Note, this thread is in English - the background, with which this thread begins, is an exchange in German.
In the Spektrumdirekt-Interview Wir müssen die Herausforderung durch die Skeptiker annehmen by Daniel Lingenhöhl, published 30. Juli 2010, I had said:"Wir müssen die Herausforderung durch die Skeptiker annehmen und in die Auseinandersetzung mit ihnen einsteigen, um sie zu gewinnen. Viele Physiker, Chemiker, Ingenieure oder Geologen haben offene Fragen zum Klimawandel, die sie noch nicht beantwortet sehen. Hier ist ein erhebliches und sehr berechtigtes Fragepotenzial vorhanden, auf das leider zu selten eingegangen wird. Stattdessen werden sie teilweise als Skeptiker beschimpft, was sie verärgert. Dadurch bauen wir kein Vertrauen auf. Wir müssen zu einer anständigen Gesprächskultur zurückkommen..
Werner Weber, Chair of Theoretische Physik II at TU Dortmund, has responded to this assertion. He wrote
"Ich kann relativ leicht querbeet durch das ganze Forschungsfeld 10 wesentliche Punkte nennen, wo ich das wissenschaftliche Vorgehen der Klimaforscher, sagen wir, nicht ganz nachvollziehen kann. Ich könnte diese Punkte einer Gruppe von Experten vortragen, und würde mich von diesen auch gerne eines besseren belehren lassen. Ich habe aber genug Selbstbewusstsein, dass ich die Hoffnung habe, dass es auch umgekehrt kommen könnte."
My response was to suggest that he should summarize his questions here on Klimazwiebel. He has done so now, beginning with 5 questions, the first two are specified in some detail below.
"1) The magnitude of the anthropogenic greenhouse effect is not determined by direct measurements, it is only a results of energy budget model calculations. The atmospheric infrared radiation emitted from greenhouse gases is monitored globally since the early 90ies. During those years, the CO2 concentration increased by 30 - 40 ppm, but is there any signature of this increase in the data ?
2) The energy budget model calculations yield an increase of radiative blocking of order 1-2 W/m2, mainly due to the CO2 increase. Yet the models cannot reproduce 30 W/m2 atmospheric short wave absorption (of the 90 W/m2 total). Should they be trusted for the long wave results on the level of 1 W/m2?
3) The 'general circulation models' translate 1 W/m2 radiative forcing into 0.7 Celsius temperature increase. They predict a catastrophic temperature increase in the coming decades, especially affecting the artic. The models could be easily compared to prehistoric climate situations, such as the early holocene, where the arctic was exposed to approx. 40 W/m2 more summer insolation than presently (see Milankovic) - which the Greenland ice sheet obviously survived.
4) The GCM's treat the Navier-Stokes equations in the laminar flow approximation, i.e., they treat the flow of water (and air) as if it was the flow of honey.
5) The temperature trends of the last 30 years show a strong north to south latitude decrease, while the global atmospheric CO2 distribution and its increase is very uniform."
He adds "Explanations to the above listed points 1) and 2)
"The most famous papers for energy budget calculations are those of the Trenberth group. When I started working in climate research, I studied their 1997 paper in detail and I thought that I had found an important term in the various processes which they had neglected. I approached Trenberth and he convinced me that the term was negligible.
He then pointed out to me what he considered their biggest problem, i.e. the 30 W/m2 deficit of the model for short wave absorption. I found Albert Arking's papers, who argues that most of those 30 W/m2 are absorbed in the atmosphere during fair weather situations. I found the paper of the Heidelberg group who searched for water dimer absorption as an origin for this deficit and had published positive results in a Science paper /Pfeilsticker et al/. However in the thesis of Lotter, these claims were no longer kept up.
My solar irradiation analysis results suggest that specific aerosols are the cause for the missing absorption. These aerosols are (very) small water droplets and absorption occurs at the water lines. It is textbook (Roedel) knowledge that for infrared emission in the range of 300 K, water behaves like a 'black body', i.e. it emits all frequencies in that range. So do cloud droplets and so do - most probably - smaller droplets of aerosol size. While for IR emission from clouds, the energy budget calculations include those emissions, for fair weather situations no aerosol emissions are considered. There, only molecular emissions are included which are determined using the HITRAN data base.
According to the energy budget papers, the greenhouse gas effect is considered to be strongest for fair weather situations. For cloudy or partly cloudy sky situations, the atmospheric IR radiation is more and more dominated by the clouds. If, at fair weather situations, there exists another important sorce of IR radiation apart from the greenhouse gas molecules, it would reduce the greenhouse gas effect.
There exists the PANGAEA collaboration of globally 30 to 50 stations where solar irradiation data are taken. This collaboration is coordinated by AWI. Most of the stations also measure 'long wave down', i.e. the atmospheric IR radiation. Most stations measuring LWD have 10 -15 years of data. So far, no common analysis paper on the time trend of the LWD results at fair weather situations exists, with the goal of extracting the increase of the greenhouse gas radiation due to anthropogenic effects. There exist global dimming studies, but they integrate over all solar irradiation (short wave down), including partly cloudy situations."