Parting company with McKibben and, maybe, Hansen

What is the safe upper limit for atmospheric CO2? 24

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.

So I, like the Center for American Progress and the world's top climate scientists, now believe 450 ppm is the upper bound. That said, I have spent two decades managing, analyzing, researching, and writing about climate solutions and can state with some confidence that:

  1. Staying below 450 ppm is technologically doable, but would be the greatest achievement in the history of the human race, by far. It would require a global effort sustained for decades, comparable to what the U.S. did for just the few years of World War II (the biggest obstacle is not technological, but political -- conservatives currently would never let progressives and moderates pursue such a strategy).
  2. If 350 ppm is needed (and I'm not at all sure it is) then the deniers and delayers have won, since such a target is hopeless.

In 2008, I will devote a fair amount of ink bits to laying out the solution (there really is only one), but to understand why 450 is so hard, and 350 all but inconceivable, let's look at the odd way McKibben describes the solution:

And we're already past 350. Does that mean we're doomed? Not quite. Not any more than your doctor telling you that your cholesterol is way too high means the game is over. Much like the way your body will thin its blood if you give up cheese fries, so the Earth naturally gets rid of some of its CO2each year. We just need to stop putting more in and, over time, the number will fall, perhaps fast enough to avert the worst damage.

Not a great analogy. Yes, CO2 concentrations will probably start dropping once we cut emissions 80 percent from current levels. But you can change your entire diet -- cut cholestorol intake or carbohydrates 80 percent or more -- tomorrow. Humanity cannot, however, cut its hydrocarbon diet 80 percent tomorrow or even, realistically, in 10 years. That would require replacing the world's entire energy infrastructure -- power plants, cars, planes, factories, fueling infrastructure, large parts of homes and commercial buildings -- while simultaneously deploying a hydrocarbon-free energy system in the rapidly-growing developing world.

McKibben certainly understands some of the difficulty:

That "just," of course, hides the biggest political and economic task we've ever faced: weaning ourselves from coal, gas and oil. The difference between 550 and 350 is that the weaning has to happen now, and everywhere. No more passing the buck. The gentle measures bandied about at Bali, themselves way too much for the Bush administration, don't come close. Hansen called for an immediate ban on new coal-fired power plants that don't capture carbon, the phaseout of old coal-fired generators, and a tax on carbon high enough to make sure that we leave tar sands and oil shale in the ground. To use the medical analogy, we're not talking statins to drop your cholesterol; we're talking huge changes in every aspect of your daily life.

A better analogy might be stomach stapling, but even that doesn't do justice to what we would need to do to get to 350. Hansen's three proposals are a drop in the bucket. Dealing with electricity is trivial compared to dealing with transportation.

Suppose we could get global carbon emissions to peak in 2020 at 10 billion tons, level off for a few years, and then decline 3 percent per year afterwards. No easy feat since emissions are currently at 8 billion and rising over 3 percent per year. China and India, for instance, would have to agree to a hard emissions cap in 2020. Rich countries would need to start slashing emissions immediately. CO2 concentrations in 2020 would be about 410 ppm (and rising over 2 ppm a year).

Around 2050, we'd be at 5 billion tons and very likely over 450 ppm, rising over 1 ppm a year. But remember, we need to average 5 billion tons a year for the entire century just to stabilize at 450 ppm (according to the IPCC -- and that is probably a best-case scenario)!

So the scenario I laid out won't get us to below 450 (I have a long discussion in the book about why beating 500 ppm is so hard if we try to do it the traditional (i.e., slow) way). That's why I say 450 needs a World War II-scale effort starting in the next decade. I think 350 ppm is simply beyond serious practical and political consideration. You might as well tell people we need to develop a time machine to go back 20 years and warn the world that we need to start cutting emissions then ... then again, who would listen.? (And whom would we send back, anyway? That's an interesting parlor game all by itself.) McKibben ends:

But at least we're homing in on the right number. Three hundred and fifty is the number every person needs to know.

I part company with him here. I haven't talked to Hansen yet and I'll reserve further judgment until I see a paper or PPT by him.

