At what atmosphere concentration would you like to see CO2 stabilized? 450ppm? 550ppm? 1000ppm? What ever...?

Question

Is it possible to stabilize CO2 at this concentration? What will be the likely effects on climate?

When answering his question, please keep in mind that the atmospheric concentration of CO2 HAS increased by about 35% since industrialization. The atmospheric CO2 is currently 384ppm http://answers.yahoo.com/question/index;_ylt=AtQojHGntugBYK4Azrrgb0_ty6IX;_ylv=3?qid=20080306133203AAyEY2w&show=7#profile-info-ExWAr7OQaa

Answer 1

We can not entirely stabilize CO2 levels. If you trust the work of scientists using ice core sampling you see that CO2 levels have varied very significantly without human intervention over thousands of years.

We may be able to avoid adding to atmospheric concentrations, but as temperature rises, we can not predict that CO2 sinks will continue to function as they do at lower temperatures, and the seas may give up further quantities of CO2, plus large amounts of methane in the North.

Hence, no matter what level I would like to stabilize at, I can not say we can do it.

Answer 2

I would be happy with 400 ppm.

Answer 3

Idealy we should not be changing the atmosphere at all (or destroying any natural habitat in any way).  Since we just can't build any sort of civilisation without destroying a bit of natural habitat, we will just have to accept that the natural environment will be changed in some ways due to human development.

I think the decision of what level of CO2 we can live with should be based on solid science, not faith in AGW.

Answer 4

I agree with James Hansen that we need to shoot for 350ppm.  Even that level commits us to some unknown quantity of warming for many decades to come.  We need to stop this experiement in its tracks.

Stop growth now and gradually scale back through conservation and technological replacement, and the overshoot will gradually be handled by forests and oceans.

Here's an interesting discussion of the topic:

http://gristmill.grist.org/story/2007/12...

The nation's top climate scientist, NASA's James Hansen, apparently now believes "the safe upper limit for atmospheric CO2 is no more than 350 ppm," according to an op-ed by the great environmental writer Bill McKibben. Yet while preindustrial levels were 280, we're now already at more than 380 and rising 2 ppm a year!

Like many people, in the 1990s I believed 550 was the target needed to avoid climate catastrophe -- but now it's clear that:

1. 550 ppm would lead to the greatest disaster ever experienced by human civilization -- returning us to temperatures last seen when sea levels were some 80 feet higher. This is especially true because ...

2. long before we hit 550, major carbon cycle feedbacks -- the loss of carbon from the tundra and the Amazon, the saturation of the ocean sink (already beginning) would almost certainly kick into high gear, inevitably pushing us to much, much higher CO2 levels (see here, here, and my book).

Exactly when those feedbacks seriously kick in is the rub. No one knows for sure, but based on my review of the literature and interviews of leading climate scientists, somewhere between 400 and 500 ppm seems most likely. It could be lower, but it probably couldn't be much higher.

Answer 5

James Hansen has suggested that we should eventually drop the CO2 concentration down to 350 ppm.  

"If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm."

http://www.columbia.edu/~jeh1/2008/Targe...

He concludes that 450 ppm is "far into the dangerous zone".

http://www.columbia.edu/~jeh1/mailings/2...

From the various sources I've read, 450 ppm appears to be a realistic target for the maximum atmospheric CO2 concentration.  Once we can stabilize the concentration at that level, we can attempt to decrease it to 350 ppm if necessary, as suggested by Hansen.