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We can actually know the absolute scale of temperature changes from specific causes. We don't have to guess about imaginary "climate sensitivities". The total power from changing solar irradiance alone cannot account for all the observed temperature change seen in the 20th century; it can account for a few tenths of a degree of it, concentrated in the early portion of that century. But similarly, the observed rise in CO2 concentrations cannot account for the observed temperatures, it does not remotely generate enough power. It can cause only a few tenths of 1 degree C. Furthermore, the same calculation applied to hypothetical predictions of 70% to 100% rises in CO2 partial pressures would cause warmings of half of 1 degree C or less.

What the CO2 warming nuts are doing is using a double standard. To sun forcing they ask for the absolute scale and ignore the correlation. For CO2 forcing they ignore the absolute scale, and pretend the correlation must be causation, and that the difference between them is "climate sensitivity". In plain English, this is nonsense.

The sun hypothesis has two explained amplifiers. One set of researchers focus on sun initiated changes driving CO2 concentrations themselves, independent of human uses, through dissolved oceanic carbon, and is alluded to in this article. Another group (Danish mostly) thinks increases in solar output decrease net low altitude cloudiness, via an effect of solar wind shielding from a specific energy band of cosmic rays that they posit seed cloud formation.

The cloud feedback again comes out to an absolute scale of a few tenths of a degree C, via a total net contribution of order 20-30 watts per square meter and single digit percent changes in average cloudiness.

What none of the schools of thought on the subject, including the CO2 warmer group, has every been able to allege in any way that withstands physical scrutiny and measurement, is any set of linked feedbacks (which are getting more and more epicycle baroque as time passes and the hysteria holds) that generate sufficient power to keep the entire world continually glowing 5C hotter.

Every one of the forcings involved has a measured scale or variation on the order of low single digits watts per square meter. Indeed, only a handful rise to above the full watt threshold. Most of the handwaving feedbacks alleged on any side, when measured, have proven to be random in sign and 1-2 orders of magnitude smaller than the main direct forcings. And it takes on the order of 25 watts per square meter, net new power, to maintain a 5C hotter world indefinitely.

The first order effects fully account for the *observed* warming, without any need for giant amplifiers. They point to a further warming from additional CO2 concentration increases, on the order of 0.5C over the next century.

There is also a pretty compelling argument now that CO2 partial pressures will not rise above about twice what they are today, even if all known fossil fuel deposits (including all the coal and shale and tar sands) were burnt. The reason is the ocean is a great sink for carbon and rapidly re-equilibriates with air. Force the partial pressure of CO2 away from its S curve steady point in either reservoir, and a restoring force is immediately set in motion, as the rate of CO2 flux out of that resevoir into the other one rises.

There is a lag, so the speed at which CO2 is added matters. In 500 to 1000 years, it would not matter at all if all the fossil fuels were burned. Burn all of it faster and you can elevate atmospheric CO2 by a factor of 70% and keep it there for a few hundred years. It is a stretch to get double, though that is the usual figure the CO2 warmer crowd projects, and pretends can continue to get worse indefinitely.

A 70% increase in CO2 concentrations would led directly to only a few tenths of a degree C of warming. Exactly the same absolute scale logic deployed against the direct sun warming group, applies against the CO2 driver group.

The most irresponsible and least supported claim in the whole subject, all sides, is the standing prediction of 3-5C ice age scale warming, when none of the causes being discussed and currently varying, has the physical power to drive lasting mean temperature changes of that magnitude. This has been shown repeatedly for nearly two decades now, and it has never yet led the CO2 driver group to drop the prediction. Which originated in a demonstrably false theory of the origin of ice ages themselves, and has refused all revision in the light of vastly better evidence.

The bottom line is that warming is real and modest, human activity does account for a portion of it, roughly similar in magnitude to present natural drivers like changing average cloudiness and changing solar output, all of them scale tenths of a degree C, and all of them adding up to future temperature changes of less than 1C, regardless of what humans choose to do for their energy needs. And there never was and is not now, any reason to believe modest temperature changes on that scale, will have any significant negative effects on human welfare.

The only world leader being rational about any of this at the moment in Valclav Klaus of Czechoslovakia. Nearly everyone else is in thrall to hysterics tendentiously pushing one-sided byzantine arguments, that are by now towers of epicycles. And it is all going to collapse into its physical incoherence within our lifetimes.