Cumulative carbon emissions: A new way to "frame" the climate challenge

ResearchBlogging.orgThis week's Nature includes a trio of climate features, book reviews, an essay, a pair of new papers, and and editorial highlighting how little wiggle room we have left if we want to avoid warming the planet 2 °C above pre-industrial levels. It's science journalism at its best. Sadly, it's up to us bloggers to lift as much as we can without incurring the wrath of the journal's intellectual property lawyer to spread the word. So here goes.

The most interesting of the features, in my opinion, covers the spreading meme that 450 parts per million isn't a low enough concentration of atmospheric carbon dioxide to keep us under that magical 2 degrees. For one thing, we're already up 0.7 and 0.8 degrees and comparable amount is almost certainly in the unavoidable pipeline due to the planet's thermal inertia.

The difference between 350 and 450 is not just one of degree. It's one of direction. A CO2 concentration of 450 p.p.m. awaits the world at some point in the future that might conceivably, though with difficulty, be averted. But 350 p.p.m. can be seen only in the rear-view mirror. [James] Hansen believes that CO2 levels already exceed those that would provide long-term safety, and the world needs not just to stop but to reverse course. Although his view is far from universal, a growing number of scientists agree that the CO2 challenge is even greater than had previously been thought.

Several recent studies, for example, indicate that it may be exceedingly difficult to cool the climate down from any eventual peak or plateau, no matter what CO2 concentration is chosen as a target by the international community. And by looking at the problem in a new sort of way -- by tallying the total amount of carbon injected into the atmosphere across human history -- two papers in this issue of Nature reveal how close the world has come to the danger point (pages 1158 and 1163). "It's tougher than people have appreciated. We have less room to manoeuvre," says Malte Meinshausen, an author of one of the papers and a senior researcher at the Potsdam Institute for Climate Impact Research in Germany.

Meinshausen's paper, and other related research and discussion, could prove revolutionary. That might be overstating it, but not if this new way of approaching, or "framing" the challenge of reducing greenhouse gases, helps produce viable policy. From the Nature story:

Meinshausen and his colleagues present results from a coupled climate-carbon cycle model that explores the effects of different emission pathways for CO2 and the other major greenhouse gases (page 1158). For the period 2000 to 2050, they find that the world would have to limit emissions of all greenhouse gases to the equivalent of 400 gigatonnes of carbon in order to stand a 75% chance of avoiding more than 2 °C of warming. Other greenhouse gases, such as methane and nitrous oxide, are expected to produce as much warming as 125 gigatonnes of carbon in the form of CO2 would; that means emissions of CO2 itself over the half-century have to add up to less than 275 gigatonnes of carbon. That's an extremely difficult target, admits Meinshausen, considering that emissions over the past nine years have used up almost a third of that allowance already. "Our remaining emission budget is so small," he says. "If we want to have a smooth landing and to decrease emissions in a smooth way, our options are essentially exhausted. We have to bend down our emissions by 2020."

And here's how Meinshausen et al. end their paper:

Given the substantial recent increase in fossil CO2 emissions (20% between 2000 and 2006), policies to reduce global emissions are needed urgently if the 'below 2 °C' target is to remain achievable.

Curiously, 2020 is eight years later than the deadline most frequently mentioned in these circles. Rajendra Pachauri told the New York Times that if we haven't begun to act by 2012, "that's too late." But given the declining likelihood that the U.S. Congress won't pass a climate bill of any kind this year, maybe we'd better hope that 2020 turns out to be a better guess.

Anyway, back to the Nature feature:

Although the results of the studies might seem too daunting, they do offer a few rays of hope. Andrew Weaver, a modeller at the University of Victoria in British Columbia, Canada, says that in the new studies, what matters is how much pollution goes into the sky, not when it gets emitted. "This allows you some flexibility," he says. From a political perspective, the idea of a cap on total emissions "is a lot easier to get your head around" than a concentration target or, say, a 20% reduction below 1990 emission levels. A cap is like a budget. Once you use it up, there's nothing left to spend.

