USS Clueless              Voyages of a restless mind

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Stardate 20011208.2209 (On Screen): One of the classic mistakes to make in science is to use too short a baseline for extrapolations. There are some classic examples of that. For instance, at the beginning of the 20th century, the US government decided to do some major water projects in the US Southwest, particularly with respect to damming up the Colorado river and rerouting much of its water to various states in the area. So they decided to do a study of rainfall patterns to figure out what the expected flow of water in the river would be, and then divvied it up. A study was done for 15 years watching the rainfall, and at end of that time, they made the allocations and then started building dams. The problem was that once the projects were built, the river usually didn't run as much water as they expected. Someone went back and did a more comprehensive study including things like treerings from the entire Colorado basin and came to a surprising conclusion: the fifteen years they looked at had been the wettest fifteen year period out of the last thousand. They'd lucked into a statistical freak and had overallocated the river by a substantial margin. (And for decades now the Colorado River has not actually reached the sea. It gets smaller and smaller, turns into a stream and then a trickle and actually dries up a few miles short of the Gulf of California. What the United States doesn't take, Mexico does.) When it comes to something like climate, fifteen years is infinitesimally small. In point of fact, a thousand years is infinitesimally small.

There are a lot of people out there who hate industrialization and have seized on carbon dioxide release as a way of fighting back. "Green House Effect!" they say; "Global Warming!" Oddly enough, thirty years ago they were saying "New Ice Age!" No-one seems to notice the contradiction. And now they claim that the earth is warming up even though for the last 60 years it's actually been cooling down slightly. (Details, details...)

Still, they've even gotten enough credibility to try to pass an international treaty about it, one which Bush has dumped (for which he has reaped bitter criticism). It's possible that they're right, but the science is not there to prove it yet and right now at best what they have is guesses. The studies on which they base their conclusions are highly preliminary and do not explain much that we know about. For example, it's now known that there is a climate cycle of about 1500 years which tracks activity of the Sun (which is slightly variable). It happens to be the case that we are now in the warming phase of that cycle, which was at its trough in the 16th century (during the "mini-iceage") and which is expected to peak in about another hundred years. Then it's expected to cool until about the year 3100. There is evidence that this has been going on for about 12,000 years, which is much longer than humans have had heavy industry. But there are other factors which affect global climate and we do not understand them all. Deep ocean currents in the Atlantic ocean appear to be extremely important, but no-one knows how for certain yet. And there may be other factors involved as well.

Here's a strange one; it doesn't rank as a "theory" but it's an interesting conjecture. Ice cores were drilled in Antarctica on several of the glaciers, so as to study the snowfall patterns there. When they drilled to the bottom, they were surprised to find that there was several feet of slush beneath the ice; it was actually quite warm down there. Ice is actually a very good insulator, and the heat seems to be from the friction of the glacier as it travels along at a snail's pace; the motion is slow but the actual energy release is quite large. So the entire glacier is sitting on a layer of lubricant; it's being held in place by the strength of the ice in the glacier and a few places near the top which actually do hold on, plus much less friction beneath it than had previously been thought. The idea occurred to someone: what if it broke loose? Then the entire glacier would slide off into the sea and immediately break up into millions of ice bergs, converting a substantial part of the surface of the ocean from dark to white, and that would raise the albedo of the earth by a small amount -- which would cause further cooling world wide. The guess is that it would set off a new ice age.

There's no real evidence for this, but it's an interesting fact that the recent cycle of periodic ice ages begins about the time that Antarctica moved over the south pole due to tectonic movement; it may be that every few hundred thousand years a glacier lets loose and starts a new one.

There is much more that is known; other kinds of studies on glacial cores and tree rings and deposits of pollen and numerous other kinds of indirect evidence has permitted a comprehensive evaluation of the world's temperature over the last two hundred thousand years:

(The timescale is non-linear.) Note that the stability of the last 10,000 years is a historical aberration, a freak. And extremely rapid changes in temperature are not abnormal at all, such as a 13 degree F ris