Temperatures could rise by 7°C by 2100

Climate change, aka global warmingAccording to a new study by the Massachusetts Institute of Technology (MIT) climate change may reach 7°C by the end of this century. This doubles the previous estimates by the IPCC.

As climate models become more and more complex and contain more and more data, the results are increasingly worrying. I hope this study will lead our leaders to act in Copenhagen.

I wonder how Mankind and Life on Earth in general would react to such an important rise of temperatures. It took only 2°C more of global average to come from the previous Ice Age.

As The Telegraph noted:

Global temperatures could rise by more than 7C this century killing billions of people and leaving the world on the brink of total collapse, according to new research.

The study, carried out in unprecedented detail, projected that without “rapid and massive action” temperatures worldwide will increase by as much as 7.4C (13.3F) by 2100, from levels seen in 2000.

Previous estimates have concluded that the likely increase this century would probably be 2.4C (4.3F).

However the new study by scientists at the prestigious Massachusetts Institute of Technology included projected economic growth in developing countries and new information on the affect increased carbon emissions will have on biological processes, such as the capacity of the ocean to absorb greenhouse gases.

The results are based on 400 trials of the new system, each time using slightly different variations in data at the start to try and iron out errors.

Study co-author Ronald Prinn, Professor of Atmospheric Chemistry and director of MIT’s Centre for Global Climate Change, said all the results resulted in an increase in temperatures.

The projections average out at a likely Earth temperature increase of 5.2C (9.4F) this century, and conclude there is a 90 per cent chance the temperature change will be between 3.5C and 7.4C (6.3F and 13.3F).

“Overall they stacked up so they caused more projected global warming. There is significantly more risk than we previously expected,” he said.

“This increases the urgency for significant policy action. There is no way the world can and should take these risks.”

Friends of the Earth climate campaigner Tom Picken said that if the new research by MIT is accurate the results for the planet would be catastrophic.

He called for the world to try and reduce the chance of such an increase in temperatures by committing to reduce carbon emissions at the UN Climate Change Conference in Copenhagen at the end of this year.

“The consequences of such changes would be off the known scale. They are unthinkable,” he said

“A 7.4C rise would mean severe ecosystem collapse worldwide, with total economic collapse in many parts of the world.

“The planet would face resource wars between people, and you can safely say many, many hundred of millions of people would die,” he said.

6 thoughts on “Temperatures could rise by 7°C by 2100”

  1. I think we need to have a closer look at this study itself, rather than just news reports of it, to determine its worth. Many studies projecting the worst possible climate change assume infinite fossil fuel supplies, for example.

    The news article gives no title for any paper for us to look up. Googling up Ronald Prinn and MIT brings us to here. From there we find this news release. We find that they use the Integrated Climate Systems Model; they say they consider economics, climate and ecosystems. They have published an outline of the model.

    Nowhere do they mention that fossil fuels are finite, or that production of them may decline from current rates. p.19 tells us,

    “With the reference GDP growth of 2.5% per year CO2 emissions in EPPA4 reach 25.7 GtC/yr by 2100”

    The IPCC 2007 summary for policymakers, specifically this graphic, tells us that of the 49Gt CO2e emissions in 2004, 76.7% were CO2 itself, with the other 23.3% being other greenhouse gases such as methane, etc. Thus CO2 makes up,

    0.767 x 49 x 12/44 = 10.2GtC/yr now. The 2100 projection is for 25.7/10.2 = 2.5 times as much.

    Thus, Prinn’s projection, which gives us the possible 7C warming, is that in 2100 we’ll burn fossil fuels and deforest enough to create 2.5 times as much emissions as today. If the burning of coal, oil and natural gas, and deforestation were to be increased by a factor of 2.5, that means we go from,

    COAL = 5,543Mt to 13,860Mt; world reserves are at most 800,000Mt, at Prinn’s rate of use we’d stop dead at 2100 with zero reserves left.

    OIL = 87Mbbl/day to 218Mbbl/day; world reserves are about 1,300Gbbl, depending whether you include tar sands, etc, at Prinn’s rate of consumption we’d have zero left in 2022; forget about 2100.

    GAS = 2.84T m3 to 7.1T m3; world reserves are about 180Tm3, at Prinn’s rate we’d zero out around 2035.

    DEFORESTATION = 13 million ha/yr to 33 million ha/yr; world forest cover is about 3,800 million ha, so we have enough forests to wipe out for 165 years at his rate; however, given current rates and places of deforestation, we’d see most of the Third World become deserts by mid-century, and the First World would have to start cutting everything down to keep up Prinn’s rate. This seems unlikely.

    Thus, the “7 degrees of warming” requires in their model assumptions of being able to increase production and consumption of fossil fuels and deforestation which don’t accord with models or history. We cannot say that oil peaked in 2005, or 2008, and that the peaking of gas and coal are threats, while at the same time claiming that we can increase them by 2.5 times by 2100.

    Either peak fossil fuels is not a problem, or this model has wrong assumptions going into it.

    That does not mean we could not see several degrees of warming given peak fossil fuels; I don’t know. I speak only of the assumptions of the model, which are implicit (they don’t mention peak fossil fuels) and wrong.

  2. This is the letter I wrote to Prinn,

    I am an amateur writer interested in issues of peak fossil fuels, climate change and so on.

    I read with interest in a recent Telegraph article [http://www.telegraph.co.uk/earth/earthnews/5357725/Global-warming-of-7C-could-kill-billions-this-century.html] of you and your colleague’s work on a climate model giving an average temperature rise of 5.2C given a “business as usual” scenario. This is a more dramatic result than in other models, and so I was curious about the assumptions behind it. Previous studies with dramatic results assume catastrophic feedbacks such as complete melting of Siberian permafrost, or infinite fossil fuels.

