The global warming theory was first mooted over a hundred years ago, but until the 'eighties it was regarded as nothing more than a scientific curiosity. After all, global temperatures had been dropping from the 'forties to the 'seventies, despite huge increases in CO2 emissions.
The science behind this is well-understood, and nobody argues against it.
Ultraviolet radiation from the sun warms the earth's surface which, as a result, emits infrared radiation. A particular wavelength of this radiation, at a wavelength of 15um, is absorbed by CO2 molecules - which in turn heat up.
This 15um radiation is emitted principally from very cold ground (such as within the arctic circle in winter) and, at current concentrations, is almost wholly absorbed by CO2.
Calculations show that this effect would lead to an average global warming of the lower atmosphere of in the order of 0.5 to 1 degree C, given a doubling of CO2 concentrations from pre-industrial levels. And, as the absorption of that particular wavelength is almost at saturation point, more and more CO2 will have a sharply diminishing effect.
That much is accepted as scientific fact. Such a small degree of warming will have no significant effect, and will go entirely unnoticed. We have orders of magnitude larger temperature swings between day and night, not to mention between summer and winter, or between tropics and polar regions.
Where the theory departs from scientific fact is this:
Water vapour is also a greenhouse gas, but very much more potent than CO2 - it absorbs a broad spectrum of infrared radiation, and there's also around one hundred times more of it in the atmosphere.
Now what the pro-warmers are saying is that the warming from CO2 causes more evaporation from the oceans, therefore more water vapour, and as water vapour is a very potent greenhouse gas, more warming - a positive feedback amplifying the effects of CO2 by itself. And now, all of a sudden, a less than one degree warming turns into almost ten degress.
What, of course, is completely ignored here is that most of the heat is
already coming from the water vapour, with only a tiny amount from the CO2. So, if the water vapour is amplifying any effect, it's the effect from itself.
Also ignored is the fact that the radiative forcing from the concentrations of water vapour in the atmosphere should be giving us average global temperatures of almost eighty degrees C. Clearly this is not the case - if it was then life as we know it would not survive on earth.
So there must be a powerful negative feedback effect, and there is - from the water vapour itself. Firstly, clouds reflect ultraviolet radiation back into space, and secondly, convection in clouds serves to vault huge amounts of heat into the upper atmosphere - from where it's dissipated back into space. The higher the temperature at the surface, the greater the evaporation so the more clouds there are, and the greater this effect. It's a huge thermostat.
It's precisely this effect which is poorly handled, if at all, by the GCM's (global circulation models) which they have running on their tremendously expensive supercomputers. These GCMs are really little more than sophisticated random number generators. They cannot even predict today's temperatures based on known historical data, and they don't even agree amongst themselves. To get them to produce half-plausible results they have to employ 'fudge-factors' which are often orders of magnitude larger than the input data. Even a supercomputer is hopelessly inadequate when it comes to modelling such a hugely complex system as the atmosphere - it's something like trying to work out the national budget with an abacus.
These GCM's, after fiddling, tweaking, fudging and tuning, give predictions of temperature rises of anything between 1.5C to 10C. Guess which end of the scale gets splashed in the media.
What if they're right?
1) Temperatures are rising - Wrong. Satellite and radiosonde measurements have detected no increase in global temperatures over the last two decades. Only land-based measurements, which are subject to urban 'heat island' effects, have shown any increase.
2) Sea levels will rise - Wrong. Increased sea temperatures will result in more evaporation, and more precipitation of snow over the ice caps - resulting on both counts in a drop in sea levels.
3) Glaciers are retreating - Wrong. Some are, but others are advancing. You only hear about the ones which are retreating. Glaciers are very slow-moving rivers of ice - decreased snowfall at the source of a glacier will have the effect of less flow at the foot of the glacier several decades later.
4) High CO2 levels will cause runaway heating - Wrong. CO2 levels have been orders of magnitude higher than today in bygone ages - with no evidence of runaway heating.
Ice core records also show that high CO2 levels have historically followed times of high temperatures - rather than being the cause of them. This is because as the oceans warm they release large amounts of dissolved CO2 into the atmosphere.
5) An few degrees increase in global temperatures will be detrimental, and cause a huge increase in storms, hurricanes etc - Wrong. Temperatures have been higher than today within recorded history. For example, in medieval times - wine was grown as far north as York, and Greenland was settled by the Vikings. It was a golden period for agriculture. The worst storms in recorded history occurred during the Little Ice Age, when it was several degrees colder than today.
6) There will be an increase in diseases such as malaria - Wrong. Malaria isn't a tropical disease, there was a time it was endemic in Russia.
I hope I haven't bored you all to death by this time
Cheers
Peter
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