Re: "This is the funeral pyre for thought in America today."

On Tue, 05 Jun 2007 06:43:38 +0800, Robert Bannister
<robban1@xxxxxxxxxxx> wrote:

Peter Duncanson wrote:
On Mon, 4 Jun 2007 13:12:15 +0100, Vinny Burgoo <hlunnh@xxxxxxxxxxx>
wrote:


In alt.usage.english, Richard Maurer wrote:


I was thinking that all the sediment ended up
under water. If it forms mountains then that is
different. I can readily believe that gravity is
weaker at sea level in some fjords, with the
mountains pulling things up a bit. But if the
sediment is all under water, then it just pushes
out the ocean world wide, and there is heavier
sediment where there was once just sea water,
hence more pull downwards at sea level.
Unless it is trickier than that.

Here's the passage about gravity and the effects of rising sea levels.
It's from a 2003 Bangladesh Ministry of Water Resources report.

The global rate of sea-level rise is almost certainly going to
increase over the next century due to climatic warming. However,
estimates of the change vary widely, ranging from 2-8 mm/yr in
the coming decades. The highest estimates are probably
unrealistic, and most studies are converging on the lower values
of 2.0-5.0 mm/yr in the next 50 years. Fortunately for
Bangladesh, these global rates may be suppressed in the Bengal
region. One factor that controls the regional sea level is the
strength of gravity. In the Bengal region, the extremely thick
sediment deposits (8-20 km) that underlie the region result in a
slightly weaker gravitation pull. This reduced gravity is
expressed as a slightly lower water elevation in the Bay of
Bengal, as compared with other ocean regions. Thus, it is likely
that the impacts of sea-level rise will not follow the worst
predictions.

I can accept that weaker gravity suppresses the regional sea level
(though I don't know how it does it) but I do wonder about the
suppression of the rate of rise. That "thus" seems misplaced.

It's an authoritative report.

<http://www.iczmpbangladesh.org/rep/wp017/wp017.PDF> (3.3 MB)

Is it possible that the authors nodded? Or did they just skip one too
many steps? If, as the world's oceans expand, the expansion raises
different parts of the surface at different rates, they need to say why,
no?


Forget about expansion for a moment. If there are regional
differences in gravity then we should *now* be able to see regional
differences in mean sea-level. I believe this to be the case.

I'd like to see some kind of proof that differences in gravity produce
different sea-levels. As far as I can make out, the differences that are
observable today are due entirely to prevailing currents and winds.

Fair point. I was just fumbling around with the concept of
differences in gravity and their possible effects an sea-levels. I
have no difficulty with the idea that these effects are swamped by
others.


--
Peter Duncanson, UK
(in alt.usage.english)
.

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