Our Future

I want to start talking about plans for cutting back carbon emissions, and some scenarios for what may happen, depending on what we do. We’ve got to figure this stuff out!

You’ve probably heard of 350.org, the grassroots organization that’s trying to cut CO2 levels from their current level of about 390 parts per million back down to 350. That’s a noble goal. However, even stabilizing at some much higher level will require a massive effort, given how long CO2 stays in the atmosphere:

In a famous 2004 paper, Pacala and Socolow estimated that in a “business-as-usual” scenario, carbon emissions would rise to 14 gigatons per year by 2054… while to keep CO2 below 500 ppm, they’d need to be held to 7 gigatons/year.

Alas, we’ve already gone up to 8 gigatons of carbon per year! How can we possibly keep things from getting much worse? Pacala and Socolow listed 15 measures, each of which could cut 1 gigaton of carbon per year:

(Click for a bigger image.)

Each one of these measures is big. For example, if you like nuclear power: build 700 gigawatts of nuclear power plants, doubling what we have now. But if you prefer wind: build turbines with 2000 gigawatts of peak capacity, multiplying by 50 what we have now. Or: build photovoltaic solar power plants with 2000 gigawatts of peak capacity, multiplying by 700 what we have now!

Now imagine doing lots of these things…

What if we do nothing? Some MIT scientists estimate that in a business-as-usual scenario, by 2095 there will be about 890 parts per million of CO2 in the atmosphere, and a 90% chance of a temperature increase between 3.5 and 7.3 degrees Celsius. Pick your scenario! The Stern Review on the Economics of Climate Change has a chart of the choices:

(Again, click for a bigger image.)

Of course the Stern Review has its detractors. I’m not claiming any of these issues are settled: I’m just trying to get the discussion started here. In the weeks to come, I want to go through plans and assessments in more detail, to compare them and try to find the truth.

Here are some assessments and projections I want us to discuss:

• International Panel on Climate Change Fourth Assessment Report, Climate Change 2007.

• The Dutch Government, Assessing an IPCC Assessment.

The Copenhagen Diagnosis. Summary on the Azimuth Project.

• National Research Council, Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia. Summary on the Azimuth Project

• K. Anderson and A. Bows, Reframing the climate change challenge in light of post-2000 emission trends. Summary on the Azimuth Project.

• William D. Norhaus, A Question of Balance: Weighing the Options on Global Warming Policies.

• The Stern Review on the Economics of Climate Change.

And here are some “plans of action”:

The Kyoto Protocol.

• World Nuclear Association, Nuclear Century Outlook. Summary and critique on the Azimuth Project.

• Mark Z. Jacobson and Mark A. Delucchi, A path to sustainable energy: how to get all energy from wind, water and solar power by 2030. Summary and critique on the Azimuth Project.

• Joe Romm, How the world can (and will) stabilize at 350 to 450 ppm: The full global warming solution. Summary on the Azimuth Project.

• Robert Pacala and Stephen Socolow, Stabilization wedges: solving the climate problem for the next 50 years with current technologies. Summary on the Azimuth Project

• New Economics Foundation, The Great Transition: A Tale of How it Turned Out Right. Summary on the Azimuth Project.

• The Union of Concerned Scientists, Climate 2030: A National Blueprint for a Clean Energy Economy.

• The Scottish Government, Renewables Action Plan.

• Bjorn Lømborg and the Copenhagen Business School, Smart Solutions to Climate Change.

As you can see, there’s already a bit about some of these on the Azimuth Project. I want more.

What are the most important things I’m missing on this list? I want broad assessments and projections of the world-wide situation on carbon emissions and energy, and even better, global plans of action. I want us to go through these, compare them, and try to understand where we stand.

80 Responses to Our Future

  1. Jeff Tansley says:

    I think the link to the Scottish Government might be out of date.
    BYW for what its worth
    and using the energy and fuel search gives quite few papers on energy topics. Surprising really – some of it is even policy. What difference it will make is another matter.

  2. Enrique says:

    No scientific measure is any good. You’ve got to go after the driving cause. You’ve got to find an economic scheme that can be stable and viable without growing. The continuous mandatory growth of economy is the real driving force behind all this and nobody is ready to accept this as of now, so the economy will continue to grow till it explodes in our faces.

    • John Baez says:

      Okay. You’re not the first to have this idea. So: who has tried to lay out a detailed plan to switch to “an economic scheme that can be stable and viable without growing”… and do it quickly?

      I know one group that’s tried: the New Economics Foundation. Over on the Azimuth Project we have a link to their book. It’s called The Great Transition: A Tale of How it Turned Out Right. It begins with this quotation:

      Anyone who believes exponential growth can go on forever in a finite world is either a madman or an economist.

      Thanks for reminding me of this! I’ve added it to my list above.

      But who else?

      • streamfortyseven says:

        All of the plans I’ve mentioned below involve economic growth, for the simple reason that corporations have a duty to their shareholders to produce a benefit, which is measured in cash money terms. As long as banks and lenders charge interest on the money they lend, corporations must have growth in earnings, or else there is a resultant loss. A “no growth” corporation is not possible without the cost of capital being effectively zero, because without zero capital cost, “no growth” is actually negative growth. Even with the cost of capital being zero, a “no growth” corporation will lose out in a competitive marketplace to corporations which exhibit non-zero growth, meaning their share prices will decrease as will their access to capital.

        • Enrique says:

          What’s first here? Banks that increments interest on the money? But this is the same: they do it because they’re companies that wants to increase benefits every year. But what do really motivates companies to raise benefits every year? The only real reason is greed. You could perfectly live without doing it but then, greed not-so-honest people enter the picture and discover that they can become richer by this method that nobody stops because they’re the most powerful people in the first place at the time when this operational mode began to be institutional, probably in the eighteenth century. So what would be needed is only a change of mind. But then again there are gonna be always greedy unsolidary people with the ability to act and make business, isn’t it?

        • DavidTweed says:

          Enrique wrote

          But what do really motivates companies to raise benefits every year? The only real reason is greed. You could perfectly live without doing it

          The problem with this viewpoint is that it might be possible to live on a small-holding farm in this way (although it might not be possible for 6.7 billion people to). However, that excludes a lot of human activity, from inventing technology (eg, the computing device you made your comment on), medical research, “pure” science, theatre, film and literature, etc. All the ideas embodied in these things have been created “new from nothing”: it’s not purely a zero-sum game. However, a lot of the physical elements in the world are a zero-sum game: acquiring/using some quantity means it’s not available for other purposes/people.

          The real difficulty with economics is not to about completely junking economic incentives, it’s about finding some way that continues to incentivise “intellectual development” whilst stabilising “environmental development” to sustainable levels as much as possible.

      • But who else?

