"Rodney Blackall" wrote in message
...
In article ,
Dave Ludlow wrote:
For anyone who missed the programme and/or who wants to get a fuller
picture and better balance than this week's rather sensationalist
broadcast, the Horizon webpage is the place initially to go:

http://www.bbc.co.uk/science/horizon...bigchill.shtml

It makes it plain (if you look) that only *some* scientists currently
accept the "big chill" scenario but many more think we should at least
take seriously the possibility. Clearly, though, the "big chill" and
global warming are not mutually exclusive.

I would like to (but am too busy to) check that I correctly heard "changes
in the Sun's orbit".

Well here it is;

NARRATOR: The earth's past was full of devastating climate jilts, none as bad
as a full ice age but enough to turn Britain in to Alaska. The search was on
to find out what could trigger these climatic disasters. They searched through
the ice record for clues. Had huge volcanoes blotted out the sun? There was no
evidence for that. A succession of asteroid impacts? Again, no evidence. More
wobbles in the sun's orbit? That didn't fit. In fact no one could account for
what Ally had discovered. Except for one man who thought he could. Wally
Broecker is the guru of climate science. He was convinced that it was all to
do with the oceans.

BTW Although my first name is Alastair, the Ally quoted there is not me. It is
Richard Alley.

I would have been a lot happier if the North Atlantic
had another current other than the Gulf Stream - whatever happened to the
Labrador Current et al?

I am sure that an early sequence purporting to show the course of "the
Conveyor"had the Gulf Stream rushing up the East Coast of North America so
fast that it did not have time to enter the Gulf of Mexico!

The reason that the North Atlantic is salty is because the Trade Winds carry
the water vapour evaporated in the Carribean over the Ithmus of Panama to
the Pacific Ocean. This leaves behind salty water which feeds the Gulf
Stream. The closing of the isthmus about 3 million years ago may well have
been the cause of the growth of ice sheets in the Northern Hemisphere and
the instigation of the Quaternary Ice Age which began about 2 million years
ago.

Cheers, Alastair.