Johan Rockström recently appeared on TED to present the ‘planetary boundaries’ approach, published in Nature last year. It’s a great presentation well worth the time. (You can get the paper the approach is based on, or read Nature’s special feature.)
I’ve heard a few scientists complaining about what they see as arbitrary boundary choices, or the false confidence such an approach can arouse.
Nature’s editorial acknowledges:
[E]ven if the science is preliminary, this is a creditable attempt to quantify the limitations of our existence on Earth, and provides a good basis for discussion and future refinement. To facilitate that discussion, Nature is simultaneously publishing seven commentaries from leading experts that can be freely accessed at Nature Reports Climate Change (see http://tinyurl.com/planetboundaries).
Defining the limits to our growth and existence on this planet is not only a grand intellectual challenge, it is also a potential source of badly needed information for policy-makers. Such numerical values, however, should not be seen as targets. If the history of environmental negotiations has taught us anything, it is that targets are there to be broken. Setting limits that are well within the bounds of linear behaviour might therefore be a wiser, if somewhat less dramatic, approach. That would still give policy-makers a clear indication of the magnitude and direction of change, without risking the possibility that boundaries will be used to justify prolonged degradation of the environment up to the point of no return.
Shame about the chart junk:
Here’s a (slightly) better version by New Scientist: