In article ,
Phil Hays wrote:
David Ball wrote:

Sun and Hansen does not preclude strong warming taking
place. It merely points out that deep ocean mixing could have a huge
impact on the amount of warming.

Which is no surprise. For the extreme example, consider the following:
As the climate warms, ocean circulation will become more driven by salinity
than by temperature. Currently, cold and salty water sinks near the poles,
and upwells back to the surface near the equator.
Warmer climate will imply less ice so there will be less of the very salty
and cold water left when the ice freezes.
More water will evaporate in the tropics and more rain will fall near the poles.
All of these effects will make the polar water warmer and less salty,
and the tropical water saltier.
At some point, the tropical water will become denser than the polar water,
and the circulation of the ocean will reverse.
That is, warm salty water will sink near the equator and rise near the poles.
There is paleoclimatological evidence that ocean circulation was reversed
in warmer periods.

But now think of the dynamic implications: To reverse the circulation
requires warming much of the deep ocean from the current near freezing
temperature to near bath water (20C) temperature.
This requires a fairly impressive amount of heat.
This reversal might be dynamically stable: that is the ocean would just
absorb this heat, keeping the surface cooler.
Or this reversal might be dynamically unstable:
that is the surface might warm up, the warm and salty water near
the equator sinks, cold water floods the polar oceans, leading to more
winter snow cover and more (year round?) sea ice,
leading to a much colder surface and return of more current ocean
circulation patterns, and then the surface starts to warm up again.
I have no good idea as to the period or temperature magnitude of this
possible oscillation. About the only evidence I have as to the threshold
of the reversal is from paleoclimatology.

Now, perhaps this might be an idea for Mr. Taylor's novel:
The climate warms by 5C by 2050, the tropical oceans get saltier,
the summer sea ice is gone, and the winter sea ice cover is getting
much smaller. Then downwelling starts in the tropical oceans,
and upwelling of near freezing bottom water in the Arctic and
perhaps the North Atlantic and Pacific.
This cools the Arctic (and perhaps the North Atlantic and Pacific??)
back into significant sea ice cover, leading to a very cold winter,
perhaps with England frozen into sea ice.
Then, over the next couple of years, the climate warms back to the
2050 level of 5C warmer than current. Then repeat, as needed.


Hi Phil,
I wanted to acknowledge your reply, because you took the posting
in the spirit it was offered -- as an invitation to propose
future weather behaviour given various assumptions.
Or as you took it, the underlying ocean current patterns.

Do you have a reference, btw, for "There is paleoclimatological
evidence that ocean circulation was reversed in warmer periods."?

I have written a Take 2 message to try to cut through.
regards
-het




--
"Bring me a one-handed economist." -Harry Truman

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