Tuesday, April 14, 2015

How to go about going against mainstream science - a lesson (about the Anthropocene) for climate sceptics

Sou | 12:00 AM Go to the first of 23 comments. Add a comment

An article by Bill Ruddiman, a legend in the field of paleoclimatology, has just been posted at realclimate.org. I recommend it be read by:
  1. climate science deniers who wrongly think that controversial ideas can't get published
  2. budding geniuses, who have had a brainwave that's going to turn science on its head
  3. anyone who wants to dispute the claims of 1 above
  4. everyone who enjoys reading an article written by a scientist :)

Here's a teaser:
This story began late in 2003 when I introduced a new idea (the ‘early anthropogenic hypothesis’) that went completely against a prevailing climatic paradigm of the time. I claimed that detectable human influences on Earth’s surface and its climate began thousands of years ago because of agriculture. 

Read the full article at realclimate.org.

When did the Anthropocene really begin?

Then go and read this article at MotherJones:
Scientists Are Arguing About When, Exactly, Humans Started to Rule the Planet
Then, if you want still more and can get hold of it, read this new perspective article in Science: Defining the epoch we live in. It's all about how humans started affecting the planet from the time we started hunting and burning, and caused the extinction of many species. And how we started affecting climate when agriculture began. The authors argue that the Anthropocene didn't start in the modern era - it started with us, millenia ago.

Here's a figure from the article - click to enlarge it:

What's in a name? The industrial era has been a time of greatly accelerated environmental changes (1, 2), but it was preceded by large and important transformations, including massive large-mammal extinctions in the Americas and major changes associated with the spread of agriculture, including the spread of domesticated crops and livestock (5), land clearance, forest cutting, habitat transformations (6, 9), irrigated rice paddies (7), soil erosion (10, 11), and anthropogenic emissions of CO2 and CH4 to the atmosphere (8). These anthropogenic changes would not be included if the “Anthropocene” is defined by the first atomic bomb test in 1945 (3). Future changes, e.g., in species extinctions and ocean acidification, are projected to be much larger than those already seen, but are difficult to predict.


William F. Ruddiman, Erle C. Ellis, Jed O. Kaplan, Dorian Q. Fuller. "Defining the epoch we live in." Science 3 April 2015: Vol. 348 no. 6230 pp. 38-39. DOI: 10.1126/science.aaa7297


  1. I like his hypothesis, it appears to have explaining value for the Medieval Warm Period and Little Ice Age.

    The Tyndall Lecture he gave was well-argued:


  2. Should the title of the second link actually read "Scientists Are Arguing About When, Exactly, Humans Started to Ruin the Planet"?


  3. Nice; not sure about your title, tough. Shouldn't it be rather" [...] about going again mainstream hypothesis in science... "

  4. The Anthropocene began when humans discovered fire and began to manipulate the environment. Fire was the first tool discovered, long before agriculture, and gave humans the ability to defend themselves, burn field, forests and prairie, build tools, increase populations and make it possible to "stay put" when agriculture was eventually discovered. We have the carbon records from this too, which also is another example of how humans began to alter the environment.

    This is unique to the species, no other creature ever existed that uses fire. Fire use predates agriculture by a significant period of time and without it, agriculture would have never been used. Human populations would have remain very low, nomadic hunter / gatherers would have never been able to stay put or stay alive long enough to occupy a place season to season.

    Fire is the most important tool / skill that humans have ever discovered ('harnessed' is the better term) and the beginning of the Anthropocene that gave humans the ability to stay and defend, raise crops, animal husbandry and directly manipulate the environment strictly for human benefit.

  5. The Ruddiman hypothesis is set out in his excellent book Earth Transformed which Sou kindly put in the Hot Suggestions box on the sidebar. Highly recommended. I started off very sceptical and ended up substantially persuaded. Ruddiman is a proper scientific sceptic and he and his co-authors tested the key points of the hypothesis with laudable rigour. It didn't break. See Ruddiman, Kutzbach & Vavrus (2011) ) Can natural or anthropogenic explanations of late-Holocene CO2 and CH4 increases be falsified?