        Dunno if Keynes’ classic “Widow’s cruse” qualifies as an answer. See wikipedia’s steady state economy entry or Phil Henshaw’s article. (Henshaw sees a problem with most “sustainable development” schemes.) The widow’s cup in his words:

        It may “sound funny” but it is actually the quite surprisingly practical solution. That is to persuade the Saudi’s, Chinese, our own super rich and other investors to *spend the economy back to health*, giving back to the economic system that made them rich – when sitting around and expecting it to keep making ever more earnings for them is actually failing badly.

        (hyphen added by Flori)

        • Phil Henshaw says:

          Flori, thanks for the mention. David’s objective – “some way that continues to incentivise “intellectual development” whilst stabilizing “environmental development” – is exactly what Keynes’s so called “Widow’s Cruse” model is intended for.

          The essential feature of it might be better better termed the “Vigorous youth’s cruse”, because it is about the transition from immature to mature growth, at the end of which a youth is at the peak of their vitality and endurance, not weak and vulnerable like an old widow is perhaps. I guess Keynes liked the ring of it for some reason, and the Bible story of Elijah giving an old woman an inexhaustible cup of flower and bowl of oil.

          What Keynes noticed is that investment needs to stabilize as resource use does, that to “continue to incentivise “intellectual development” the scale of investment needs to stop growing while it still produces healthy returns. Otherwise it would grow to drive the earth to producing no net returns following present practice of using the earnings to add to savings. So a new use for the earnings on investments needed to be found.

          He didn’t go beyond explaining the obvious, that either investment returns don’t materialize, or you don’t add them to the prior accumulation. I go the step further, and describe various valuable things that might be done with them. It’s essentially a kind of “peace dividend” for declaring an end of our ever growing war with nature, limiting the expansion of the global pool of investment funds while they still produce earnings, making investment system as a whole sustainable in the bargain.

          You can see my various approaches by searching my site for mentions of Keynes, using [site:synapsee9.com keynes] as the search string.

  3. Tim van Beek says:

    That’s an impressive list of references!

    Yet there are more :-)

    Here is DESERTEC on the Azimuth project, with links to articles about the potential of solar power.

    The German federal government has some data and graphics about increased energy consumption versus better energy productivity between 1990 and 2006, and CO2 production here.

    • John Baez says:

      I hope it’s clear: when it comes to references, I’m asking for broad assessments and projections of the world-wide situation on carbon emissions and energy, and global plans of action. I want us to go through these, compare them, and try to understand where we stand.

      There are of course millions of more specific references, and it’s great if people put those on the Azimuth Project… but there’s no way I can talk about all of them!

      I’ll try to make my blog entry a bit clearer about this point.

      • Tim van Beek says:

        Sorry, maybe I was misled by some of the references of the blog post:

        • “Do governments have the right mix in their energy R&D portfolios?” is about 28 countries not including China, Russia, India (or any other country of Asia except Japan),

        • “Climate 2030: A National Blueprint for a Clean Energy Economy” is about the USA,

        • the last link to the Scottish government seems to be broken…

        • John Baez says:

          Yeah, some of the references I gave are on the brink of being too narrowly focused. But a plan of action that focuses on a specific country can still have a useful analysis of the huge range of decisions that people are trying to make: how much of different kinds of energy, how much conservation, what level of CO2 to aim for, etc., etc., etc., etc., etc…

          It’s this “big picture” stuff that I want us to talk about, right now…

          But of course I’m not trying to scold you. Desertec is big enough to actually matter. I just want to point people in the direction I’m most interested in.

        • Tim van Beek says:

          John said:

          But a plan of action that focuses on a specific country can still have a useful analysis of the huge range of decisions that people are trying to make: how much of different kinds of energy, how much conservation, what level of CO2 to aim for, etc., etc., etc., etc., etc…

          It’s this “big picture” stuff that I want us to talk about, right now…

          All right :-)

          BTW: On the page I linked to, there is a chart with CO2 emissions of G8 and O5 countries, comparing values of 1990 and 2004 and the percentage of worldwide emissions. (This includes China, India, Brazil and the Russian Federation).

          Regarding Germany only:

          The other graphs on the page I linked to show e.g. that, partially as a side effect of increased taxes on energy and fossil fuels, we have

          – a 31% increase in energy productivity (this term is defined over there), but a

          – 27% growth of the adjusted GDP, and therefore

          – only a 3% decrease of consumption of primary energy (again, this is defined over there).

          Lessons learned: Increasing the price of energy and fossil fuels by taxes and other measures supports the increase of energy productivity, which seems to have a lot of potential: A 31% increase in 15 years is not bad, and all of this without any catastrophic damage done to the economy.

          On the other hand we see that the continued growth of the GDP eats up almost all of the gain of energy productivity, so we’ll have to figure out how to remedy that.

        • John Baez says:

          Tim wrote:

          On the other hand we see that the continued growth of the GDP eats up almost all of the gain of energy productivity, so we’ll have to figure out how to remedy that.

          How about another economic meltdown?

          According to Wikipedia, in 2009, world energy consumption decreased for the first time in 30 years, by 1.1%, as a result of the financial and economic crisis, which caused a GDP drop by 0.6%. Energy consumption growth remained vigorous in developing countries, and in Asia it rose 4%. But in the OECD, consumption dropped 4.7% in 2009 and was thus almost down to its 2000 levels. In North America, Europe and CIS, consumptions shrank by 4.5%, 5% and 8.5% respectively due to the slowdown in economic activity.

          Of course, I’m not really hoping for another economic meltdown. For a more optimistic scenario, try The Great Transition: A Tale of How it Turned Out Right.

        • DavidTweed says:

          One of the things about hoping for change via economic “catastrophes” is that a very large amount of the reduction comes from people who are out of work and hence engaged in different behaviour. As someone who has ended up in this position in the middle of the current economic situation, a lot of my energy/carbon reduction will revert to what it was once I’m gainfully employed again. There is certainly some efficiency transformations going on as a result of financial difficulties, but AFAICS they’re relatively minor compared to the energy “saved” by people being out of work.

          I suspect that the last thing on people’s minds when/if things recover is going to be investing to reduce energy usage and carbon dioxide emissions. (It’s a bit like the complaint about Keynesian economics that no-one actually saves for the bad times during the good times.)

  4. John Baez says:

    By the way, I’m also interested in reading projections and plans of action written by:

    pessimists who think we’re doomed to global warming, economic collapse due to energy shortages, etc…


    optimists who think everything will be fine without much work.

    However, I’m only interested in serious, detailed reports — not stuff like “Joe Sixpack says on his blog that global warming is a myth and everything is getting better.”

    I’ll add an optimistic plan of action to my list above: Lomborg’s new book. That way everyone will be pissed off by at least one of the plans I discuss.

