“American Scientist”, solidly warmist yet likely to be among the first publications to recognize the failure of AGW sometimes in the future, has a topical book review article (Runaway Change by John R. McNeill) of what appears to be a more-reasoned-than-most “tipping point” book, Marten Scheffer’s “Critical Transitions in Nature and Society“:
Runaway Change by John R. McNeill
November-December 2009, Volume 97, Number 6
Scheffer defines “critical transitions” as “sharp shifts in systems driven by runaway change toward a contrasting alternative state once a threshold is exceeded.” His interest includes but also goes beyond doom and gloom, as the aim is to apply system dynamics to nature and of society so that we might in the future have “the possibility of predicting, preventing, or catalyzing big shifts in nature and society.”
However, Sheffer’s ultimate goal (large-scale “predictability” e.g. in lake ecosystems as it is already possible in “petri dishes“) doesn’t appear easy to reconcile with all the examples he describes.
For one thing, transitions (critical or otherwise) do not necessarily include just one beginning state and one final state. And what a “state” actually is, gets less clear the more an example is studied
Scheffer begins with lakes, one of his areas of expertise. Lakes, especially small and shallow ones, can tip from one fairly stable state to another easily enough. But the more closely one looks, the less the behavior of lakes matches theory, because the theory is too simple. There are more than two possible states; indeed, there are infinite gradations. Moreover, as Scheffer notes, the notion of stability is fraught.
The situation is even more difficult about climate:
Scheffer turns next to climate systems. In contrast to lakes, the opportunities for controlled experiments on climate systems are nil, and our knowledge of critical shifts, positive feedback and runaway trends is all inferred from slim evidence.
Among possible example of climate-related critical tranistions, Scheffer lists “the oxidation of 2.4 billion years ago“, “snowball Earth”, “glaciation“, “Milankovitch cycles“, “Younger Dryas” and ENSO. Buf if McNeil is right in stating that “climate history (as currently understood) presents many examples of critical shifts on various timescales“, then doesn’t that also mean there is no such a thing as a stable climate?
Natural history doesn’t clarify much about tipping points either. The underlying theme is that “critical transitions are rare“:
A chapter on oceans shortens the timescale, discussing regime shifts in Pacific and Atlantic waters and focusing on sardine-anchovy cycles, the famous cod collapse of the North Atlantic, and, in coastal ecosystems, on coral reefs, kelp forests and estuarine oyster beds. These matters remain comparatively mysterious, and the role of human actions in them is uncertain, but the pattern of sudden dramatic shifts from one state to another is unmistakable. Scheffer follows with a chapter on terrestrial ecosystems that includes several more examples of transitions between alternative stable states on geographic scales ranging from the Sahara desert to peat bogs. Here he emphasizes that critical transitions are rare, which is true in other contexts as well, but which he does not emphasize elsewhere in the book.
The argument appears to collapse when human sciences are included, where Sheffer is mostly guided by his own preferences (Jared Diamond, “the role of charismatic opinion makers“). That is a pity as obviously the most important aspect of being able to manage tipping points, is to be able to effectively inspire people in..managing tipping points.
Consider also the fact that
the existence of alternative states within a system and the nearness of tipping points often prove hard to figure out, especially with larger-scale systems
and, regarding climate change,
We do know that there are potential alternative states and probably tipping points. But we don’t know what those alternative states are; nor do we know where the tipping points lie.
The end result can only be that effective action, of the kind that might benefit all but only if everyone participates, would be next to impossible even if everybody suddenly became an AGW believer.
And so at the end of the day for all the efforts activists will ever put in the idea of AGW, the most likely way forward will be, as usual in the history of humanity, “to act blindly in the future, as we have in the past”.