Friday, June 26, 2009

Comments on Ryan's Post

This started out as a comment on Ryan's post, but got far too long. Here are four points I'd like to make:

1)There is a clear link between atmospheric CO2 levels and global temperatures. This can be seen in historical records from ice-core and tree-ring analysis, climate simulations, and especially in direct observations from satellites over the past three decades. Additionally, it's clear that human activities have increased the amount of atmospheric CO2 dramatically in the past century. However, the feedback mechanisms that higher CO2 levels may trigger are also poorly understood, so predicting future CO2 levels is made even more difficult than just predicting what humanity will do.

2)Most predictions about future climate change are based solely on global climate models. We talk with climate modelers often, in fact a member of my comprehensive exam committee does global ocean models (one component of the big climate models), and while I think their models are very good, even the modelers wince when they see some of the doomsday scenarios in the media. Large climate models cannot capture many physical and chemical processes directly and so things like clouds, rain, chemical mixing, trees, cities, volcanic emissions, forest fires, etc. are "parametrized". Essentially this gives these models over 150 parameters, most of which are very poorly constrained, to fiddle with in order to get the “right” answer when they feed in historical data.

3) There are a number of scenarios for humanity to mitigate effects of climate change. Ryan has made the point that assuming our current climate is the optimal one is probably wrong. A couple of papers have shown that worldwide food production would likely increase substantially if the CO2 concentration increased by 50% and the average global temperatures went up by 2-3 degrees C. But even assuming that we prefer our current climate, there are proposals of ways humanity can counteract what we've done to our climate. One such proposal is to make solar-powered calcium carbonate factories in places like the Australian outback or the American southwest, whose product could then be dissolved in the oceans, causing the oceans to absorb large amounts of atmospheric CO2 and become less acidic. Or we could build large “solar shades” that would decrease the total global solar irradiance by as much as 1%. We caused global warming with 20th century technology. Assuming we won't be able to fix it with 21st Century technology seems silly to me.

4) In most projections, it is better economically to spend a little more now to prevent climate change than it is to try to fix it all later. Additionally, America's dependence on fossil fuels has a high political cost (think Iraq and Iran). Here an ounce of prevention is probably worth a pound of cure.

1 comment:

  1. In the article the person writing it makes a fairly substantial claim that global temperatures have been flat over the past few years. I was wondering if there was anything in that or if they were just blowing smoke.

    But Nick I agree with what you have to say, modeling is very hard, and there are some technologies that we have available that may help us affect the climate, without having to tax the American people.


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