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Please sir, can I have some more?
January 22, 2008 12:45 PM   Subscribe

How many tons of CO2 should I be allowed to emit each year?

So Al Gore has gone carbon neutral, but the idea that we're going to reach a carbon neutral civilisation in the next hundred years seems pretty laughable. So what I want to know is how much carbon each one of us can get away with emitting so that we manage to limbo under the level that pushes us over 350ppm, or whatever is considered the target these days; bearing in mind that

1. Poor people have a right to fuck the planet up too.
2. The world population hasn't stablised yet.

(As global emissions are going to have to decline gradually, the figure I'm looking for is really what I'll be allowed to emit in 2050 or some arbitrary date in the future.)

posted by greytape to Science & Nature (7 answers total) 3 users marked this as a favorite
At least make sure not to emit as much as Homem peido (YT)
posted by growabrain at 12:57 PM on January 22, 2008

US citizens emit 20 tons of CO2/yr on average. I've heard it bandied about that we need to reduce this figure by 70%; there are some people who have taken it on as a personal challenge to reduce their own footprint by 90%.

Actually, this page suggests that 90% reduction should be the target.
posted by adamrice at 1:35 PM on January 22, 2008

Carbon neutrality is a difficult notion to assess economically or monetarily because so much of tat economy is still function in a staged development mode. For example, my 4,000 mile flight from San Francisco to Washington, DC was offset for $19. However, I have no way of knowing how that money was used and how the offsetting would occur. The general idea is that companies are putting their money in carbon offset credits that offset their own industrial pollution and also selling on credits in a like-for-like exchange. There is for example, the Chicago Carbon Exchange, which seems to be a certifier of many non- and for-profit offsetting regimes. I surmise that these groups, like Ford Motor, AgraGate Carbon Credits, Collective Wellbeing LLC, and so forth are buying these credits with consumer-provided monies in hopes that the market will actually improve and other companies, facing a lack of first-use credits in the marketplace at lower prices will have to buy their credits at a higher rate from companies that got in early. So, you are essentially placing a bet that, in fact, pollution will go up and then collect revenue based on that prediction.

This might be true. The problem is that when you put anything in the listed securities marketplace, it will probably fluctuate with the course of the market. Witnessing current market turmoil, Chicago Carbon Exchange's credits, which seem to be a five year bond, have lost more than 50% of their value and are now trading at less than $2 a share, rather than the high of over $5 in the summer of 2006. The reason: the truth is that the amount of metric tons of carbon offset in 2007 by the members of the Chicago Carbon Exchange in 2007 totaled 4,961,600 tons. That is actually a decline from 2006 when 7,665,000 tons were offset. This certainly raises questions about the viability of the marketplace - considering that in the years 2004 to 2006 the Chicago Carbon Exchange managed to raise the amount of offsetting by more than a million tons each year.

I had a PR friend who claimed he's racked up more than 22,000 tons of carbon savings personally in 2007. But if that figure is to be believed and by the price estimates of CCX, he paid just under $50 to offset his entire annual total. That makes Gore's contribution seem equally meaningless given the present data.
posted by parmanparman at 1:56 PM on January 22, 2008

I'll take a stab at an approximation:

Here is a simple chart from the USGS showing the global carbon budget (scroll down). Note that the about 4 Gt (Gigatonnes) can be absorbed by the earth (land and ocean) per year above the normal emission/absorption of the non-anthropogenic carbon cycle. This article cites an a paper from 2003 which also claims 4 Gt. Assuming you want to distribute carbon emissions equally over the world's population of 6.6 billion people, that would be about 0.6 tonnes per person.

Unfortunately, it seems that as atmospheric carbon levels, emission rates, and global warming increases, global carbon absorption capacity decreases, so we would probably need to aim for a lower figure in the short term.

The UN predicts that the world population will reach about 9 billion in 2050 and not grow much further after that. Using that figure, we arrive at about 0.44 tonnes per person.

Note that these figures are for all carbon emissions, including deforestation, etc., not just the burning of fossil fuels. This also doesn't take into account the effect of other greenhouse gases.
posted by ssg at 2:14 PM on January 22, 2008

Here are some corrections for your numbers, all of which are off, I'm afraid. First of all, 350 is not a terribly realistic goal for stabilization. We've already eclipsed it, in fact-as of 2005, CO2 was at 379ppm, and is increasing at a rate of 1.9ppm per year (IPCC, 2007). Multiple stabilization scenarios have been examined, and there is some discussion I found helpful in Hoffert et al., 2002. One applicable quote from Hoffert et al. "Targets of cutting to 450ppm, and certainly 350ppm, could require Herculean effort. Even holding at 550ppm is a major challenge." I think this quote may be about a different paper that Hoffert et al discuss, actually. So...yeah. We're at 379ppm now, and if we're able to stabilize at 550pm by 2100 or so we'll actually have done a pretty respectable job of things.
posted by HighTechUnderpants at 4:02 PM on January 22, 2008

Have a look at "Contraction and Convergence", this basically sets out a scenario for what global emission reductions will have to look like over the next 100 years if CO2 concentrations are going to be held to 450ppm by 2010. (450 ppm is regarded as the upper limit of concentration which will correlate with no more than a 2 degrees centigrade increase in global temperatures.) IIRC, for the US I think this correlates with a need to reduce emissions by ~80% over time.

As HighTechUnderpants points out, even achieving 550ppm by 2100 would be impressive, so not much of an expectation that we will be able to do get to 450ppm.
posted by biffa at 1:43 AM on January 23, 2008

I think some have targeted 450ppm as a level at which we would avoid completely dicking over coral reef ecosystems, too. There are excellent reasons to aim for just probably isn't going to happen, unfortunately. Also, I am assuming biffa means 450 by 2100, not 2010.
posted by HighTechUnderpants at 12:37 PM on January 23, 2008

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