[extropy-chat] Global warming news

[Hal Finney]

A few random comments on this topic:

First, the headline that I quoted a few days ago from the London Times
was apparently not accurate.  It said that we could see 20 feet of sea
level rise by 2100.  It would be more accurate to say that we could
see temperatures by 2100 which, if maintained, would eventually lead to
a 20 foot sea level rise.  However it would probably take 100 or more
additional years for that to happen.  Most scenarios forecast about a
3 foot rise by 2100, which sounds a lot more manageable.

Second, some questions have been raised about whether warming is even
something to be avoided.  Perhaps being able to grow forests or crops
in what is now desolate tundra and permafrost would actually be an
improvement.

The problem here is that it is not easy for plants to adapt to movements
in latitude.  This is one of the reasons Jared Diamond cited in Guns,
Germs and Steel for why Eurasian civilization progressed more rapidly
than in the Americas or Africa.  Eurasia is primarily laid out east-west.
This gives a very long path, from the Mediterranean to China, where
trade routes flourished.  Plants can easily adapt to different longitudes
as long as the climate is similar.  However, moving even a few hundred
miles north or south produces different seasons, lengths of days, and
climatic patterns.  It is much harder for plants to adjust.

Moving crops or trees from southern Canada to the northern tundra
will not be an easy transition.  Those plants will have to adapt to
the peculiar arctic seasons, the long winters with almost no sunlight,
and summers with extremely long days and short nights.  You can't just
transplant existing plants and expect them to flourish.

Another problem is with the soils.  Plants are generally adapted to soils
where plants like themselves have been growing for many generations.
This is going to be very different from what they find when they are
transplanted into a new geographical region.  It's very questionable
whether our crops or our forests can do well in recently-thawed
permafrost.  The soil type and nutrient availability is likely to be
completely different from what the plants have adapted to.

Then of course there are infrastructure issues.  Civilization has
adapted to recent climate patterns, and enormous investments in fixed
infrastructure have committed us to exploiting existing conditions.
We can't just transplant every form of agriculture 1000 miles north
and expect things to work smoothly.  New transportation, irrigation
and other systems must be created and adapted to the new conditions.
It takes a long time to work out what methods will work best in a given
region, and we have spent generations doing just that.  Moving everything
means starting over and is going to be enormously expensive.

That's the bottom line, really: the expense.  Of course we hope that
future generations will be enormously wealthier than us, so perhaps they
can afford all this and more.  Nevertheless it makes sense for them
(and us, to the extent possible) to look at the least expensive ways
of responding.  Pulling up stakes and moving an entire civilization
gradually north as the earth warms is not likely to be the best solution.

One final point, I got some data about forest uptake of carbon from this
web site:
<http://www.whrc.org/new_england/Howland_Forest/Carbon_Sequestration.htm>.
They measured their growing forest as taking in carbon at a rate of 1.7
megagrams per hectare per year.  This is 170,000 kg per square kilometer
per year.  According to the information I presented earlier, carbon is
accumulating in the atmosphere at a rate of about 4 gigatons per year.
This would be about 4 trillion kg per year, divided by 170,000 gives
about 24 million square kilometers of forest to compensate for current
levels of excess CO2 production.  That's a square about 5000 km on a side,
exactly what Spike estimated using totally different methods:
<http://lists.extropy.org/pipermail/extropy-chat/2006-March/025965.html>.

Having said this, the big problem with growing massive new forests is
water, as well as land.  Many areas are running short of fresh water,
and I don't know if there are any regions where there is plenty of fresh
water, thousands of miles of land suitable for growing forests, and no
plans to use that land (or water) for the next several centuries.  It is
definitely a long-term commitment of a pretty big chunk of the planet.
This is more than 3 times the size of Texas, and I should note that the
Wikipedia article quotes Bill Schlesinger of Duke as claiming that it
will actually take an area 10 times the size of Texas.  Couldn't find
any of his technical articles, though.
http://en.wikipedia.org/wiki/Carbon_dioxide_sink
http://www.env.duke.edu/people/faculty/news/schlesinger-hs4.7.04.html

Hal