Heliophage


Eathrise @ 40
December 24, 2008, 5:04 pm
Filed under: Earth history, Global change, Nature writing, Published stuff

From today’s New York Times

It takes nothing from the beauty and power of the image, though, to point out that it was the photographer, far more than its subject, who was isolated, and that the fragility is an illusion. The planet Earth is a remarkably robust thing, and this strength flows from its ancient and intimate connection to the cosmos beyond. To see the photo this way does not undermine its environmental relevance — but it does recast it.

To substitute these flows for the fossil fuels poised to despoil our planet and also run out on us — worst of both worlds — is an epic task. But the message that frames all the other messages of “Earthrise” is that we can rise to epic tasks. Look where the photo was taken. “If we can put a man on the Moon …” quickly became shorthand for society’s failure to achieve goals that seemed far simpler. But still: we put a man on the Moon, and that does say something. Efforts on a similar scale aimed at harvesting the energy flowing about us are entirely appropriate, and could make things a great deal better. We cannot solve all problems; some climate change is inevitable. But catastrophe is not.

“Earthrise” showed us where we are, what we can do and what we share. It showed us who we are, together; the people of a tough, long-lasting world, shot through with the light of a continuous creation.

Happy Holidays

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American Geophysical Union

Just to say that I am and a few other people at Nature are blogging the AGU Fall Meeting in San Francisco over at Nature’s In the Field blog.



Review: Jim Lovelock in Prospect
November 23, 2007, 8:22 am
Filed under: Books, Earth history, Reviews received

Prospect cover december 2007After my having written about Jim for a couple of decades, Jim now gets to write about me. And he says kind things (for what it’s worth, I think this piece was almost certainly written before I heaped praise on him in Time).

Adverse climate change makes this a most important and timely book—not just for scientists, but for anyone who can think. Oliver Morton writes so engagingly that it reads as a well-crafted biography of the earth on behalf of the plant kingdom, tracing its evolution from tiny cyanobacteria 3.5bn years ago to the giant trees of today. Unlike a botanical text, Eating the Sun reveals the intricate chemical mechanisms by which sunlight is used by plants and how the sun powers everything that matters on earth.

Morton’s book is also about earth science, my own Gaia theory and the lives of the scientists most involved. He explains why Gaia theory is still regarded as a heresy against orthodox science. From my viewpoint he is very fair, especially since many of his witnesses are passionate defenders of orthodoxy

[…]The key to understanding why the earth is growing too hot for comfort is to understand that it is in some sense alive. Morton clearly presents a vision of a living planet, albeit one that would appear eccentric to life scientists … Soon the incremental heating from the earth itself will exceed our inputs and then further heating is unstoppable. Fortunately for us, earth history suggests that positive feedback will come to a natural stop and temperatures will stabilise five degrees above the present. The idea that we can stabilise rising temperature at some convenient level, say just two or three degrees above the pre-industrial norm, is probably the delusion of computer modellers.

[…] What makes this book so good is the way that Morton, as well as dealing with the issues, gives us portraits of the leading personalities. I was especially moved to be reminded of that rare figure Bob Spicer. Spicer is a real naturalist—one who wears muddy boots. Not one of those whose view is limited to a computer screen, like the environmental scientist who once said, “With a click of a mouse I can change the whole earth.” … A few good scientists bring us what Nasa calls “ground truth”—the solid facts we can rely on. Men and women like them grow rarer, as those who manage science believe that research money is better spent on modelling and brainstorming sessions than on messy and dangerous experiments and observations in some distant field. We … seem to have lost the checks and balances that were part of our earlier class-based society, one that scorned egalitarianism but welcomed merit.

Read the whole thing over over at Prospect.

And while logging media coverage, here’s something nice, suprising and odd — an appearance in a “books of the year” list. Nice for the obvious reasons, surprising because the Spectator is not necessarily a place that I would have expected so to appear (and Gary Dexter is not someone I know or know much of) and odd because I doubt anyone else will ever pair me up with Les Dawson (whose work as a science fiction writer had previously passed me by — a good thing, says Langford). But odd doesn’t mean unwelcome, or unininteresting — IDIC, as we say on Vulcan:

I bought Les Dawson’s Secret Notebooks (JR Books, £15.99) to see if it could furnish an explanation of why Les wrote A Time Before Genesis, the only serious fiction he ever produced, a disturbing novel of alien conspiracy, sexual mutilation and global apocalypse. Unfortunately it couldn’t, being mainly scribblings for his show spots and monologues — but it contained some gems of Dawsonian surrealism, such as: ‘I came from a very poor neighbourhood. Petty theft was rife. It got to the stage where we had to brand the greenfly.’ Continuing with the horticultural theme, Eating the Sun: How Plants Power the Planet by Oliver Morton (Fourth Estate, £25) was a timely book. After 400 wide-ranging pages it was difficult to gainsay the author’s conclusion that the best prospect for future energy generation is solar: ‘new technologies that sit in the space between the photovoltaic cell and the leaf’.



