James Annan wrote:
Eric Swanson wrote:
>
> James Annan wrote:
>>
>> > After all, we cannot simply assume that future generations are richer,
>> > or more adaptable.
>>
>> Well if we do not get richer rapidly and keep on increasing GHG
>> emissions then the rate of climate change will tail off substantially in
>> any case... (and certainly will not accelerate, which is the assumption
>> underlying Stern).
>>
>> I conclude that neither climate change nor energy costs are going to
>> prevent crop yields increasing for the foreseeable future over any
>> reasonably broad scales and would happily bet on that proposition. Any
>> takers?
>
> Is your bet to be based on crop yields or total crop production? If
> it's the latter, then there may be some unforseen bumps in the road.
I don't think it makes much odds, but yield seems most logical.
Yeild is a particularly difficult variable to assess, given that we
know how to increase yields for many crops thru the use of various
energy intensive techniques. Those techniques have been widely adopted
for some crops in a few countries, but there are many other areas where
the yield increasing technologies still have not taken hold. Given
that there is may still be a large gain in global average yield yet to
be realized, betting that climate change might reduce this metric would
most likely be a losing proposition. From an economic and social point
of view, a more appropriate metric might be production per capita, as
it is to be hoped that food production will increase along with
increasing population.
> So much for the fresh produce from the Central Valley until the next
> crop comes in. the freeze also hit Arizona as well, which is another
> area of citrus production. This reminds me of the freezes in the early
> 1980's, which destroyed much of Florida's citrus crop, killing the
> trees as well. Similar impacts were felt in Texas. We've had late
> freezes in my area over the past few years as well. A couple of years
> ago, the trees were fully leafed and a hard freeze killed almost all
> the foliage. It looked like the Fall colors had returned, only it was
> May.
If you are relying on extreme cold to keep yields down then ISTM you are
clutching at straws, since the future reduction in cold extremes over
most of the globe is just about as robust as the increase in hot ones
(although this attracts a lot less attention).
As I've pointed to previously, I think the cold conditions of the late
1970's and early 1980's may have been related to the Great Salinity
Anomaly. If there is a weakening or, worse, a shutdown of the THC, I
would expect to see more frequent transients in the form of cold and
warm extremes. That's because I think that a shutdown of the THC would
result in a corresponding increase in thermal energy carried by the
atmosphere between the tropics and the North Pole.
> Also, some models have suggested that the American Great Plains
> will experience more frequent drought, which will cut into the
> production of corn and wheat.
I've already noted here that the US National Assessment of the Potential
Consequences of Climate Variability and Change explicitly predicts
increased yields to a degree that will be harmful to farmers through
depressing prices!
I haven't looked at that one.
http://www.usgcrp.gov/usgcrp/nacc/default.htm
"The National Assessment was forwarded to the President and Congress in
November 2000 for their consideration."
Do you think Gee Dubyah looked at it?
See above comment regarding the THC.
> I might take your bet, except that your "foreseeable future" is likely
> to be longer than mine.
Of course there will be local and short-term bumps in the road, but I'm
thinking about the (inter)national scale over 30 years, like for global
warming itself. It's got to be a long enough time scale to actually see
the predicted effects over natural variability.
Yes, on that scale, I probably won't be able to witness the end of the
bet!
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