Friday, April 11, 2008

Global Warming: The Hidden Assumption

On the face of it, there is no obvious reason why making the world a few degrees warmer would be a bad thing. Yet many people regard global warming not merely as a random element that might make things better or worse but as something obviously bad and obviously worth going to a lot of effort to prevent. Part of the reason, I think, is an unstated assumption—that, absent human intervention, climate is stable. Given that assumption it seems natural enough to worry about the destabilizing effect of human action, such as increases in carbon dioxide. We know the present situation is tolerable; who knows what change might bring?

That assumption is contradicted by massive geological evidence. As my geologist wife likes to point out, at various points in the past million years England has gone from being warm enough for hippos to live there to being buried under a mile of ice. And while the major glaciations are spaced out at intervals of about a hundred thousand years, they are separated by multiple smaller swings in climate. Looking at an even shorter time scale, it looks as though more than half of the temperature increase from 1600 to the present, at least in Europe, was merely bringing the temperature back up to where it was in 1100, before the start of the little ice age.

If earth's climate is inherently unstable, with or without human interference, the argument that we should play safe by not interfering looks a lot weaker.

All of which raises a factual question to which I think I know the answer but am not sure. If we consider global warming in the context not of the effect of human action but of past swings in climate, which is more dangerous—the hot or the cold end of the range? Given that the cold end involved glaciers covering much of North America and northern Europe, my guess is that it is worse, but I don't have any very detailed idea of just how hot the hot end got, and where.


Tim Lambert said...

We built our civilization for the current climate, so any large change. warmer or cooler, is going to be expensive.

And yes, the climate system is unstable and small forcings can start or end an ice age. This seems to me to be a good reason not to mess with it.

David Friedman said...

Tim writes:

"We built our civilization for the current climate, so any large change. warmer or cooler, is going to be expensive."

The current IPCC estimate is .2 degrees centigrade/decade. That's not a rapid change. While it's true that the projected effects over a century would be significant, over a century lots of other things will change anyway. I think it unlikely, for instance, that the same crops will be being grown--and switching to crops that do well a little farther south, or in a climate different in other ways, isn't a big change over a century.

Similarly, how many of the houses now standing to you expect to be still in use a hundred years from now?

Stephen Smith said...

I think this would be a valid discussion topic if global warming and environmental damage (if you think it's a bad thing) or change (if you don't make a judgment) seemed to be an inevitable consequence of human progression, but it doesn't seem to me like it is. The determinants of our energy usage are in large part subsidized by the government, resulting in perverse outcomes from an economic and ecological standpoint. Our heavy subsidization of the internal-combustion-engine-machines-on-paved-roads system naturally cheapens the cost of this very inefficient technology. Because of this cheapening of transportation, we live very far apart and in comparatively large settings which must be heated, cooled, built, transported, and maintained.

Even on a more fundamental level, are we sure that the current level of cheapness of transit is a market-based phenomenon? Even though private ownership of the seas is almost definitely cheaper than public ownership (factoring in mostly defense costs), the apparent cost to the consumer would still be higher – the shipping industry doesn't pay a special, higher tax for the military: to them, it's free. Military technology has often driven innovation in transportation (ships during the seafaring age and General Eisenhower's Interstate System being obvious examples). The discovery of the Americas was spurred by the loss of trade routes with Asia (or so says Murray Rothbard), so even that you could say was not a market phenomenon. While I'm disgusted with protectionist sentiment, I do think there is some truth to the fact that we might be a little too global – that we're not internalizing fully the costs of transporting goods over such great distances. Same with advocates of public mass transit – while I don't like their reliance on public funding, I do sympathize with them in that in a true market place, mass transit (it's important not to confuse mass transit with public transit) would likely be the norm as it was a millennium ago (not that that was a pure marketplace, but it was probably a purer transportation/energy market than we have now).

