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Are Scientists Overestimating — or Underestimating — Climate Change, Part III

By Joe Romm  

"Are Scientists Overestimating — or Underestimating — Climate Change, Part III"


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I’ve argued that scientists are not overestimating climate change and in fact are underestimating it because they are omitting crucial amplifying feedbacks from their models. In this post, I’ll show how these omissions suggest the climate has a “point of no return” that severely constrains the safe level of human-generated emissions.

A major 2005 study (subs. req’d) led by NCAR climate researcher David Lawrence, found that virtually the entire top 11 feet of permafrost around the globe could disappear by the end of this century. Using the first “fully interactive climate system model” applied to study permafrost, the researchers found that if we somehow stabilize CO2 concentrations in the air at 550 ppm, permafrost would plummet from over 4 million square miles today to 1.5 million. If concentrations hit 690 ppm, permafrost would shrink to just 800,000 square miles.

While these projections were done with one of the world’s most sophisticated climate system models, the calculations do not include the feedback effect of the released carbon from the permafrost, which has locked in it more carbon than the atmosphere (and much of that is in the form of methane, a potent greenhouse gas).

That is to say, the CO2 concentrations in the model rise only as a result of direct emissions from humans, with no extra emissions counted from soils or tundra. Thus they are conservative numbers–or overestimates–of how much CO2 concentrations have to rise to trigger irreversible melting.

How do carbon cycle feedbacks constrain future safe levels of CO2 emissions? There’s really only one major climate model that can answer that crucial question.

The United Kingdom’s Hadley Centre for Climate Prediction and Research has one of the few climate models that incorporates a significant number of carbon cycle feedbacks, particularly in soils and tropical forests. In a 2003 study, (subs. req’d), they found that a typical fossil fuel emissions scenario for this century, which would have led to carbon dioxide concentrations in 2100 of about 700 ppm without feedbacks, led instead to concentrations of 980 ppm with feedbacks, a huge increase. Even ignoring feedbacks, keeping concentrations below 700 ppm requires the United States and the world to start slowing carbon dioxide emissions from coal, oil, and natural gas significantly by 2015 and to stop the growth almost entirely after 2025.

In 2006, the Hadley Centre, working with other British researchers, published an important study, “Impact of Climate-Carbon Cycle Feedbacks on Emissions Scenarios to Achieve Stabilisation,” that included both ocean and terrestrial carbon cycle feedbacks (though they do not specifically model carbon emissions from defrosting tundra). The study found that such feedbacks reduce the amount of fossil fuel emissions we can release by 21 percent to 33 percent.

We have no room for error. Buried in the IPCC’s Fourth Assessment Report (Working Group 1) is a stunning paragraph, which shows that the consensus is finally shifting on this issue:

Climate-carbon cycle coupling is expected to add carbon dioxide to the atmosphere as the climate system warms, but the magnitude of this feedback is uncertain. This increases the uncertainty in the trajectory of carbon dioxide emissions required to achieve a particular stabilization level of atmospheric carbon dioxide concentration. Based on current understanding of climate carbon cycle feedbacks, model studies suggest that to stabilize at 450 ppm carbon dioxide could require the cumulative emissions over the 21st-century be reduced from an average of approximately 670 gigatons carbon to approximately 490 GtC.

Ouch. We need to average 5 billion tons of carbon this century to avoid catastrophic warming. We’re already at 8 and rising fast.

There thus appears to be a threshold beyond which it becomes more and more difficult for us to fight the feedbacks of the carbon cycle with strong energy policies that reduce fossil fuel emissions into the air. While the threshold is not known today precisely, it appears to be somewhere between 450 ppm and 650 ppm [and probably between 450 and 550]. If we cross that point of no return, we’ll probably shoot to 1000 ppm, and maybe much more — ruining this planet for centuries if not millenia.

By 2025, we’ll know much better where the point of no return is. Unfortunately, on our current path, the world’s emissions and concentrations will be so high by 2025 that the “easy” technology-based strategy will not be able to stop us from crossing the very high end of the threshold range

That’s why, in my book, I call the 2025-2050 period Planetary Purgatory. Barring a major reversal in U.S. and world policies in the very next decade, come the 2020s, most everyone will know the grim fate that awaits the next fifty generations. But the only plausible way to avoid it will be a desperate effort to cut global emissions by 75 percent in under three decades–a massive, sustained government intervention into every aspect of our lives on a scale that far surpasses what this country did during World War II.

