by fire and ice and ...

The Life and Death of Planet Earth
By Peter Ward and Donald Brownlee
Henry Holt/Times Books, 2002
RATING: **1/2 (of 5)

How many ways can the Earth end?

Probably more than anyone with anything less than a (slight) obsession with the concept is willing to consider.

Just so happens, I guess I have such an obsession, at times anyway. So do Ward and Brownlee, who spend over 200 pages exploring just about every possible doom the Earth will eventually face over the next 6-8 billion years.

Before I get into analyzing what they say, I'll give a quick timeline as they see it (not quoted from them, but culled from various places in their book. The quotebox layout is simply for display. All dates, obviously, are estimates.):

Next few centuries: Global warming sparked in part by human actions.
2-10 MY: Ice Age resumes, with periods of warming just like last million-plus years.
100 MY: Continents begin to re-coalesce into a new Pangaea.
250 MY: New Pangaea firmly established, with extremely arid interior and stagnant oceans, sparking large-scale extinctions.
500 MY - 1 BY: Solar warming moves habitable zone beyond Earth's orbit.
500-700 MY: Plant photosynthesis ends as CO2 levels gradually fall below 10 ppm, with periods of oscillating plant expansion and dieoff; growing heat causes life to retreat to poles.
approx. 15 MY after that: Atmospheric O2 levels have fallen to about 1% of present, extinguishing what's left of animal life. Beyond 60 deg. C, only bacteria, algae and some fungi survive.
1 -1.2 BY: global mean temp. is about 70 deg. C. Oceans begin evaporating, causing the "moist greenhouse effect" that features brutal storms. Plate tectonics comes to a halt from lack of water, eventually resulting in a global ocean. Last bacteria fry around 235 deg. F. @
2.5 - 3.5 BY: "Runaway greenhouse effect" takes over at about 200 deg. C, after all water is gone. Earth becomes like Venus.
3 - 4 BY: Andromeda Galaxy (M31) merges with Milky Way. Gravity and other forces might sling solar system into deep space, or might not.
6 - 7 BY: Sun expands to giant size, possibly reaching Earth orbit. Solar effects cause Moon to swirl back to collision with Earth & possibly cause Earth to spiral into Sun. If not, Earth ends up scorched cinder orbiting white dwarf after Sun goes nova.

Whew. Anything I left out?

Oh, yeah, the "accidental armageddon" causing events -- huge comets or asteroids (it took one about 10 km across to cause the K/T extinction 65 MY ago, and would take one about 100 km across to sterilize all life) or supernovae in the galactic neighborhood (think Sirius; when it goes, its gamma rays will have some serious effect on everything within about 30 light years. We're 12 LY away).

This catalog makes nuclear war look like a game...

Now, I can't realistically refute most of what they say; it seems pretty plausible that, essentially, Earth's life path from here on will retrace its path of the last 4.5 BY, as they propose. But I do take issue with some of their assertions within the various future periods.

First off, obviously, is the near future. There, they allege that the combination of global warming and subsequent ice age return will cause survivors to be "starving" even "thousands of years forward." I strongly doubt that; human gene-lines flexible enough to survive the coming few centuries will have adapted to the new conditions and created or found new food sources. Yes, the short-term will probably see extensive starvation as our ability to fuel modern agriculture runs dry (assuming we don't get our collective head out of our ass very soon and change gears completely), but the population will eventually decline to a stable level. I suspect we'll still have agriculture in some places, maybe even cities, but having people recall what the Space Needle or global warming is (p.71) after a few thousand years is nonsense.

The resumption of ice age doesn't mean civilization has to vanish, although there's little doubt large swaths of the planet will be inhabitable only by the most intrepid folks, as in Antartica today. I could see people having outposts on the ice caps, even towns if we have the foresight to plan technology for that purpose. I'm not the first to think of this, BTW; Michael Kube-McDowell envisioned the Weichsel people with whole cities on the ice, and even an ice-based construction technology, in his novel Empery.

It will, however, mean major changes. Most humans will have no choice but to retreat toward the equator and change how, where, and maybe even what we farm, but I think we're capable of that. Earth will be a drier place, but we've lived through such times before. We can do it the same way we did it then -- by having very dispersed paleolithic-sized (or maybe medieval) populations or by taking the genuinely global outlook that is today struggling to be born and nurturing it. The former would be a likely consequence of nations feuding over dwindling resources; the latter is the only way to face our future and still retain those elements of civilization that are actually beneficial. Not all of them are.

