M.I.T. joins climate realists, doubles its projection of global warming by 2100 to 5.1°C

The Massachusetts Institute of Technology Joint Program on the Science and Policy of Climate Change has joined the climate realists. The realists are the growing group of scientists who understand that the business as usual emissions path leads to unmitigated catastrophe (see, for instance, “Hadley Center: “Catastrophic” 5-7°C warming by 2100 on current emissions path” and below).

The Program issued a remarkable, though little-remarked-on, report in January, “Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters,” by over a dozen leading experts. They reanalyzed their model’s 2003 projections model using the latest data, and concluded:

The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model’s first projections were published in 2003 substantial improvements have been made to the model and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections, e.g., the median surface warming in 2091 to 2100 is 5.1°C compared to 2.4°C in the earlier study.

[Note:  That rise is compared to 1990 levels.  So you can add at least 0.5 °C and 1.0 °F for comparison with pre-industrial temperatures.]

Their median projection for the atmospheric concentration of carbon dioxide in 2095 is a jaw-dropping 866 ppm.


Projected decadal mean concentrations of CO2. Red solid lines are median, 5% and 95% percentiles for present study: dashed blue line the same from their 2003 projection.

Why the change? The Program’s website explains:

There is no single revision that is responsible for this change. In our more recent global model simulatations, the ocean heat-uptake is slower than previously estimated, the ocean uptake of carbon is weaker, feedbacks from the land system as temperature rises are stronger, cumulative emissions of greenhouse gases over the century are higher, and offsetting cooling from aerosol emissions is lower. No one of these effects is very strong on its own, and even adding each separately together would not fully explain the higher temperatures. Rather than interacting additively, these different affects appear to interact multiplicatively, with feedbacks among the contributing factors, leading to the surprisingly large increase in the chance of much higher temperatures.

The carbon sinks are saturating, and the amplifying feedbacks are worse than previously thought — that, of course, is a central understanding of all climate realists (see Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius” for links to the various feedbacks that have been ignored by most climate models).
Andrew Freedman at has one of the very few stories on this important study and reprints this useful figure from MIT:


He explains:

Results of the studies are depicted online in MIT’s “Greenhouse Gamble” exercise that conveys the “range of probability of potential global warming” via roulette wheel graphics (shown above). The modeling output showed that under both a “no policy” scenario and one in which nations took action beginning in the next few years to reduce greenhouse gas emissions, the odds have shifted in favor of larger temperature increases.

For the no policy scenario, the researchers concluded that there is now a nine percent chance (about one in 11 odds) that the global average surface temperature would increase by more than 7°C (12.6°F) by the end of this century, compared with only a less than one percent chance (one in 100 odds) that warming would be limited to below 3°C (5.4°F).

To repeat, on our current emissions path, we have a 9% chance of an incomprehensibly catastrophic warming of 7°C by century’s end, but less than a 1% chance of under 3°C warming.

“The take home message from the new greenhouse gamble wheels is that if we do little or nothing about lowering greenhouse gas emissions that the dangers are much greater than we thought three or four years ago,” said Ronald G. Prinn, professor of atmospheric chemistry at MIT. “It is making the impetus for serious policy much more urgent than we previously thought.”

The time to act is now.

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33 Responses to M.I.T. joins climate realists, doubles its projection of global warming by 2100 to 5.1°C

  1. So the big unknowns are slowly starting to come into view: How bad? And how soon?

    Given that the predictions for 4 and 5 degrees are so dire, I would expect MIT to become a little more vocal. How much longer do they plan to be a viable university?

  2. Gail says:

    I know you are all sick of hearing this from me.

    I’m sick of thinking it!

    But I’m telling you.

    The vegetation is dying. It is a RAPIDLY ACCELERATING MASS EXTINCTION.

    Maybe, we can figure out ways to grow food.

    But, there is no question in my mind, that there are going to be horrid dislocations.

    I hope we can, as humans, band together to help each other through a very threatening and traumatic time.

    If we don’t and we turn towards war, combat, and competitiveness, we face a Mad Max future.


  3. I have to correct my unfair comment … this is an excellent report. MIT did a terrific job of visualizing both the danger and the opportunity.

    And thank you Joe for making this better known.

  4. Gail says:

    Yes and I would add my voice to you Richard Pauli, THANK YOU JOE. You seriously have the best blog, the most lucid comments, the best readers and responses.

    Actually, you keep me sane, sort of.


  5. Bill says:

    Please take this message beyond the blog world to the real world ASAP.

  6. Nigel says:

    Who you gonna call?

