Planetary boundaries


There is a provacative series running in Nature about planertary boundaries and a “safe operating space for humanity”.  Everything in the series is free/open access here.   There is a main article and a series of essays and editorials about the approach.  Note, none of this is peer-reviewed science.  I have mixed feeling about it.  At first, it seemed like a useful framework, at least to scare people.  But after reading the paper and thinking about the boundaries (see the table below) the whole exercise seems arbitrary and subjective.  But when you are a gray-beared elder scientist, with your own institute in Stockholm, I suppose you can say anything you want in Nature or Science.

In this issue of Nature, a group of renowned Earth-system and environmental scientists led by Johan Rockström of the Stockholm Resilience Centre sets out to define boundaries for the biophysical processes that determine the Earth’s capacity for self-regulation (see page 472). The framework presented is an attempt to look holistically at how humanity is stressing the entire Earth system. Provocatively, they go beyond the conceptual to suggest numerical boundaries for seven parameters: climate change, ozone depletion, ocean acidification, biodiversity, freshwater use, the global nitrogen and phosphorus cycles, and change in land use. The authors argue that we must stay within all of these boundaries in order to avoid catastrophic environmental change.

The boundaries are based on existing data. For some processes, such as anthropogenic climate change and human modification of the nitrogen cycle, we may already have crossed the line, and need to back-pedal quickly. For others, such as ocean acidification, we are rapidly approaching a threshold beyond which there may be abrupt and nonlinear changes.

The exercise requires many qualifications. For the most part, the exact values chosen as boundaries by Rockström and his colleagues are arbitrary. So too, in some cases, are the indicators of change. There is, as yet, little scientific evidence to suggest that stabilizing long-term concentrations of carbon dioxide at 350 parts per million is the right target for avoiding dangerous interference with the climate system. Focusing on long-term atmospheric concentrations of the greenhouse gas is perhaps an unnecessary distraction from the much more immediate target of keeping warming to within 2 °C above pre-industrial levels. Nor is there a consensus on the need to cap species extinctions at ten times the background rate, as is being advised.


3 thoughts on “Planetary boundaries

  1. Hi John,

    In all honesty I do share some of your reservations with this piece. But the cards have always been on the table with this one; it has never been “masked” as peer-review and is meant to stimulate discussion on some extremely important issues and make a first stab at identifying potential tipping points (which almost certainly do exist, at-least for some of the “boundaries”) and estimates of their values.

    And really, as a “doomsday” paper, it could have been much worse. For most identified boundaries the authors make the point that we still find ourselves within the safe operating space. Concerning the jab at the “gray-beared, elder” scientist with his own centre in Stockholm: Firstly, Johan Rockström is a sprightly, energetic character and doesn’t sport a beard, and secondly this is far from being a SRC-only piece, as indicated by the range of scientists involved from other, renowned institutes and universities.

    Myles Allen (who is one of the seven experts that was invited to provide commentaries on the “Boundaries” paper) has an interesting post on the Nature peer-to-peer blog:

    “As a vocal supporter of the traditional system of scientists communicating through peer-reviewed channels ( Nat. Geosci. 1, 209; 2008 and associated debate at Peer-to-Peer), I was hesitant about writing a critical Commentary on the Feature ‘A safe operating space for humanity’ by Johan Rockström et al in the 24 September issue of Nature (Nature 461, 472-475; 2009) in a non-peer-reviewed forum. The Nature and Nature Reports Climate Change editors had clearly thought through this argument: the Feature was not itself peer-reviewed, so no golden rules would be broken in publishing a series of commentaries alongside it in Nature Reports Climate Change.
    The problem is that packing the point into a few hundred words, and slipping into the usual bloggers’ trap of feeling you have to shout loudly on the internet or no-one will listen, means that the end result reads very black-and-white. Corresponding with Johan Rockström over the past week, it emerges we agree on far more than the tone of my Commentary, ‘Tangible targets are critical’ (Nat. Rep. Climate Change doi:10.1038/climate.2009.95), probably implies. I understand that Rockström et al. had not originally intended to make the link between a six-degree climate sensitivity, the two degrees target and 350 p.p.m. a focal point (as I read it) of their Feature. Likewise, they observe, reasonably enough, that limiting cumulative carbon dioxide emissions to one trillion tonnes of carbon is just another way of framing the climate boundary, with (as I acknowledge) remarkably similar implications to 350 p.p.m.
    If this had been done the old-fashioned way, Rockström et al. would almost certainly have had to qualify their reliance on a six-degree climate sensitivity in the course of the usual to-and-fro with referees. And I in turn would have toned down a lot of my objections. The end result would undoubtedly have been blander on both sides, but would that really have been much of a loss? Following what was, for me, an experiment, I still feel it is very much an open question whether scientific communication in general benefits from direct publication rather than allowing rough edges to be smoothed off through traditional peer-review.”


  2. Thanks Albert, I appreciate your comments. After I made that post, I did have a gut feeling that it was a tad too sharp. I agree w everything you said. And I was thinking about the original paper yesterday and do see the value in getting the world thinking of global boundaries, even as a general concept, for the really big problems.

    BTW, in N America at least, the term “gray beard” is euphemistic, not literal (you don’t need a gray beard to be a gray beard). Regardless, I wouldn’t put Johan Rockström in that category. He is young and spry! But you you have to admit, some of the other authors are pretty firmly in the party elders club. Not that there is anything wrong with that-aren’t we all heading there!

  3. The paper as a whole presents a new policy paradigm rather than new science as such, so I don’t see that peer review was desirable or appropriate. It’s sort of a cross between an editorial and a review paper. IIRC the 6 degree business in particular did get peer-reviewed (along with the 350 ppm target) in Hansen et al’s (referenced) “Target CO2” paper. It’s very interesting that Allen chose to correspond with Rockstrom rather than Hansen (among other things a guy who runs an even more prominent institute), don’t you think?

    (Actually I just now read Allen’s piece, in which he puts forward a non-peer-reviewed attack on “Target CO2” and promotes his own approach. Eh. So, Myles, can you guarantee that there’s no scenario under your approach that would threaten a runaway melt of the ice sheets? Myself, the latest IceSat results on the ice sheet flow rates make me just a little nervous on that point. The problem with the tonnage limit approach is that it helps justify a continued sharp CO2 increase followed by a hoped-for rapid drawdown, and so far the evidence would seem to be that this is a poor fit with human nature.)

    I can think of one good historical parallel for this exercise, that being the Doomsday Clock. I would be surprised to find out that the issue of how close it was being set to midnight ever got peer-reviewed. Even so, it was a very useful policy tool in the hands of its scientist-sponsors. Interestingly, climate change has now been added to the criteria for setting it, and IIRC was responsible recently for it being set a couple of minutes closer to midnight. A more complex metric seems to me to have more utility, so I’m quite happy with Rockstrom et al even as a rough draft.

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