No it's not. They can't address the most simple and obvious contradictions and omissions.
It is often repeated by sources such as the BBC that
Solar energy radiating back to space from the Earth's surface is absorbed by greenhouse gases and re-emitted in all directions. This heats both the lower atmosphere and the surface of the planet. Without this effect, the Earth would be about 30C colder and hostile to life.
1. Temperature increases with pressure, gas giants like Jupiter and Saturn get hotter the deeper you are into the atmosphere. Same goes for Venus. The temperature at the height where pressure = atmospheric pressure on Earth is roughly the same as the temperature on the surface of the Earth, having adjusted for distance from the Sun, regardless of what gases make up the atmosphere. Mars has a thin atmosphere and Earth's Moon none at all, which provide counter-examples.
So a large part of that 30C is due to this effect IMHO and only a small part due to the actual composition of the atmosphere (H2O and CO2), but let's go with the 'consensus' that's it's all of it.
2. Of that 'consensus' 30C, how much is due to H2O and how much to CO2? On average, there is 500 times as much H2O as CO2 in terms of parts per million (400 x 500 = 20,000). H2O appears to reflect/absorb at many more wavelengths than CO2. See see this table. So CO2's contribution, relative to H2O, must be infinitesimaly small.
Nonetheless, most people seem to assume that CO2's contribution is about one-eighth of the total. So let's just accept that as well and see where it takes us.
3. One-eighth of 30C is just under 4C. Other sources say 3C.
4. Skeptical Science jumps the shark on this topic:
The question of how the climate would change in a completely CO2-free atmosphere was brought up recently in a testimony to the subcommittee of the House Science and Technology Committee. An answer was provided by MIT scientist Dr. Richard Lindzen, who suggested that such a hypothetical removal of all the CO2 in the air would translate into a global cooling of about 2.5 degrees, presumably in Celsius...
In the Lacis et al experiments, removing the CO2 from the atmosphere generates a cooling of around 30 C, an order of magnitude difference from Lindzen's answer.
5. Next, I think the logarithmic effect is also broadly accepted, it makes sense. Extreme sceptics say the effect is already saturated and extreme alarmists (e.g. some contributors on Skeptical Science) claim it is close to linear, they cancel each other out.
CO2 concentrations (just under 420 ppm) are 50% higher than pre-industrial levels (280 ppm, which we have to accept as being natural, normal and thus harmless).
So of that 3C extra warmth, considerably more than two-thirds is due to the background 280 ppm and less than one-third is due to the additional 140 ppm, so CO2's contribution to temperature increases over the last 150 years or so is than 1C.
The figure for average temperature increase since CO2 was at pre-industrial levels (when we were coming out The Little Ice Age) is between 1C and 2C. The implication is that all of this 1C or 2C is due to CO2, rather than less than 1C, which would at least seem plausible (if you ignore all the above niggles).
(Skeptical Science side-step the logarithmic issue by fudging their Y-axis and setting 'radiative forcing' at zero for 280 ppm, which is meaningless. As their chart shows, if you fudge it like this, 'radiative forcing' at a lower CO2 level of 140 ppm would be negative, i.e. it would have a cooling effect.)
6. So you have to ignore several glaring contradictions and omissions to reach the conclusion that CO2 increases have pushed up average temperatures by even 1C , that is at the upper, upper range of the even remotely plausible. (If you factor in items 1, 2 and the logarithmic effect, the impact of CO2 is immeasurably small).
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7. What if Skeptical Science is/are right and a) temperatures really are 30C warmer because of CO2 and b) the effect is close to linear? In that case, average temperatures would have increased by about 10C since the 19th century, which clearly they haven't, even if we pretend that The Little Age was somehow normal and a reasonable base line.
Do they not read what they write and think it through to the logical conclusion and realize how stupid they sound?
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