Under a Green Sky

Under a Green Sky: Global Warming, the Mass Extinctions of the Past, and What They Can Tell Us about Our Future

How’s this for a writer’s motivation? “I am as scared as hell, and I am not going to be silent anymore!…Thus this book, words tumbling out powered by rage and sorrow but mostly fear, not for us but for our children – and theirs.” The book is Under a Green Sky: Global Warming, the Mass Extinctions of the Past and What They Can Tell Us About our Future, first published  in 2007 with a paperback version in 2008.  The scared as hell author is Peter D. Ward, a paleontologist and and professor of Biology and of Earth and Space Sciences at the University of Washington, Seattle.

The book certainly shows why the author has reason to be scared, but he lets us know gently, with a mixture of patient explanation and lively narrative.  He has worked at many interesting sites and he knows how to bring his visits back to life for the reader, whether gently chipping at cliffs on a heavily populated French beach or spending a week of 18-hour days in unceasing rain with a small group of colleagues on a remote Queen Charlotte Islands beach and running out of food the day before weather permitted the helicopter to return.

Mass extinctions in the past are his focus.  His work helped to confirm the 1980 hypotheses of the Alvarez team that the extinction which saw the end of the dinosaurs some 65 million years ago was catastrophic and caused by an asteroid striking the earth.

There have been other sometimes greater extinction events in the past, especially the “Great Dying” at the end of the Permian period some 250 million years ago.  Were they too the result of asteroid impact?  If it could happen once, why not other times as well? Ward explains the investigations that lead to the conclusion that only the one extinction  was the result of impact.  The rest were different.

He takes the reader carefully through the discoveries which point to the proposal that they were greenhouse extinctions, the result of complex processes which began with releases of carbon dioxide and methane (sophisticated estimates of past carbon dioxide levels show sharp increases at the time of each extinction), caused initially by volcanic activity on a large scale. This meant a warmer world which affected the ocean circulation systems and disrupted the conveyor currents. The oceans were a key factor. Bottom waters started to have warm, low-oxygen water dumped into them, ocean winds and surface currents came to a near standstill so that there was less mixing of oxygenated surface water with the deeper waters and, gradually, ever-shallower water changed from oxygenated to anoxic.  When it moved high enough for light to penetrate, green sulphur bacteria expanded in numbers and filled the low-oxygen shallows.  Accompanying them were other bacteria which produced toxic amounts of hydrogen sulphide which rose into the atmosphere.  There it broke down the ozone layer and the subsequent increase in ultraviolet radiation killed much of the green plant phytoplankton.  As the hydrogen sulphide moved up into the sky it also killed some plant and animal life and its combination with high heat increased its toxicity.

This summary conclusion is supported by a wealth of careful detail.  Like most climate history it is based on a great variety of evidence from people working in many fields of study.  Much of the work and hypothesising is quite recent, and will no doubt be put to much examination  before it can be regarded as established.  In the meantime it’s a fascinating read, fully accessible to the non-scientist. (It helps to have a chart of the geological periods alongside though if, like me, you’re a bit hazy about them.)

But the book doesn’t finish there.  Ward is all too aware that we also are living in a time of rapidly rising carbon dioxide levels – not from volcanic sources this time but from burning fossil fuels.  The question he addresses is whether the rate of increase today is on a par with the rate during those times when greenhouse extinctions occurred. He concludes that the present rise seems to eclipse any other rate of increase in the past. Oceanic acidification is an indication of this, since the natural buffering systems need time to strip the carbon dioxide out of the water. We are “hurtling towards carbon dioxide levels not seen since the Eocene epoch of 60 million years ago, which, important enough, occurred right after a greenhouse extinction.”

Would it matter if human civilisation was transported to the Eocene world?  New Caledonia everyone?  Any apparent attractions are rapidly punctured.  He instances the harshness of tropical life, the catastrophe of sea level rise, high mortality rates, widespread infectious diseases, famine and war.

If we can sharply curtail emissions in the 21st century we have a chance of getting carbon dioxide levels down to 400 ppm, even if we overshoot it briefly, and hence have some chance of limiting temperature rise to 2 degrees.  If not we are heading for an ice-free world, a change in the thermohaline conveyor belt currents and a new greenhouse extinction. “The past tells us that this is so.”

Towards the end of the book he records a memorable interview with David Battisti of the University of Washington, a notable climate scientist, one of whose lectures stimulated Ward to write this book. He asks Battisti to describe verbally the world we are headed for on our current trajectory. It’s a very different world and it’s not nice, though Battisti still hopes that under the pressures of climate change we will put into place a political structure able to implement the global regulations and incentives that might rescue us.

