måndag 15 januari 2018

The Atmosphere Effect vs Climate Sensitivity

The global mean temperature on the Earth surface is about 15 C or 288 K. What would the temperature be if there was no atmosphere on Earth, that is what is the atmosphere effect? Klimatrealistene suggests 90 K after a comparison with an observed mean temperature of the Moon claimed to be 198 K. IPCC suggests 55 K.

But one can also argue that it is about 15 K  based on the attenuation effect of the radiation from the Sun surface at 5778 K spread over the Earth surface in a direct application of Stefan-Boltzmann's radiation law for a black/grey body, see earlier post, which gives Earth a temperature of about 273 K.

For Mars with a very thin atmosphere the same computation gives about 230 K in accordance with observation.

So we have a wide range for the atmosphere effect, from 15 K to 90 K, and one may say that the bigger the atmosphere effect is, the bigger can the effect be from changing properties of the atmosphere such as the amount of so called "green house gases". So which value for the estimated atmosphere effect is more relevant? 15 K or 90 K? Or the IPCC value in between?

The 90 K posted by Klimatrealsitene comes from an estimate of the mean temperature of the Moon (198 K) at the same distance to the Sun as Earth and without atmosphere, seemingly the perfect factual evidence. But the Moon-day is about 28 Earth days and so the temperature from day to night on the Moon varies from 100 K to 400 K (with then a mean of 250 K and not 198 K) and so a mean value may not be very meaningful.

With the evidence from Mars the value 15 K would seem to be a better estimate of the atmosphere effect, suggesting a climate sensitivity 0.15 C as the warming upon doubling of CO2 representing a 1% change of atmosphere properties, compare upcoming talk.

4 kommentarer:

  1. In an earlier post you endorsed the Nikolov & Zeller paper with the 90 K moon comparison.
    Have you changed your mind completely now?

  2. This post

  3. Well, what I menar to ”endorse” was the gravito-thermal effect and not the specific idea of a mean value temperature on the Moon of 198 K suggesting an effect of the presence of the atmosphere as high as 90 C. I still think that a value 15-20 C suggested by a direct application of Stefan-Boltzmann could be more relevant, but the whole idea of comparing with a hypothetical Earth without atmosphere is questionable. In the same sprit one could ask about an Earth temperature without a Sun, for which an answer could be given but it would say very little...