    • DavidTweed says:

      Regarding “optimists”:

      I’ve been contemplating trying to do an article for the wiki about “the law of accelerating returns” held by people like Ray Kurzweil. If you disregard his increasingly “enthusiastic” views concerning the far future, then you get some hypotheses about the next 20-30 years. Some people think that even these are “obviously crazy”. I’m inclined to the view that his ideas may very well be a wrong hyper-generalisation from some observed things, but the key will be whether real-world “knowledge/capacity growth” will follow his projected results. (I’m sure someone must have done a recent check of some of his projected timelines against actual developments.)

      • John Baez says:

        In a while, This Week’s Finds will feature an interview with Eliezer Yudkowsky. I would consider him an optimist as well. He says it’s a waste of my time to work on environmental issues: better to plan for an intelligence explosion.

        (If you click the link, you’ll see his quick summary of the difference between his views and Kurweil’s.)

        I think it’s important to consider wildly different scenarios, ranging all along the optimism-pessimism axis, and lots of other axes too. I think it’s good to consider them all together in one place, because right now, different communities of people tend to form their own ‘bubbles’ where different assumptions become established wisdom, not sufficiently questioned. They can’t all be right. Most of them must be missing pieces of wisdom or information that others have.

        The future will, nonetheless, still surprise us.

        • DavidTweed says:

          I’ve spent a lot of time thinking about Kurzweil type accelerating returns argument (since it’s very related to my field). AFAICS, the only difference between Kurzweil and Yudkowsky is about whether lots of things we think of as intelligence can as effectively be done by “just” “automation” (in the sense that, for example, using incredibly fast brute force search rather than actually developing a conceptual model).

          Either of fhese are reasonable hypotheses — the key question is how the observational data matches up since the predictions have been made. Of course, attempting to discern the difference between a linear and an exponential curve on noisy data at the origin is very difficult.

  5. Graham says:

    The 21 Oct edition of Nature has a section on cities and sustainability.


    One article discusses the The World Mayors Council on Climate Change (WMCCC) which has some action plans. In particular, New York is highlighted. “New York has won considerable recognition for its long-term growth and sustainability plan, PlaNYC 2030. This aims to reduce greenhouse-gas emissions by 30% from 2005 levels over the next 20 years.”

    I am puzzled as to how green cities are. One article says

    “… doubling the population of any city requires only about an 85% increase in infrastructure, whether that be total road surface, length of electrical cables, water pipes or number of petrol stations. … there are similar savings in carbon footprints – most large, developed cities are ‘greener’ than their national average in terms of per capita carbon emissions. It is as yet unclear whether this is also true for cities undergoing extremely rapid development, as in China or India, where data are poor or lacking.”

    while another says that about half the global population live in cities and

    “The International Energy Agency estimates in its most recent survey that urban areas are responsible for 71% of global energy-related carbon emissions, although the numbers vary widely depending on how cities or urban areas are defined.”

    • John Baez says:

      Thanks for pointing out PlaNYC 2030 — I’ve added a link to the Azimuth Project, and this graph too:

      (Click for a readable version.)

      Stewart Brand says cities are green, and I’ll report on that someday, but it sounds like this needs investigation. Maybe CO2 per GDP makes them look greener than CO2 per capita.

  6. streamfortyseven says:

    Try this: “Climate Change: An Agenda For Global Collective Action”, Aldy, Stiglitz, Orszag

  7. Pacala and Socolow’s carbon wedges do not include pulverization and dispersal of mantle silicates, which gets nicely around the “Durable storage” entry in their rightmost column.

    I’m still looking for dollar one for my proposed method of nuclearizing the car. That will be several wedges when it gets going.

  8. streamfortyseven says:

    More: “Beyond Kyoto: Advancing the International Effort Against Climate Change”, Aldy et al., 2003

    Click to access BeyondKyoto_Dec03.pdf

    180 page book…

  9. umass1993 says:

    According to wikipedia, global carbon emissions in 2007 was about 30 gigatons.

    Doing a quick estimate, the world would be over 100 gigatons if it consumed like the US.

    There is massive pressure for each nation to achieve an american lifestyle. So my guess is that global co2 emissions will continue to grow as long as concrete and fossil fuels are are available.

    • John Baez says:

      As you note below, it’s carbon dioxide emissions that totalled gigatons in 2007. Carbon emissions were 8 gigatons.

      Certainly there is huge pressure to increase CO2 emissions. If this goes on unchecked until we run out of carbon to burn, we’ll have a major ecological disaster on our hands, with roughly half of all species going extinct, sea level rise of 7.2 meters due to the melting of Greenland and 4.8 meters due to the melting of the West Antarctic Ice Sheet, more floods and droughts, extremely hot summers in many places, etc. So the question is just: when will we wise up, and what will we do then?

  10. We can’t wait for serious cutting back of emissions. Starting with sequestration is also urgent.

    There are only 2 schemes that I know of would make sense, and they take some time to bootstrap:

    Leonard Ornstein, Igor Aleinov and David Rind: Irrigated afforestation of the Sahara and Australian Outback to end global warming.

    Needs closer examination and modelling. I would combine that with biochar production, so soils hold more water.

    It meanwhile seems to me nothing serious will get done unless mankind starts appreciating its relation to “Mother” Earth, which seems to have gone lost with civilization and its religious delusions. Forget heaven and cosmos, hominids! Get your heads out of the clouds and your feet back on the ground!

    I got that crazy idea of a self-evident self-organizing epireligious quasimonastic order who takes serious the 2 inevitable natural philosophic ethic conclusions forced by state of the biosphere: 1) Live carbon negative 2) Do not multiply. (Poverty and chastity not necessary, having fun would be more constructive…) Some elaboration here and here.

    Ceterum censeo:
    Quoth Lomborg, “we all need to start seriously focusing, right now, on the most effective ways to fix global warming.” One being not wasting any more time and brains on the Lomborgs. (Cf. e.g. Romm’s 2 cents instead.)

    • John Baez says:

      Thanks for the Ornstein et al. reference. I’ll add it to the Azimuth Project if you haven’t already.

      Good luck on your quasimonastic order. How about calling it Ordo Florifulgis?

      (Sorry, my Latin isn’t any good, you’ll probably need to polish that.)

      Personally I think something like the Transition Towns movement is a bit more likely to succeed. But maybe you could join them.

      • I don’t plot to become a new St. Pachomius or St. Benedict etc. etc. We’ve had enough of “leadership” and hierarchy – if that would be necessary, the order wouldn’t work. (For an example that things could work well without see the Rainbow Family, the world’s largest non-organization.) As a name for the order I suggest Earth’s witnesses. Or perhaps Gaia Satyagraha, for it might also serve as empowerment for the poor. The order’s purpose is anthropogenic carbon sequestration – in a double sense of anthropogenic. Another purpose is to support precious folks like you with food and carbon footprint neutralization.