Since beating 450 ppm is doable and certainly necessary, that's where I draw the line. One advantage of pursuing 450 is that if we do get some sort of unexpected breakthrough -- a cheap and practical way to draw CO2 out of the air (that doesn't use a lot of land, water, or energy) and stick it someplace permanent -- then we would have a system in place to deploy it fast enough to perhaps get to below 400 ppm. And even if turns out 450 doesn't avert catastrophe, it will surely slow down the impacts enough to make adaptation more viable.

So I'm sticking with 450. Implausible? Yes. Impossible? No. Less costly than inaction? By far.

Joseph Romm is the editor of Climate Progress and a senior fellow at the Center for American Progress.

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  1. Jon Rynn's avatar

    Jon Rynn Posted 10:47 am
    31 Dec 2007

    A World War II type effort......was the subject of a post of mine, the gist (grist?) being that the Federal government just about took over the entire economy during WWII.  In fact, some scholars have claimed that the Feds' control of the economy was greater than the Soviets, mostly because the population saw the effort as legitimate and enthusiastically pitched in.  I think a good place to start is talking in the range of governments at all levels spending a trillion dollars per year, if you want to go the WWII-effort-route, but I don't know if that's what you mean, Joe, or what most people mean when they use that term.

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  2. GRLCowan's avatar

    GRLCowan Posted 1:31 pm
    31 Dec 2007

    Not unexpectedif we do get some sort of unexpected breakthrough -- a cheap and practical way to draw CO2 out of the air (that doesn't use a lot of land, water, or energy) and stick it someplace permanent --
    Already seen happening, as I've said before.
    How shall the car gain nuclear cachet?

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  3. Anna Haynes's avatar

    Anna Haynes Posted 3:02 pm
    31 Dec 2007

    Looming environmental disaster,time travel to warn> "You might as well tell people we need to develop a time machine to go back 20 years and warn the world that we need to start cutting emissions then.... And whom would we send back, anyway?"
    Tachyons? Gregory Benford seems to have gotten the rest right...

    (Although he didn't predict the denial industry, IIRC.  If he had, the book wouldn't have had an upbeat ending.)

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  4. Anna Haynes's avatar

    Anna Haynes Posted 3:05 pm
    31 Dec 2007

    a better linkTimescape on Wikipedia

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  5. Earth Shaman Posted 3:59 pm
    31 Dec 2007

    Rev, Revv, RevvvOh Mr. Romm,here you go again ,claiming terrible disaster if the PPM goes above a certain level,my ,my, I say even some of the accepted science peerage have stated that the ice core evidence has shown vey high carbon ratio evidence and you still fail to stop and smell my beautiful roses and those periods didnt burn the carbohydrates to form the carbons at all or did they? Methinks you will not task me back at all because you know you are caught and caught big time and your ego just will not let you regroup.Every since you took my taskings evidence off your blog without so much as a query, I knew I had you fully in hand and would soon spank you and spank you in public for your impertinence.Try Maalox sir,as you will only get twisted more and more as time goes forth. Ta Ta.

    Earth Shaman

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  6. amazingdrx Posted 4:00 pm
    31 Dec 2007

    The endGreat topic Anna.
    Will linear mechanistic culture end when the first signals from the future are sent back through the tachyon accelerator?
    Think about it.  Once the future opens up, cause and effect linear perception and everything that depends upon it evaporates.  Stock markets, banks, governments.  
    2012 is the year of change in the mayan calendar.  Is this the cause?  A tachyon digital stream sent back to the present from the future.  with the information that wrecks it all.  

    http://amazngdrx.blogharbor.com/blog

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  7. Earth Shaman Posted 5:12 pm
    31 Dec 2007

    The EndOh boy Dr, X, might want to slow down on the caffeine,but your comment on the Mayan 2012 calendar prompted me to remind you that the 1050 anomaly is what the mayans were tasking to caledarize, it is the time of the great flood when the remnants of a system explosion re-visit us and beat us up with weather. And Tachyons,ah yes spin energy ,a different but valid process.But certainly not such futuristic digital streaming as you would dream aloud,but you may have fun in the spin if you wish.Tachyon accelerator ,NO,Dr.X spin,yes. Try some valerian root for sleeplessness,you might need a rest from the shunt or the spin man in your nose. Process....