That would indeed be punishment for our sins of inaction. It would also be a great irony if conservative Denyers — who are blocking serious mitigation today because they don’t like (a certain kind of) government intervention in our lives — ended up forcing the country into far more government intervention in the near future.

Failing that desperate effort, we would end up at mid-century with carbon emissions far above current levels, and concentrations at 500 ppm, rising 3 to 4 ppm a year–or even faster if the vicious cycles of the climate system have kicked in. That would propel us to the point of no return in the third quarter of this century.


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17 Responses to Are Scientists Overestimating — or Underestimating — Climate Change, Part III

  1. Ron says:

    [also posted in part one]

    Over or under estimating isn’t the point. When the climate doesn’t behave the way a model predicts it means the model is flawed. It doesn’t tell you why, it only means that the scientists who designed the model didn’t fully understand climate.

    We are a long way from fully understanding how climate works. Real scientists will tell you the same thing. Even most of the devout AGW believers admit to a lot of uncertainty.

    I’m not saying the failure of an arctic sea ice model or hurricane season model is proof that AGW is a farce. In fact, you can’t use an inaccurate model as proof of anything.

    Come on, guys. Let’s do some scientific thinking here.

  2. Earl Killian says:

    To Ron: the greater the uncertainty, the greater our caution should be. Imagine a reality TV show producer proposes you and your friends participate in a game of Russian Roulette for a small payment (to you or your estate). He says he doesn’t know how many chambers of the revolver are loaded, and points out “it might be none” (typical salesman). The consensus of various people with more knowledge of the particular revolver suggest probably 3 chambers are loaded, but estimates range from 1-5. Does the controversy about the number of loaded chambers make you more willing to play? The question is why do you want to point a potentially loaded gun at your head at all? (Or more accurately, your children’s heads).

  3. CL says:

    Models are not 100% correct, but they are not 100% wrong, either. They still provide useful information, though. We have to act with the knowledge that we have, while simultaneously building on that knowledge. Waiting until we ‘fully understand’ the climate is folly; it’s going to be while before that goal is met.

    Will there be climate surprises? Of course. We’ve only been observing ‘the climate’ systematically for a handful of decades and we don’t have a grasp of many of the subtleties yet. We’ve not seen an ice cap melt or a 35% increase in CO2, so we’re a bit fuzzy on the finer details. We do understand (and can model) the basic picture, though.

    It’s most likely to be something we don’t like, and history suggests that even small climate changes can bring down a civilization (e.g. “The Winds of Change” by Linden). If we want to avoid that fate, or even thrive, the time to act is now.

  4. Hank Roberts says:

    Ron, who tells you that any imperfection is reason to throw out what’s useful? Sounds religious to me.


  5. David D. says:

    are these the same models that are not able to reproduce historical climate data? Are these models that – like hurricane predication models – consistently have to be reworked to fit the data? Are these the models whose algorithms are not available for evaluation? Are these the models that – according to the IPCC report – at one time predicted 20 foot rises in sea levels but now – according to the 2007 IPCC report – predicts sea level rises of inches over decades?

  6. Craig Dillon says:

    And you have not identified other important feedbacks — loss of albedo as arctic ice melts, and release of undersea hydrates. Loss of albedo’s effect can be calculated. We do not know enough about undersea hydrates to predict anything — but the possibility is there.

    Personally, I believe that the current huge decline in the summer arctic ice coverage minimum shows that we have already gone past the Point of No Return.

    I think we are witnessing the end of the Holocene. Struggle as we may, I doubt we can anything about it.

  7. David D says:

    Yah. Life as we know it is over. There’s no use, we’ve destroyed our planet. The Hale Bop dudes had the right idea – they just killed themselves over the the wrong catastrophe. I mean a single molecule in our enormous atmosphere has increased by about 0.010% – that is one hundredth of one percent – and we’re doomed. So – since we are already past the point of no return, we might as well make the best of it and live it up! Too late now. The days remaining until humans are extinct is set!