    The news article, typical of sloppy journalism, gives no title for any paper for us to look up. But simple web research led me to your Integrated Climate Systems Model [http://globalchange.mit.edu/igsm/]. The model outline [http://globalchange.mit.edu/files/document/MITJPSPGC_Rpt124.pdf] does not mention catastrophic feedbacks, nor does it mention limits on fossil fuel use.

    p.19 tells us,

    “With the reference GDP growth of 2.5% per year CO2 emissions in EPPA4 reach 25.7 GtC/yr by 2100”

    The IPCC 2007 review told us that of the 49Gt CO2e emissions in 2004, 76.7% were CO2 itself, with the other 23.3% being other greenhouse gases such as methane, etc. Thus CO2 makes up 10.2GtC/yr now. Your 2100 projection is for 2.5 times as much.

    If the CO2 comes from the same sources as today – burning coal, oil, gas and deforestation – that implies that together those four will have 2.5 times the emissions of today. That means oil going from 87Mbbl/day to 218Mbbl/day, which would completely deplete reserves by the late 2020s; coal reserves would run down to nothing by 2100; natural gas run out in the 2030s; and also by the 2030s the Third World would have no forests left to cut down, and the First World would have to cut down more to keep up the emissions to the supposed rate.

    Current models of coal, gas and oil production, and forestation and deforestation, don’t support that huge growth in consumption. It’s widely believed that oil has peaked and will only drop in production from here on, natural gas will peak by 2020 and coal by 2040. Forests are less certain, but the current trend of Third World deforestation and First World forestation would have to be broken to support the model.

    That is, assuming I have understood the model outline correctly, it does not appear we have enough fossil fuels and forests to get the emissions supposed by your model, or at least not by the model’s date of 2100.

    Amongst the peak oil community there are a distressing number of climate change denialists. In the climate change community, there seem to be many people unaware of the issue of peak fossil fuels, simply assuming that whatever the resource constraints, they exist far beyond the limits of any climate model. To my mind this is a great pity, as the two issues are so closely linked. Fossil fuel scarcity may lead to lower emissions from burning them, but may lead to higher emissions in the Third World as the people respond to the scarcity with more deforestation. Or there may be more than enough fossil fuels to toast us thoroughly, but the economic difficulties we have with the scarcity (eg oil over $200/bbl for a decade or more) may choke back economic activity and thus emissions growth, or may prevent investment in new renewable generation. And so on.

    I understand that the climate itself is complex enough to model without introducing resource constraints. But it seems to me that it’s something which should at least be noted in passing, “this model could not consider” – etc.

    For my own part, as an amateur I make no predictions as to likely warming; obviously burning all that stuff so quickly is not good and will hurt us. I simply question the assumptions of models which give us startling results, and wish that the peak oil and climate change communities would talk more.

    I look forward to reading the full paper when published.

  3. Wow, that’s extremely interesting Kiashu, many many thanks for that.

    This is so big that I would like to publish this as a guest article from you. What do you think about that ?

    I really look forward to reading your answer and even more Mr. Prinn’s one.

  4. You can do that, yes. But it’s written as a comment, not an article, which means lower standards of fact-checking, arithmetic, and clear writing, do you really want to inflict that on your readers? 🙂

    Also, it may simply be that the things which appear to be missing in Prinn’s model are in fact there, just buried somewhere in the article where an amateur like me would never think to look. So we should wait to see if he replies. If he doesn’t, I can also write to some of the other article authours – perhaps one of the PhD students, those are normally more responsive than professors.

  5. Well I dare say my dear Kiashu that I inflict worse to my dear readers: my own writing. 😛

    Agreed on waiting for Prinn’s answer. When you have it and still are ready to publish both your analysis and his answer, please tell me.

    Meanwhile enjoy your day ! 🙂

  6. Prof Prinn wrote back,

    Please see our Report 125 for details relevant to your query.
    Information about the fossil-fuel proven reserves and total resource estimates in the EPPA model is provided in Tables 5-8 of the MIT Joint Program Report 125 available at:


    I had a look, and what it comes down to is that they take the highest possible estimates for world fossil fuel reserves, add in “undiscovered” reserves, and assume that the only thing stopping us digging them all up is the price.

    p.31 of the pdf “Included, for example, are estimates of in-place resources that would not be recovered with current technology”

    Translation: “We’ll even burn the stuff we don’t know how to get yet.” May as well include the hydrocarbons on Titan, then…

    Then they add in shale oil for good measure – and shale oil, most of the processes for extracting it have an EROEI less than 1, ie it takes more energy to get the oil out than you’ll get from burning the oil.

    Thus Tables 6-8, pp.33-35 of the pdf gives reserves of,
    Oil, 35,226 EJ, 2,310Gbbl
    Tar sands, 7,100EJ, 1,202Gbbl
    Gas, 18,956 EJ, 13,648,663 Gcf
    Coal, 178,959 EJ, 985Gt

    which are MUCH higher than supposed by even BP’s press announcements. And of course take no account of production limits; as with Titan, just because the stuff is there doesn’t mean we’ll be getting it. If fossil fuel production reaches a certain level and afterwards drops, we simply can’t burn it all by 2100. For example, if oil had a very modest decline after 2009 of 2.5% (lower than suggested by most peak oilers), we’d have burned 1,107Gbbl by 2100.

    Once again, just as peak oil studiers are sometimes climate change denialists, so too are climate scientists in effect peak fossil fuel denialists.

    I think I ought to write an article on this, but I have to think how best to approach it. Give me an email and we’ll discuss it.

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