        The Transition Towns are all well and good, but it’s about c20th “sustainability” or “permaculture” and only aspires to carbon neutrality. It is local thinking of last century. Today (c21st) we’ve got a global problem: Not carbon negative = not sustainable, not perma: Meanwhile, positive carbon cycle feedbacks are kicking in, e.g. ocean phytoplankton decline and global plant productivity decline, and there’s much more in the pipeline like permafrost methane release, forests burning away, etc.

        So, quite probably Earth will outdo any emission reductions. Another purpose of the order is to hand down a repair tool and it’s philosophy to the survivors. Without that, it would be better no hominids survive, so Life has a chance to heal itself from the damage done by its hominid infection. (Yet another natural philosophic ethic imperative to get the order running.)

        “We should be the heart and mind of the Earth not its malady.” — James Lovelock, 2006

      • John Baez says:

        Florifulgurator wrote:

        Meanwhile, positive carbon cycle feedbacks are kicking in, e.g. ocean phytoplankton decline and global plant productivity decline, and there’s much more in the pipeline like permafrost methane release, forests burning away, etc.

        So, quite probably Earth will outdo any emission reductions…

        If you believe in the Gaia Hypothesis, why do believe most of the feedbacks will make the CO2 worse? I thought the Gaia Hypothesis was all about how “the biosphere and the physical components of the Earth (atmosphere, cryosphere, hydrosphere and lithosphere) are closely integrated to form a complex interacting system that maintains the climatic and biogeochemical conditions on Earth.”

        (I should ask Lovelock, but I’ll ask you.)

        • Thanks for reminding me of important homework and making me feel uncomfortable playing “Lovelock’s bulldog“… :)

          Alas I currently have neither access to the university network nor much time – so I answer straight out of my weak head:

          The CO2 decay diagrams you present below seem to suggest fast negative (stabilizing) feedbacks. And methinks that’s why we got a stable Holocene climate state. Up till yesterday. I guess the model behind the diagrams does not take into account influence of climate stress on plants and/or plankton. From the NASA page I linked:

          Global plant productivity that once flourished under warming temperatures and a lengthened growing season is now on the decline, struck by the stress of drought.

          One stabilizing feedback gone – Liebig’s law of the minimum kicking in, turning off the feedback. (Some of my pending homework: Get grasp on the role of ocean phytoplankton, check 2010 data with Lovelock’s & Kump’s 1994 simulation of “failure” of climate regulation). Plus, raising temperature means raising soil metabolism, so less humus is formed (instead even some of the 50% of not agrotechnologicly ruined soils might start emitting CO2).

          I haven’t yet heard of any fast stabilizing feedback (except that possibly the Sahara could get green again). To the contrary, from the news these days one can readily imagine rapid destruction of vegetation cover (e.g. Pakistan, Russia 2010, Australia 2009).

          From Lovelock & Kump:

          As the temperature rises to present-day values, algae lose their strong climate influence, but terrestrial ecosystems continue to regulate the climate. But if global mean temperatures rise above about 20 °C, both terrestrial and marine ecosystems are in positive feedback, amplifying any further increase of temperature. As the latter conditions have existed in the past, we propose that other climate-regulating mechanisms must operate in this warm regime.

          What are these other mechanisms?

        • John Baez says:

          I hope someone can help us with the questions you raise! The fate of the world may depend on the answers.

  11. streamfortyseven says:

          “Climate policy, as it has been understood and practised by many governments of the world under the Kyoto Protocol approach, has failed to produce any discernible real world reductions in emissions of greenhouse gases in 15 years.
           The underlying reason for this is that the UNFCCC/Kyoto model was structurally flawed and doomed to fail because it systematically misunderstood the nature of climate change as a policy issue between 1985 and 2009.
           The result of three months’ intensive work by a group of 14 authors from Asia, Europe and North America, ‘The Hartwell Paper’ argues that a radical change of approach is required, given that the 1992 United Nations international climate policy framework has failed to produce any discernible real world reductions in greenhouse gases. The crash of 2009 is a crisis that must not be wasted.”

    • The Hartwell Paper: a new direction for climate policy after the crash of 2009. Institute for Science, Innovation & Society, University of Oxford; LSE Mackinder Programme, London School of Economics and Political Science, London, UK. (2010) at:  http://eprints.lse.ac.uk/27939/

  12. Giampiero Campa says:

    I have a question, perhaps someone here can direct me to an approximate answer.

    How many gigatons of carbon will go in the atmosphere if we burn all available fossil fuels ? (by “available” i mean “feasibly extractable at today’s prices with current technologies”).

    If the above happens, how much will the final CO2 concentration in ppm be ?

    How many centuries will it take, under a BAU scenario, to get there ?


    • umass1993 says:

      This figure is not known. Global reserves of fossil fuels are not well documented. For example, the amount of oil in Saud Arabia is a royal secret.

      This shows how seriously the world views global climate change. They can’t even be bothered to take transparent stock of their fossil fuel reserves… a relatively painless first step in addressing the problem.

      • umass1993 says:

        One methodology for determining peak CO2 levels would be to look back in geologic time. By releasing the carboin naturally sequestered, we are essentially setting the climate clock back millions of years. Each ton of carbon released brings us one ton closer to pre-Carboniferous times.

        One possible method for determining steady-state temperature is figuring when an equivalent amount of carbon was sequestered in the earth and determining what the climate of the earth was at that time. Corrections for land mass and vegetation, etc. would no doubt need to be made.

    • DavidTweed says:

      In addition to transparency issues, some people would argue that “feasibly extractable at today’s prices with current technologies” is not the right viewpoint. Historically there’s been both an increase in what is technologically extractable and the price that the “world economy” can support, so it’s they aren’t really the constraints that will “bite”. They’d argue that the relevant question is how much of all the potential fossil fuels in the world would have been burned at the point where the price causes an almost complete switch to alternative energy sources.

      That’s one conceivable future scenario, but I’m not convinced that this is definitely what’s going to happen.

    • John Baez says:

      Giampiero writes:

      How many gigatons of carbon will go in the atmosphere if we burn all available fossil fuels? (by “available” i mean “feasibly extractable at today’s prices with current technologies”).

      One can’t be completely sure, but one can guess. If you read this comment to “week305”, you’ll see that Nathan Urban’s work uses this source:

      • William D. Nordhaus, 2007. The challenge of global warming: Economic models and environmental policy, Technical report, http://nordhaus.econ.yale.edu/DICE2007.htm.

      • William D. Nordhaus, A Question of Balance: Weighing the Options on Global Warming Policies, Yale University Press, New Haven, 2008.

