Kronikk: Lindzen svarer

Det meste av det Richard Lindzen hevder kan tilbakevises, skrev professor Sigbjørn Grønås i sin kronikk den 9. mai. Idag svarer "Verdens mest respekterte klimaskeptiker": "Prof. Grønås' remarks are so silly as to make one wonder what value one can attach to either his agreement or disagreement."


Prof. Grønås is right about what I think the climate sensitivity to be. However, that was not what I was explaining to the House of Lords.

There, I was simply explaining what is generally agreed on, and pointing out that these points of agreement did not offer support for alarm.

The points were:

1. Global mean temperature had increased on the order of 0.6 degrees Celsius over the past century.

2. CO2 had increased from about 280 ppmv to about 380 ppmv since the 19th Century and man’s activities are likely to have accounted for this.

3. CO2 is an infrared absorber and hence its increase should lead to some warming though water vapor and clouds are far more important greenhouse substances.

4. In terms of radiative forcing of climate, man’s contributions already are at about 3/4 of what one expects from a doubling of CO2. Without any feedbacks at all, this should lead to about 0.9C warming which is more than we have seen.

5. In current models, due to the water vapor and cloud feedbacks in these models, the expected response is several times what is given in item 4.

6. The IPCC argues that the hugely uncertain (and, therefore, essentially adjustable) aerosols have cancelled most of the greenhouse warming. This is hardly compelling evidence for the correctness of the model climate sensitivity.

Does Prof. Grønås really disagree with any of the above?

As concerns the water vapor feedback, Prof. Grønås’ remarks are so silly as to make one wonder what value one can attach to either his agreement or disagreement.

Warmer ocean surfaces only lead to more evaporation (and more relevantly more cumulus flux) if relative humidity remains the same or decreases.

Increases is evaporation would only impact water vapor in the boundary layer where their impact on greenhouse warming is negligible especially in the all important tropics.

Water vapor at upper levels, which is relevant to greenhouse warming, depends critically on evaporation of precipitation from high clouds which are agreed by all modelers to be very poorly handled in their models.

Professor Grønås’ description is either hopelessly naive or meant to mislead uninformed readers.

Neither situation does much credit to Norway’s great tradition in meteorology associated with names like Vilhelm and Jacob Bjerknes, Arnt Eliassen and Ragnar Fjørtoft.