What we do and which elements we keep may determine how long humanity survives as a species, because events AFTER the ice age are likely to be far less hospitable, if Ward and Brownlee are right.

As they note, "we must either take steps to sustain the habitability of our own world or find another at a younger stage of planetary life. ...If we can't engineer or evolve our way around our planet's inevitable decline, then we'd better go planet shopping." (21-22).

The former is, is the sense of planetary time, a band-aid approach -- it's necessary if WE want to stay alive over the short-term, but won't have much effect on life's overall path; only planet-hopping can keep us alive indefinitely, if that's even possible or desirable. In general, I think it is, at least for the next several millennia; as I've said elsewhere, it's necessary if we want to evolve AND maintain civilization. The neo-paleolithic option above will allow for evolution, but not civilization.

If finding other living worlds proves to be effectively impossible, survival will require us to change our attitude to one that sees our talents as being in the service of Earth-life as a whole -- a change we really need to make anyway, since other Earths won't be accessible for a long time.

This outlook flies in the face of a thread that pops up occasionally in this book. On several occasions, Ward & Brownlee express a clearly biased view of other lifeforms. For example, they note "human-level intelligence and technology would never develop on a water-covered planet. There would be neither the need nor the opportunity" (31) -- How would they know? This assertion might be true of technology, but not necessarily true of intelligence; they admit whales and dolphins have "large brains and some level of sophisticated communication," but aren't willing to acknowledge that much of our complexity is cultural, not due to basic intelligence. We have the advantage of being FIRST, but not (hopefully) the only Earthlife to become technological; I strongly suspect we can help other species to do at least some of what we've done.

Elsewhere, they attribute the fact that our current climate "norm is not normal" (79) to long-term causes -- a 70 MY greenhouse gas cycle, orbital cycles#, and continental drift (specifically, the creation of a land bridge between North and South America). While all are indeed factors, they never mention a factor that at least needs to be considered because it's far more timely -- agriculture. Starting just after the Wisconsin/Wurm glaciers receded, people made major changes to the tree cover around the world in an accelerating manner. Apparently, the use of fossil fuels for 150 yrs or so will have a long-term climate effect more profound than 10,000 yrs of slash-and-burn agriculture? That may be true, but evidence would be far better than simply asserting it as fact.

Speaking of evidence, their attribution of sources seems very unprofessional. Yes, they have a pretty lengthy bibliography, but have almost NO references within their text: No footnotes (except to some photos), no direct quotes, and few references to other scientists by name. In several places, I found comments that were clearly referring to something they'd read, but there's no way to actually find out what that was without reading EVERY bibliography source. In some cases, I've seen sources that contradict them (for example, they assert that Ice Age America included "huge deserts and sand dunes" (74), but an Oak Ridge Nat'l Lab map I've seen says only one pocket of America was sandy desert then), and I'd love to see their source. Same's true of their core point that earth's biological fecundity peaked around 300 MY ago and is now slowly declining; Science Daily says the oceans experienced a huge peak 4-6 MY ago.

While I understand they're writing for a popular audience, that's not an excuse for inaccuracy and dumbing down the text. They have a lot of material to work with and the thesis makes sense, but the inaccuracy, occasional redundancy, and spots of arrogance only weaken their ideas.

________________

@ -- This figure is how they wrote it (it stood out as one of two Fahrenheit references, p. 143, amid all of the other Celsius and metric references. I'm not sure if they meant F or C, but there is a significant difference between them.) For scientists, their phrasing is woefully imprecise in other places, too. On p. 34, they write, "Earth's proportion of water to its weight is small ... less than one-tenth of one percent." Weight means nothing in science; the term is mass, and that figure is accurate, but WAY off -- the actual figure is 1/50 of a percent (.023%), if I'm calculating the figures here properly. Saying that is similar to saying "Earth's population is less than 30 billion" -- true, but it gives an extremely distorted impression of the facts.

# -- There are three orbital cycles -- of 95,000, 41,000, and 22,000 yrs. Regarding the first of these, they contradict themselves. On p. 80, they say we're currently at a position where Earth's orbit is closest to the Sun in January and farthest in July, meaning that "summer [sic] snows may last longer than the long-term norm." On p. 82, they note that a previous interglacial (i.e. WARM period) was at a time when "orbital eccentricity was at a minimum" and "just such a pattern of minimal orbital eccentricity is underway now." Huh?!? Only one of those assertions can be correct. For more info, see the Naval Observatory's orbital cycles page.