Ward concludes with three possible scenarios based on what he has written in his book and the “massive scientific literature” dealing with global warming and climate change.  The first is the only one I can bear to contemplate.  It’s bad enough, but the sea level will have risen by ‘only’ a metre, the conveyor belt current system will not have stopped, the ocean will stay mixed.

The political solution is out of the hands of the scientists.  But the policy makers can’t say they aren’t being warned. “This book is my scream”, Ward writes. It’s a very civilised scream, like that of many other scientists, but we must hope like hell enough politicians have ears to hear it.

14 thoughts on “Under a Green Sky”

  1. Bryan, what basis is stated for the idea that winds and currents will slow as the climate warms? That idea seems to have been considerably revised in the last few years. I’m not certain if the new view is universally accepted as yet, but I’ve seen no arguments agains it. See here and here. When was Ward’s book put to bed, BTW?

  2. Steve, Ward mentions the decrease of equator-to-pole temperature differences, a consequence of continued warming, as being responsible for the near standstill of ocean winds and surface currents in the greenhouse extinction events. Although I stuck closely to his own summary statement, I condensed it a little when opportunity seemed to allow, omitting this step in the process – looks like a mistake on my part.

    I’m a general reader and in no position to offer any judgment on what he says. And I’m not confident that I can identify anything more which could be described as a basis for this statement. He spends quite a bit of time in the course of the book describing the stratified oceans of earlier geological times, and far more common over most of geological time. He speaks of the main drivers that created the mixed oceans which we still enjoy as being the extreme temperature differences that came to exist and still do between the cool polar regions and the tropics. I notice he also stated that it may not be the presence of any of these ocean states that causes distress to life but the change from one state to another.

    In the case of the biggest extinction event, the Permian, he refers the 2005 work of climatologists Jeffrey Kiehl and Christine Shields. (Geology 9:757-760) They used a global circulation climate model, put in the known positions of the continents and imputed a warmed world as well. Their modelled Permian world showed a shift in the positions of the conveyor belt currents. He notes that they proposed that sudden global warming caused a change in ocean state. But again I’m not sure that is fully relevant to your enquiry.

    The book was published in 2007 and he refers to publications as recent as 2006.

  3. …quite a lot of equivocation there Bryan…

    For every scary warming voice, there’s a note of caution…

    “This AGW struggle will fade away. In the past, we were afraid of the Y2K bug that was going to paralyze the world, we were afraid of the tail gases of a comet that was supposed to strike the earth – none of this happened. In the last 10 years, the earth’s temperature has not risen. Over the last century, it has risen 0.75 degrees. Less than a degree. My guess is that even if we double the amount of carbon dioxide by 2100, the temperature will only rise by one degree, and we needn’t be afraid of that.”

    Prof. Nir Shaviv’s,Physicist, Hebrew University


  4. Ayrdale, I’m not sure what you mean by equivocation in this context. If you’re referring to my reply to Steve’s question it wasn’t intended to be equivocal, merely indicating the limits of my ability to know what further information Steve may have been looking for. I am not a scientist.

    Quoting Nir Shaviv’s assurances does nothing in the face of Peter Ward’s and so many other scientists’ concern. Shaviv does not engage with the realities. You can hardly oppose the paragraph you’ve quoted against the vast body of scientific work represented in many of the books I’ve been reviewing on this website. You’re welcome to take comfort from him yourself, but it’s pointless offering him in this context.

  5. Ayrdale, the conference you anticipate is sponsored by the Heartland Institute , whose free market ideology brushes aside science whenever it gets in the way. The health effects of tobacco smoking, or the dangers of global warming can both be ignored – or, if not ignored, questioned by selective tactics. Take a look at what the passage you quote from Shaviv actually says:
    1. There have been worries in the past which haven’t eventuated. Therefore global warming won’t happen
    2. On the rising incline of global temperature in recent decades 1998 was warmer than subsequent years (albeit arguably in relation to 2005). Therefore the earth’s temperature has stopped rising. Ignore the incline.
    3. The rise in temperature over the past century is less than a degree. This is evidently insignificant. Never mind that this level of warming ensures further inescapable warming already in the pipeline.
    4. He has a guess, which is wildly at variance with the careful estimates of a vast scientific literature, that doubled CO2 will mean a rise of only 1 degree in global temperature.

    Is this science?

  6. In the last 10 years, the earth’s temperature has not risen.

    That would be devastating, if it hadn’t been rebutted approximately 940,000 times. He’s either totally ignorant, highly credulous, or dishonest.

  7. Thanks Cindy. At least that explains where he gets his “guess” about temperature rise in relation to doubled CO2 from. But Ayrdale can’t claim that Shaviv’s article has been ignored. Those are some distinguished climate scientists who have examined it and found it wanting.

  8. “In the last 10 years, the earth’s temperature has not risen.”

    Does that mean that every day gets a bit colder than the previous one? That is just crazy…

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