    Earth Shaman

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  8. LGT Posted 5:35 pm
    31 Dec 2007

    Flap your wings to save the world"2012 is the year of change in the Mayan calendar."
    What coincidence! :)
    According to at least two dynamic models the worst case scenario could unfold by as early as 2012, when...
    http://edro.wordpress.com/butterfly-effect/
    Future, in its fullest definition, is no longer an option, at least AFA humanity is concerned. At the current rate and mix of events, future is an ever-shrinking apparition of what "future" could have been!
    CO2PPM
    Here's a short, but interesting discussion about the CO2 concentration in  the atmosphere. In December 2006, my colleague briefly commented on "The Stern report, Stern Review on the Economics of Climate Change"

    http://groups.yahoo.com/group/naspir/message/2379
    The biographer of Noam Chomsky, of all people (!), replied:

    http://groups.yahoo.com/group/naspir/message/2380

    And...

    http://groups.yahoo.com/group/naspir/message/2381

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  9. Steve Bloom Posted 6:32 pm
    31 Dec 2007

    450 ppm max., then back to 350 ppm ASAPJoe, given the apparent lack of loud shrieking following Hansen's AGU presentation, I can only assume he was talking about the need to drop back to 350 ppm as soon as possible; i.e., that we can probably survive an excursion to 450 ppm without extreme damage, but will need to keep that as brief as possible.  Given that 450 PPM likely is incompatible with significant amounts of permanent ice, is there a reasonable alternative view?
    There's another aspect to this:  We probably won't reach the 450 ppm limit for another 20 years or so, and arguably that results in the problem being viewed as far less urgent than it actually is.  The evidence seems to be that most people -- even very intelligent ones -- have a conceptual block when it comes to this sort of problem.  Please have a look at this key paper if you haven't already:
    "Understanding Public Complacency About Climate Change:

    Adults' mental models of climate change violate conservation of matter
    "Public attitudes about climate change reveal a contradiction. Surveys show most Americans believe climate change poses serious risks but also that reductions in greenhouse gas (GHG) emissions sufficient to stabilize atmospheric GHG concentrations or net radiative forcing can be deferred until there is greater evidence that climate change is harmful. US policymakers likewise argue it is prudent to wait and see whether climate change will cause substantial economic harm before undertaking policies to reduce emissions. Such wait-and-see policies erroneously presume climate change can be reversed quickly should harm become evident, underestimating substantial delays in the climate's response to anthropogenic forcing. We report experiments with highly educated adults-graduate students at MIT-showing widespread misunderstanding of the fundamental stock and flow relationships, including mass balance principles, that lead to long response delays. GHG emissions are now about twice the rate of GHG removal from the atmosphere. GHG concentrations will therefore continue to rise even if emissions fall, stabilizing only when emissions equal removal. In contrast, results show most subjects believe atmospheric GHG concentrations can be stabilized while emissions into the atmosphere continuously exceed the removal of GHGs from it. These beliefs-analogous to arguing a bathtub filled faster than it drains will never overflow-support wait-and-see policies but violate conservation of matter. Low public support for mitigation policies may be based more on misconceptions of climate dynamics than high discount rates or uncertainty about the risks of harmful climate change."

       

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  10. amazingdrx Posted 1:41 am
    01 Jan 2008

    2012I couldn't find the specific article about the tachyon accelerator time device.  Who can censor google?  Only Cheney, his residence is the only spot on spaceship earth not shown by google earth.  
    No conspiracy necessary (mwahahahaha..hehey)
    Anyway, how this is supposed to work is that laser beams projecting in such a way to produce a vortex accelerate a tachyon stream (carrying internet signals, on/off digitally, just as electrons are carrying this information on the regular internet) past the speed of light.  That sends the tachyon stream back in time, upon emerging from the other end of the vortex.
    A scientist gets this device working (in say 2012) and starts receiving information from the future (stock prices, commodity prices, lottery numbers, details of future events) sent by himself in the future, back to himself in the present.
    Being a mad scientist who wants to rule the world, he first wins the lottery, then starts to use his future information to take over markets, corporations, governments.  Of course he is soon found out and the CIA starts manipulating everything on a massive, secret scale.  Once news leaks, no one's pension, paycheck, or currency for that matter is safe.  
    It all becomes meaningless, everything based on linear time cause/effect thinking.  The shock to the whole of linear thinking humanity renders it inoperable, only the Zen survive.  Those who don't depend on bottomline thinking.
    Go with the flow and survive.
    Hehey, it makes a great sci-fi plot anyway.

