Sunday, September 23, 2007

Continuity and change

... it is like a running blaze on a plain, like a flash of lightning in the clouds. We live in the flicker--may it last as long as the old earth keeps rolling! But darkness was here yesterday.
Joseph Conrad, Heart of Darkness

Richard Dawkins coined the phrase "the discontinuous mind" in the context of evolution, but it applies more generally than that. Species aren't neat and defined stages between which evolution carries creatures. It's more that whenever we look at an animal, we see them in the lightning flash. All life is in a process of change; we see a snapshot of a process. This is clear when ring species are considered:
The best-known case is herring gull versus lesser black-backed gull. In Britain these are clearly distinct species, quite different in colour. Anybody can tell them apart. But if you follow the population of herring gulls westward round the North Pole to North America, then via Alaska across Siberia and back to Europe again, you will notice a curious fact. The 'herring gulls' gradually become less and less like herring gulls and more and more like lesser black-backed gulls until it turns out that our European lesser black-backed gulls actually are the other end of a ring that started out as herring gulls. At every stage around the ring, the birds are sufficiently similar to their neighbours to interbreed with them. Until, that is, the ends of the continuum are reached, in Europe. At this point the herring gull and the lesser black-backed gull never interbreed, although they are linked by a continuous series of interbreeding colleagues all the way round the world. The only thing that is special about ring species like these gulls is that the intermediates are still alive.
This is more than an insight into evolution. It's a deep insight into the nature of the universe. One of the biggest problems science has had is the shifting of perspective from that of a single human lifespan, when species, continents, solar systems and the stars that seem fixed need instead to be seen in a longer timescale as a glimpse, as in the flash of a camera, of a process of change and movement.

This is surely one of the problems that the debate about climate change faces, but in this context it is overlaid with irony. NASA Administrator James Giffin made this point recently:
To assume that [global warming] is a problem is to assume that the state of Earth's climate today is the optimal climate, the best climate that we could have or ever have had and that we need to take steps to make sure that it doesn't change. First of all, I don't think it's within the power of human beings to assure that the climate does not change, as millions of years of history have shown. And second of all, I guess I would ask which human beings — where and when — are to be accorded the privilege of deciding that this particular climate that we have right here today, right now is the best climate for all other human beings.
James Hansen, also of NASA and perhaps the world's senior alarmist, tries to paint this differently:
“Civilization developed,” Hansen writes, “during a period of unusual climate stability, the Holocene, now lmost 12,000 years in duration. That period is about to end.”
In this argument, Hansen tries to suggest that although the climate is a changing process, it hasn't been changing significantly for some twelve millennia, but now it is. Is it?

This really isn't clear from the evidence. Modelling - some modelling - suggests it is the case, and this deserves attention. But in all this there must at least be the suspicion that Hansen, in his attempt to argue that we've seen a 12,000 year stabilisation of the climate, is suffering from a version of the discontinuous mind. He has been associated with alarmism for a long time - more than three decades, and the alarmism hasn't been consistent except in its basis in an idea that any sign of trend in either direction - colder or warmer - is a calamity.

And this is, ultimately, an anti-scientific idea. It's the scream of the hind brain: "I was born into a static universe and now it's changing!"

1 comment:

dearieme said...

That's rather a generous intepretation of Hansen's way with numbers.