Although the titel suggests that the thread is about another planet, the real subject is the forcing character of CO2 greenhouse gas and so it's about global warming and hence it should belong in the Earth forum. If you write a Assessment Report for the IPCC about greenhouse effect on Earth, with much uncertanties, you would certainly want to compare with other cases like Mars to validate assumptions. That's Science and the scientific method, assuming that the same physical laws are correct on Mars as well. There isn't any. Not a single study. **** Hans Erren calculates the CO2 forcing like this: http://members.lycos.nl/ErrenWijlens/co2/howmuch.htm Now if you would really want to calculate greenhouse gas forcing, there is a splendid object for that. Mars and its CO2 atmosphere. So let’s do an attempt. Mars fact sheet: http://quest.nasa.gov/mars/background/vitals.html Median value is not necessarily the average value so let’s peek some more for an average temperature: http://science.howstuffworks.com/terraforming1.htm On the other hand it’s -55C in several other sources like: http://www.nineplanets.org/mars.html So let's use both values, then the average Mars temperature is about 210K/218K; 6 degrees lower or 2 degrees warmer than Black body but Mars albedo is 0.16. Suppose that relationship was linear (it probably isn’t), then the basic temp of a 16% reflecting body could be (273-217)*0.16= 9 degrees lower, hence 208K. So, if that’s to be correct, then the greenhouse gas effect on Mars is 2K or 10K degrees. But I’m sure that this linear relationship that I assumed is wrong. Who can help? Now, 95% of the 7 millibar atmosphere is CO2, let's say: 7 millibar CO2. Earths atmosphere contains 380 ppmv CO2 (0.38 pptv) in a one bar atmosphere, this is equivalent to 0.38 millibar. So, You’d need a little more than 4 times doubling (0.38 -> 0.76 -> 1.52 -> 3.04 -> 6.08) to get to the Mars CO2 concentration. So Mars greenhouse effect of CO2 is over 4 times as strong as on Earth. But the greenhouse effect appears to be only 2K or 10K degrees, hence Earths greenhouse effect in total for CO2 should be one fourth of that: 0,5K or 2,5K? But then again, is there greenhouse effect on Mars? http://www.deccanherald.com/deccanherald/feb282005/snt2.asp Conclusion. There is no chapter in the Third Assessment Report of the IPCC about greenhouse effect of CO2 on Mars, to validate Earth greenhouse effect because the greenhouse effect on Mars is negliglible, despite the strong CO2 concentration. So, one more example of the negative scientific value of the IPCC Third Assessment Report.