Mars: Mars Atmospheric Pressure = 6.7 mb = 0.097 pounds/sq in
Mars atmospheric Density = 0.020 kg/m3 = 0.0012 pounds/cubic ft

Earth: Earth atmospheric pressure = 1014 mb = 14.7 pounds/sq in
Earth atmospheric density = 1.23 kg/m3 = 0.0768 pounds/cubic ft
From:
http://www.imagineeringezine.com/e-zine/mars-data.html

Mars' atmospheric pressure is less than 1/100th than Earth
Earth's atmospheric density is 61.5 times more dense.
Now in a cubic meter of Earth air there is .035% of it CO2 or per million parts there is 350 parts CO2. This means that in a cubic meter of Earth air the density of CO2 is .0004305 kg/m3. Which means there there is 46.4576 times CO2 in a cubic meter of Mars air as there is in Earth's air.
Actually this isn't precise because Mars air only has 95.32% Carbon Dioxide. But doubt that the .020 kg/m3 is exact enough to warrant figure trying to get very exact, so let's say to be generous it's 45 times more of the Greenhouse gas CO2 in Mars' atmosphere than Earth's*.

Now let's return to my model in my above post. I had figured what 10 times increase in CO2 would generously add to Global temperature, but I did not figure what a 45 times increase would be. Bringing it back:

"In Earth's atmosphere in Parts Per Billion: H2O: 20,000,000 ppb [a rough average]. CO2: 350,000 pbm. CH4: 1750 ppb. "

Times 350,000 by 45 gives 15,750,000 ppb of CO2, so:
Add all the Ppb together you get 35,751,750 ppb and divide this into 35 C you get 19.579 C due to H2O, 15.419 C due to CO2, and .002 due to CH4.
Interesting. Well over at Nine Planets, they say: "Mars' thin atmosphere produces a greenhouse effect but it is only enough to raise the surface temperature by 5 degrees (K)"
http://seds.lpl.arizona.edu/nineplanets/nineplanets/mars.html
I got 15.419 K, but I haven't allowed for Mars' greater distance and significantly less sun radiation which about .42 of Earth's giving 6.48 C.
I had thought the numbers would not have come close, but I was wrong. I wonder how they came up with their number?
Now this might seem like a waste of time, but it brings up some rather interesting things to me. Because if CO2 greenhouse affect is going to be reduced factor of .42 that also means the water and other greenhouse gases in the atmosphere would reduced by the same factor.

If you put Earth at Mars' orbit increased CO2 levels by 45 times, which would probably make the air pretty unbreathable, Earth would still be a deep freeze. Which seems to indicate that only way to terraform Mars so that somday a human could breathe the air, would be to increase the amount of Sunlight energy hitting Mars- such as using reflectors in orbit. [Not that was a fan of terraforming Mars].

*Some details about the amount of CO2 relative to altitude on Mars, but leave for another day.