Plows, Plagues and Petroleum

Plows, Plagues, and Petroleum: How Humans Took Control of Climate

William Ruddiman’s book Plows, Plagues, and Petroleum: How Humans Took Control of Climate has attracted a good deal of interest in the climate history world since it was published in 2005.

His major thesis is that even before the industrial revolution, human activity over a period of 8000 years was responsible for a significant rise in carbon dioxide and methane levels in the atmosphere.  After explaining orbital changes and their effect on ice-age cycles and monsoon cycles he turns to what he considers an anomalous rise in methane concentration in the atmosphere which began 5000 years ago – anomalous in that the naturally declining solar radiation would be expected to result in gradually lowering methane levels as wetlands diminished in size.   He patiently works his way through what can be inferred of early agriculture to a hypothesis that increasing rice irrigation was mainly responsible for the methane increase, with lesser contributions also from domestic grazing animals and biomass burning.  His next step is to look at CO2 changes, where he detects a similar anomaly beginning 8000 years ago when the natural downward trend was interrupted at around 260 parts per million to rise to around 280 ppm by the start of the industrial revolution.  In the case of CO2 he attributes the rise to deforestation for agriculture, aided perhaps by some peat and coal burning. This attribution is tested against the population levels and likely amount of deforestation resulting from agricultural activities; he explains the calculations which he undertook to establish its credibility.

If he is correct this would mean that the warm and stable climate of the last 8000 years has been due to unwitting human intervention which offset a natural cooling that would otherwise have gradually developed.  He sets out reasons for the conclusion that a degree of glaciation may by now have been occurring in Canada were it not for human farming activities.

His hypothesis has been challenged, as he expects and, as a scientist, welcomes. He responds in his book to two of the challenges, both of which he acknowledges to have merit.  One is that he did not go far enough back in the sequence of ice-age cycles when looking at the pattern of previous interglaciation periods for a comparison of what might be expected from natural processes today. The other is that humans could not possibly have cleared and burned enough forest to account for such a large CO2 anomaly.  He considers that with some adjustment his hypothesis survives these challenges.

He then considers the “wiggles” that have occurred in the CO2 increases over the 2000 years prior to the industrial revolution, particularly the so-called Little Ice Age, when the CO2 level dropped somewhat.  He doubts natural causes and looks instead for processes that might have reversed the slow deforestation which he has suggested responsible for the gradual CO2 increase.  He rules out war and famine as not disastrous enough on a large enough scale and settles on disease, especially the plague.  He theorises that as epidemics and pandemics caused major drops in population, reforestation occurred in abandoned farmland, there was a slowdown in new deforestation, and in China a decrease in the amount of coal burning.

The question Ruddiman then proceeds to address is why the relatively modest rise in greenhouse gases caused by humans before the Industrial Revolution led to so relatively large an increase in temperature – 0.8 degrees – while the relatively large rise in greenhouse gases since the Industrial Revolution has been accompanied by a still relatively small increase in temperature.  His answer lies in the response time required for the full effects to be felt and he explores this in some detail in relation to both land and ocean, showing how response times vary in different environments.

Ruddiman’s hypotheses continue to be debated by climate scientists.  In fact Wallace Broecker, one of the world’s leading experts on climate history describes them as “total and utter nonsense”, according to a September 2008 New Scientist article.  The article reports Broecker reckoning there’s a natural explanation for the CO2 rise. Deep-sea sediments record a drop in carbonate concentrations that could account for the rise in atmospheric CO2.  But others find Ruddiman at least worthy of further consideration.  His book is certainly a fascinating detective science story, readily accessible to a general reader.

But I enter a caveat in relation to his closing chapters where he looks at future warming prospects as the full effect of the large post-industrial revolution rise in greenhouse gases begins to be felt. His prognostications are more optimistic than many climatologists would be willing to offer today. He gives us a century or two to melt much of the world’s sea ice and mountain glaciers and push back the seasonal limits of snow cover, but considers the two great ice sheets will be largely intact. The book was published over three years ago. One wonders whether he would be as sanguine now.

When he wrote the book he was certainly disinclined to see climate change as an overwhelming challenge. In fact he is quite testy about what he describes as the alarmism of extreme environmentalists and their organisations. He doesn’t name them, but he accuses them of oversimplifying the complexities of the global warming issue. He should have identified the organisations he refers to. Maybe he has noticed more alarmist predictions than I have. Major environmental advocacy groups such as Greenpeace and WWF seem to me to stay well within the bounds of responsible science on climate change.

He finally states that the depletion of precious resources – naming water, topsoil and fossil fuel – poses a greater threat to the human future than the threat of global warming does.  There are certainly many serious threats to the continuance of human society, but he provided me with no grounds for relegating global warming to a secondary rank.

12 thoughts on “Plows, Plagues and Petroleum”

  1. 1) I discussed this in how to learn about science, as it’s a wonderful example of the way science actually works:

    a) It’s a much more generally-accessible argument than many things scientists actually argue about.

    b) It’s going on *now*, so people can watch it happening.

