Can someone explain % vs. Quantity for Mars Atmospheric CO2?

Question

We've been seeing a lot of posts and questions from people that don't seem to understand the difference between percentages and quantity. They seem to think that because Mars has a high % of CO2 in it's atmosphere it should be hot, if greenhouse gas theory of warming were real.

I'm looking for a concise, easily understandable (for the math impaired around here) explanation of why Mars atmosphere is high in CO2 yet Mars isn't hot. I know there are many detailed explanations and analysis of Mars atmosphere, but I think a 3 - 4 sentence paragraph might be better to help these individuals understand. 10 points to the best explanation.

Answer 1

A wool sweater keeps you warm, but wearing twelve is going to keep you alot warmer than wearing one. Quantity matters.

Answer 2

For starters, the main reasons Mars is colder than Earth is that it's further from the Sun and contains almost no water vapor - a strong greenhouse feedback.

http://www.mit.edu/people/goodmanj/terra...

To answer your question, Mars' atmosphere is about 95% CO2 (as opposed to 0.038% on Earth), but the percentage doesn't matter.  It's the total amount of CO2 that matters.

Mars' atmosphere is about 1.5% as dense as Earth's.  

http://www.imagineeringezine.com/e-zine/...

Combine that with a CO2 concentration 2,500 times greater, and you get

2500*0.015 = 37 times more CO2 in Mars' atmosphere as Earth's.

However, the fact that it's 50% further from the Sun and doesn't have the large water vapor greenhouse feedback as compared to the Earth makes it much colder.

Answer 3

The reason is simply because Mars has a smaller atmosphere than Earth does. If Mars has an atmosphere made up of 10 units, and 5 of the units are CO2, then Mars has an atmosphere of 50% CO2. If 10 units of Earth's atmosphere are made up of CO2, but Earth has 100 atmospheric units, then only 10% of Earth's atmosphere is CO2. So Earth actually has a higher *quantity* of CO2 than Mars does, but a lower percentage.

That explanation may be too simple (Mars is mostly colder than Earth because it's further from the sun and has a thinner, shallower atmosphere than Earth), but it should convey the idea of different ratios well enough. And hey, at only 4 sentences, it's a real bargain!

Answer 4

We may want to start with distance from the sun.

Mars has been thought to be warming like earth suggesting that our warming is also caused by the one thing we have in common...the sun. Other planets are also experiencing warming trends. More study will need to be done, but when it looks like a warming planet, and acts like a warming planet, it's probably the sun.

Answer 5

Dana is exactly correct - The Sun is responsible for a planets warmth.  The amount of CO2 makes little difference.