    Just a side-note: the LIA may have been in some part forced by a drop in CO2 (and CH4) resulting from substantial mortality in the Americas (~50m) and China (~20m) between 1525 and the 1600s. The high resolution CO2 data from the Law Dome cores capture this clearly: you can see the sharp drop just before 1600 and levels stay depressed until almost 1800.

    I don't think Ruddiman or anyone else is arguing for an anthropogenic component to the MCA.

    1. "I don't think Ruddiman or anyone else is arguing for an anthropogenic component to the MCA. "

      Actually, he does, but does not over-emphasize the short-term anthropogenic effects on temperature:

      Go back to ET:
      A) pp.166-167 and p.218, t latter showing the CO2 departure from average trends during interglacials: during MCA, CO2 "should have" been down arund 250-255 (and there are several different analyses that get that), rather than the 280+t seen in Law Dome CO2 - 2000 years.

      B) go back and read p.332 of ET and consider the implications of Fig 21-1. It looks like the lack of plagues allowed deforestration that boosted the CO2 from below 280 to above 280 ... but a smaller effect than the long-term anthropogenic influence, i.e., the long-term added at least 20ppm, and the short-term another 5-8ppm. Jiggles come from volcanoes, solar changes, and CO2/CH4 human gyrations, and it is an interesting *attribution* research problem to sort those out. See also p.343.

      C) The CO2 drop into 1600AD is the *most* visible such, because it is *really hard* to draw down CO2 that far that fast.

      Once again, if you want to understand the Holocene and human influences, Earth Transfomed is the book, IMHO a multi-disciplinary tour de force.*

      (*Admittedly, I may be biased since BIll said nice words about me in the book. :-))

    2. Thanks John, that's interesting. I shall have to go back to the book. I didn't pick up on that first time around.

      (*Admittedly, I may be biased since BIll said nice words about me in the book. :-))

      I did notice that, however. I bet you were tickled pink ;-)

    3. I should add that I bought ET on your recommendation John. I hope I've since thanked you for the tip, but if not, then I'm doing it now ;-)

      You also pointed me at RK&V(2011) which encouraged me to get the book.

    4. BBD: thanks, I think you'd mentioned that before.

      Note, of course that snow-albedo feedback magnifies the effects of jiggles in CO2, CH4, volcanoes, sun ... in areas that can be snow-covered part of the time, but not all the time. I.e., Northern Europe is a good example.

      Again, anybody interested in having the Holocene make a lot more sense than "climate has just changed naturally" needs to watch the video and reading the book.

  6. The story of Bill Ruddiman fits to my experience. I have been very critical of our abilities to remove non-climatic changes from climate station data. The least I can say is that it did not hurt my career, I would think it helped a lot.

    Unclear thinking, presenting flimsy evidence, overstating your case, that is bad for a scientist. An interesting challenge is welcome. You will naturally be challenged, but that is good, it would be weird and bad for science if it were different.

    More at Variable Variability: How climatology treats sceptics.

  7. For some additional context, it is worth reading Andy Skuce's article on the "Great Acceleration" which pointed out that

    "Annual emissions from land-use changes were the biggest single source of man-made emissions—bigger than coal or oil—until as late as 1967. Annual land-use emissions were bigger than all fossil-fuel-sourced emissions combined until 1915."


  8. For mine the only thing controversial about Bill Ruddiman's hypothesis is that so many people apparently found it controversial. Perhaps this reflects my ecology bias, as many in my discipline have long (as in many decades) given due regard to the effects that human use of fire, tools and agriculture have had on the environment.

    I'm very pleased to see that Bill's work is gaining much more widespread traction though, and I would like to tip a hat to John Mashey, Lotharsson and BBD who have each repeatedly pointed folk and Ruddiman's books for insight into the influence of humans. There's a profound consequence that arises from the premises of Bill's work, and I suspect that those implications are still to properly filter through much of the scientific sphere, let alone the more general lay domain...

    1. ...at Ruddiman's...

    2. I didn't think his work was controversial either, I thought it was a given!

      There is so much charcoal in places in South America from deliberate pre-Columbian production they are still digging it up and using it as fertilizer.