    I have been alive now for five decades and have heard it all. In the 60′s and 70′s the defined catastrophes were nuclear holocaust, lack of oil reserves (oil was suppose to run out by the year 2000), Global cooling (the coming ice age), Lake Erie was a “dead lake” (it would take until the year 2000 to clean it up) and over population leading to mas starvation and disease. In the 80′s times changed a little. The decade rang in some new and a few old catastrophes: nuclear holocaust remained while aids was a new catastrophe set to surely result in mass death and destruction. Ah, then we have the glorious 90′s: Global Warming, The Ozone and Y2K – oh and my favorite Hale Bop. Finally, in the 21st century comes Global Warming, the bird flu and radical Islam.

    As a scientist, my analysis of the last five decades reveals that every generation has to have at least one major catastrophe that will alter mankind – one that will devastate the world as we know it. As with ancient humans who were afraid of the God of the Volcano, I can only come to the conclusion that man is not secure without a “God of something” whose power will one day destroy him. Today it is the “God of MAN-MADE Global Warming” Let us all lay down our money and lifestyles at the altar of the God of MAN-MADE Global Warming and perhaps he will have mercy on us. All hail to the God of MAN-MADE Global Warming – the most high.

    Fortunately, I have more common sense then that and, therefore, I refuse to submit to the God of MAN-MADE global warming. I want real scientific evidence not stupid hype. If I wanted hype and emotion, I would go get my palm read. Oh yes, I am not a scientist paid off by “Big Oil”. That being said, who pays those who support the man-made global warming alarmists? BP? you mean the company that wants to increase it’s market share in alternate fuels? GE? you mean the company that wants to increase it’s sales in those mercury filled light bulbs? (I use them, they save a lot of money) When it existed, Enron? the company that wanted to increase it’s market share in expensive solar and wind technologies? Farmers who make more money on their corn? “Green Credit Companies” that make their money on the hype? etc… etc… etc…

  8. Hank Roberts says:

    Joe makes a good point in his third piece:
    “It would also be a great irony if conservative Denyers — who are blocking serious mitigation today because they don’t like (a certain kind of) government intervention in our lives — ended up forcing the country into far more government intervention in the near future.”

    Ha. And a far greater irony if these folks are being used by those happy to have already begun imposing an iron-gauntlet government — they will need a permanent state of crisis as an excuse to maintain and extend the interventionist government we’re wrestling with now, eh?

    Permanent war, permanent Cheney?

  9. Timothy Chase says:

    The longer we wait to do something about climate change, the worse it will get and the more likely that it will lead to government intervention on a larger scale – this is something which I would most certainly agree with. But depending upon the severity of the crisis and the potential for a severe economic crisis, the more likely that people will be willing to give up their liberties in exchange for the promises of any demagogue who promises to do something – however unrealistic. Furthermore, a free society which preserves the independence of the scientific enterprise and preserves economic freedom will be more likely to react rationally than a demagogue who has no genuine interest in trying to deal with severe climate change or the resulting economic crisis, but who is far more likely to be intent upon simply maintaining power.

    And make no mistake – if we are talking about droughts on the scale of what is projected under BAU in formerly good farmlands (e.g., with the US no longer able to grow wheat in the lower 48) and rising sea-levels due resulting from the nonlinearity of the response of glaciers Greenland and the West Antarctic Peninsula being in the neighborhood of several meters with so much of humanity living near the coastlines (roughly half of humanity lives within 100 km of the coastlines), there will be a severe and prolonged economic crisis.

    At that point, the crisis will be much more severe and prolonged than it needs to be, we will have far less resources with which to respond and we will be less able to respond rationally with what little resources we will have. And we aren’t simply speaking of one nation of many who will be experiencing a severe reduction in their resources. It is already believed that reductions in resources due to climate change is making war more likely – as in the case of Somalia. For those who genuine care about the freedom of future generations and the conditions under which they live, it is imperative that we start doing something about climate change now.

  10. Aaron says:

    I am appalled that “Science” is now afraid of being called “alarmist.” There was a time when raising the alarm was seen a good thing – it allowed your group to survive. If you raised the alarm in time, you city could put out the fire before the fire engulfed the city. A few false alarms are the price we pay for staying alive.

