Carbon dioxide levels have never been higher – almost

The highly respected journal Science published research recently which has attempted to discover what the world atmosphere’s carbon dioxide levels were for the past two million years. Bärbel Hönisch, is a geochemist at Lamont-Doherty Earth Observatory and with her colleagues she has been looking at the shells of single cell plankton which have been buried under the Atlantic Ocean.

Once the shells are dug up they are then dated. Then having been dated their ratio of boron isotopes is measured and this tells the researchers (they comprised also Jerry McManus, of Lamont, David Archer at the University of Chicago and Mark Siddall, of the University of Bristol) the amount of carbon dioxide in the atmosphere when the plankton were alive.

The only other way of measuring carbon dioxide in past atmospheres has been to take ice cores and analyse them. These enable us to discover the carbon dioxide levels going back 800 million years but Ms Hönisch’s methodology enables us to go back 2.1 million years and find carbon dioxide levels with precision.

The results of the research show peaks and troughs of carbon dioxide in the atmosphere, as you would expect. However, they also show that the peaks hit an average of 280 parts of carbon dioxide per million. Today, with carbon dioxide somewhere between 385 and 390 parts per million, our world is significantly higher in atmospheric carbon dioxide than at any time in the past two million one hundred thousand years.

This reveals two problems that we had thought that we had previously solved. The first is that the records of atmospheric carbon dioxide are such that we cannot blame a lack of carbon dioxide for the coming of the ice ages 850,000 years ago. Then it seems that carbon dioxide levels were relatively flat. If we cannot blame carbon dioxide for the coming of long and intense ice ages does that mean that we cannot associate high levels of carbon dioxide with warmer world climate periods?Actually the answer seems to be “no”. Ms Hönisch’s research shows that higher carbon dioxide levels corresponded with periods when the world’s climate was warmer. Ms Hönisch concludes that her data suggests that carbon dioxide levels and global climate are intimately linked.

We will have to fall back on other theories as to why the ice ages came. These other theories may also shed light on climate change. We know that 55 million years ago the world suffered a very large and rapid increase in carbon dioxide levels, although we cannot measure the actual levels. The increase caused the oceans to become more acidic and many bottom dwelling ocean creatures became extinct. The acidic oceans dissolved the shells of these many sea creatures.

With oceans becoming measurably more acidic and carbon dioxide levels still rising we run the risk of repeating the climate changes of 55 million years ago, which we imperfectly understand but do know that many animals then became extinct.

2 Responses

  1. Great article and I think (although you might not think so) that you and I are possibly in more agreement than is immediately obvious: I have no argument with the evidence that global warming is happening at the moment (though it appears that the world has been hotter in “relatively” recent times); it’s clear there is a significant increase in carbon dioxide levels; it’s seemingly true that co2 is a so-called greenhouse gas and it’s undoubtedly a fact that the destruction of the rainforests will be seen as a huge crime in the not too distant future (but not necessarily for that reason) – and we could easily do something about that if we talked to places like Brazil with an open mind!

    I have two questions, though:

    1) Where is the evidence that all these “facts” are actually connected at all and, if there is a link, is it the “obvious” one that’s bandied about as scientific fact?

    2) We bang on about carbon dioxide, but a far more powerful greenhouse gas is methane (and there are others too). Have the (currently seriously increasing levels largely due to our obsession with dairy products and beef) been compared with the past and is there any link there – and can we prove it?

    I’m not trying to deny what might well be accurate; I’m simply saying there are FAR more factors here than are usually discussed and no one has so far even attemted to seriously think all this all the way through. It’s even possible (though I agree unlikely) that the “symptoms” we are looking at are the result of something we haven’t even thought of yet and, if that were true, it might even be that we could do with MORE co2 rather than less since it might be planet Earth’s way of balancing itself.

    What we need is proof, proof and more proof – not assumtions on which we base actions that just might actually be counterproductive – a little learning is STILL a very dangerous thing!

  2. C.J., I understand your confusion. Climate change is a complex subject, probably much more so than we currently understand. But as for “proof,” we don’t need scientists to tell us we have a big problem. Each year, more and more of the Arctic sea-ice disappears, and we know that as this happens, the exposed water will be warmed by the sun. The Polar ice melt will warm our whole planet, and this process will continue until all the ice is gone. And THIS means that vast areas of our planet will become unlivable. We won’t need scientists to tell us that there will be millions of refugees seeking survival in cooler latitudes or conducting deadly wars for dwindling water resources.

    We don’t need scientist to tell us that to stop the Arctic sea-ice from melting, we have to lower the temperature of the air and water surrounding it. We all know from childhood that if you put an ice cube in a glass of water, it will continue to melt until it’s gone, unless you cool the ambient temperature down enough to stop the process. The only way we have of cooling our planet is to lower carbon dioxide emissions, which, incidentally, would keep all that methane in Canada and Siberia in a frozen state and relatively harmless.

    The folks who deny global warming may be accused of creating a deliberate snarl of useless and conflicting information to keep our politicians in a paralytic state, to their own and their childrens’ detriment.

    For some really useful information, just Google “abrupt climate change.” The Wikipedia article on the Google list that will pop up is particularly comphehensive.

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