Unfortunately, the world is behaving as though it expects to be able to arrange a large overdraft. And researchers can only come up with so many ways of presenting the gravity of the carbon problem to the rest of the world. "At some point, you begin to throw your hands up. It's very frustrating," says Weaver, who pulls a reference from an ancient global crisis. "Climate scientists," he says, "have begun to feel like a bunch of Noahs -- thousands of Noahs."

I think I've stretched the fair use clause far enough, so that will have to do. Are Meinshausen and Weaver right? Will shifting to a cumulative emissions approach make it any easier to do what needs to be done? I am skeptical.

The rest of the Nature package includes a (freely available) editorial that concludes "there is still time left to act, and there is hope to be found in human ingenuity..." But there's also a worst-case scenario that "explores what a world with 1,000 parts per million of CO2 in its atmosphere might look like" as imagined by Stephen Schneider. He writes that "A whole range of policies will be needed, with international cooperation, and they cannot wait for the outcome of the current political negotiations."

Consider that just about everyone who understands the problem agrees that a flat carbon tax is the best way to bring down carbon emissions and a cap-and-trade mechanism is seriously flawed. Yet Washington is pretty much committed to cap-and-trade. Or so the conventional wisdom goes. Can we expect our politicians to embrace this new way of thinking about emissions at this late stage? Would that slow things down even further, or would it spur action?

Sure would be nice if we had been at this juncture a bit earlier, say eight years ago....

Monastersky, R. (2009). Climate crunch: A burden beyond bearing Nature, 458 (7242), 1091-1094 DOI: 10.1038/4581091a

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If carbon dioxide is so powerful, why has CO2 been rising for the past several years but the temperatures haven't been rising with it? Why does CO2 increase after the planet warms?

By Enonymous (not verified) on 30 Apr 2009 #permalink

Enonymous, stop JAQing off.

1) No scientist claims CO2 is the only factor -- only inactivists strawmanning the scientific position say that. As you say, it's a small one that can be overwhelmed by other processes in the short run. However, a sustained light push can still have catastrophic effects in a complex system like climate due to feedback.

2) The ice core lag is easy to explain. By analogy, since heat can cause fire, your logic would dictate that fire cannot cause heat. On the flipside, increasing any GHG leads to an increase in temperature from basic physics (the magnitude of the feedbacks is the only thing uncertain about this). So, choosing between option 1 (physics holds, you're mistaken) and option 2 (you're brilliant where scientists aren't, and physics has been overturned), which is more rational?


James, the "conventional wisdom" that I've been hearing is that cap-and-trade's flaws stem from three things: Loopholes (i.e. offsets), allocations (permits given away) and speculation (buying carbon assets with intent to sell instead of reduce emissions). It's quite possible to design a system like this that patches all three holes AND still gain most of the benefits of a tax, such as revenue neutrality (most proponents of a carbon tax that I've spoken to prefer reducing income taxes by an amount equal to the carbon tax, or some similar method of buffering consumers from higher prices) and simplicity. In fact, there is such a bill before Congress right now. (It doesn't have the price certainty a tax would have, but it is a mere fraction of the size of Waxman-Markey, and is thus much, much easier to understand).

For the record, I prefer taxation to a system like Waxman-Markey, but would argue that a cap/dividend system, if done correctly, can easily outdo a tax.

From an economics standpoint, emissions trading is more efficient. The problem with an emissions tax is that misestimating the social cost of pollution leads to tax rates that either don't fully cover the social cost or are higher than necessary and thereby impose their own social costs. Emissions trading is theoretically equivalent to an optimal emissions tax.

The devil's in the details, of course. Aside from the potential for loopholes, there's the question of how emissions rights should be distributed when the market is first formed. There's also the issue of determining the appropriate scope of the market. Depending on the effects of a pollutant, a nationwide or global market may not be appropriate, or there may need to be additional restrictions on local concentrations within a market, especially for pollutants whose effects are a nonlinear function of concentration.

