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Wednesday, November 14, 2007

Global Warming Explained

Okay, not really. But Power Line posts some quotes from a real live scientist concerning a few things we know and/or don't know about global "warming" or "climate change" or whatever it is we are calling it this week.

I'd been wondering why I never see these sorts of step-by-step discussions of how global "warming" supposedly happens, and what still needs to be proved before we can know it really is happening. Maybe the reason we don't see many of these explanations is that they make it clear no one really knows what significant effect - if any - man truly has on the overall temperature of the planet's atmosphere.

2 comments:

Glenn said...

I could go with one of those "on the one hand ..., on the other hand" comments that I think of as balanced, but that I'm sure many readers think of as waffling. Instead, I'm going to go at one word here: infancy.

Well, actually, I'm going with two words: "scientist" and "infancy."

First, I really, really, really dislike the characterization of some author, speaker, researcher as a "scientist." Science, the activity formerly known as natural philosophy, is extremely diverse. While the comments of a biologist, say, on global warming's effects on the habitat of penguins might the interesting, the same "scientist's" comments on the causes of climate change have no more authority than, well, Agim's.

"Infancy" is the word I'd like to stress today, and I'd like to point out that any critique based on this is a two-edged sword.

The Earth is about 4.5 billion years old, give or take a few hundred million years. There is some evidence of climate changes in various places around the globe. Aside from the latest Ice Age, in which we may still be living, there is evidence for glaciation in a number of far more remote periods. (Mostly we get the striations on hard rocks which are characteristic of the passage of glaciers in their slow, grinding way. I might note that some geologists, such as the late, great, Louis Agassiz of Harvard, thought that these same marks "proved" the Biblical account of the great flood. Evidence is one thing; interpretation is another.)

Some of this climate change in the distant past was, apparently, due to the effects of continental drift. When you find coal, which comes from organic matter, chiefly plants, formed in tropical or sub-tropical climes, in Colorado or Pennsylvania, it's a good bet that the land has moved. (Before the theory of continental drift was accepted, there were, as I recall, some remarkable theories about the Earth "flipping" on its axis, every now and then.)

The one thing that I think can be said with some confidence is that processes of climate change are very slow: they proceed at a glacial pace, so to speak. I could look up better figures, but the "recent" series of glaciations occurred over a period of a million years or so, and consisted of five or six distinct episodes or cycles of glaciation and melting.

We have been collecting weather and climate data for about 100 years, if we're looking for any kind of systematic process. Most of the data we have come from areas which were occupied by people who were interested in Western-style science, and who had the equipment to carry out observations. In other words, we have data going back about 200 years in England, France, and other points in Northern Europe. We also have observations of European sea captains in various areas. The more recent the date, the more data, the better the data, and the more widespread the data. It is well to remember that weather satellites, the source of a lot of our current data, were only launched in the 1960s.

What I am suggesting is that meteorology and climate science are in their infancies in a couple of senses. They are fairly new sciences, of which only one instrument, the thermometer has been around and in widespread use for a long period of time. The technology is still in flux, and the observation series are still changing. Go find a series of observations which are exactly comparable extending over more than 50 years: I don't think such a thing exists.

But, more importantly to my mind, is that our sampling range is extremely limited compared to the phenomenon we are trying to observe. Let us suppose that we are looking at the last one million years, during which the continents have not moved significantly. This is, by the way, the Pleistocene period. Most, if not all, of this period was occupied by the Ice Ages. At least, the end of the Ice Ages is marked by the rise of sea level by some 300 feet to its current level 8,000 to 10,000 years ago. (Please note the 20% uncertainty in a major event. Does this mean that the rise took 2,000 years, or that it happened sometime during those 2,000 years, or that we don't really know when it happened?)

To look at it one way, I have a line on the X axis about one million years long. I am trying to figure out what's happening to the average temperature, tracking on the Y axis. I have a sample of about 100 years' worth of data, or 1/10,000 of my time period, all at one end of the period. (I know about glacial ice and other supposed records of ancient climate: I think there are methodological problems there, and the samples are still infinitesmal.)

As a calculus problem, this is like estimating the formula for a curve from the derivative (slope) at a single point on a long and complex curve. The result is the sort of "calculation" that tells us that the population of Las Vegas will be one trillion people by 2050. This is like estimating the Dow Jones Industrials average movement since 1980 based on Thursday's figures. (Thursday was down; if it's been down like that since 1980, the average in 1980 must have been over 30,000 points.)

In other words, in my humble opinion as a "scientist" (political, in my case), we don't have enough data to make accurate estimates of the trend lines, let alone to determine causes.

Now, on the other hand, that cuts both ways. I'm not about to say that Al Gore is absolutely right, and that there is no doubt that 1) the sea level will rise more than one foot in the next 100 years; 2) this is caused by man-made pollutants; and, 3), therefore, we can reverse the warming trend by changing our behavior. (I have a lot of trouble with the "no doubt" part.)

I am, however, ready to deny that anyone can state with any certainty that 1) the climate is not getting warmer (after all, we've been in a warming trend for 15,000 years or so); 2) that human by-products such as soot, carbon dioxide, and hydrocarbons have absolutely no effect upon the climate; and 3) that decreasing the burning of coal would not lead to a moderation of the rate of climate change.

Lloyd said...

> ...some quotes from a real live
> scientist concerning a few
> things we know and/or don't know
> about global "warming"...

It's important to understand something that most non-scientists (and I'm a non-scientist) have trouble with: At its cutting edge, the activity that we call "science" is non-linear and recursive. One scientist hypothesizes an explanation for an observed phenomenon, then he and other scientists test various theories that might explain it. That work, in turn, leads to other hypotheses and theories. It often takes years-- decades, even-- for scientists to fully form a good theory and have it accepted.

It's thus no surprise at all that there are "real live scientists" who disagree with current explanations of how climate change works.

> I'd been wondering why I never
> see these sorts of step-by-step
> discussions of how
> global "warming" supposedly
> happens, and what still needs to
> be proved before we can know it
> really is happening.

I've seen such discussions in popular publications such as Discover Magazine and in more specialized publications such as Scientific American. There are also many, many book-length discussions of global warming.

(And why the quotation marks around "warming"; there's no credible doubt that warming is taking place. The question concerns the mechanism.)

> Maybe the reason we don't see
> many of these explanations is
> that they make it clear no one
> really knows what significant
> effect - if any - man truly has
> on the overall temperature of
> the planet's atmosphere.

Quite so. I've never seen a good discussion of global warming that supports the notion that man is its *sole* cause. Indeed, most scientists seem to agree that it is caused by a complex interaction of many variables, among them human activities.

So, there's no doubt that "real live scientists" disagree about many facets of the global warming issue. In my view, that's a good thing; such disagreement is evidence that science is working as it should.