> Clearly none of the direct extraction methods seem close to viable in
> current economic terms, but I wouldn't like to say it will still be
> impossible in 100 years or more!
But is that because of unpredictable technological developments, which
because they are unpredictable we mighn't want to rely on, or because
of quite anticipateable economic trends?
Currently, you wouldn't want to dedicate a nuclear plant to removing
CO2 from the air, you'd produce electricity and displace coal
generation. As long as nuclear is cheaper than coal, that even gives a
negative cost per tonne of CO2 avoided/removed.
When, say sometime beyond 2100, there are no more coal fired power
plants, and assuming there's a willingness to spend 2% of GDP purely
to remove CO2 from the atmosphere, things look different.
What this also assumes though is that the IPCC scenarios for economic
development are vaguely reasonable. In a scenario of societal
breakdown, due to warfare, the end of cheap oil, whatever, removing
CO2 from the air mightn't be an issue of dedicating 2% of GDP to the
removal, but dedicating more than 100% of available clean energy
supplies.
> OK, that ignores
> the threat of long-term sea level rise which some nations might
> reasonably be upset about - but would they be rich and powerful enough
> to do anything about it?
In a "troubled world" type scenario, where Bangladeshis have a life
expectancy of 35 in the year 2200, rather than the life expectancy of
100 and GDP of 100000 Dollars per head you'd estimate from the IPCC
scenarios, maybe they wouldn't be.
What I've also been wondering about is how expensive, given current
technology with only incremental progress (again, anything might be
possible with new technology, but we mightn't want to bank on that),
it would be to protect against 5 m of sea level rise. The report I
mentioned earlier in this thread suggested that the Netherlands could
cope with 5 m of sea level rise, if it spent 5% of GDP or so on dikes,
but it would be economically optimal to accept some loss of land
rather than spend all that 5% of GDP required to avoid any loss of
land. The Netherlands are already partially below sea level, the
lowest point is some 6.5 m below sea level.
Presumably, if sea level were to rise by 5 m New York and London
wouldn't just be abandonned, but a few hundred billion would be
invested in dikes (unless London in 2100 resembles Somalia today, in
which case retreat shouldn't be too costly, because most of the city
would be in ruin anyway).
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