    3. Really, it was controversial (and for some still is) in somewhat the same way as the ulcer/H. Pylori history.

      1) If you read the sequences of IPCC reports, it's quite clear that people were primarily concerned with evaluating the extent to which the AGW single rose above the natural noise, and over time, improving the attribution quality.

      2) Of course people knew about human changes on the environment, and by 1990s anybody reasonable knew that humans were now contributing the bulk of multi-decadal/century-scale climate change. ...,
      but looking backwards, saw that starting and growing with the Industrial Revolution. It's hard to find people treating pre-I.R. climate as something already having strong human influences ... and in fact, as best as I can tell, a lot of models just assume that pre-I.R. variability is all or mostly natural.

      You need to read the books (PPP and ET), which include some fo the back and forth.
      There were serious arguments by serious people in peer-reviewed papers.

      1) Bill claimed that human influence started changing the natural trajectory of *our* interglacial starting thousands of years ago. BUT, he had to infer what it "should" have been in part from past interglacials, and there were a lot of perfectly legitimate arguments over the right analogs, alignments, etc ... and ice cores going further back helped Bill.

      2) There were lots of arguments about "trigger levels" for reglaciation, and serious guys like David Archer were (properly) skeptical.

      3) There was a lot of argument about population growth curves and inferred footprints of agriculture in different eras. Many people simply could not believe there were enough humans early enough with big enough footprints to fit Bill's hypotheses ... I think people ahve come around, but they were still arguing in 2011, in that special issue of The Holocene.

      REALLY, people should read the book. The 5 hypotheses that comprise the full story have different trajectories.

      1) Scientists were trying very hard to calibrate the relative extent of human effect on climate over the last century or two ... while others kept saying :
      "humans insignificant, climate changed before, MWP, LIA, see..."

      2) But since the focus was there, the default assumption was that humans really only started having clear climate effects starting with the Industrial Revolution... a bit like "ulcers are caused mainly by stress".
      Then, finally, somebody good takes a serious look at that assumption.
      This one is tricky because it is seriously multi-disciplinary and the required references are spread across a wild range of journals.

      But, go over to RC and add a question to Bill about challenges and controversy. I think he's still watching that.

    4. For some more flavor to the arguments, which are real science arguments, see W.F. Ruddiman, J.E. Kutzbach and S.J. Vavrus (2011) which is a free version of one of the papers in Aug 2011 special issue of the Holocene. Part 3 summaries pro and con arguments, with citations.

      Anyway, while the ET book is pitched a bit more generally, that paper has a lot of the key arguments, including good discussions of alignment of interglacials for good comparisons.

    5. Harry: re charcoal
      Have you read in that Aug 2011 The Holocene issue, Neotropical human–landscape interactions, fire, and atmospheric CO2 during European conquest by
      R.J. Nevle1⇓
      D.K. Bird2
      W.F. Ruddiman3
      R.A. Dull4

      This is a dandy multidisciplinary paper, in which archaeology of charcoal (66 hits in 13-page paper) gets combined with agricultural practice knowledge and evidence of the size of pandemics, plus ice core records of CO2/CH4. The CO2 drop into 1600AD shows strongly.

    6. I'm with Harry.

      I honestly cannot remember when* I first heard the idea. But it's been a "given" underlying my thinking for a very long time.

      *If you told me it was a speculative piece in ye olde B&W issues of New Scientist I wouldn't be shocked at all. It could well be that long ago - but it could just as easily have been a throwaway line in one of those anthropology tv docos at any time in the last 30 years.

    7. Again, human impact on environment has been well-accepted for a long time ... but I'd be interested in old references that claim noticeable human impact on *global climate* thousands of years ago.

  9. Heh. Reading that article on Mother Jones, where Ruddiman was understandably none too happy with 1945 being declared as the starting point of the Anthropocene, reminded somehow of this:


  10. Bill was following this, but seems to be having (paleo) browser problem here, asked me to pass along:
    "Climate-change research doesn't easily lend itself to humor. My thanks to Metzomagic in #17 for unearthing that 2009 Onion piece. Some studies say that humor favors longevity, but laughing that hard at my age is probably dangerous.

    Bill Ruddiman"


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