Is Mars' High CO2 Atmosphere a Good Model for Earth's Greenhouse Effect?

[Andre]

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

The effect of CO2 on temperature is the Arrhenius law. dE=[alpha]ln([CO2]/[CO2}orig), where alpha is 5.35 (Myhre et al.) http://www.grida.no/climate/ipcc_tar/wg1/222.htm

E is change in forcing

using the derivative of Stefan-Boltzmann:
dT/dE = 1/(4[sigma] T^3)

gets:
dT=[alpha]ln([CO2]/[CO2}orig)/(4[sigma] T^3)

This is the equation without all feedbacks.

Substituting a doubling CO2 level (unrealistic, according to Lomborg) and substituting T= 15 degrees C = 288.16K

dT=5.35*ln(2)/(4*5.6705E-08*(288.16^3))

or

dT=0.6833 centigrade for a doubling of CO2 !

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

Maximum Surface Temperature 310 K
Minimum Surface Temperature 150 K

(Thus median value: 230K)

Atmospheric Pressure 0.007 bars
Black Body Temperature 216.6 K
Carbon Dioxide CO2 95.32%

Median value is not necessarily the average value so let’s peek some more for an average temperature:

http://science.howstuffworks.com/terraforming1.htm

The average surface temperature on Mars is a frigid minus 81 degrees Fahrenheit (-62.77 degrees Celsius)

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.

 

[quantumcarl]

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.

Lets imagine we could have taken a reading of the Earth's atmosphere 3600 - 20,000 years after what is thought to have been the dinosarid extiction event 65 million years ago... (<>100 kilometer sized asteriod collides with Earth at the gulf of mexico). Not only would there be a great release of ejecta, crust and substrate because of this collision but also a lot of fires burning down forests around the world. Massive release of CO2, CO and so on.

I'm giving the timeframe of between 3600 to 20,000 years ago because it was inside this time period that Mars experienced a similar collision with a similarily large, greater than 100 kilometer, sized object. This collision was so massive that it took half the Martian crust off and created huge other features that I can't name right now.

Would the measurements of our atmosphere's CO2 content, 20,000 years after our entire planet was on fire, read "7 millibar CO2" as is indicated by readings taken on Mars?

 

[ravenprp]

Thank you for sharing your calculations and thoughts on the greenhouse effect on Mars. While it is true that Mars has a much higher concentration of CO2 in its atmosphere compared to Earth, the differences in atmospheric pressure, albedo, and other factors make it difficult to directly compare the greenhouse effect between the two planets. Additionally, as you mentioned, there is still much uncertainty and debate surrounding the exact impact of CO2 on Earth's climate. As scientists continue to study and gather data, it is important to look at other examples and cases, like Mars, to help validate assumptions and better understand the complex phenomenon of global warming.