Keeling curves and carbon milestones

By   /   May 1, 2013  /   33 Comments

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The last time there was this much CO2 in the air — about three million years ago, during the Pliocene — the planet was 3ºC warmer than today and sea level was 25 metres higher.


A carbon dioxide milestone approaches, but it’s a carbon millstone for our civilisation.

As I write, the amount of carbon dioxide in the atmosphere as measured at the Mauna Loa observatory in Hawaii stands at 399.50 parts per million. In the next few weeks that figure will tick past 400 parts per million, hover there briefly and then turn downwards as the summer growth of plants in the northern hemisphere extracts carbon from of the atmosphere. It’ll be a short respite. Some time in the next year or two the global annual average will blow past 400 ppm, because the world shows little appetite to reduce the use of fossil fuels.

The last time there was that much CO2 in the air — about three million years ago, during the Pliocene — the planet was 3ºC warmer than today and sea level was 25 metres higher. At the poles, average temperatures were at least 10ºC warmer. The Greenland ice sheet was much smaller than at present, and West Antarctica was a group of islands in an open ocean, not a great block of ice. Forests grew down to the shores of an Arctic Ocean that had no summer sea ice. It was a radically different planet to the one we inhabit, but it’s where our consumption of fossil fuels is taking us.

Pliocene climate is not something that crops up in many history lessons, but what it tells us needs to be much more widely appreciated. It shows where we are heading — where our apparently insatiable appetite for coal and oil is taking us: a drowned world. That simple fact needs to be shoved under the nose of anyone who argues that climate change isn’t happening, won’t be too bad, or will be something we can adapt to. It needs to be engraved on the hearts of the people negotiating international action on emissions, and the politicians legislating to do little or nothing.

Most importantly, the Pliocene tells us that aiming to limit global warming to just 2ºC by capping atmospheric carbon at 450 ppm is a chimera, an illusion — a short term possibility but a long term disaster. As I argued in my first post for The Daily Blog, there is an urgent need for the world to go beyond emissions reductions and start removing carbon from the atmosphere — and we need to start on the project now, not at some indeterminate future point when it might be politically expedient to do so.

Meanwhile, the American team on top of a Hawaiian volcano will continue recording the ups and down of carbon in the atmosphere, watching the Keeling Curve kicking upwards towards disaster. You can follow that trajectory in near real time here. In human terms it’s a slow-motion train crash. In the context of the history of our planet, it’s meteoric.

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  1. […] station is going to bump through 400 part per million, and stay there for a week or two. In my Daily Blog column this week I ruminate on what that means by taking a look at the last time CO2 stayed over 400 ppm for an […]

  2. Arfamo says:

    I’m a believer in AWG. The loss of ice mass and rising ocean temps have pretty much confirmed it for me. But have the avg global air temps risen again or are we now at a 17 year hiatus, as the denialists claim?

    • Global surface temps never stopped rising. The “17 year hiatus” claim is based on an apparent slow down in rate of increase, not a halt. Meanwhile, the sea ice, Greenland etc kept melting, and the oceans warmed…

  3. Robert Atack says:

    ‘we’ are saying +6 C ,,, and no ice @ around +4
    Humans are gone burger @ + 2 – 3 which is kind of fortunate as @ around +4 it is buy buy oxygen, that is when the deep oceans catch up with the atmosphere.
    Near Term Extinction .. bring it on.

    Large-scale assessments

    Intergovernmental Panel on Climate Change (late 2007): 1 C by 2100

    Hadley Centre for Meteorological Research (late 2008): 2 C by 2100

    United Nations Environment Programme (mid 2009): 3.5 C by 2100

    Hadley Centre for Meteorological Research (October 2009): 4 C by 2060

    Global Carbon Project, Copenhagen Diagnosis (November 2009): 6 C, 7 C by 2100

    International Energy Agency (November 2010): 3.5 C by 2035

    United Nations Environment Programme (December 2010): up to 5 C by 2050


    Positive feedbacks

    Methane hydrates are bubbling out the Arctic Ocean (Science, March 2010)

    Warm Atlantic water is defrosting the Arctic as it shoots through the Fram Strait (Science, January 2011). This breakdown of the thermohaline conveyor belt is happening in the Antarctic as well.

    Siberian methane vents have increased in size from less than a meter across in the summer of 2010 to about a kilometer across in 2011 (Tellus, February 2011)

    Drought in the Amazon triggered the release of more carbon than the United States in 2010 (Science, February 2011)

    Peat in the world’s boreal forests is decomposing at an astonishing rate (Nature Communications, November 2011)

    Methane is being released from the Antarctic, too (Nature, August 2012)

    Russian forest and bog fires are growing (NASA, August 2012)

    Cracking of glaciers accelerates in the presence of increased carbon dioxide (Journal of Physics D: Applied Physics, October 2012)

    The Beauford Gyre apparently has reversed course (U.S. National Snow and Ice Data Center, October 2012)

    Exposure to sunlight increases bacterial conversion of exposed soil carbon, thus accelerating thawing of the permafrost (Proceedings of the National Academy of Sciences, February 2013)

    Summer ice melt in Antarctica is at its highest level in a thousand years: Summer ice in the Antarctic is melting 10 times quicker than it was 600 years ago, with the most rapid melt occurring in the last 50 years (Nature Geoscience, April 2013)

    But all is good, because the Greeds gave us Kiwi Saver, and Labor have their climate change spokesperson at #1, ops sorry not even in their top 20.
    We are utterly fucked, makes you want to go out have a child, doesn’t it.