    2) Regarding environmental extremists, I actually agree with Ruddiman, having read about “penguins disappearing from the *Arctic*” for example. I’ve been in meetings with (for example) someone from the Environmental Defense Fund describing serious unhappiness with people who they felt were getting in the way of actual progress. The popular press often exaggerates (in either direction). We (happily) live in one of the most intensely environmental-conscious towns in the SanFrancisco Bay Area [which says a lot]. Our town logo is a tree, we have a few redwoods on our lot, and cutting down any big tree requires a permit [all of which is fine.] Founders of the Peninsula Open Space Trust live here [people pay to buy property to keep as open space/trees.]

    Lumber companies vary widely in their level of responsibility, and reasonable people can disagree about details, but I’ve seen cases where:

    a) Responsible logging would keep a forest healthy, and pay for keeping the brush cut. Forest fires are relevant here.
    b) Most rational environmentalists are quite willing to work with reasonable lumber companies. After all, trees used as lumber actually sequester carbon, if one farms them, and forest management in wildfire country requires care.
    c) But some people aren’t so reasonable, i.e., *any* lumber company is Evil, by definition, and the only desired outcome is bankruptcy.

    Anyway, I think the issue is that most environmentalist organizations are rational, but it doesn’t take very many irrational ones to irritate even reasonable people. In some ways, this is akin to the old temperance union “it’s immoral to smoke” views, which in some cases seemed unhelpful, even though science later showed the downsides.

    3) In any case, Bill has done substantial work since the book, and keeps trying to get Broecker to debate him, but without luck so far.

    Here’s an interview with Robyn Williams in 2007,
    a long piece in 2007 (subsc rqd, sorry), a 2008 piece on early rice farming in China (subs rqd), and a few weeks ago at AGU meeting is Stanford research on reforestration.

    I haven’t seen the actual last paper yet, but looks interesting.

    4) Anyway, this is probably my favorite current case of “historical science as really done, by real scientists, with hypotheses proposed, changing, evidence (pro and con) accumulating. Of course, Bill’s career has been in paleo-science, not thinking so much about modeling the future.

    IF I had to bet, I’d guess that his 3 hypotheses [CO2, CH4, and plagues] will get adopted to some degree or other.

  2. John, PV is a lovely town, but let’s not forget about the horrendous per-capita carbon footprint of such wealthy enclaves, however eco-conscious some of the residents of this particular one may be. Re environmentalism generally, it’s a large and diverse movement with its fair share of both ideologues and sell-outs. Usually the aforementioned ED (note no more F) is mentined as the prime example of the latter, although they have plenty of competition. On the forestry stuff, my personal litmus test (for what it’s worth) is whether a company is committed to ceasing cutting of old-growth, if not now then very soon.

    I have a mostly unrelated question for you:

    Do you know anything about Ed Ring or his EcoWorld site? Somehow I’d manage to miss it or more likely had just forgotten about it, but was reminded today when it was plugged on the Watts cold weather blog. Ring himself seems to have major SV VC connections (see this conference site), and has managed to put together a web presence with apparent participation by some real environmentalists (e.g. Randy Hayes) notwithstanding his climate denialism (the postWatts referenced, e.g.) and some even more, ah, gobsmackingly unique views for an environmentalist (see this conference video and this unrelated column e.g.).

    I’ll pass this along to Frank as well.

  3. Gareth, I just now tried to post a longish comment (unfortunately not saved) and the blog software appeared to devour it without a trace. Any hope?

    FYI it had about a half dozen links including several “nofollow”s, which I belatedly notice aren’t listed as acceptable.

    [Rescued. It was the number of links that did it – not the “no follow” term. I have the spam filter set to three max. I’ll increase that, because now that I’m using registration the spam’s almost non-existent. For now. – GR]

  4. John, my problem with Ruddiman’s comments on environmental extremists in relation to climate change was the conjunction of his not identifying them and his not seeming greatly troubled himself by the impacts of future warming. If he is not perturbed does that mean that he is more inclined to see extremism in anyone who is? I found it difficult to get clarity about this from his final chapters. He is, thankfully, scathing of contrarian positions on global warming, but suggests that the alarmists whom he doesn’t identify are almost equally guilty of playing fast and loose with the science. I am no scientist, but I have tried hard to understand the science of climate change as presented in a considerable number of books for the general reader written either by scientists or by science journalists. What I read I find more alarming than Ruddiman appears to and, although I would be greatly relieved to discover that after all there was no need to be unduly concerned, it seems to me that my alarm is inescapable in view of the science. I am grateful for the work of many campaigning organisations on climate change issues. I haven’t seen much evidence that I recall of their overstating the science. It is compelling enough as it stands. Indeed the issue is so overwhelming that, far from exaggerating, most campaigning groups seem to have to struggle to keep up. There may well be some who outrun the science – but I think they need to be better identified than just referred to as “environmental extremists.”

  5. Steve: I don’t know Ed Ring, but EcoWorld looks like an unusual mix of things, including Endorsing McCain. I’m not sure how close his connections are to SV VCs, I think he conference was really AlwaysOn’s, and I think he’s based in Sacramento.

    At first blush, it looks like EcoWorld is designed to appeal to businesspeople who want to feel green, but it certainly has the strangest mix of ads I’ve seen in one place.

