"Andrew Mawson" wrote in message
...
"Rod Speed" wrote in message ...

Dave Plowman (News) wrote
NY wrote

Climate change happens: it is incontrovertibly warmer now than
it was in the 1800s, given that the Thames doesn't freeze over.

Think that's a poor example.

I don’t.

The Thames may have frozen over for reasons other
than just ambient temperature. The speed it flows at,

That would be easy to see by considering just how common
it was for other rivers to freeze over at the same time and
whether it happened at a time of very low rainfall etc.

and water pollution.

That normally has the reverse effect, polluted water
is less likely to freeze solid enough so you can skate
on it and walk on it like they did at that time.

And of course the ambient temperature in cities is higher than
surrounding areas - I'd guess more so than in those days.

Sure, but presumably the parts of it well
outside London proper froze over too.


Global warming definitely happens, as the UK was once covered in sheet ice
to a considerable depth, but now isn't. Global cooling also happens, as
there was a time before the ice when it wasn't there. Natural phenomena
that now may very marginally be affected by man's activity. After all
the Romans farmed what is now the Sahara once !

Its not in dispute that climate varys. What we are discussing
is whether man has much effect on the variation in climate
that has certainly happened.