Before the coal industry told him to quit putting his foot in his mouth, even George W. Bush, born and bred in a Texas oil patch, subscribed to the notion that global warming is largely caused by the so-called "greenhouse gasses," the responsibility of us humans. Bush's Treasury Secretary, Paul O'Neill, hands out to his fellow cabinet members horror scenarios about the earth frying.

But do all those gloomsters about global warming really know what they're talking about? Remember those dud forecasts of a blizzard-of-the-century in the northeast United States earlier this month? If the weather folk can't figure out what's happening for the rest of the week, why do they think they can tell us what the climate will be across the next decade, the next 50 years or the next century?

Answer: They can't, and that summary judgment includes the 995 experts who participated in the "Third Assessment Report of Working Group 1 of the Intergovernmental Panel on Climate Change" (hereinafter called the IPCC Summary), a creature of the UN and of the World Meteorological Organization, which seized the headlines recently with clamorous fears about the role of greenhouse gasses in the creation of global warming.

The IPCC Summary makes much of the fact that across the last 1,000 years (a nano- nano-second on the scale of planetary time), "the rate and duration of warming of the 20th century has been much greater than in any of the previous nine centuries." But to take a slightly longer-term view, the present warming trend is well within the fluctuations of the last 100,000 or last million years.

As Pierre Sprey, former government analyst, statistical expert and veteran of many battles over inflated eco-catastrophic predictions, puts it, "This is like a pimple on the ass of climate change. To take one example of the monumental differences in geological record: Today, oxygen is somewhere between 18 and 20 percent of atmosphere. But there was a period of geological time when oxygen was way over 30 percent of the atmosphere, thus prompting monstrously large species. The proportion of carbon dioxide (CO2) was way higher. And here they are today, arguing about differences of one part per million of CO2."

The central premise of the greenhouse gas model of global warming is that during daylight hours our globe gets its huge heat input in the form of short infrared rays from the sun. In close balance, the globe releases this heat in the form of longer waves in infrared radiation during the night hours. In the greenhouse model, malign gasses such as carbon dioxide and methane happen to absorb the long infrared radiation more strongly. Thus, these allegedly malign gasses let the short infrared rays in, but when heat tries to escape each night they hold it in the atmosphere. The more CO2 we humans create, the more heat is trapped and the hotter the world gets.

That's the theory that drives all the greenhouse computer models. But any halfway- watchful reader of the IPCC Summary will note that in all the graphs and trendlines there is one extremely significant absence: the role played by water vapor. This is a very striking omission because, as Sprey emphasizes, "water vapor is the single largest factor in the heating and cooling of the earth. There is far more water in atmosphere than CO2, and it absorbs a lot of infrared radiation. But from the computer modeler's point of view, water vapor is very variable. Rain, they can't predict; clouds, they can't predict. So, if your computer model can't deal with water, forget it."

Think of the heating/cooling equation as a giant seesaw, with a billion tons at each end. You are arguing about a few pounds making the seesaw tilt. And it's true. A few pounds do make a difference. But which few pounds are you talking about? And how do they affect the overall balance? Take aerosols -- particles fine enough to float in air. As we know from the seeding of clouds by aerosols, they can cause rain. The more rain we have, the less water vapor in the form of clouds, hence the less heat trapped by this water vapor. Though plainly aware it's inconvenient to their greenhouse model, the UN's experts are forced to admit in their report that there's been more rain this century over much of the northern hemisphere and even the tropics.

As Sprey emphasizes, since the role of water vapor is much larger than of CO2, it's crucial to understand what draws water vapor out of the ocean and into the atmosphere, thus making the world warmer. Oceans are by far the largest part of the earth's surface. Ocean currents transfer heat from the tropics to the Arctic. They are also important because they release water vapor. So, changes in ocean currents alone could easily account for global warming or cooling.

A recent article in Nature caused a hubbub by reconfirming what we already knew, that greenhouse gasses in the atmosphere do in fact absorb long-wave infrared radiation. But what went entirely unnoticed in that same article was a confirmation of how little we understand the effect of water vapor as a greenhouse gas, and secondly, intriguing measurements showing that the heat trapped in the atmosphere may have decreased over the 27-year duration of the study.

It may well be that when CO2 goes up into the atmosphere, it rains more. Aerosols feed clouds and increase precipitation, meaning less water vapor, hence less heat trapped at night. Since the aerosol effect is as poorly understood as the water effect, who knows whether the earth is cooling or heating due to human activity? Certainly not the computer modelers.

The nearest the IPCC Summary gets to this is their models "cannot yet simulate all aspects of climate" and "there are particular uncertainties associated with clouds and their interaction with radiation and aerosols."

We like catastrophism. It's part of the eschatology of guilt. But it has more to do with faith than with science, and the IPCC Summary only serves to buttress that basic point: The global warming/ greenhouse gas thesis is most emphatically non-proven.

Alexander Cockburn is coeditor with Jeffrey St Clair of the muckraking newsletter CounterPunch. To find out more about Alexander Cockburn and read features by other columnists and cartoonists, visit the Creators Syndicate Web page at COPYRIGHT 2001 CREATORS SYNDICATE, INC.