      Based on Nordhaus’ work, Urban estimates that in a “business as usual” scenario, by the year 2300 we will have burnt 4800 gigatons worth of of carbon, compared to the roughly 500 gigatons we’ve burned far.

      This assumes we get desperate for cheap energy and extract not only coal, oil and gas but also all the hard-to-get fossil resources in oil shales and tar sands, all the remaining coal, etc.

      It does not include the methane clathrates at the bottom of the sea. It’s currently estimated that there are somewhere between 500 and 2500 gigatons of carbon in this form.

      Also: the figure of 4800 gigatons in the year 2300 is not the end of the story, because in his book Nordhaus estimates that 6000±1200 gigatons of carbon are available to be burnt (again, not counting methane clathrates).

      Here’s a graph from Nathan’s paper:

      In this scenario carbon emissions peak around 2150 at about 23 gigatons carbon per year (84 gigatons CO2). By 2300 they’ve tapered off to about 4 GtC (15 GtCO2).

      I do not instantly know the answer to your most interesting question, which is what the CO2 concentration will be in 2300, according to this scenario! I hope Nathan can tell us.

      • Nathan Urban says:

        I forget what the CO2 concentration gets up to in 2300 in that BAU scenario, but it’s similar to the RCP8.5 scenario I mentioned in the comments to “Week 305”, so probably around 2000 ppm.

        This is different from Giampiero’s question, which I interpret to be about the carbon content of “proven reserves” of fossil fuels. (i.e., stuff that we’re pretty sure is there and is economically extractable at today’s prices, with today’s technology and today’s demand.)

        As I said in the other thread, I don’t know if I believe myself that we will literally dig all that fossil carbon even if there’s as much there as these estimates say. But I think there’s a real possibility that we’d ultimately consume at least half that amount, under “business as usual”.

      • John Baez says:

        Let me do a rough overestimate of how much carbon dioxide there will be in the atmosphere by the year 2300. I will assume, falsely, that all the carbon dioxide we put into the atmosphere stays there. And I’ll assume we’ve burnt a total of 4.8 teratons of carbon by then.

        By burning .5 teratons of carbon we have boosted the CO2 levels from its preindustrial figure of 290 ppm to the current 390 ppm — that’s 100 ppm.

        So, naively, we can estimate 200 ppm of carbon dioxide per teraton of carbon burnt. If we burn 4.8 teratons by 2300, we’ll then have 960 ppm carbon dioxide in addition to the original 290, for a total of 1250 ppm.

        This should be an overestimate, since in fact CO2 leaves the atmosphere, following a complex decay curve sort of like this:

        So, I’d need to write a computer program to convolve the CO2 emissions curve with this sort of decay curve to see what’s going on. And of course even that would be neglecting nonlinear effects.

        However, Nathan has already done simulations of what happens up to 2300, so he can say what he got. And I’m sure other people have studied this too.

        • John Baez says:

          Whoops, Nathan answered while I was writing my answer. Why is my supposed ‘overestimate’ of 1250 ppm so much lower than the number he cites, 2000 ppm?

          Maybe because it’s taken us a long time to burn the first 0.5 teratons of carbon and raise CO2 concentrations by 100 ppm? So that lots has left the atmosphere during this time? So that as we burn carbon faster, this effect will do less to help us?

          I see now that I was being silly in feeling sure my calculation was an overestimate. The error could go either way…

        • Nathan Urban says:

          I think that’s an underestimate, not an overestimate.

          The actual conversion factor is 2.12 GtC/ppm, or 470 ppm/teraton.

          You assume that all the 0.5 teratons of carbon produce a 100 ppm increase. In reality, only half that stays in the air, so really you get a 100 ppm increase from only 0.25 teratons.

          Using my conversion factor, 4.8+0.5 = 5.3 teratons of carbon should give a CO2 concentration of 290 + 5.3*470 = 2780 ppm.

          To get an actual concentration of 2000 ppm, more than half of the CO2 would have to stay in the air. Since currently about half is staying in the air (airborne fraction ~ 0.5), this would correspond to weakening carbon sinks.

        • Nathan Urban says:

          My reply was too hasty. Your calculation should work even if all the carbon doesn’t stay in the atmosphere, as long as the airborne fraction is constant. Your calculation doesn’t actually assume all the carbon stays in the atmosphere.

          When you calculate your historical conversion factor, it goes from carbon emitted to ppm in the atmosphere, which (if you use the actual ppm in the atmosphere) already factors in the fact that only some of the carbon emitted stayed there.

          So you didn’t really calculate an upper bound. You’re got the expected result, if the airborne fraction is constant. A larger projected CO2 concentration than what you got means that the airborne fraction will increase (carbon sinks weaken in the future).

          Let me just recheck everything. First, the historical data. Poking into the RCP emissions database, I get 355 GtC of fossil fuel emissions from preindustrial to today, and about 160 GtC of “other” CO2 emissions (mostly land use changes, I guess), for a total of 510 GtC. About what you said.

          So … do the numbers add up? 510 GtC should give an increase of 240 ppm using 2.12 GtC/ppm. The actual increase is 100 ppm, for an airborne fraction of about 0.4 (not quite my “about half”), which agrees with numbers I remember.

          So: X GtC corresponds to X/2.12*0.4 or about 0.2 X ppm in the atmosphere. So 1 teraton emitted ends up 200 ppm in the air. Which is what you got.

          Without the 0.4 factor for the airborne fraction, it would be the 470 ppm per teraton factor I quoted. A 2000 pm figure should correspond to the airborne fraction increasing from 0.4 to about 0.7, mostly from the ocean carbonate feedback, I guess.

          I should dig into my model output and see what’s really happening. A peak airborne fraction of 0.7 is consistent with other work, so I think all is well.

          The Archer et al. (2009) review I’ve cited previously shows the recovery from a 5 teraton pulse of carbon, starting from what looks like about a 2500 ppm peak concentration. It also has a figure with airborne fractions (about 0.35 in this case), but these are in equilibrium, long after ocean invasion is complete.

        • John Baez says:

          Nathan wrote:

          Poking into the RCP emissions database, I get 355 GtC of fossil fuel emissions from preindustrial to today, and about 160 GtC of “other” CO2 emissions (mostly land use changes, I guess), for a total of 510 GtC.

          How do you get the RCP database to give you historic totals — or did you total them up yourself?

          I can see year-by-year figures by going here and clicking on “historical data”, “Historic: from 1850”, “CO2 emissions”, and “total”.

        • Nathan Urban says:

          I added the emissions up up myself. You can download Excel spreadsheets and modify them to do this. I prefer not to do data analysis in Excel, so I converted the spreadsheet to CSV format and loaded it into R.

        • umass1993 says:

          I don’t believe these decay curves.

          I don’t know how they arrived at these curves but carbon leaving the atmosphere must go somewhere.