The American model (which before it was the American model was Hitler's model) has been adopted throughout the world (partially by necessity – there is no technological spilloff from Western countries for truly market-based transportation solutions), and I have a feeling that the consequences when countries much larger than ours adopt this model (I'm lookin' at you, China) are going to be not great. I'm not a climatologist or anything, but given what I've heard, and given the inherent cost of adapting to anything, I personally fear massive environmental change. Especially considering that it has its roots in statism – never a good sign.

Beastin said...

From what I can tell from a quick internet search:

There was never widespread concern about the danger of global cooling. Some scientists speculated that an ice age might be on the way soon (where soon meant a few thousand years), but many others disagreed. Not a lot of research effort was directed at the question, and the scientific consensus at the time seems to have been that we didn't really know what would happen.

Carbon dioxide released into the atmosphere sticks around for something on the order of 100 years.

We've not got enough coal to last more than a few hundred years as our primary energy source (at present rates of energy usage).

Our current best guess (and I do mean guess) for the time of arrival of the next ice age is order 10000 years.

In the past, ice ages tended to end much more quickly than they began.

The temperature difference between the present and the depth of the last ice age is about 10 degrees C in the average world temperature.

For the last 10000 years or so (basically since the last ice age) average global temperature has fluctuated over a range of only about 4 degrees C, less than it is predicted to increase in the next 200 years (expected increase > 4 degrees C) if we continue to use fossil fuels as our primary energy source.

My personal thoughts:

One of the things I like about your blog David is that you tend to argue not that global warming isn't occurring, but that we're better off not trying to stop it. I feel like that is a much more defensible position.

I think that the most immediately disruptive effects of global warming are likely to be regional changes in precipitation. This is not a prospect that readily excites the imagination, but both droughts and excess rainfall can cause famine through crop failure. This problem already exists, and I don't expect added variability to improve things. Of course, you might argue that it would be cheaper to improve our aid systems for impoverished countries than to try to reduce carbon emissions. (Rich countries are better able to adapt and less dependent on cheap food supplies.) As David is fond of pointing out, it will cost money either to adjust or to avoid changing the climate.

As for wildlife, I don't know how much ecological damage would result from a temperature shift of 4 degrees C over 200 years, and I'm not eager to find out. Given a few thousand years to adapt, most species would presumably just migrate to a new latitude, but 200 years isn't much time to adjust. I also don't see any practical way that we could (directly) intervene in this case. We can't just truck ecosystems north.

If we're trying to prevent the next ice age using carbon dioxide then, given its shelf life in the atmosphere and the time scale of glaciation, we should be saving our fossil fuels for a burn just as the temperature starts slipping.

If we want to heat up the planet, however, we know how to make much more effective greenhouse gases than carbon dioxide... Perhaps we should be sinking some research dollars into methods of actively reducing the greenhouse effect.

I don't consider the problem to be that the temperature is going up a few degrees. It might be preferable to increase the average temperature of the world by a few degrees. Mainly I worry because, first, we're causing a faster shift in temperature than has occurred in the last 10000 years, and, second, it seems not implausible that we could trigger a much bigger climate change. You noted that 13000 years ago there was a sudden (maybe 6 degrees C in 100 years), brief (order 1000 years) drop in temperature. That was during the transition from the last ice age to the current warm period. I don't think that means 6 degrees in a hundred years is okay. I doubt we want to see the kind of temperature swings that happen when the planet thaws.

David Friedman said...

Beastin talks about a 4 degree increase in two hundred years. My problem with that is that I don't think we have much idea of what will be happening in even a century, let along two centuries--the rate of technological change is just too fast. Think about how large the changes have been in the past century.

I argue in my forthcoming Future Imperfect that there are at least three different technologies that could wipe out our species in well under a hundred years--or make us very much richer and better able to deal with things than we now are.

Anonymous said...

As I don't know much about science, I prefer to simply accept the doom and gloom predictions offered.

