"Norman Lynagh" wrote in
message news
This is the first time I recall the changes to the British climate from
global warming being discussed on this newsgroup.

My reading is a little bit wider than merely u.s.w. :-)

As is mine :-)
But this newsgroup seems to confine its discussions as to whether
global warming is a political plot conceived by New Labour.
Admittedly the more senior members concede that global warming is
happening, but seem to doubt whether is caused by the increase in
carbon dioxide of about a third since the Industrial Revolution.

What I assume you are saying is that the sub-tropical ridge will move
polewards, presumably in each hemisphere. The climate zones exist as a
result of the large-scale mean pressure patterns, not the other way
round.

That thought occurred to me after I wrote that post. In fact, although the
warming is global it does not need to have the same effect in both
hemispheres. The land/ocean configuration is opposite between the
two hemispheres, and the response to climate change differs between
lands and oceans.

If the sub-tropical ridges move polewards, what happens to the tropical
belt? Does it merely get wider? I find it hard to visualise that there
could be such a huge increase in the area covered by the equatorial
barotropic airmass

The Intertropical Convergence Zone (ITCZ) is already skewed into
the NH. If the Arctic ice disappeared while the Antarctic ice remained,
not inconceivable, then the ITCZ could move even further north. This would
bring tropical weather to the southern Sahara, moving the high pressure
zone north to southern Europe. Moreover, with greater forcing from CO2
the ITCZ might widen and/or intensify.

Cheers, Alastair.