Andy wrote:

I would like to know:-

How much global warming is anthropogenic and how much natural ( e.g. the
little ice age was caused by the sun, but what were the early middle ages
and Roman warm periods caused by? It wasn't C02. It was warm enough to farm
in Greenland in 1000AD, its not that warm now, how come ice caps didn't melt
and the atlantic conveyer halt then? )
[snip]

That global warming is happening is a matter of fact, and not something
that I wish to rake over again. However the implication that it is man
made and that we can do anything about it are things I take with a pinch
of salt.

It's something that gets overlooked that only 120,000 years ago London
was a tropical paradise. Note that's 120 *thousand* years, a mere blink
of he ye in geological time. We're in an interglacial period, which way
would you expect the global temperature to be heading?

The evidence that it is human activity resulting in global warming is
IMO circumstantial.