          The only place it could go on these time scales is the ocean.. (it certainly won’t be processed back into coal again!)

          Is that the presumption, is that all the CO2 goes into the ocean? If not, then where does it go? Otherwise it must stay in the air.

          I could see how a graph like this could be arrived at by a perturbation of CO2 levels (by a volcano eruption, say) and watching the CO2 levels decay to “normal”. But that isn’t what we are discussing here.

          I just have a tough time accepting the above graph without a full explanation of how it was created.

        • John Baez says:

          umass1993 writes:

          I just have a tough time accepting the above graph without a full explanation of how it was created.

          Good! Nobody should believe a graph without some evidence. When I show a graph, I usually try to make it easy to find the supporting data. So: click on the graph and you’ll read a description of it; at the bottom you’ll see references to journal articles where the calculations were done.

        • Giampiero Campa says:

          So if i get this correctly the picture is closer to 2000 ppm than 1250 ppm because we are quite convinced that the carbon sinks (that is the ocean) are going to weaken. This is an important point, and i’d like to understand it better. The Archer paper is a very interesting read, perhaps it will help.

          For 1200 ppm it seems we are looking at a temperature increase from 4 to 8 degrees, with substantial uncertainty on the upper side due to possible positive feedbacks (e.g. methane), and with the arctic getting above-average increases.

        • Nathan Urban says:


          Yes, a lot of the increase in peak CO2 is due to weakened ocean sinks; possibly also due to weakend land sinks. (I’d have to dig into this a bit more to tell whether increased soil respiration would outweight increased productivity from CO2 fertilization.)

          The main ocean effect is probably the carbonate feedback I mentioned in an earlier interview.

        • umass1993 says:

          After reading some about the source of the graph, I trust it less.

          I think the above graph is just wishful thinking. The Paleo-Eocene event isn’t the same thing as what is happening now.

          Carbon is being absorbed, not reabsorbed. The sponge hasn’t been squeezed dry and then expected to reabsorb. The sponge is wet and expected to absorb even more.

      • Nathan Urban says:


        First off, these are modeling studies, not data from the PETM. The model predictions are supported by PETM data, but the model itself is just biogeochemical kinetics and such.

        Even if PETM data was crucial in determining these curves (which it’s not), I don’t understand what is your objection to the PETM as an analog for today. Both involved massive fluxes of carbon to the atmosphere, and subsequent recovery.

  13. umass1993 says:

    I see. the 7 gigatons is of carbon, not CO2. This is confusing because you refer to CO2 levels, but emissions weighted in Carbon only.

    So world Carbon emissions is 7. World Carbon Dioxide emissions is 30.

    • John Baez says:

      Yes, it’s easy to get mixed up:

      • Joe Romm, The biggest source of mistakes: carbon versus carbon dioxide. A factor of 3.67 makes a big difference when discussing climate.

      Just remember: C has atomic mass 12, O has atomic mass 16, so CO2 has atomic mass 12+16+16=44, so a molecule of carbon dioxide is

      44/12 = 3.666…

      times as heavy as the carbon that was burned to form it.

      Worldwide carbon emissions due to fossil fuels and the manufacture were about 7 gigatons in 2004, and about 8 gigatons in 2007.

      • streamfortyseven says:

        Right, and the weight of one mole of carbon dioxide is 44 grams, and the volume of one mole of carbon dioxide is 22.4 liters.

        One gigaton is 1,000,000,000 x 2,000 pounds x 454 grams/pound so the equivalent amount expressed in grams is 908 trillion grams, and the number of moles of CO2 is
        908,000,000,000,000 grams x mole CO2/44 grams = 20,600,000,000,000 moles and the resultant volume of CO2 produced is 462 trillion liters. A liter is a cube 10 cm on a side, so there are 1000 liters in a cubic meter. 1 kilometre is 1000 meters long, so one cubic kilometre has 1,000 x 1,000 x 1,000 or 1,000,000,000 cubic meters, or one trillion litres.

        One gigaton of CO2 occupies 462 cubic kilometres, therefore… And 8 gigatons occupy 3456 cubic kilometres.

        Assuming that the atmosphere extends 8.2 km (roughly 27,000 feet) from ground level, the volume of the Earth’s atmosphere is about 4.2 billion cubic kilometres, so the 8 gigatons correspond to a contribution of 3,456 cubic km/4,200,000,000 cubic km = 0.000000823

        0.000000823 x 1,000,000 = 0.823 ppm contribution to total.

        • Nathan Urban says:

          The official IPCC conversion factor is 2.12 GtC per ppm, or 7.77 GtCO2 per ppm, which comes to 0.13 ppm per GtCO2. I’ve never tried working this out myself, but I dug up a citation to this paper. Briefly glancing at it, I don’t see the 2.12 figure, but presumably it contains the necessary information.

        • streamfortyseven says:

          I used their figure for total mass of the Earth’s atmosphere, 513.7 x 10**16 kg, and did the following calculation:
          The total mass of the atmosphere is 513.7 × 10**16 kg

          78.09% nitrogen, 20.95% oxygen, 0.93% argon = 99.97%

          28.0134 g/mol N2 x .7809 = 21.88 g/mol

          31.9988 g/mol O2 x .2095 = 6.703 g/mol

          39.9500 g/mol Ar x .0093 = 0.3715 g/mol

          so wt of 1 mole of dry air is roughly 28.95 g/mole

          Adding in the contribution from CO2:

          44.0000 g/mol x .000039 = 0.0017 g/mole, no sig change from 99.97% figure to 99.999% figure

          mass of atmosphere = 513.7 x 10**19 g, 1 kg = 1×10**3 g

          513.7 x 10**19 g/28.95 g/mole = 17.74 x 10**19 moles

          17.74 x 10**19 moles x 22.4 litres/mole = 397.47 x 10**19 litres (no CO2 contrib)

          1000 litres = 1 cubic meter

          1,000 x 1,000 x 1,000 = 1,000,000,000 cubic meters/cubic km
          thus 1,000,000,000,000 or 1 x 10**12 litres/cubic km

          397.47 x 10**19 liters/1 x 10**12 liters/cubic km =

          397.47 x 10**7 cubic km for volume of atmosphere…

          3,974,700,000 cubic km

          3456 (+ 345.6, correction for metric tonnes) = 3802 cubic km CO2/3,974,700,000 cubic km atmosphere =

          0.000000957 x 1,000,000 = 0.957 ppm contribution to total

        • streamfortyseven says:

          0.13ppm CO2/gigatonne CO2 x 8 gigatonnes CO2 = 1.040 ppm CO2 …

      • John Baez says:

        Streamfortyseven wrote:

        One gigaton is 1,000,000,000 x 2,000 pounds x 454 grams/pound…

        Nice calculation! Ain’t math great? There are some issues like how the atmosphere gets less dense as you go up, but it’s a good back-of-the-envelope estimate.

