Wednesday, September 20, 2006

What is the Earth's ideal climate?

In another thread, a commenter asked an interesting question: what is the Earth's ideal temperature? This question is often used as a version of the "AGW might be good argument": the point was that perhaps the ideal temperature was warmer than today's, so climate change might actually be beneficial.

Given everything else equal, one might be able to make an argument that a warmer world might be better. However, everything else is NOT equal. Rather, we have adapted to our present climate and made significant investments in these adaptations. We build cities in places where it makes sense to put them (with the notable exception of New Orleans), we build infrastructure where it makes sense to put infrastructure, we perform economic activity where such activity makes sense. If the climate changes significantly, it might take enormous investments to adapt to our new climate. Our previous investments in infrastructure might become worthless.

Consider this example. You build a sawmill next to a roaring river, using the river as a power source for the mill. Now AGW causes the precipitation pattern to change and the river moves miles away. In this new world, the river might have higher flow rates, which would provide MORE energy to the mill, which would be a good thing --- if the mill were still on the river. But the mill is no longer anywhere near the river. So you have to build a new mill on the banks of the new river. This investment in new infrastructure is potentially expensive, and some countries will not be able to afford it.

My point here is that any question about suitability of future climates has to take into account our investment and adaptation to our present climate.


Bill F said...

"we perform economic activity where such activity makes sense"

Some could look at the growing of water intensive crops in arid regions of California using water brought in from hundreds of miles away and question that statement. However, I think it is actually a valid point. I think it makes a strong argument for trying to look at potential regional impacts of climate change moreso than the overall global impact. Describing to people what is likely to happen in their area is more likely to resonate with them than a global forecast of a X degree C rise in average temperature. It is harder to bring an issue home to people and spur them to action if they are listening to the news and thinking "so it will be 100 for a high in the summer instead of what?" Unfortunately, long term regional predictions are probably even more error prone than GCMs.

Dano said...

The earth, IMHO, has no ideal climate. It has particular climates during epochs and periods, to which organisms adapt (or not).



coby said...

Yes, that argument was a common one on sci.environment, which made it indespensible in the How to Talk to a Sceptic Guide...

Dano said...

Coby, had I known that was there, I'da linkied to your post!

Keep up the good work, both o' youze.



EliRabett said...

As I said somewhere else, you ask what was the idea global temperature, well, I guess that depends if you own land on one of the US east coast barrier islands which would be comprehensively flooded on a temperature rise of a few degrees C.

However, recalling that civilization has existed while the global temperature was in a rather limited range, maybe +/- 1 or 2 C from today, I think that the answer is rather clear. Given that the global temperature in recent ice ages was only about 8 C lower than today, I think we have a pretty strong lower bound on that too.