    http://amazngdrx.blogharbor.com/blog

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  11. amazingdrx Posted 1:51 am
    01 Jan 2008

    Ancient RomeWith the destruction of aqueducts Rome could only support a few thousand people, millions just left.  The same with mysterious dissappearances of ancient mezoamerican city populations?  They vanished overnight according to archeaological discoveries.
    With the end of money, the same would happen to modern cities.  Mass migration back to rural life, with many dying from conflict, privation, and disease in the process.  
    Information from the future, the end of civilization as we know it?

    http://amazngdrx.blogharbor.com/blog

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  12. enki Posted 1:51 am
    01 Jan 2008

    RE: Rev, Revv, RevvvShaman?
    At any rate, yes there were very long periods in the Earth's history when there were much higher levels of CO2 in the atmosphere. Assuming that, during those periods the Earth's atmospheric density was the same as it is today then some other gas would have had to have been displaced by that CO2. The most likely candidate would be oxygen since oxygen levels are falling in our atmosphere today due to CO2 displacement.
    One other interesting thing to factor into your argument would be that, in all those periods of the planet's history when CO2 levels were very high, there were no human beings on the planet. In fact we humans are a relatively recent addition to the biosphere and evolved in our present form with essentially the atmosphere that we have today.

    Mike Johnston

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  13. LegumeSam Posted 2:30 am
    01 Jan 2008

    CO2 was higher hundreds of millions of years agobut also the Sun wasn't as bright then as it is today.  The luminosity of a mature star increases as it gets older, up to the point at which it becomes a white dwarf...

    http://www.dailykos.com/User/Cassiodorus

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  14. Jon Rynn's avatar

    Jon Rynn Posted 2:44 am
    01 Jan 2008

    Thanks Joe, some quotes from your book...Hell and High Water (p.234-236) (by the way, makes a great gift):...if we wanted to avoid climate catastrophe while avoiding economic collapse, we would have no choice but to scrap most of this polluting capital long before the end of its natural lilfe, while replacing it with clean, efficient capital at a rapid rate.
    This national (and global) reindustrialization effort would be on the scale of what we did during World War II, except it would laswt far linger...
    The scale of the war effort was astonishing...[quoting Teller speaking to Bohr] "You see, I told you it couldn't be done without turning the whole country into a factory."
    Such desperate and undesirable national actions are a long, long way from mandated controls on carbon dioxide emissions...The ultimate irony would be if conservative disdain for straightforward government-led solutions today forced the country into far more intrusive and onerous government solutions tomorrow.


    Exactly!

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  15. amazingdrx Posted 4:04 am
    01 Jan 2008

    Real capitalismYep, it would be far better if subsidies were shifted to new energy policy now.  Impelling real competitive capitalsim to revive the economy right now when it is needed.
    Remember the jeep, government directed design and production that spawned a decades long very successful, profitable car line.
    The same could happen for plugin hybrid design.
    Floating wind/wave generators are analogous to the Liberty ships.   Assembled in ship yard dry docks and towed out to sea and anchored.

    http://amazngdrx.blogharbor.com/blog

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  16. LegumeSam Posted 5:34 am
    01 Jan 2008

    Real capitalism is on its way outthat's why "real capitalism" became the imaginary sort that runs the world through "finance capital" today: the demand for growth has been outstripping the supply for thirty years, now...
    Real capitalism will eventually damage its ecosystem substrate through what the economists call "economic growth," beyond repair.  From Paul Prew's "21st century world ecosystem":
    The question to be asked, really, is whether we proceed with capitalism until we reach an ecological bifurcation point that leaves the habitability of the earth in question for the vast majority of the population, or we reach a social bifurcation point that leads us to a social system of production that is dissipative, nonetheless, but does not threaten the flowing balance of nature. We must develop a metabolic interaction with our natural environment that is based in a logic of production consistent with renewable sources of energy and does not significantly add to the volatility of variables leading to an ecological crisis.



    http://www.dailykos.com/User/Cassiodorus

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  17. Jon Rynn's avatar

    Jon Rynn Posted 7:31 am
    01 Jan 2008

    LegumeSam --So when are you going to write a book that explains in clear English all of those interesting authors you keep bringing up that I can't understand what they're talking about? y'know?