Evidence and early oxygen
September 14, 2007, 7:01 am
Filed under: Earth history, Warning: contains molecules

There’s an interesting paper in Proceedings of the National Academy of Sciences this week which adds a small new twist to a great double-headed mystery concerning the beginning the history of photosynthesis on earth (which thus comes pretty near the middle of Eating the Sun: it’s a book with a rather arcane relation to chronology.) When did photosynthesis of the oxygen producing persuasion start, and why did the oxygen produced not immediately turn up in the atmosphere?

There’s pretty hard-to-doubt evidence that the earth’s atmosphere did not have a significant amount of oxygen in it on a permanent basis before about 2.45 billion years ago. (Some people do manage to doubt this, but they have to work fairly hard in order to do so — most people in the field accept it.) At the same time, shales dug out of a borehole in Australia contain various chemicals that suggest a) that there were cyanobacteria, which produce oxygen, living 2.7 billion years ago and b) that some other creatures were using this oxygen for their own metabolic needs. There are persistent rumours of similar results from even older shales, but as far as I know they haven’t actually made it to publication.

This creates a seeming paradox: how can it be possible to have a biosphere that produces oxygen through photosynthesis and at the same time see no oxygen in the atmosphere. And how can such a state of affairs go on for at least 250 million years, and quite possibly a lot longer. The bottomline of most of the answers to this conundrum is that there was enough other stuff — organic carbon and reduced gases from the mantle — for the oxygen to react with that it could never build up stably in the atmosphere. Only when the supply of this “other stuff” was changed, through some mixture of an increased rate of burial of organic carbon, a lessened flux of reduced gases from the mantle, and an increased oxidation of the atmosphere as a whole due to the escape of hydrogen into space, did it become possible for oxygen levels to rise, at least a little. This fascinating interplay between life and the planet it enlivens is gone into in some detail in the book: David Catling has provided a helpful pdf update on the state of the debate for those who want more.

The new paper, Biosynthesis of 2-methylbaceriohopanepolyols by an anoxygenic phototroph (PNAS doi/10.1073/pnas.0704912104), comes out of the labs of Alex Sessions and Dianne Newman at CalTech, of and from which many good things are heard. The lead author is Sky Rashby, for more on whom see this post; also on the team is Roger Summons of MIT, who with colleagues published the evidence for cyanobacteria at 2.7 billion years ago (Newman has just moved to MIT, too). To some extent this new paper challenges that evidence, in that it removes one strand from it. Cyanobacteria make chemicals called 2-methyhopanes, and until now nothing else has seemed to do so, and so the presence of those chemicals in the ancient shales seemed good evidence for cyanobacteria. The new paper shows that a bacterium called Rhodopseudomonas palustris also makes the molecules in question. R. palustris is a photosynthesiser, too — but not an oxygen producing one (there is a wide range of bacteria that use sunlight this way without producing oxygen). So the idea that there were cyanobacteria present long before there was atmospheric oxygen can no longer rely on the methyhopanes for support.

At first blush, this might seem to give comfort to those who, like Joe Kirschvink, also at Caltech, want to argue that oxygen-producing photosynthesis led to the oxygenation of the atmosphere directly — that an evolutionary transition led directly to a geological one, as outlined in this PNAS paper. But the methyhopanes aren’t the only evidence for an earlier origin. What was particularly interesting about the 2.7 billion year old shales Summons and his colleagues studied was that they contained both what seemed to be evidence of oxygen producing cyanobacteria and what seemed to be evidence of oxygen consumption, in the form of molecules called steranes. Producing steranes is thought by most people to require oxygen. And so it’s not special pleading to say that while cyanobacteria are no longer the only possible source for the 2.7 billion year old 2-methyhopanes, the oxygen requiring steranes in the same sample make them the most likely source, and pretty much require that something photosynthetic somewhere was producing oxygen at the time. (There is also, as I understand it, evidence elsewhere that oxygen-requiring methane eating bugs were around before the oxygen hit the atmosphere. Not all methane eaters require oxygen — but some do, and apparently there are molecular markers that can tell you which sort was present where.)

So the idea of a lag between the evolution of oxygen production and the arrival of free oxygen in the atmosphere has at worst only taken a minor knock; from what I can gather most people in the field are still fairly convinced on the matter. It would take a second dramatic finding — for instance evidence that the steranes in the 2.7 billion year old samples are contaminants — to really throw things into doubt. As far as I know there is no indication that any such second shoe is about to drop.

Meanwhile, the molecules involved in this identity parade may well prove interesting in and of themselves. The fact that they are present in two different photosynthetic bacteria suggests that they might have a photosynthetic purpose of some sort. What that might be remains to be seen, though there are already some theories. If the genes for the pathway that makes the stuff can be found, then it might be possibleto be more definitive about which bugs use it and under what conditions.