House of Eratosthenes

“It is impossible to talk about a single temperature for something as complicated as the climate of Earth”, Bjarne Andresen says, an an expert of thermodynamics. “A temperature can be defined only for a homogeneous system. Furthermore, the climate is not governed by a single temperature. Rather, differences of temperatures drive the processes and create the storms, sea currents, thunder, etc. which make up the climate”.

He explains that while it is possible to treat temperature statistically locally, it is meaningless to talk about a a global temperature for Earth. The Globe consists of a huge number of components which one cannot just add up and average. That would correspond to calculating the average phone number in the phone book. That is meaningless. Or talking about economics, it does make sense to compare the currency exchange rate of two countries, whereas there is no point in talking about an average ‘global exchange rate’. [emphasis mine]

I saw this on Misha’s blog yesterday, too, and I’m going to caution people where they go with this.

I do it .
- philmon | 03/21/2007 @ 10:30
ahem… sorry about that.

I do it here in this post

Dang shift key.
- philmon | 03/21/2007 @ 10:42
I wish I could find that comment I left lying around somewhere on FARK.

I agree they’re oversimplifying it, but of course all they’re doing is attacking the notion of “average,” not describing what is to be done in its place. Obviously, the earth is a mass, and as such has the capacity to store a measurable amount of heat energy.

My point was a little more complex. Anytime you measure an “average,” you have to define how it is computed, and this has to be done along a singular metric. We measure the average I.Q. of people in a room…if we measure it along the metric of “noses,” we simply add up the points and divide by the number of people. If we measure it along the metric of body weight, then things become somewhat more complex. Some guy weighs 100 pounds and has an I.Q. of 140, another guy weighs 280 and has an I.Q. of 90. Harder to compute. But it’s still do-able.

The issue with global warming is heat applied to the planet. Whether it is absorbed more quickly, or dissipated more slowly.

So an “average,” to be meaningful in exploring this concern, has got to be concerned with heat density. I’m using the physics term here: The number of calories required to increase the temperature of a kilogram of a given material by one degree Celsius. One-point-oh for water, something much lower for steel wool, or flour, or salt, or whatever.

You have to take this into account. There is no alternative, for the residual heat energy is the item of concern.

The oceans have become slightly cooler while the land masses have become significantly warmer, since 1970 to 1975. “Mean global temperature” is going up during that time, because the increase over land is greater than the decrease over water.

I’m taking that as a “mean” calculated according to square miles. This, of course, would be poppycock. Dirt has grown warmer by a variant greater than that by which the water has become cooler, and from this I am to conclude that the “net” is on a slight increase.

This is not a trivial concern, as some seventy percent of the earth’s surface is made of water. This may explain all of the 0.4 to 0.8 degree C by which they think they can assert that the earth has been warming up. Even if it doesn’t, however…there is still the consideration of eight thousand miles of matter beneath the surface, that isn’t being measured. This, too, absorbs and dissipates heat, and I don’t hear anyone talking about that at all.
- mkfreeberg | 03/21/2007 @ 11:00
Yep. There is no single definition of “Global Temperature” that we have (nor could we have) applied any sort of consistent measurement method to to come up with a history to do comparative analysis upon.

I guess what I was cautioning against was the temptation for people to dismiss the whole issue because of the fact that there’s no agreed upon definition of such a “value”, let alone the fact we don’t have any way of applying one, if we were to come up with a meaningful one, to the earth system going back in time.

I believe average atmospheric temperatures do go up and down over time. After all, at one time grapes were grown in England, and at other times gigantic glaciers covered North America and Asia down past the 40th paralell.

People probably don’t talk too much about the earth’s temperature below the surface because most of the radiative balance between the sun and the earth — on land anyway, happens in a very thin layer at the surface. The oceans are different, as they do circulate heat up and down. But I think, on the whole, the earth as an entire system is generally understood to be very slowly cooling as far as that molten stuff a few miles below our collective feet is concerned. What’s happening in the biosphere (this bit we wander around in every day) is what we call “climate”.

The “no global temperature” point is an extremely good point as long as people understand why it is a good point and don’t get too simplistic with it. I’m pretty sure you understand it — I’m mostly cautioning others who may read this and go make bad arguments by declaring that there’s “no such thing” as a global temperature. Technically, this is true since there’s no widely agreed upon definition. But intutively, it’s not because the balance in the biosphere clearly changes over time. One would expect it to as it turns out that the solar “constant” isn’t and the earth’s tilt “wobbles” and cosmic rays have a positive effect on cloud development (among other things). Our climate, like everything else in the universe, oscillates.
- philmon | 03/22/2007 @ 12:29

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Is There A Global TemperatureWednesday, March 21st, 2007

Is There A Global Temperature
Wednesday, March 21st, 2007