcular
data-set in their field. As to the interpretation of that data,
especially as to its place in a much wider world view, well that's a
different matter.

(I should add that I'm not necessarily disagreeing with the current GW
consensus at all, merely taking issue with the idea that because a
majority of scientists might agree with a given interpretation of data
at some point in time then this is automatically going to be borne out
long-term as an accurate interpetation.)

In my experience, most scientists do not form their own independent
perspective on major scientific issues. Rather, in the main and much
like the rest of humanity, they get caught up in whatever the
prevailing bandwagon might be in their own department or peer group or
sub-discipline. Fortunately there are a few who can genuinely think
for themselves and it's these folk who introduce the real advances.
The trick is in spotting these people ahead of time and jumping on
their particular bandwagon.

John Dann

I am wondering if a word or two on the topic of causal relationships
would help. Not everyone is trained in statistical analysis and I
apologise to those who are for my simple examples below.

Silly example:
Strychnine has an LD50 of 1mg/1kg, so assuming no medical intervention,
if one eats 1 gram of the substance, one will die. The link between
eating the toxin and death is causal, and confidence in the outcome is
very high.

Serious example:
Someone already mentioned (quite accurately) smoking [tobacco] and the
increase in risk of respiratory problems.
There *is* a causal link in the use of tobacco and the *increased risk*
of such illnesses.
But there *is not* a causal link between the use of tobacco and
respiratory illness ... i.e. it cannot be said that if you smoke n
cigarettes you *will* contract a certain illness.

Climate change:
There is evidence that the amount of CO2 in the atmosphere has
increased, and that human-related CO2 emissions have increased, and
these two sets of data somewhat inevitably appear related.
The increase in atmospheric CO2 and the decrease in tree populations
(worldwide) is worth a look.

There is also evidence of an increase in global temperatures, and there
is a correlation between the temperature rises and the CO2 rises.

I am unaware of any high confidence causal link between the two sets of
data (either way around).

This does not mean that I deny that humans are causing, or contributing
to, global warming. Nor does it mean that I think we should not change
our behaviour.

It means quite simply that the causal link has not yet been
mathematically established.

My personal view happens to be that *if* the current climate change is a
result of human activity, then preventive action needed to have been
taken between 1960 and 1970.
If on the other hand, it is a completely natural event, then no action
was possible.

The most likely situation is perhaps that the changes are a combination
of both the above, and anything humans can do to minimise their
contribution is a good idea. I try to do my bit.

Gianna