    You might want to reread PPP Chapters 18 and 19. The book’s focus is *not* on future climate change issues and current politics: he avoided mentioning anybody on any side, although he certainly knows some personally. He mentioned a few specific issues (without names), but I think it’s pretty clear which extreme he thinks is causing the real trouble. Like many scientists, his primary focus is *not* fighting the PR battles. [You can argue whether or not more scientists should, but I’d just observe that most scientists do science to do science, and the Little Ice Age is about as close to the present as Ruddiman’s research has gotten.]

    Many scientists I’ve met:
    a) Think we have Real Big Problems and
    b) That the exaggerations that have popped up, often via the popular press (or at least one movie), simply make it harder for scientists to communicate their best understandings, and offer openings for denialists to cast doubt. You should hear Stephen Schneider talk wryly about the way the somewhat-speculative paper by him & Rasool turned into “imminent ice age” in the popular press.

    Of course, even pretty reasonable people make mistakes. For instance, “Beating the Heat”, by John J. Berger, 2000, is generally good, but it opens with a description of flying around the Arctic in 2100, including:
    “You search in vain for the seals, walrus, and penguins that used to live there in large numbers.”

    Here’s a book written by a smart, good guy, with blurbs from John Adams (NRDC), Lester Brown (Worldwatch Institute) for example. It’s really painful to see something where you basically agree with almost everything, and then you see a careless exaggeration that damages credibility.

    I don’t think Ruddiman is *unconcerned* about climate change, but again, that wasn’t the focus of the book. He is certainly worried about the *other* problems (chapter 19) that he thinks are more immediate, and that is a reasonable view, and I even agree with it, in the following sense:

    – Peak Oil, topsoil depletion, and water problems are like a heart attack that will weaken you badly in 30 years, and any children will inherit the weakness.

    – Global warming is like lung cancer that will kill you slowly over the centuries after the heart attack, also exacerbating the heart problems. Your descendants will inherit this one for many generations.

    Fortunately, at least part of the common solution is to STOP SMOKING, but the complexity of the issue is that we have to solve *all* these issues. The water issue is already bad enough *without* AGW, for example, but I can’t think of water solutions that don’t involve energy&AGW solutions as well in the long term.

  6. John, I have already reread chapters 18 and 19 several times! I agree with you that it is pretty clear that he finds most fault with the denialists. If he and you are thinking of global warming exaggerations that can appear in the popular press I have no problem with that (though in this country it is just as likely to be false comfort from contrarians that gets press space). It was the possibility that he may have been referring to campaigning organisations like Greenpeace or WWF that bothered me. I rather wish he hadn’t written his epilogue, for I found the rest of the book a very interesting read. My own solution to the disquiet he occasioned is to reflect that as a scientist he should be attended to for his science, but not necessarily taken too seriously for other opinions. I entirely agree with you that we have to solve all the issues, and that they are intermingled.

  7. I have had my attention drawn to a review of Bjorn Lomborg’s book Cool It which Ruddiman wrote for the journal Science in 2008. I was unaware of it. He was generally appreciative of Lomborg’s book, albeit not uncritical, and reading his review has helped me understand why it might be that Plows, Plagues and Petroleum relegates climate change mitigation to a secondary rank behind other environmental concerns.

    Lomborg argues that we should spend relatively small amounts of money now on measures which improve global standards of living and the environment rather than commit larger amounts to reducing carbon emissions to reduce future global warming. He is also doubtful that people are willing to sacrifice now for the good of future generations, a theme which Ruddiman echoes in his book when he speaks of draconian sacrifices that almost everyone would find intolerable. In his review Ruddiman claims that Lomborg’s recommendations dovetail with most economic models, which indicate that the most cost-effective way of dealing with global warming is to spend modest amounts reducing carbon emissions now and then ramp up expenditures later, when global wealth is greater.

    I am unimpressed by the kind of economic reasoning Lomborg represents. It doesn’t face up to the full seriousness of global warming but atttempts to subsume it under an overarching economic theory. The matter is too serious for that. We are under a moral obligation to do whatever it costs to address the problem while it may still be manageable, and this doesn’t mean ignoring other pressing environmental matters. In any case the costs of action now may be nowhere near as large as some claim. Economist Jeffrey Sachs in his book Commonwealth, for example, seems to me to be a much more reliable guide than Lomborg. In his view modest investments will do what is required – he estimates well under one percent of annual world income to convert to a sustainable energy system, less than one tenth of one percent of the annual income of rich countries to slow the runaway population growth in the poorest countries, and less than one percent to finance the crucial investments needed in the poorest countries to extricate them from the poverty trap. He sees a huge imbalance between the modest costs of action and the huge costs of inaction.

    I remain interested in the science that Ruddiman proposes in his book, but at variance with his final chapters.

  8. It’s possible that Bill may have been taking Lomborg at face value, and from PPP, we know Bill is especially concerned about water (I live in CA, I am too), but I suspect something else is going on with Lomborg, although it has taken me a while to articulate it. See ThingsBreak for a discussions of sophisticated misdirection arguments.

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