Text 19139, 68 rader
Skriven 2014-11-08 14:11:37 av Michiel van der Vlist (2:280/5555)
     Kommentar till en text av Ward Dossche (2:292/854)
Ärende: Life Under the Democr
=============================
Hello Ward,

On Friday November 07 2014 09:46, you wrote to me:

 Mv>> You forget the termal expansion of the water. If the average water
 Mv>> temperature of the oceans rises by 1 degree, the expansion
 Mv>> accounts for a rise in sea level of about 2 meters.

 Mv>> I can show you the calculation if you want.

 WD> Yes.

OK. The estimated amount of water on earth is 1.4 miljard kubic kilometers or
1.4 x 10^21 liters. 97% is in the oceans, say 1.35 x 10^21 liters or 1.35 x
10^18 m^3.

The cubic expansion co‰ficient for water is 0.21 x 10^-3/C. so one degree higer
temperature means 0,21 x 10^^-3 x 1.35 x 10^18 = 0.25 x 10^15 m^3.

The surface of the earth is 510,072,000 km^3 or 0.5 x 10^15 square meters. 2/3
of that is water, so the water surface is about 0.3 x 10^15^2 m^2.

Spread 0.25 x 10^15 cubic metres of water over a surface of 0.3 x 10^15 square
meters and yuo have just onder a meter.

I said about two meters earlier, it seems I made a small error. Never mind, it
is a rough calculation anyway just to refute your claim that there is not
enough water on earth to get wet feet in Antwerp.

I am not saying it will happen that way, just that if it doesn't happen it is
not because of lack of water.

 WD> It's not that I don't believe that, it's that it fascinates me.

 WD> The whole process, and you will agree with me, is very complicated.

Indeed. It is very complicated. The assumption made in my calculation that the
all the water in te ocean will rise by one degree everywhere is not realistic.
There are plenty of local effects.

 WD> More water in the oceans due to melt-run-off and increasing water
 WD> levels will create a larger watery surface which will fuel a
 WD> cooling-effect.

The increase in water surface is neglegible. Most of the land is way above sea
level plus one meter. More important is the change in albedo. (reflection
co‰ficient of heavenly bodies)

Ice is white. It reflects most of the light. Contrary to water. So if the ice
melts (North and south pole) the average albedo of the earth sinks and less
light is reflected. This results in a rise of temperature. Which in turn causes
more ice tio melt -> positive feedback.

 WD> We have just no idea where this is gooing to take us in the long term.

What will happen is very hard to predict. There is no doubt that global warming
is real. There is also no doubt that mankind will see some drastic changes in
the coming century. But how and where exactly remains to be seen.

Here in The Netherlands we just had the warmest 1st of November ever measured.
OTOH we had the coldest ever Ascension Day earlier this year. If there is a
visible trend it is that we see more extremes in the last decades.


Cheers, Michiel

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