  7. Joe,
    If you went to your MIT Seminar Series, you would have heard Peter Stone give the preliminary results for this as early as Nov. ’07.

    [JR: Actually, I heard this back in January, but I dawdled blogging. I boycotted the MIT Seminar Series since they invited deniers to speak.]

  8. paulm says:

    The report is still obfuscating. You don’t need sophisticated models to tell us that were going to be in for 3C or more, what ever we do now. Every report turns out to be an under-estimate.

    I am afraid it really is catastrophic, what ever we do. We are at 0.854321C higher and look at the extreme events occuring. At 2C, I cant see global civilization surviving.

    But we cant take this thing lying down.

  9. Thank you MIT for this contribution to estimating and visualising our future.

    I would like to see a “best-case” wheel, assuming action is taken worldwide at emergency speed to reduce emissions to near-zero as soon as possible and draw down atmospheric carbon to restore a safe climate (~300 ppmv).

    Sort of a global implementation of Al Gore’s “100% renewables in 10 years” challenge to America. Of course this would need a global social movement and international cooperation on a scale barely imaginable now, but technologically I believe it is within our grasp.

  10. paulm says:

    Talk of the devil….

    Lower increases in global temps could lead to greater impacts than previously thought, study finds
    Princeton, NJ – February 23, 2009 – A new study by scientists updating some of the findings of the Intergovernmental Panel on Climate Change (IPCC) 2001 Third Assessment Report finds that even a lower level of increase in average global temperatures due to greenhouse gas emissions could cause significant problems in five key areas of global concern.
    Joel B. Smith, a Vice-President at Stratus Consulting in Boulder Colorado, said, “Based on observed impacts and new research, the risks from climate change in general now appear to be greater than they did a few years ago.

    [“…a few years ago.” – I think he meant to say a few weeks ago!]

  11. Anthony, rabid doomsayer says:

    866ppm we won’t even need the kool aide. I though I was the doomsayer.

    Mass extictions will become a certainty. James Hansen’s 5 meter rise by 2107 is now looking conservative, and the sea level rise will not stop there. Would the East Antarctic Ice Shelf survive the resultant warming?

    Where are the paleo climatologists going to compare that to. Talk about levels that are out of the box.

  12. RevDoug says:

    “We’re standing at the precipice of hell. If everybody else was to live like an American, then the planet is doomed.”

    SUNITA NARAIN, Ctr. for Science and Environment, New Delhi:

  13. Mark says:


    Wow. Insulting an entire country! You sound just like the neocons in America! You’d fit right in. After all India doesn’t have CO2 emissions, right?

  14. OO says:

    Mark: India has 17 times lower emisions!

  15. GreenPRGuy says:

    New Rule:

    If you want to talk to ordinary Americans, do the conversion to Fahrenheit. Always.

  16. Sasparilla says:

    Its good to see consensus building around these updated estimates – at least it makes it easier, with the projections moving to the same page, to get started trying to fix the mess we’re building for ourselves.

    Something to keep in mind, a large group of scientist believe the items that would lead to runaway feedbacks (methane release, tropical forests drying and burning with massive CO2 releases – Amazon etc.) are out there lurking in the ~ 2 – 3 degree range – we need to get moving.

  17. paulm says:

    Anecdotal evidence of a changing world….

    Rats spark Bangladesh plague fear
    ….bamboo forests, which are blossoming for the first time in decades.

    Grizzlies wake early from winter slumber
    …The extraordinary sight of four grizzlies walking around out of hibernation has perplexed the Wuikinuxv people living in the isolated aboriginal community of Rivers Inlet on the B.C. coast.

    She said elders in the community of about 75 have never seen anything like it.

    Morris said the first grizzly appeared in the village in mid-January,

  18. Gail says:

    Even my beloved significant other, who has been subjected to my Cassandra calls for months now, still says silly things like:

    But those Australia fires were set by arsonists!

    Yes, I say, but the 117 degree (Farenheit, I agree Green PRGuy, otherwise Americans just don’t get it!) days that preceded the fire, and the tinder dry trees, and the winds, THOSE are predicted by climate change! (And apparently, they’re starting up again).

    And then he said well, maybe all those trees are just set biologically to die at a certain time and they’ll come back to which I said,

    So HOW COME 5 year old trees and 20 year old trees and 3 year old shrubs and 250 year old trees are all at death’s door within the space of one year???

    The capacity of humans to ignore their own self-destructive behavior is infinite.

  19. Mike Davis says:

    This has got to be one of the funniest sites on the web.
    This is comedy Right?

    [JR: Huh? Ain’t nothing funny about 5C or 7C warming.]

