David Friedman on Nordhaus and Boyer

We may have evolved over a time period in which the climate fluctuated significantly, but moderns humans have made large fixed investments based on the climate as it is. Even if climate change does not turn out to be catastrophic, the adjustment costs will be significant. That's over and above any net decrease in the abstract favorability of the climate to human civilization. For climate change to be neutral, there would have to be net benefits to suitability that match the adjustment costs.

Hi,

"Humans were "designed" for earth's climate over a period for most of which its climate was quite different from the present--we are currently in an interglacial, a relatively short period of warmth in the current long ice age."

Evolution, shmevolution. Our technology trumps evolution by orders of magnitude. There's no way I'd want to live in North Carolina without air conditioning. With air conditioning, it's a wonderful place to live.

Similarly, there are new sports jerseys that have fabrics that wick away sweat. I'm too lazy to look up what they are, but I know it's a lot more comfortable to wear them playing sports on a hot day than with a conventional fabric, like cotton.

And it's very easy to envision a time when clothes use photovoltaics or some other means (wireless grid power?) so that they essentially act as air conditioners.

Not to mention the fact that it's likely we'll soon all have chips that continuously monitor our vital signs (like body temperature) and report any unusual readings immediately.

Even if the temperature this century climbs by 5 degrees Celsius or more, it is very likely that the number of people dying of heat-related causes will be one or more orders of magnitude less by the end of the century. (And the benefit that fewer people will die of cold-related causes is just icing on the cake.)

While I'm skeptical about how negative the costs of global warming will be, or whether those costs are more or less than the costs of many proposed solutions, I think what's important to discuss is not whether or not human bodies are designed for a certain climate, since obviously we live and thrive in a wide range of temperatures, but rather whether our creations (cities, ports, farms) are.

My point is that we have historical path dependencies -- cities are built near rivers or shorelines for a reason, and if global warming changes where those are, or causes previously fertile land to become less so, then that's not good, even if it might cause other places to become nice to live in or farm. We'd have to spend a lot of resources to adapt to that, which otherwise we wouldn't have to. Now, perhaps that's a worthwhile trade given what we'd have to give up to prevent that warming, but "what climate were humans designed for" isn't the right question.

@Gabriel Weil,
David answers your point here:
http://daviddfriedman.blogspot.com/2012/03/nordhaus-on-global-warming.html#c5249927218700958877

Surely the more relevant point is that human civilisation has evolved over the past 500 years in the current environment. Thus our civilisation maybe quite fragile to changes in the global temperature.

Secondly sure human beings as a species have adopted to changes in our climate, but that has always been at a much slower pace then the current changes being induced by carbon emissions.

I think there are many parallels between market economy and the climate. Both, for example, are the result of an evolutionary process.

Many classical liberals argue that interfering with the market economy is a priori bad because of unintended consequences.

Shouldn't the exact same argument that liberals use to justify not interfering with the market place apply to not interfering with the climate?

All discussion about the effects of human induced climate change seem to ignore the climate change that was going to happen anyway, the direction of which is completely unknown. But in a choice between a bit of extra heat and a new glaciation, I'll say pass the sunscreen. I wonder how we would adapt to the accumulation of 2 miles depth of snow and ice across a large part of the northern hemisphere?

In fairness, the species may not have evolved in interglacial conditions, but what about civilisation? Few nomads may well survive the change in climate, but that's probably not the outcome the skeptics are looking for.

Surely the more relevant point is that human civilisation has evolved over the past 500 years in the current environment. Thus our civilisation maybe quite fragile to changes in the global temperature.

Human civilisation evolved over rather more than 500 years, and over time periods warmer and colder than the present. If you mean that we have adapted especially to just the last 500 years then earlier forms of civilisation managed to adapt to changes with fewer resources than we command.

Characterizing 3 degrees warming over a century as a slow change is misleading. It implies that the changes will be fairly uniform in time and space. The projected changes, by contrast, will be acute and rapid in some and will generally increase the frequency of severe weather events.

"For climate change to be neutral, there would have to be net benefits to suitability that match the adjustment costs. "

Of course, the flipside to this is that for climate change to be neutral, there would have to be net decreases to suitability that match the prevention costs.

The net change to suitability won't be realized until the future, which attenuates its impact when thinking about it now. Likewise, adjustment costs won't happen until approximately the time of the change, reducing the present value of their costs. However, prevention measures cost us right now- there's no time discount to those expenditures.

When comparing prevention costs vs. adjustment costs, it's important to remember to discount the adjustment costs.

Gabriel, the current pace is about 1 degree C per century - which is milder than some of the other changes in the past 1000 yrs. We have much more to worry about the impending end of the interglacial period. Doomsday scenarios are based on feedbacks which have never in history existed before. I would not worry.

The projected changes, by contrast, will be acute and rapid in some and will generally increase the frequency of severe weather events.

Two words: Hurriquake nails.

Another important fact: In Indiana from 1996 to 2007, 93 percent of tornado deaths occurred in trailer parks.

I see that the overall percentage of deaths from tornadoes that occur in trailer parks is about 50 percent.

Here is a graph of tornado deaths in the U.S. from 1940 to 2010:

U.S. tornado deaths, 1940 to 2010