But then what's the best policy response? Well, it is to allow an energy market free of government distortions. Many governments spend billions in corporate welfare subsidising fossil fuel companies. Any government subsidy that encourages something that has as a by-product greater consumption of natural resources or pollution should cease. We could have a field day identifying all of them.

Adaptation is also not that hard. A long-range perspective of human development would suggest that, provided government's don't to anything silly, technology will improve.

But the worst thing we can do is dream up schemes that put the government in charge of 'managing' the environment. The unintended consequences that are guaranteed to result scare me more than global warming itself!

We could talk about a carbon tax (in exchange for reductions in other taxes) as a last resort. But only as a last resort.

Anonymous said...

My girlfriend is also an accomplished geologist/geographer and it always gets her all uppity when the news people start banging on aout how we are causing global warming, oh sorry I mean global climate change.

Thing is Im a scientist and find the scientifc consensus on the subject to be laughable at best, most scientists testing climate change arent doing so for any reason other than its easy to get funding if you drop the global warming phrase in the hypothesis a couple of times.

montestruc said...

My take is that the bad has less to do with the exact temperature, and a lot more to do with sea level change. Sea levels going up (or down) significantly can be a very real problem for many people. Just look at the issues faced by port owners, let alone farmers and other owners of low laying real estate.

The worst rise that can happen is about 250 feet, which I think you can see would be a very big deal, however having done some back of the envelope calculations I think the time scale for that happening is centuries at least, the latent heat of fusion of that huge mass of ice is about 1.7 years worth of solar output that falls on the earth. So you need to get large amounts of any increase in heat retained by the earth to melt the ice, and much over 1% seems crazy to me.

Note however, sea levels *are* rising, not real fast on the order of about 3 mm a year in most places around the US coast see site.

Some of that is rise and fall of the ground obviously due to geologic phenomena, but when the broad trend over many locations is up, then sea levels are rising, as I said not fast, but rising, and the rate can accelerate.

jimbino said...

Hell, I'm 63 and deliberately childfree. Why should I give a damn about any climate change? Let those breeders who do care find and pay for the questionable solutions themselves!

Not to mention that I care more about plants and animals, who would thrive if the human race were to be wiped out by "climate change."

Anonymous said...

Sea levels have risen over 400 feet since the end of the last ice age (about 20,000 years ago), so the average rate of rise was 2 feet per century. IIRC, the rise over the 20th century was about half of that.

Even if the sea level was constant, many seashore cities would still have to move because the land under them rises or falls. New Orleans has been sinking much faster than any changes in sea level since it was founded. Venice has been steadily sinking ever since Roman times, and they adapted by becoming a city of canals. OTOH, at Thermopylae in 480 BC, the beach was a narrow strip between the sea and a mountain, so 300 men could temporarily hold back a huge army. Now it's a half-mile from the mountain to the sea. Various ancient ports are now high and dry; in most cases the associated cities were deserted, although a few survived as business centers with a road out to the new port.

The big problem is sea-side property owners who don't know their history and geology, and so don't realize that their property value is only temporary - and when that lesson is hammered home by a hurricane, they want to blame someone else.

Danny Shahar said...

My intuition is that even if you built your house in an area where natural mudslides were common, it would still constitute an infringement of your rights to direct a bunch of mud at your house. That is, the possibility that similar consequences could be caused naturally does not absolve us of accountability for those harmful consequences which are caused by our actions.

Andrew said...

Have you ever discussed these questions with a real climate scientist? You'd learn a lot more doing that than posting here.

Stephen Schneider would be the best expert to talk to in the Bay Area, he's at Stanford. I think he'd be happy to talk to you; his contact information is on

I think you'd learn more talking to him for an hour than you have learned in all of your global warming posts here.

Anonymous said...

it is better to be prepared when that major change comes. climate change will definitely happen, we could not prevent that but we can help to minimize the effects.

we can start from doing simple things like doing activities that prevents global warming