  20. Gail says:

    Mike Davis, aka Troll,

    Yeah, it’s really really funny.

    Har har har.

    Where are you? Anywhere around NJ?

    Come on over for a visit and I will show you enough dying trees and other plants that it will scare your pants off.

    Have you ever been in New Jersey when a large snowstorm is forecast? The grocery stores are MOBBED!

    Just wait until people notice next April that the trees only have half the leaves they should, and the evergreens are bare, and fields stay brown.

    Can you imagine the run on stores? The food trucks overturned?

    No of course not! That doesn’t happen in America! And who could have predicted 9/11 (Osama determined to attack inside America) or airplanes being used as weapons or the financial crisis??

    Sorry. I am getting less patient with morons than I used to be.

  21. paulm says:

    @Mike Davis, hope that means you’ll be back.

  22. caerbannog says:

    Mike Davis Says:
    February 24th, 2009 at 7:26 pm

    This has got to be one of the funniest sites on the web.
    This is comedy Right?

    Do you know why the current interglacial period will last at least 10,000-20,000 more years?

  23. cait says:

    I fight hard to retain a feeling that fighting for change will make some difference, and that it’s not just fighting to stop the destruction of nearly every species on the planet that might be able to cope with at least most of the changes (with humans prety much already screwed). It might still be fighting for my kids to be able to choose to have kids, even – as if that doesn’t already sound far fetched.

    THe thought I have debated with my husband is, and I would love any feedback from anyone involved with the analysis of data so far given that obviously I am merely a consumer of said analysis: at present we are still in a position where there is an exponential rise, not only due to warming that has already happened, but because carbon emmissions are still actively climbing, and the perverse situation we find ourselves in is that we are fighting to reduce the *increase* currently, and will be for some time to come.

    Given that, we have long since passed the point of no return, and it almost doesn’t matter what we do, the extermination of pfffttt…. I mean, I’m amongst friends here aren’t I. I can say that we’re facing the end, basically.

    Every model has been revised and revised over the last couple of years. In truth, we can’t really tell how far up it’s going to go given that arguably, any data based analysis will be hopelessly outdated almost at the point of print, given that we don’t really know what effect the change in CO2 absorption by oceans, plus combines increase methane from permafrost, plus an actual increase, still, in emissions *and so on* is going to have. that’s not to say that this latest study isn’t a damn good guess, obviously.

    I’d really welcome any discussion from scientists on the front line – do you believe that estimations like these from MIT may be worth pinning to the board as a worthy estimate of change? Or do you think that it’s inevitable that these figures will be revised up within a couple of years / on an ongoing basis?

    Thanks for putting up with a bunch of waffly questions and feel free to rip them apart immediately ;)

  24. Gail says:


    I think we should all scream that from the rooftops!

  25. Sam says:

    I wonder what Richard Lindzen says about this, lol.

  26. Norman Dale says:

    Regarding R. Pauli comment: What is the connection between the rhetorical (I hope) question about MIT’s viability and the fact that one program within it is publishing information and views on climate change? I congratulate MIT for being clear without being “more vocal”. What we need most at this time is measured voices from science, leaving to others (e.g. Al Gore) to get the word out.

  27. BBHY says:

    I don’t think replacing our lightbulbs is going to be enough.

  28. Dr Peter Carter says:

    Re. your report on the MIT integrated model result of Jan 2009 the A1F1 global warming median is 5.1oC and 95%tile to 7.4oC from year 2000.
    That makes 5.5oC from pre-industrial.
    The IPCC AR4 projections were also from year 2000 (1980-1999).
    That makes MIT the same as the latest Hadley business as usual model global warming from pre-industrial.
    So at current BAU (above A1F1) we are looking at over 5.5oC.
    Both models omit carbon feedback from permafrost (0.8oC CSIRO) and methane hydrate (possible 1.5oC by a Hadley model)
    So our fossil fuel economy has today’s kids on the way to well over a 6oC warming in their life time.
    That’s human extinction warming and runaway Venus hot house warming.
    It’s far beyond time nations pushed the panic button.

    in the subcommittee on Energy & ENvironment,

    Click their names, then it will send you to their page. Call their DC office.

    (Read this if you don’t know whats going on: )

  30. Will Anderson says:

    Would everyone please send this to your politicians, a corporate president and to one of the mass media. We need action.

  31. “Poppy cock” — this from the fellow who does not know the difference between a “metalurgist” and a “meteorologist.” Do please see Chris’s previous comedy styling at:

  32. Wm b says:

    To a child what is Global Warming?

    I think it’s something about the world getting hotter and
    the smart grownup people keep arguing an Stuff.