    More folks should spend some time fighting fires. It is amazing how fast a fire can explode out of control. Fighting fires reminds us that we must catch problems early on. Someone must raise the alarm as soon as possible. Better to raise the alarm on a little fire that can be put out in half a minute with a bucket of water, than let the fire grow into a firestorm that consumes the countryside and destroys whole communities. Right now global warming is our “FIRE”, and it is time to raise the alarm.

    If people act as the alarm raised, then there will be less of a long term problem. That does not mean that it was a false alarm, that means that it was a good alarm, people took action, and survived. That is what raising the alarm is all about. Raise the alarm on global warming.

  11. exusian says:

    Re David D.: For a self-descried “scientist” you sure use a lot of off-the-shelf denier rhetoric and precious little–zero, actually–science in your comment.

  12. Gary Chambers says:

    Thinking out Loud
    (Gores Fools)
    This old earth has been through this warming cycle hundreds of times since its birth. There were no humans around most of the times when it turned from the freezing ice age to the hot steaming grounds of volcanic heat. There were no automobiles spewing greenhouse gases, but there were millions of prehistoric animals producing large amounts of greenhouse gases. This planet was like a giant greenhouse several times throughout history. We never were sure what happened to the dinosaurs, but we know they weren’t smart enough to protect their selves from the ice age, falling meteoroids or a pandemic virus. We do know that we are smarter than animals and we humans can adapt to any climate on this earth and probably could adapt to a lot of other planets in our solar system. The humans who are not so smart are the ones who listen to a character on a soapbox carrying a sign and yelling that the end of the world is coming. This fool thinks we can change the climate of this vast earth like changing a flat tire. I cannot believe that this man was awarded the Noble prize for his prediction of doom. I guess he didn’t read the same science fiction books that I read when I was a boy.
    Most everything I read is no longer fiction. Man has turned all those Jules Verne stories into reality. Any thing a man has imagined and dreamed about seems too eventually become reality, because man has a knack for invention. I can remember the books I read back in the 1950’s about the cities in the future covered with large glass bubbles and men and women traveling from planet to planet.
    Man has not developed the God like powers to change a natural evolving climate.
    A smart man swims with the current.
    Jules Verne should have got the Nobel Prize, not a fool that has filled his Ship with fools.

  13. Jeff says:

    I have been debating denailists on a forum for about 6 months now. Its interesting to me because as I really delve into the science, it weakens their arguments and even people with more advanced degrees that mine, go to rhetoric. Good science is the denialist weakness. But the interesting thing is this rhetoric appeals to people who may not understand the science.

  14. kiwichick says:

    We face 3 major problems

    #3: Climate change
    #2: Resource depletion;oil,gas,copper,gallium,rhondium

    but the over whelming cause is
    #1:Out of control human population growth

    We need to discourage human reproduction

  15. Frank says:

    I am utterly awe-shocked that David D, Gary Chambers and other denialists are even capable of sentience. I wonder whether these people have ever picked up a science book, worked the process out, or questioned their white-suit ‘Praise the Lord!’ pastors. If you continue with your perpetual psuedo-science and psycho-babble, you will cause people to DIE, you will cause all that is alive to die; how can you not grasp this concept? The geological records of the end-Permian era (the greatest mass-extinction the earth has ever seen) shows the events happened over at least 10,000 years. This epoch’s mass extinction is already happening: the Holocene Extinction event- and it’s happening over a few centuries. The rapidity of the loss of Earth’s biodiversity is unprecedented, due to human development. We are having a larger effect than tectonic processes, you can bet your ass on it.

    I think it imperative to pursue the dramatic portrayal of what we already know to the public (they like a bit of drama) and Government intervention may be necessary at this time. More scientists need to be blunt, bold and fearless in getting the truth out there…

  16. Frank says:

    I’d like to add that I’m not always so passionate; only when millions will die and we lose 70-90% of life on Earth. I’m sorry if I don’t get as excited seeing George W. Bush hit a good drive.

  17. Jon says:

    That all too true. Couldn’t have said it better myself.

    No kidding. I just watched a YT video claiming CO2 was life and didn’t raise temperatures in the slightest.
    And you’re totally right. I once had to do a school project on the history of the earth, and there were 10,000-100,000 year gaps in between the periods.