What do you think is the business-as-usual limit for CO2 concentrations?

Okay well let's assume that not only has nobody suggested that increasing CO2 causes global warming and ocean acidification, but nobody ever figures it out, either. Under a business as usual scenario, we're looking at in the ballpark of 1000 ppm by 2100 (yeah that's right, I used 2100 as a reference point. So sue me!).

http://climateprogress.org/2008/06/19/nature-publi...

However, I think in this scenario, catastrophic climate change is triggered before the year 2100, because that corresponds to more than 5°C warming. From what I've read, we're looking at several major feedbacks triggered around 3°C.

But even at that point, say around 700-800 ppm, there would be a lot of energy use in response to climate change, like desalination of water, increased cooling, increased transportation, etc. But eventually, large numbers of people would die off, and CO2 emissions would decrease in response. So somewhere around 1,000 ppm is probably plausible in this scenario, maybe a bit higher.

Then the question is will fossil fuel supplies and use allow this scenario to happen. Peak oil would eventually require a movement to another fuel for transportation, but we still have plenty of coal. In fact, coal use would probably increase to offset the decrease in oil use. Although recent studies have concluded that we don't have nearly as much coal reserves as we previously thought.

http://www.energybulletin.net/node/29919

Nevertheless, I think we have enough to get us to 1,000 ppm CO2 (especially considering feedbacks). Since there wouldn't be a price on carbon emissions, coal would remain the cheapest source of energy (at least until its peak production were reached), so I don't think fossil fuel availability would be enough of a limiting factor. Nor would technology, because without concerns about climate change, there wouldn't be sufficient push to develop cleaner technologies.

I think the upper limit will be reached as we "run out" of fossil fuels. We won't ever actually run out but production will seriously decline and the price will go up. David Rutledge of Caltech has estimated that this will keep us under even the strictest of Kyoto Protocols. If that's true (and Rutledge is no dummy) then it's good news for climate, but probably bad news for the economy, unless we can adapt quickly. He comes up with a peak value of 443 ppmv in 2065. After that CO2 levels slowly decline. If this is true then it should make deniers happy, because there would be little point in capping CO2 emissions.

You can see his presentation at his website http://rutledge.caltech.edu/

Not withstanding AGW from CO2 is complete junk science, changing the atmosphere isn't a good thing and may have predictable and unforeseen consequences.

If you're sitting in a sealed air conditioned building, you're breathing air around 1000 ppm CO2. That's the threshold that engineers use for designing ventilation systems as it's below what can be detected by humans. If the outside atmosphere ever gets to 600ppm, it will start to have negative consequences and more fresh air will be required to ventilate the built environment to maintain comfort levels. By this time CO2 will be a genuine pollutant. It would be prudent to take action to reduce CO2 by this time. This would probably be the limit it would be allowed to reach.

Ocean acidification is not going to amount to much. You could more the ph scale of water by a 0.1 of a unit by doubling atmospheric CO2.

CO2 levels may climb from around 350 ppm to maybe 700 ppm at most. Remember that there is a cycle that takes in CO2 and changes it to O2. As long as there are any plants left, CO2 levels will not sky rocket out of control. The upper limit will be reached as the Earth creates a new equilibrium. That is another key flaw in the whole CO2 is driving climate change. As nature and man puts CO2 into the air, nature removes a certain amount. Also, since most scientists use words such as high degree of certainty when talking about climate change this means that they don't have fully proven evidence to back up their science. It is like a drug maker saying that they have a high degree of certainty that no one will die from their new drug because a small sample of people didn't die.

Well.....

"Just because you didn't KNOW your about to get a flat tire, doesn't prevent you from running over that nail...."

co2 concentrations will get as high as the global oceanic circulatory system will allow, bearing in mind that co2 raises global temperatures [wether we noticed it or not, given this questions scenario]

to the point that overall global temperature increase allows for a sudden input of cold, dense, FRESHWATER into the oceanic conveyor, which in turn causes a massive global weather destabilization, which in turn causes irrevocable climate realignment [ie. Ice Age] which is just ONE of many of mother earths tricks to cleanse herself....

We could hypothesize about PPM concentrations till were all bored n out of citations, but humans have never been around to observe while reaching a tipping point that occured unnaturally such as whats happening now...

I think serious SERIOUS events will transpire long before we come to a feasible "end" of fosssil fuels....

Won't happen.

Plants eat CO2. We might have plants growing at record rates, but beyond that we would see very little effect.

It's a nonsensical theory anyway. Human beings create a trivial portion of atmospheric CO2.

Ahh, good question!

I think you would find that the sky is the limit. These people don't want any limits on their earning or polluting capacity.

Unless you want to become a Vegan and help reduce the methane then you should not complain about CO2