It seems to me that we skipped a step.

On the topic of “global warming” I somehow missed the transition from speculations based on a limited set of observations, to apparent iron-clad certainty about cause and effect.

We humans have only made direct, accurate measurements of world-wide temperates and CO2 levels for a very short period of time. A single century is just a fleeting moment when talking about long-term planet-wide climate changes, and our direct measurements cover less than a century. We really need a much much longer record to go from interesting (short-term) observations to any sort of long-term conclusion.

We seem to see rising levels of CO2 in the atmosphere. We also know that humans as a group are burning a lot of fossil fuels, and thinning out a lot of the land-based greenery. We (reasonably) suspect the two are linked.

Interesting stuff – but not conclusive.

To guess at temperature and CO2 levels over a longer term, we have to resort to indirect means. Indirect measurements come from gas bubbles in rocks and ice, tree rings, and other observations from which we draw inferences. Pretty interesting stuff, but we should be wary of the derived data. Chemical reactions involving carbon and oxygen are common, and the time scale over which we want to infer measurements is very long. It would be very easy for some secondary unaccounted-for reaction to radically distort our indirect measurements.

Also we have to account for all those pesky planet-wide secondary processes. To pick a couple examples: Pollution May Feed Plankton Oceans Absorbed Missing CO2

We know there are natural processes that put CO2 in the air. We know that there are natural processes that remove CO2 from the air. What we do not know and should not assume is that natural processes keep CO2 at the same level at all times. What we do not know is the effect of man-made sources dumping CO2 into the air – will this increase CO2 levels, or will natural processes absorb the excess?

Remember we are talking about planet-wide changes where a century is just a flicker of time.

Changes in planet-wide temperature levels are also just as tricky to interpret. We know the planet-wide climate has changed quite a lot in the past. We have some evidence the climate may be going through a long-term change at present (though over the lifetime of the planet likely the climate is always going through some sort of change). What we do not know is if any present climate change was in any way effected by recent human activity.

We suspect that additional CO2 in the atmosphere acts like a “green house” and may trap heat that would otherwise escape. What is not clear is how this effects the long term. If more CO2 in the atmosphere means more captured heat, then we might expect more water in the air (evaporated from the oceans that cover most of the planet). More water in the air means more clouds. Clouds reflect the sun’s heat, so temperatures would likely drop. Right - so will additional CO2 in the air make things on the ground warmer or colder?

Taken together what we do not know is rather a lot. We do not know if the man-made CO2 will stay in the air or be absorbed. We do not know if CO2 will make the long-term climate warmer or colder. We do not know if the recent changes in the climate are due to natural or man-made causes. That is a lot of unknowns!

So why does public discussion refer to “Global Warming” as a fact? Does the “scientific community” show a sort of herd mentality?

This seems to be a case where we leapt from an early set of interesting observations, to a popular cause based on a conclusion about cause and effect. Seems like we skipped over an awful lot of middle ground.

Please do not think this puts me in agreement with the Bush administration. I believe their handling of the issue has nothing to do with the science, and everything with money and politics. I doubt anyone admires the Bush administration for their scientific acuity.

We have another recent case that seems to show the same sort of herd mentality.

Not so long ago Dupont funded a researcher at UCI (University of California, Irvine) who somehow “proved” that flourocarbons were going to destroy the ozone layer. Now this was quite a remarkable notion. Oddly enough this was when Dupont’s very profitable patents on flourocarbons were about to run out (and Dupont had newly-patented replacements ready).

In the 1960’s they used to give demonstrations where the demonstrator would “pour” freon out of a container, and you could watch the gas extinguish lit candles in it’s path. The gas flowed very much like a liquid, and showed a remarkable disinterest in mixing with the general atmosphere. Flourocarbon molecules are remarkably heavy compared to the nitrogen that makes up the bulk of the atmosphere. You might wonder how such a heavy gas would end up at the incredible heights of the ozone layer.

Not long after we had observations that seemed to show the ozone layer thinning, and a bigger hole in the ozone layer at the south pole. Pretty interesting stuff, but the observations cover only an extremely short period of time. We should not assume that the ozone layer is always constant, and we should assume the existance of “natural’ processes that cause the ozone layer to vary. If we do not have a good understanding of the natural variations, it may be impossible to determine if a short-term variation is due to man-made causes.

Somehow I seem to have missed the leap from interesting theory, to certainty about cause and effect.

More herd-like behavior? Could it be this has more to do with money and politics than science?