  4. Chris Miller says:

    I’m gonna take a guess that the fact that last time it was so much warmer is due to how fast we’re pumping out CO2 and the environment hasn’t actually had a chance to catch up yet…

    • Robert Atack says:

      Yeah Chris
      It is like taking a beer out of the fridge, it takes a while to get to room temperature, ice and the cold deep oceans have been the fridge.
      And it would be a lot warmer if it wasn’t for Global Dimming.
      There are only 2 ways of avoiding human suffering due to Climate Change/peak energy/peak food, die soon or not being born.

    • Correct. At the end of an ice age, the planet warms by about 5ºC in 5,000 years. We’re likely to do the same in 100. It will take the oceans a long time to catch up…

  5. Nitrium says:

    That global warming/climate change (or whatever they want to call it) is happening is painfully obvious to all. That it is IRREFUTABLY being caused by human beings, however, is not. CO2 concentrations have, BEFORE mankind even walked upon this planet, been MUCH higher than they are even now (2-3x as high). Shit happens. We live on a rock that has a HUGE history, including massive spikes (and DROPS during ice ages) in temperature. I’m 100% for dealing with the EFFECTS of climate change, but am 100% AGAINST trying to stop it, since it is NOT clear that we are PRIMARY cause of it.
    Our biosphere has a remarkable capacity to deal with climate change, as the last 4 BILLION YEARS have PROVEN to be true. It has recovered before, and there is no reason to think it won’t recover again. That WE, as a species, will have a lot of serious survival issues is a given. And we will certainly need to make major changes and expenditure to adjust. That much is certain. However, spending money to try and fight NATURE is a lost cause.

    • Sorry, Nitrium, but you have been grievously misinformed. The current increase in CO2 (40% in 150 years) is entirely down to human actions. Proven beyond any doubt whatsoever.

      • Nitrium says:

        Even if that was true (which I still don’t see as being irrefutably proven at all, given the assumptions that are required to model something as ridiculously complex as the global climate), trying to stop the inevitable (and further CO2 emissions are inevitable, given the politics of both developing and developed nations) is completely pointless. Especially, in light of the fact that far, far more severe climate changes have DEFINITELY occurred in Earth’s mind-bendingly long history ENTIRELY DEVOID of homo sapiens’ influence. What we learn here, might even be useful for generations in the coming millennia who will undoubtedly STILL be dealing with the effects of Earth’s changing climate, man-made or otherwise.

        • Modelling is not required to measure atmospheric carbon isotopes. Please, do some reading on this issue before attempting to gainsay an entire scientific field.

          • Nitrium Nitrium says:

            That is true, BUT modelling is REQUIRED to gauge the effect of said CO2 concentrations on the climate. And they do that with modelling. And this requires assumptions. Lots, and lots of assumptions.

          • I think you mean physics. Lots of basic physics.

        • Richard Christie says:

          Nitrium I am always dumbfounded by those who dismiss the considered conclusions of every major scientific body on the planet in regard to earth’s climate, in all of the physical and earth sciences, with no exceptions.

          Given the choice between accpting your opinion as to what is “true” or “irrefutably proven” and accepting NASA or the Royal Society’s opinions, what is a reasonable person to do?

        • Thomas says:

          Nitrium, as Gareth pointed out already: It is not only the level of CO2 and the eventual temperature but it is especially the rate of change that will cause us so much grief.
          If changes happen naturally and slowly then adaptation over many generations is much more plausible with each generation sharing some of the burdens. But what is awaiting us will cause massive disruption to the entire biosphere within the lifetime of many people living today and certainly their children. You have simply not thought through the actual implications of what is upon us I believe.

          • Nitrium Nitrium says:

            There is no way of knowing if previous climate changes occurred rapidly or not. What we do know, is that they have often occurred “instantaneously” on the planetary timescale, which is anything from years to milennia – it is (currently) impossible to accurately measure the speed of events that happened millions of years ago.

    • Afewknowthetruth says:


      Whilst CO2 concentrations have been a lot higher in the past, no humans existed at the time.

      The kind of temperature rises we are in for as a consequence of CO2 absorbing and re-radiating (Tyndall worked that bit out in 1859) will annihilate most of the plant species that make the Earth habitable for humans.

