Quote:
Originally Posted by Kakero
Just wondering, if I chop down every trees on the planet and cemented every inch of the ground with concrete. Will my action makes the earth warm up?
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You know you actually touch on a pretty good question, and a pretty tough one to answer. There are a lot of things you can speculate with that question, but lets focus on simply what happens to CO2 if you scenario became a reality (that would frighten me!)
The first place we should go to is the Carbon Cycle; how organic (CO2,fossil fuels,etc) and inorganic carbon (rock and marine shells) is exhanged with various earth systems (terrestial ecosystems, ocean ecosystems, the atmosphere, etc).
By far the largest reserve of carbon is found in the ocean. The ballpark numbers changes from source to source, but usually ~39000Gt (gigatonnes!) of carbon is in the ocean. That's a huge number that I don't think anyone can mentally wrap their brain around. Soils/Vegetation (land stuff) have about 2500Gt, the atmosphere has ~760Gt.
CO2 is the greenhouse gas of focus because of it's ability to trap heat, so lets focus on that. Since CO2 is an organic form of carbon, we need to look mainly at organic processes that release and fix(trap/store) CO2. I mentioned it earlier with the plant statement, but the process that fixes carbon is photosynthesis, the process that releases carbon is respiration. Microbial activity can also fix carbon, but that gets rather technical.
All living cells undergo respiration; it is how they generate useful energy from sugar bonds. The main byproduct of respiration is CO2. Not all living cells undergo photosynthesis however, only plants do.
Now back to your question of removing all soil/vegetation and replacing it with concrete. With terrestial (land) ecosystems there are a handful of key interactions that allow for large transfers of CO2 in terms of release and fixation. Listing the big ones:
Plants: They draw CO2 from the atmosphere and fix it in their wood via photosynthesis.
Soils: There is a huge amount of microbial activity in soils which result in huge amounts of respiration (certain microbes do fix carbon, but by and large soils are a net source of CO2 release, not a sink). Soils are a huge contributor of CO2 to the atmosphere (excluding humans)
Humans: Obviously we release a huge amount of CO2 via burning fossil fuels.
So if you replace everything with concrete, you eliminate the plants and the soil transfers of CO2. The main players in the carbon cycle at this point would be humans and the ocean, and humans would probably dominate and dramatically alter the cycle. We'd also have a lot bigger problems in the world if everything was concrete (mainly where would we get our food?)
What would happen is purely speculation, obviously there would be a lot more release of carbon than fixation of carbon. Interestingly enough, we don't know whether or not terrestial ecosystems are a source or sink of CO2; there are a lot of conflicting reports that can go either way.
So my somewhat educated guess would be that we would increase the levels of atmospheric CO2 by replacing all vegetation/soil with cement. Quantifying the rate of increase would be hugely important, but I would bet it would be something signficant. What would the result be if there was a lot more CO2 in the air in terms of temperature? Well some some 200 million years ago, the atmospheric CO2 levels were much higher than they are today, 1000ppm+ (for reference we are around 350ppm today). That is around the time of the dinosaurs, and the earth was a much warmer place back then than it is today. Is that due to the CO2 in the atmosphere? Yes! Is it due to other factors as well? Probably!
This is obviously a huge simplification of your question, as the very fact that the entire earth is concrete would probably lead to additional heating as well.