humanities.philosophy.objectivism

On Mar 29, 9:40 pm, "Matt W. Barrow"
wrote:
> "Al Montestruc" wrote in message
>
> news:24c13834-6439-4ff7-add1-b26432e8180b@m73g2000hsh.googlegroups.com...
>
> > On Mar 21, 1:37 am, Brian Bagnall wrote:
> > Sea levels rising could be a bit inconvenient even if it is only a few
> > inches a year. I have looked into this and crunched some numbers.
> > Worst case making improbable assumptions, and all the ice melts, then
> > sea levels go up about 250 feet, but it would take centuries to
> > thousands of years for that to happen based on the amount of heat
> > needed to melt all that ice, and the heat available to do it.
>
> Which, IIRC, hasn't been since the age of dinosaurs.
>
>
>
> > Even so sea levels rising say 6" a year or more would be very annoying
> > to shipping/port companies and to the Dutch and other owners of low
> > lying real estate.
>
> Six inches? Per year?
>
> How much would the earth temps have to rise to produce that much SL??


It is not so much a matter of temperature rise as heat flux change.
It takes large amounts of heat to melt ice, so the temperature rise
often (in part anyway) would follow the melting of the ice rather than
precede it.

The heat balance goes something like this:

net heat in from the sun + geothermal heat= heat radiated by the earth
to space + heat used melting ice or heating the environment

The heat loss to space are complex function of radiation heat transfer
factors (functions of chemistry of the atmosphere, and lots of other
things) times the temperature of the earth to the 4th power.


Higher fractions of CO2 (or H2O or CH4) in the atmosphere tends to
reduce the rate of heat loss to space.

Anyway no one has been able to reliably solve those equations such
that you can make useful predictions using them. However the fourth
power aspect of the equation tends to make them stable. As in a small
change in the temperature at the surface of the earth, has a large
change in heat flux radiated to space, so it takes big changes in
other things to make the mean temperature of the earth change.





>
> During the last 100 years and 1F rise, the change is measured in
> millimeters. Per century, I believe.

No it is more than that in recent years.

http://tidesandcurrents.noaa.gov/sltrends/slrmap.html


The big island of Hawaii is seeing between 3 & 6 mm per year while the
mainland coast varies from 0 to 12 mm per year and noplace on the US
mainland coast sees a net decline in sea level, however some stations
in Alaska are seeing a net drop in sea level of perhaps as high as -12
mm/year. Some of that is not sea level change but land level change
like plate tectonics (land rising or subsiding), but the average for
most of North America is clearly for sea levels to be rising on the
average of somewhere between 0 & 6 mm per year.

Net it seems pretty clear that the sea level is rising, and on the
order of 3mm per year. Which is about an inch every ten years or
close to a foot every 100 years.

One of the things that Stossel points out that I think is important is
that historically (geologic history) it seems that the rise in CO2
seems to lag behind the rise in temperature. If that is true, and not
an artifact of the method of taking the data, then this CO2 level rise
we are seeing may not be important.

However historically our current level of CO2 is about 380 ppm, it was
about IIRC 270 ppm around the time of the American revolution(before
the bulk of the industrial revolution), and in the geologic record
levels of CO2 over 1000 ppm are associated with very high global
temperatures and all of the ice melting commonly called Anoxic events.


http://en.wikipedia.org/wiki/Anoxic_event

Looking at it that way, we have a lot of rope yet before we hit a
limit.