The Natural Philosopher wrote:

snip

It actually doesn't matter if the major causes of global warming aren't
man made if the man made contribution is enough to make a significant
difference.

As I said in the last post, just because a tree may fall on the road in
front of your car is no reason not to fix the brakes. Indeed, its
actually the reverse.

The ONLY way in which the deniers case makes sense is if man made CO2,
now 50% of all atmospheric CO2, has negligible impact on anything.

That should be a third, not a half.

Who wants to claim that?

A denier by the name of Piers Corbyn among others. The list is quite
long and probably includes such well known names as Lawson (both Nigel
and Dominic)and Monckton as well as Dennis and The Medway Moron.

The deniers case has never made sense but the skeptics might just have a
point. Somewhere within the link below is a claim that if atmospheric
CO2 doubled from 300 ppm to 600ppm the rise in average temperatures
would be just 0.4C. I can't see anything obviously wrong but you may
have better luck than me.

At that level shouldn't we be concentrating on just about anything else
aimed at reducing global warming and forget about reducing CO2 output?

http://www.john-daly.com/forcing/forcing.htm