I am appalled at the lack of depth in the position taken by Professors Austin and Happer in the debate on climate change (feature, March 17). Surely, as physicists they must be aware of and should have given consideration to the well-established principles that (1) a complex non-linear system can produce unexpected short-run oscillations in the variables that define its state-space, especially when such systems enter state-space domains characterized by criticality where systems’ stability and predictability can deteriorate into chaos; and (2) that major meteorological systems are prime examples of such complex non-linearity – as demonstrated mathematically by Edward Lorenz, the “father of chaos theory” and meteorologist – and exemplified historically by the 1,000-year deep freeze of the Younger Dryas, which occurred during the period of great global warming following the end of the last ice age.
Principle (1) entails that yearlong and decadelong examples of ambient cooling or glacial thickening have little if any bearing on the overall longer-term trends and, in fact, the oscillations can serve as a warning that our global meteorological system may well have entered the potentially unstable domain of criticality. If the system under consideration is defined over a geometric space, this principle also means that one can expect the distribution of values for any system variable can at any one time vary widely geographically and individual measurements can be contradictory. The validity of virtually every empirical example supposedly supporting the climate-change skeptics is rendered questionable by the above considerations. It also means that, in principle, within the domain of criticality, no mathematical model can ever predict accurately future (or relevant past) conditions. Paraphrasing Lorenz’s conclusion, the flutter of a butterfly’s wings in California can result in a hurricane in the Caribbean.
The crucial issue in considering the threat facing mankind today from climate change is the possibility that our global meteorological system is approaching or is entering the domain of criticality (similar to the period that initiated the Younger Dryas). Evidence supporting such a hypothesis would be an increase in the incidence of extreme (“all-time record”) events of any kind around the globe – whether or not they seem to fit or refute the apparent long-term trends.
And it should be noted that whether or not human activity has “caused” or “is causing” the long-term trend supporting “global warming” is irrelevant – the hypothesis is dubious at best if taken seriously. What is crucial is whether human activity is contributing in any way to the system variables – and hence to its increasing instability – in a way analogous to the butterfly flapping its wings. That is, our contribution does not have to be primary or major – if our activity in any way is pushing the system into the domain of criticality, we should examine how best to reduce or modify our contribution.
As for the pathetic argument that humanity thrived when temperatures were warmer and hence we can expect to benefit from global warming, the homo sapiens population that supposedly “thrived” numbered less than a million over the surface of the Earth and as hunter-gatherers were socioeconomically free to move quickly to more favorable geographical locations (which they did). It also might be noted that by the end of the Younger Dryas – which created extreme conditions – according to recent estimations, the total population of homo sapiens fell to less than 100,000. But more to the point, the current socioeconomic constraints on the current world population of 7 billion human beings would make impossible any geographical adaptations to cope with the most likely consequences. Rather, the most likely outcome of continued global warming would be a demographic apocalypse around the world – and with it, severe economic collapse – as the most densely populated areas are very close to major ocean systems – or depend upon predictable water flows from what would become greatly diminished or no longer extant glacial systems.
One more crucial observation is that rising sea levels are almost certainly not the most immediate threat implied by the current dynamics within the world meteorological system. Much more devastating would be more frequent and violent weather events, severe multiyear shifts in rainfall patterns producing destructive floods or droughts, collapse of ecosystems upon which human populations depend, and the interruption of the flow of major ocean currents due to buildup of fresh water on the surface of the oceans. Any or all of the above could occur without any major shift in the mean values of any “key variable” such as CO2 emissions.
I strongly suggest that Professors Happer and Austin stop trying to win specious arguments and instead do some revision in the fundamentals of complex system theory – after which they then could make much better use of their energies by considering how our institutions can best organize to meet the possible consequences of the looming instability in the world meteorological system.