How is this skeptic wrong?

You AGWer refer to the ice cores records, but ignore the fallacy in logic that naturally occurs when you do so. Now we have a correlation between CO2 and temp increases, but we also know that a rise in temp will cause a rise in CO2. So CO2 is indeed a cause and an effect of warming. Now this means that when looking at ice core data we are seeing both a cause and effect of CO2, but there are many other factors that effect the climate temps that we have no way of measuring far into the past. So if we are currently artificially raising the amount of CO2 in the atmosphere, which I think we can agree on, then when we use a very limited amount of factors which include CO2 concentration, we are naturally going to overestimate by assuming that the cause and effect relationship between temps and CO2 levels is solely a cause relationship. Now since we know that CO2 ability to warm the atmosphere alone, the entire difference between the correlation between CO2 and temps, that is not explained by the amount of energy CO2 can actually capture, has been placed into the positive feedbacks. This includes the entirety of the effect relationship, which may cause the problem. It would be completely acceptable to place the remaining warming not see by CO2 alone from the causation side onto the positive feedbacks, but we have no way of currently seperating the cause of effect of CO2 versus temps. But there seems plenty of other evidence to suggest that the strength of the positive feedbacks that have been placed into the models are overestimated. One such line of evidence is the 15 years of no statistically significant warming, plus the earth climate is relatively stable or at least has been for the past 100,000 years. During this time we have seen only a 10 degree variation in total.

Now if the AGWers would realize this and start to warn about a moderate warming as opposed to a runaway warming, then the changes that could and should be made can be made in a manner to minimize human suffering and the warmers may gain more traction because they would no longer be alienating those that see a problem, but not an end of the world scenario.

Dana,
If you took away the atmosphere, the ocean would quickly recreate at least a portion of the atmosphere, plus the oceans capture a ton of energy. But I do agree that the oceans is not the only reason for warming....Show more

Based on your question, I think the skeptic was referring to this web page:
http://www.nov55.com/crunch.html
which provides that the total heating by all the greenhouse gases that the warmers claim is 33 Kelvins verses what would be if there were no greenhouse gases.

Doubling any greenhouse gas will have less effect than the zero to present concentration of the gas. Doubling a minor greenhouse gas will have limited effect.

Warmers assume that additional CO2 in the atmosphere would have a known effect on the average earth's temperature.
http://www.nov55.com/equations.html
This has not been supported by the ice core records:
http://wattsupwiththat.com/2009/01/30/co2-temperatures-and-ice-ages/
So none of the calculations based on CO2 concentrations warming the earth lead to reliable results.
http://www.nov55.com/dispa.html
They have not done so in the past.
http://www.co2science.org/articles/V13/N9/C1.php
Just look at what recent temperatures have done,
http://www.ssmi.com/msu/msu_data_description.html#msu_amsu_time_series
verses what the atmospheric CO2 concentrations have done.
http://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide-en.svg
The temperature of the earth is determined by the Stephan=Boltzmann law which states that the heat released is proportional to the fourth power of the absolute temperature.
http://en.wikipedia.org/wiki/Stephan-boltzmann_law

Edit @Beren:
nov55 does indeed have some silly stuff including on AGW, but the writers do try to make the known case against AGW intelligible to all, and get it mostly correct. It is a good place to start. I include it as a source for more information, not a peer reviewed authority.

Furthermore, from reading the question, it appears that the confusion originated on that site. That makes citing it for this question particularly relevant. Note that I included more reliable references for the scientific points in addition to the nov55 web pages, and used the nov55 pages specifically with regards to clarifying the point that nov55 was trying to make.

BTW: news.bbc.co.uk is not a credible source for science information either.

The Stefan-Boltzmann law most certainly does apply to our atmosphere, and governs the equilibrium of the earth's temperature. There are no true black bodies, but in the infrared range our atmosphere is a fairly good one....Show more

I find it very alarming that somebody who supposedly has a science background actually tries to use nov55.com as a legitimate source.

I have showed that website to a several colleagues, all with advanced physics or engineering degrees and got a chuckle from all of them. One even called the website scary in how wrong it is on so many things. The most absurd thing on the website is the claim that E =mc^2 is wrong because nothing can go faster than the speed of light.

The common mistake that many deniers make (those with just enough science background to be dangerous) and the mushroom researcher at nov55 make is that the Stefan Boltzmann law applies to all matter. It applies to matter that has properties close to a black body. Gases like the atmosphere are not black bodies.

The Stefan-Boltzmann constant is not wrong. What is wrong is how a certain mushroom researcher applies the Stefan-Boltzmann law.

Edit: The atmosphere is definitely not a black body even in the IR range. If the atmosphere was a good black body in the IR range then the IR absorption spectrum would be completely featureless. If it were a black body, you can completely forget about applying Beer's law....Show more

As I say in reply to your later more quantitative question:

The "CO2 is saturated" argument is simply bad physics, and was explicitly rebutted in the Scientific American article on global warming. However, denialist arguments don't vanish merely because they are shown to be wrong.

John Houghton in "Global Warming" discusses what he calls "grey body radiation". We can consider absorption and readmission, as you indicate, from successive layers of the atmosphere. Final emission into space will take place, on average, from a layer at a characteristic depth below the top of the atmosphere, and that depth is inversely proportional to concentration of the gas. The higher, the colder. So more of the gas means less energy reemitted at the frequencies where it absorbs, creating a disequilibrium that is ultimately removed only by raising the surface temperature.

So there you have it, in language that I hope even Conservative Agenda can understand....Show more

When I read the first statement, I did a double-take and had to read it several more times. The oceans are what warm the planet? Huh?? Why does he put the word 'oceans' in parentheses after 'atmosphere'? Is he saying the atmosphere acts like the oceans or something? Honestly I can't figure out what he's trying to argue, but he's disputing a physically correct statement, so no doubt he's wrong.

The second statement he seems to be assuming that the relationship between radiative forcings and temperature changes is linear, which it's not. As deniers often like to point out, it's logarithmic. It's just a ridiculously oversimplified back of the envelope calculation which is completely physically unrealistic....Show more