        I should warn you, though — and the rest of the world too — that when I say ‘ton’, I’m always referring to a metric ton, i.e. 1000 kilograms.

        This is a bad habit: I should probably say tonne instead of ton to make this clear, and I’ve started doing so on the Carbon emissions page over on the Azimuth Project.

        So, anyway, you don’t need to convert to pounds and then to grams like that: when I said ‘gigaton’, I meant ‘metric gigaton’, and that’s exactly 1015 grams, as opposed to the American ton, which is a mere 0.908 × 1015 grams.

        So, increase your final answer by about 10%.

        • streamfortyseven says:

          I kind of figured that this might be the case, so that works out to about 0.905 ppm contribution for 8 gigatonnes of CO2….

        • streamfortyseven says:

          In addition, I’d think most CO2 ends up in the more dense as opposed to less dense parts of the atmosphere, so that 8.2 km is a reasonable estimate of the upper bound to CO2 distribution. The reasoning of course is that CO2 tends to be heavier than air – fill a balloon with CO2 and see how far it rises… N2 is the principal component of air at about 78%, followed by O2 at about 20%. That’s 14g/mole, then 16g/mole. CO2 is figured to comprise about 0.00039%, at 44g/mole…

  14. ar18 says:

    Over the last 100 million years, CO2 levels have averaged 610 ppm with a peak of 1200 ppm. Over the last 500 million years, CO2 levels have averaged 1700 ppm average with a peak of 4600 ppm. Yet all throughout those time periods, temperatures similar to today’s, rain forest’s thrived, the climate was stable — all in direct contradiction to what we are being told. Furthermore, there was a time when global temperatures were one degree higher than they are today, and you know what they called the time period? The Medieval Climate Optimum. You have to wonder why scientists called it an “optimum” and not a world-wide disaster.

    Don’t forget, just because the average has risen one degree in the last 100 years (ever since the Little Ice Age ended), does not mean that all temperatures everywhere have risen one degree. The vast majority of temperature change has been in the Arctic, with a smaller amount in the upper mountains, and very little everywhere else. If I raised the temperature of the room you are in right now by one degree, you wouldn’t even notice. Yet we are being incorrectly told that this one degree can be felt everywhere and it has a drastic change on climate everywhere.

    Temperature after C.R. Scotese

    CO2 levels after R.A. Berner, 2001 (GEOCARB III)

    • Nathan Urban says:

      What do you think “we” are being told (“incorrectly”), and by who? Citations, please.

      Yes, CO2 levels have been higher than today. So were temperatures. While dinosaurs enjoyed a Cretaceous climate, life today is not currently adapted to that. It is questionable how well it can adapt to a return to a Cretaceous climate within the span of a century or two, especially with the massive effects on ecosystems that humanity is causing.

      I am not sure what “climate stability” you are talking about. After global warming, the Earth’s climate will probably become “stable” too, but it’s the transition, and the rate at which we and species can adapt to the changes, that are the concern — not that the new climate will perpetually undergo massive fluctuations or whatever is implied by “instability”.

      I wouldn’t read too much into “Medieval Climate Optimum”. There are lots of periods called “climate optima” throughout geologic history, and while I don’t know the etymology, I’ve always assumed it came from the mathematical synonym for “maximum”.

      I also dispute that the period of time you’re talking about has been established to be 1 degree warmer than today, globally averaged, especially if you’re talking about Celsius degrees. But that’s somewhat moot, as there are other periods of time in the Earth’s history when the planet has been 1 degree warmer, or much warmer than that.

      It is a fallacy to claim that because we wouldn’t notice a 1 degree change in room temperature, that therefore a 1 degree change in global temperature is insignificant. A 1 degree shift can cause noticeable changes in ecosystem zones, precipitation patterns, etc. A 2 degree shift may be enough to eventually disintegrate a major ice sheet. And we’re not just talking about a degree. We’re talking about probably at least 3 degrees, and maybe a lot more. If climate sensitivity is 3 C and we wind up with a quadrupling of preindustrial CO2, that will be a 6 C warming. Note that 5-6 C is about the difference between a glacial period (“ice age”) and today.

      It is also fallacious to argue that a degree or two of warming is insignificant because ecosystems survived such warmings in the past. Again, rate of warming and other anthropogenic influences are key factors here as far as ecosystems are concerned. A completely separate issue from ecosystems is how well human civilizations respond to such climate changes. (For example, nomads can simply move, but countries and their infrastructure can’t always relocate so easily.)

      Certainly there is polar amplification of warming. Who is claiming that warming is spatially homogeneous? Here is a spatial pattern of warming so far (including a nice plot of warming as a function of latitude). Here is a spatial patterns of projected warming in 2100.

      • Giampiero Campa says:

        This might be a simple question but i haven’t been able to find the answer. What is the physical reason behind the fact that the radiative forcing (and hence the climate sensitivity) depends logarithmically on the amount of CO2 ? That is why is around 3C per DOUBLING of CO2, instead of being 3C for each quantity X of CO2 added in the atmosphere ?

        • Nathan Urban says:


          It’s related to how extra CO2 changes the effective radiating height in the atmosphere. I haven’t found an “elementary” derivation I’m really satisfied with, but you could look at these notes.

    • John Baez says:

      Since I’m the only one who can post graphics on this blog, here’s the map of current-day global warming that Nathan mentioned above:

      The color shows current-day changes from the temperature back in 1880-1899. Here is a graph of the average temperature change as a function of latitude:

      Here are projected future temperatures in 3 different scenarios:

      In this one the color shows changes from the temperature back in 1980-1999.

      As usual, click on the images for bigger pictures and more information.

  15. Nathan Urban says:


    What don’t you believe about the decay curves? That they’re too fast? Or too slow? Or too large/small an initial atmospheric concentration? And what curves? The Archer curves?

    Roughly: on decades to centuries, the land carbon sink is important; on centuries to millennia, the ocean carbon sink is important; on millennia to tens of millennia, the geologic carbon sink is important. Most of it does end up in the ocean over 300 years or so.

    You can dig into some of these biogeochemical models; look at Archer’s references. For ocean biogeochemistry, the book by Sarmiento and Gruber is good background.

    • Nathan Urban says:

      I think my above comment went to the wrong part of the thread.

      Also, I guess you’re talking about the curves in John’s comment. Yes, those are derived from a sudden pulse injection of carbon. For a more gradual injection, look at the curves at the top of this blog entry. They don’t decay at all (because they’re designed to stabilize CO2 concentrations by tapering off emissions). For a BAU scenario where emissions increase past 2100, you’ll see increases in CO2, not a decay. You can see those curves here. (Actually, those assume CO2 stabilization too, just at a later date.)

