Fin Del Mundo Part 2: Accounting for Delay

Where Next?
Bob Williams
Sun 21 Feb 2010 00:09

Alongside Ushuaia
Wind: West, light to moderate
Weather: Partly sunny, cool

Things are progressing along slowly but steadily. With a little bit of luck the engine and forestay should come together mid next week. If so then I will probably still try to explore south of Ushuaia while waiting for the mainsail.

I was cleaning up some of my computer files this afternoon and came across this extract from a Science magazine article (see below). I have stopped getting too concerned about global warming myself, but will continue to do what I can, including slipping the odd soapbox stand into my blog.

I was talking to someone recently about the idea of a tipping point, and this article gives an example of one. The interesting point (to me at least) is that a long time ago the concentration of oxygen in the atmosphere was very small, and all of a sudden it changed, probably due to biological activity. Some people argue (Singer et al) that we human beings are so puny that we couldn’t effect the planet’s atmosphere significantly. Well I reckon if a single cell organism can tip the planet’s biosphere then we humans as a slightly more complicated biological organism are quite capable of tipping things back or in a different direction. What is different is our ability to imagine versus the single cell organisms which were probably responsible for oxygenating the planet. Will our intelligence be sufficient I wonder? I am hopeful but not particularly optimistic; not fin del mundo but maybe fin del homo sapiens. I think it is a case of applying the rationale behind Pascal’s wager.

Evolution at work. And another interesting thought occurs to me about the word evolution and the implication we tend give it which is not necessarily justified; but … another time.

All is well.

Bob Cat:

OK, much as it is against my feline nature I will add to the skipper’s comment; the fate of we domesticated cats is after all, for better or worse, inextricably linked to you humans, whether I like it or not. Do I care beyond my own lifespan, and a good sleep? I think my fans know the answer to this question, for those in any doubt . . . Zzzzzzzzz.

Accounting for Delay

Brooks Hanson

Earth's early atmosphere was lacking in oxygen for nearly 2 billion years; a variety of data imply that the concentration of the oxidizing gas began to rise abruptly about 2.4 billion years ago. The degree to which biological processes may have contributed to this rise remains subject to debate—some evidence suggests that cyanobacteria, which produce oxygen as a by-product of photosynthesis, appeared at least several hundred million years earlier, but why then the delay? Two isotopic studies from rocks several hundred million years older than the prominent oxidation event imply that some feedbacks may have been involved. Godfrey and Falkowski show that nitrogen isotopes record a type of nitrogen cycling in the oceans requiring the presence of free oxygen. In turn, this cycling would have depleted inorganic nitrogen required by cyanobacteria or plankton for growth, limiting their oxygen production. Frei et al. report a chromium isotope record, which traces oxidative weathering. Their data implicate small and transient amounts of oxygen in the atmosphere and ocean during this time. Together these and other data imply that the final abrupt oxidation of Earth's atmosphere reflected some fits and starts over the previous several hundred million years.

Nat. Geosci. 2, 10.1038/ngeo633 (2009); Nature 461, 250 (2009).