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  18. LegumeSam Posted 7:47 am
    01 Jan 2008

    Jon --Since I'm not one of the "contributors" here (although I certainly could be such a thing, given my abilities as a researcher/ writer), I don't write here often.  But I do publish "diaries" on various subjects at DailyKos.com...  

    http://www.dailykos.com/User/Cassiodorus

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  19. picassotrigger Posted 12:14 pm
    01 Jan 2008

    It may be impossible, but Hansen is probably rightI'm not a climate expert, but I think Hansen is probably right in suggesting 350 ppm as the upper target for atmospheric CO2.
    If the arctic polar ice cap has been receding and thinning for decades, and if the Greenland ice sheet is melting today--at atmospheric CO2 levels below 380 ppm--what exactly will a stabilization at 450 ppm accomplish?
    Perhaps it will save the antarctic ice sheet, and perhaps not.
    I would argue that nothing focuses the mind like an impossible goal. Whether or not you actually attain that goal is immaterial.

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  20. Delay And Deny's avatar

    Delay And Deny Posted 3:34 pm
    01 Jan 2008

    Global Deluders Go Off The Scale!

    How about (c) -- CO2 doesn't matter at all.

    My Log

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  21. Kit Stolz's avatar

    Kit Stolz Posted 2:31 am
    02 Jan 2008

    tipping points vs. points of no returnDespite my respect for the talented Mr. McKibben, his piece seems to me to confuse the point that Hansen made at the AGU. In response to comments from within the scientific community, Hansen reframed the concept of tipping points to make clear that when we as a species pushed the levels of atmospheric CO2 past 300-350 ppm (depending on the category; ice sheets, shifting of climactic zones, etc.) we committed the planet to long-term changes. He then went on to make clear that we are approaching points of no return, in which those changes become irreversible and (most likely) ruinous, as climactic feedbacks accelerate, and overwhelm our attempts to stabilize the biosphere.
    Why McKibben obscured this point I do not understand. Hansen's distinction seems very useful, and plenty easy to follow, both scientifically and in English. I blogged about it here on Grist earlier, but for another longer version take a look at a piece from a National Geographic reporter at the same press conference, who makes the same point with some extra quotes.
    http://news.nationalgeographic.com/news/2007/12/071214-ti ...

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  22. LegumeSam Posted 2:41 am
    02 Jan 2008

    A trip to Venus!CO2 doesn't matter at all.
    Perhaps Exxon/Mobil can fund the next Venus expedition for those who believe that 90 atmospheres of CO2 won't matter at all...

    http://www.dailykos.com/User/Cassiodorus

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  23. amazingdrx Posted 2:52 am
    02 Jan 2008

    Corporate feudalismI believe you are talking about corporate feudalsim Sam.  
    I make the distinction between corporate feudalsim, ie. monopoly capitalsim (not capitalism at all) in which corporations control markets and government policy....  and real competitive capitalism, the type still practised by many small and medium sized businesses all over the planet.
    Real competition spurs innovation.  It has real risk and reward for capital invested.  
    That could pull us out of this downward spiral, environmental and financial.  But monopolies control goverment policy, which used to reign in the tendency of huge conglomerates to destroy real competitive capitalsim.  As Walmart, for instance, destroys local businesses, retailers and manufacturing.
    Imagine local small businesses assembling and installing solar and wind and biogas equipment in every local community.  And converting used cars to plugin hybrids.  now that would revive our economy.  Instead of all that local money going to big oil and coal and gas corps, it would go to local businesses.
    This is why the corporatistas passed a bill through congress to allow the halliburtons to gobble up local utility companies.  To monopolize the grid, in case it becomes renewable, and to prevent that renewable distributed grid from being built for as long as possible..

    http://amazngdrx.blogharbor.com/blog

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