By Treppenwitz (not verified) on 30 Apr 2009 #permalink

The focus on CO2 is always on emissions.
I can't help but wonder if something about the conversion of CO2 to O2 is in play.
I wonder if that part of the cycle has some problem.

I don't pretend to know too much about it. It just makes me wonder.

The problem with cap-and-trade is that it only would work in a truly free market. Despite the rhetoric, no market is truly free. All markets are gamed.
I agree that, in an efficient market, emissions trading would be theoretically equivalent to an optimal emissions tax. As Treppenwitz mentioned, the devil is in the details. How to you assure that both parties to each transaction have total access to the same information? That is necessary for a free market, but it rarely happens.

"James Hansen's views are not universal", now there's an understatement. All computer models which predict catastrophic global warming incorporate unproven positive feedbacks between CO2 and water vapor. Almost no physical scientists outside the tight-knit modeling community predict such consequences and many question the whole premise of CO2 induced global warming. As more contrary evidence trickles out from scientists with enough balls to risk their careers by challenging the modelers, the modelers just become more and more hysterical in their predictions. Hansen is no longer - was he ever - an objective scientist; he is an ideologue who cannot and should not be trusted by thinking people. When a scientist becomes a political advocate, he loses credibility. Hansen would never have become head of Goddard without the backing of gore. He and the IPCC have turned science on it's head. This is Lysenkoism. It will not stand. Don't build your ark yet.


"He and the IPCC have turned science on it's head. This is Lysenkoism."

This is the greatest conspiracy of all time. It was started by Fourier and Arrhenius more than 100 years ago. They knew they could create opportunities for research grants more than 100 years into the future.

"It will not stand."

It has stood for more than 100 years. It will stand forever.

By Chris O'Neill (not verified) on 01 May 2009 #permalink


Loved how you clubbed Enonymous with your "science bat," then dusted off and donned your policy cap to engage with James in an oh-so-serious discussion of the various means of taxing carbon, wherein you whip out your econo-cap and assert that "It's quite possible to design a system [that includes mechanisms capable of] buffering consumers from higher prices..."

I would set up a false choice here, pitting you and your dubious sources of "conventional wisdom" against "basic economics" and "brilliant" economists, wherein you must opt between your having stumbled on a gotcha that invalidates both else elementary economics hold, but that would be unsolicitous of a clarification from a fascinating polymath such as yourself. It would also be rude.

Perhaps by "buffering from" you mean "allowing to subsist despite," or I've misread the "scientific position" and its ramifications for the consumer. Without price increases, how does the end user get the message? Or perhaps you don't really care if carbon is actually reduced as long as a top-down, technocrat-crafted "market" is whirring along free of speculators and profit motive. At least we can point and laugh at objectivists while we sweat in our huts.

Or maybe you think you can guilt China and India into giving up on that whole "crawling out of the 18th century" nonsense? The military's off the table, right? (You've got a lot of hats, BrianD, maybe one's Kevlar).

In my opinion, sufficient global carbon abatement to meet even Kyoto targets is a fantasy. We can shuffle our deck chairs all we like, but if Asia won't leave the buffet on the Lido deck and go back to stearage for a century, it's a useless enterprise.

I don't know much about the science, but I'm pretty sure we're going to test AGW theory in the lab. God help us, but we'll have our answer.

James, I'll gladly revise to survive moderation.

By Ursel Boggs (not verified) on 01 May 2009 #permalink

I retract, James. You don't moderate.


By Ursel Boggs (not verified) on 01 May 2009 #permalink

So Ursel Boggs's objections to cap-and-trade are the following:

1. The market will be set up by "technocrats" I don't like!
2. We must wait for China and India to act!
3. I am aware of all economics traditions.

-- bi