    • umass1993 says:

      I don’t believe them because they are based on data that was recorded when no fossil fuels had been burned….55 million years ago when all the carbon we are concerned about now was still in the ground.

      Expecting the oceans to behave the same independent of the amount of carbon sequestered in the ground, does not seem reasonable to me. It seems analogous to expecting a wet sponge to act like a dry sponge.

      • Nathan Urban says:

        As mentioned above, your focus on the PETM is a red herring. The above curves are not PETM data. The geological sequestration part of the model was checked against PETM data when forced with PETM conditions, but that doesn’t mean that the model itself will behave exactly like the PETM under modern conditions. And the terrestrial biosphere and ocean biogeochemistry parts of the model are developed independently of the PETM. They’re tested against modern data.

        Anyway, the oceans don’t really know or care how much fossil carbon is in the ground. They respond to how much CO2 is in the atmosphere, largely independently of how that carbon got there, or where it came from. (One exception is if the carbon came from the ocean’s store of dissolved carbon, changing the ocean’s initial biogeochemistry before it has to process the atmospheric carbon. But that’s not the case here.)

        • umass1993 says:

          1) Red herring? I wasn’t being rhetorical, I was expressing a genuine concern.

          2) John said to click on the graph and that is exactly what I did. The link explicitly mentioned the PETM as leading credence to the graph. I couldn’t and didn’t make this stuff up myself.

          3) As to the carbon coming from the ocean not being “the case here”,, this does not comport with my reading of http://geology.geoscienceworld.org/cgi/content/abstract/25/3/259

          “significant CH4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum.”

          4) The abstract at http://www.nature.com/nature/journal/v408/n6809/abs/408184a0.html seems to lend more credence to my skepticism of the above graph. Since the authors state, “By 2100, the ocean uptake rate of 5 Gt C yr-1 is balanced by the terrestrial carbon source, …”

        • Nathan Urban says:

          1. I know you have a genuine concern, but the PETM is a red herring, in the sense that the curves are model simulations and not PETM data. They’re not even simulations of the PETM.

          2. As I said, the model is tested against PETM data when forced with PETM boundary conditions. This does not imply that the model reproduces the PETM under modern boundary conditions. Nowhere does the model assume that the PETM and modern conditions are identical.

          Yes, the PETM is informative about biogeochemical processes which are used in the model. No, this does not mean the model assumes that modern and PETM conditions are the same.

          3. I referred to dissolved carbon already in seawater, not carbon in seafloor hydrates. Maybe methane from melting hydrates reacts with seawater enough to change the ocean sink chemistry appreciably, but I know paleobiogeochemical modelers who treat the whole PETM as an effectively atmospheric injection, so my guess is that it’s not a major factor (maybe due to a presumed slow ventilation to the atmosphere). Regardless of whether it does not, this doesn’t change point 2.

          4. What does the Cox et al. paper have to do with your objections? The mode that generated the curves John posted also has a terrestrial carbon cycle. I don’t know if it flips from a sink to a source as in the Cox paper; that depends on which terrestrial feedback wins. I’d have to read the Wigley paper more closely to try to tell what’s going on.

          But the terrestrial sink turning into a source doesn’t contradict the weakening of the ocean sink, which is what I thought you were talking about.

          I still don’t know which of John’s curves you’re even objecting to – the stabilization curves in the main post or the decay curves in the comment. I’ve been assuming decay curves. There, a terrestrial carbon source under warming is irrelevant, because those curves aren’t supposed to represent a warming scenario. They’re supposed to represent an impulse carbon source scenario at constant temperature.

          If you’re referring to the stabilization curves, a terrestrial carbon source instead of a sink changes the concentration as a function of emissions. But the concentration curves will stay the same, because the emissions curves are tailored to produce concentration stabilizations.

      • streamfortyseven says:

        How do you know that there weren’t massive forest fires, or grassland burns? Both of these are natural features of many ecosystems, and put lots of CO2 into the atmosphere; same case for the aftermath of volcanic eruptions. Fossil fuel burning isn’t the sole source of atmospheric CO2.

        • Nathan Urban says:

          I don’t see where anyone claimed that fossil fuel burning is the sole source of atmospheric CO2. In fact, umass1993 was talking about the PETM, where carbon input was not due to fossil fuel burning.

  16. Robert Smart says:

    For some interesting and relevant views of the new leader of Australia’s 2,300 professional geologists, Professor Brad Pillans, see http://www.climatespectator.com.au/commentary/science-over-scepticism. Sorry about the free registration required. This is filtered through a freelance writer. So for example the first paragraph is hard to parse until you realise that it is in the context that some (many?) people believe, or claim to believe, that climate change is not something that would happen without human involvement.

    • streamfortyseven says:

      His stand goes beyond that:
      “But he says it is those variations in earth’s spin and orbit that dictate the broader pattern of glacial and interglacial periods, with the world’s average temperature varying by five to six degrees Celsius on each swing of the climate pendulum. 
      By varying the amount of sunlight reaching the poles, these orbital changes have either resulted in the melting of ice, snow and glaciers at the poles, or promoted the expansion of massive ice sheets that have scoured higher latitudes or North America, Russia and Scandinavia in particular, he says.
      That same evidence strongly suggests that right now the world should be cooling, not growing warmer, he says. Indeed, without global warming the average temperature of the globe would be more than 2°C lower than at present.
      “At the present time, the earth is in a period when we should be having cooling and growth of ice sheets at high latitudes, particularly in the northern hemisphere, where summers are receiving less radiation and therefore less heat than they were 10,000 years ago when radiation budgets were at their maximum.
      “In fact, we’re well on the way to a minimum in the solar radiation budget at high northern latitudes, which suggests from the Quaternary record that we should be heading into another glaciation – but we’re not.
      “One very strong possibility is that changes, brought about by human activities, to the composition of the Earth’s atmosphere have largely counteracted that natural tendency to be cooling and things are not cooling in the way that they ought to be.”
      So is there an upside to this period of human-induced warming, by deferring the next glaciation?
      “Well, look, there’s an argument of that kind to be made, absolutely: The estimates made by modellers suggests that the world is at least a couple of degrees warmer – averaged over the globe – than it otherwise would have been without the anthropogenic emissions. 
      “Now if you make the world 2°C cooler you would certainly create problems in a number of areas where humans are farming and living today. Siberia’s bad enough today, but imagine if it was even colder.
      “Probably we are better off in a warm world as we are today than during a glacial period. The Neanderthals in Europe may have perished because of the dramatic climate changes that happened during the glacial periods and modern cities such as Toronto, New York and places further north would be non-existent, buried under ice, during a major glacial period.”

  17. Giampiero Campa says:

    Slightly off topic perhaps, but it’s interesting that he’d like to write a cartoon book about the latest IPCC report:


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