  6. Robert Atack says:

    It will take the oceans a long time to catch up…

    Will it matter?
    We are ‘only’ @ +.8c ish now, what is the great NZ drought going to look like @ + 1.6c ?
    And the USA is in about month 22 of its drought, they are only surviving on million year ‘old’ water from the Aquifer, which they have over half drained in 50 – 60 years, that equals a lot less food if nothing else.
    Is that a positive/negative feedback? less food = less humans.

  7. Afewknowthetruth says:

    It is worth noting that the CO2 level is rising faster than exponentially. In fact, a lot faster than exponentially. The 1ppm per annum rise that characterised the 1950s has increased to around 3ppm per annum, Indeed, one recent year-to-year figure was up 3.3ppm. (Just in case anyone does not know, exponential functions always go near vertical, whatever the percentage increase.)

    As the global economy becomes ever more dependent on energy sources with low EROEI, greenhouse gas emissions will surge, even as available energy declines and the global economic system implodes. I would not be at all surprised to see the annual increase in CO2 rise to 5ppm by 2020, taking us to 450ppm around 2025. And the 0.8oC rise in average temperature we have from past emissions is already generating climate chaos.

    There is no will whatsoever to even talk about such matters at central government or local government levels, let alone actually DO ANYTHING. Indeed, the mayor of the district where, I live, Harry Duynhoven, (ex Labour MP -that says it all !!!) does his best to ban discussion of reality. Like all the cretins who pretend to be leaders, he is a bought-and-paid-for liar.

    Therefore, as Robert Atack has pointed out, the human race is on track for Near Term Extinction some time around 2040, one of the most insane forms of self-annihilation one could imagine.

    Life at the End of Empire on the Planet of the Maniacs.

  8. Paula says:

    I watched a not so new Ted talk yesterday from Naomi Klein, where amongst other things she talked about climate change.
    “The climate crisis calls for us to act based on the precautionary principle, the theory that holds when human health and the environment are significantly at risk, and when the potential damage is irreversible, we cannot afford to wait for perfect scientific certainty. Better to err on the side of caution.”
    I’m with Naomi.
    “What if the IPC scientists are wrong?…”what if those scientists are right?”

    • andyS says:

      The precautionary principle is based on the “better safe than sorry” kind of thought process
      However, you have to balance this against the potential downsides of rapidly decarbonising the world economy

      I am all in favour of research and development into new energy sources that help reduce CO2 emissions, but currently these are not being actively pursued by most industrial nations – my favorite example being that of Thorium energy. So if we don’t pursue these, then we are faced with a rapid reduction in GDP, with the attendant loss of health and well-being in the population

      • Paula says:

        I’ve just read a really interesting article by George Monbiot and he states, “Here’s how the Rio Declaration, which the UK, with 171 other states, signed in 1992, defines it:

        “Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.”

        Those signatories to the declaration that are failing to fulfil their responsibility, he describes as following the Providential Principle, “if there’s even a one percent chance that our policy will not cause catastrophe, we’ll take it.”
        There is no economy, no GDP, on a dead planet.

        • andyS says:

          Fine, as long as you are prepared to put up with poverty and ill health yourself. Walk the walk

  9. John L says:

    “Especially, in light of the fact that far, far more severe climate changes have DEFINITELY occurred in Earth’s mind-bendingly long history ENTIRELY DEVOID of homo sapiens’ influence”

    It always amazes me when people pull out statements like that and try to use them as justification for a particular course of events – totally meaningless! Australia was once attached to Antarctica..!
    Is it because people are just scared, or what. Going out of their way to deny reality because it doesn’t fit their internalised view of what the world once was and should forever be! AFKTT is pretty much on to it.

    • Robert Atack says:

      John, it is called cognitive dissonance – when a belief and a fact conflict most people will default to belief .
      Or driving with your eyes fully on the mirror.

    • Nitrium Nitrium says:

      Not at all. Having read the entire IPCC report, I (as an actual scientist) simply came out being less than convinced (not in “denial” per se, just not convinced). That is all. Any scientist will tell you that “correlation is NOT causation”, yet that is largely what we have here. CO2 levels are rising (that is undeniable), and the climate is changing (also undeniable), therefore rising CO2 levels cause climate change. Now we will create complex models of how that might be happening, filled with assumptions to make the observations fit the data. If you don’t see the problems with this process, well, I have a nice bridge to sell you.

      • On other hand, you seem rather keen -as a scientist who has read the entire IPCC report – to ignore the well-established radiative properties of CO2. There’s the causal link.

        • Nitrium Nitrium says:

          Also true. However, you will also note that CO2’s greenhouse contribution is anywhere from 9-26%. If that range isn’t a MASSIVE problem for accurate/predictive climate models, well I don’t know what is. Also note the ranges for the other greenhouse gases:
          My viewpoint remains that we simply don’t know enough about our biosphere to (as yet) produce accurate models as to the effects of CO2 emissions (or any other gas for that matter) on our climate over the long-term. The fact that many plants thrive in higher CO2 environments is but one factor the climate models entirely ignore.

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