tisdag 3 februari 2015

Why is it so Darn Hot on Venus, and so Comfortable on Earth?

The surface temperature on both Venus (460 C) and the Earth (15 C) is set by a common temperature of about 220 K at the top of the atmosphere (at 100 km for Venus and 10 km for Earth) and a common thermodynamic lapse rate = $g/C_p\approx 7C/km$ through the atmosphere, with $g$ gravitational constant and $C_p$ atmospheric heat capacity, see data presented by NASA

CO2-alarmism preaches that CO2 is a potent "greenhouse gas" capable of causing dangerous global warming, a risk which must be countered by drastic reductions of burning of fossil fuels. As a warning example the following data for Venus is presented: The atmosphere on Venus consists of 96% CO2 and the surface temperature is about 460 C. The conclusion is obvious: CO2 is a potent "greenhouse gas" capable of massive global warming, on Venus and hence also on Earth!

Lennart Bengtsson as leading Swedish meteorologist has authored a statement by the Royal Swedish Academy of Sciences entitled The Scientific Basis for Climate Change, which essentially gives pray to the IPPC CO2-alarmism and thus serves as the scientific basis of current Swedish climate politics aiming at a fossil-free society.

Bengtsson writes in his introduction to Towards Understanding the Climate of Venus (eds Bengtsson et al):
• The main reason for the very high temperature of the surface of Venus is its atmospheric composition that consists of some 96% carbon dioxide as well as other constituents such as clouds of sulphuric acid and water vapor.
Bengtsson follows up in talk:
• Is it a risk that there will be a run-away climate on the Earth?
• It can not be excluded that Venus has undergone a climate run away.
Bengtsson is frequent writer on the Swedish blog Anthropocene edited by Lars Bern, who also presents support of the idea that CO2 is a potent "greenhouse gas" on Earth because of the apparent "run-away-effect" of CO2 on Venus with reference to Skeptical Science.

Both Bengtsson and Bern thus propagate the idea that CO2 is a potent "greenhouse gas" and as such  is a potential threat to humans on Earth. On the other hand, both Bengtsson and Bern present themselves as skeptics to inflated CO2-alarmism, and so their message is a mixture of alarm and no-alarm, which does not ask for a change of current Swedish climate politics, unfortunately.

But is true what Bengtsson claims, that The main reason for the very high temperature of the surface of Venus is its atmospheric composition that consists of some 96% carbon dioxide..?

No, it is wrong. It is wrong because the very high surface temperature is an effect of
a thermodynamic (without radiation) lapse rate acting over a thick atmosphere from a top at 250 K, and the (dry adiabatic) lapse rate depends on the gravitational constant and heat capacity and not on the presence of 96% CO2.

This is in fact also acknowledged in Towards Understanding the Climate of Venus:
• So surface temperature on Venus is largely controlled by the altitude of the surface along a nearly uniform lapse rate with height. (P. Read in Chap 6 The Dynamics and Circulation of Venus Atmosphere).
• Another factor (for the very high temperature of the surface of Venus) is the depth and size of its atmosphere, which insures that the temperature broadly follows a dry adiabatic lapse rate through a depth of some 70 km above the surface. (Bengtsson again)
Bengtsson thus sends the message (repeated by Bern) that The main reason for the very high temperature of the surface of Venus is its atmospheric composition that consists of some 96% carbon dioxide... which is in direct contradiction to the acknowledged fact that it is the thermodynamic lapse rate that sets the surface temperature.

In this way, Bengtsson can both serve as the scientific alibi of the current Swedish CO2-alarmistic climate politics, as e.g. the author of the Royal Academy statement, and appear as a critic of the same politics.

It would be much better for both science and politics if Bengtsson decided to serve only one of these contradictory roles. Can we hope for such a change, Lennart?