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Retorts

Warming Debate Continues

The critique by the NZ Climate Change members [Dec/Jan] is deficient in several points.

Water vapour feedbacks over warmer waters do not create additional warming, as they imply. The extra water vapour has little additional greenhouse capability, as the tropical infrared absorption bands are already saturated. The resulting additional cloudiness and deeper tropical convection will clearly have a cooling effect.

The tropics have not warmed at all in spite of an increase of 46% in CO2 equivalent gases. The maximum temperature increase from the increased surface energy flux is calculated at 0.25oC, and the actual outcome has been found to be even less.

The members admit that negative feedback from clouds was handled incorrectly but still insist on a positive "ice-albedo" feedback. A satellite imaging study has shown that summer overcast cloud at the ice fringes largely neutralises any albedo feedback from variable ice cover. In addition, sea ice has been found to be an efficient insulator, and its loss allows rapid cooling of the exposed ocean. This results in a powerful negative feedback overall in the polar regions.

There are five major models of warming, suggesting warming, if CO2 doubles, of less than 2oC to over 5oC. Consequently, 1.5oC is a reasonable average of what our temperature should now be, given that we are halfway toward CO2 equivalent doubling. The lower figure quoted by the authors reflects some recent back-pedalling by modellers. The 1988 figures have been halved, but these downward revisions have not had the widespread attention of the early scary predictions.

The 0.3-0.6oC warming recorded this century is only an IPCC average of estimates ranging from 0.0-0.7oC. This variation is largely due to the heat island effect which is a serious distortion to data, even after "careful correction". This is currently a controversial point among researchers and MIT's 0.2oC estimate appears the most realistic, given their sound methodology.

Observed regional changes not only differ from the models, but do not support them at all. The big regional warmings predicted -- such as 10oC for Alaska -- simply have not eventuated. If anything, many places, such as the U. S., are cooler, not warmer.

The Toronto prediction of a 1.5-4.0oC warming by 2040 amounts to 0.3-0.8oC per decade. The NASA satellite study, which found no warming from 1978-1988, had an adequate timespan to observe the accelerated changes which the greenhouse theory predicts.

The 1980s have been touted as proving that we were heating up, with individual years being used by some researchers. In effect, 10 years or even one year is "OK" if it indicates warming, but insignificant if it doesn't.

Solar forcing is very evident on long-term climate change, such as the Little Ice Age and the Maunder Solar Minimum of 1650-1710. Short-term effects are masked by the oceans' thermal inertia. A particularly intense solar maximum (such as in 1980 or 1990) can cause short-term warming. The sun has been slightly hotter this century, raising global temperatures by about 0.1oC based on radiation increase alone.

In summary, the greenhouse warming theory appears simplistic, seriously flawed, unsupported by physical evidence and totally reliant on computer models which, for all their complexity, are little more than high-speed three-dimensional spreadsheets.

John Daly, Tasmania