Snowball Earth: Manufacturing a Narrative

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Posted on September 2, 2013 in Dating Methods, Dumb Ideas, Geology, Philosophy of Science, Physics, Solar System

The press and TV treat presumed scenarios like a “snowball Earth” as historic facts.  A look at how the sausage is made, however, shows little empirical meat and mostly filler in a process characterized by tweaking, picking, and constant debate.

In a recent PNAS commentary, Boswell A. Wing of McGill University is glad that two geochemists appear to be buttressing the primary supporting evidence for a snowball earth (a presumed period of ice from poles to equator): a relationship between higher carbon dioxide levels and the end of the snowball.  Careful reading of his commentary, though, shows a number of twists, turns, reversals, proposals and anomalies in the efforts to keep the narrative going.  The following paragraph extracts out some of the hedging and fudging words that Wing used in efforts to support the snowball earth narrative:

The proposalcreative solutions … the snowball debate … Whether the “original pillars” of the snowball hypothesis have survived this scrutiny is an active debate … elevated CO2 levels—is primarily inferred through the intricate veilpromised to lift this veil … what seemed to be direct evidence … This conclusion was recently turned on its head inferred from the same evidenceconflicting interpretationsgiven a fixed atmospheric lifetime … estimated if an appropriate record … can be identified … This exercise requires two assumptions … must have remained close to modern estimates … the framework laid out above … originally seemedhypothesized snowball state … not only a function of atmospheric CO2 levels … increased photosynthetic O2 dilutes the isotopic anomaly … another potential control knob that could have amplified or suppressed … recently called upon to explain the large … anomalies … in an atmosphere not much more CO2–rich than today’s … A less-dilute signal would compensate for … Under the assumption of … this scenario is consistent with … very different from … that had originally been proposed … This dilemma has been neatly resolved with a unique mechanistic model … Relying on a clever calibration … to release the constraints of geochemical uniformitarianismcan produce … only if … recent bold extrapolation … is not applicable … seemsinference … dynamic … enabled a pair of unique constraints … two styles of snowball glaciations … delayed development … different timescale … leads to a pair … in South China … suggests … more likely … as might be expectedprovocative hintsmay eventually be overshadowed … can constrain … this approach should be applicable … holy grail … exploratory … consistent with a few previous quantitative estimatesmay reflect a less pervasive process than the geologic record suggests … or perhapsappears to have had … a quantitative narrative … the viability of this narrative .…

These words vastly outnumber the actual appeals to empirical data, such as levels of oxygen-17 in ice cores or measurements of sulfide minerals.  The empirical data, however, are useless without an interpretive framework.  They could be interpreted various ways.  In fact, Wing discussed a situation in which the very same data were “used” to produce opposite conclusions – one that suggested CO2 levels were much higher at the end of the snowball, and one that estimated they were the same as today.

Wing does produce one graph of “normalized gross biosphere production,” which only indirectly relates to the snowball earth hypothesis.  It’s clear that someone must make assumptions to assess what the dozen or so data points mean.  Since they cover 310 million assumed years, is there enough resolution to conclude anything?

It appears that having a narrative is the real motivator here.  The proposal of a scenario – even if mythical – provides jobs:

The proposal of a “snowball” Earth, covered in ice from poles to equator, occupies a special place in the hall of fame of Earth science hypotheses. Spectacular geological evidence for an icy Earth, creative solutions for the initiation and escape from a snowball state, a multitude of directly testable consequences and potential links to the origin of animals all speak to the fundamentally integrative nature of the proposal. This integrative nature allows for a broad range of scientific specializations—from astrophysics to molecular biology—to contribute to the snowball debate, but has also brought the hypothesis under continuous critical scrutiny. Whether the “original pillars” of the snowball hypothesis have survived this scrutiny is an active debate.…

Wing briefly mentions “spectacular geological evidence for an icy Earth,” but within two sentences questions whether the “original pillars” of the hypothesis have survived scrutiny, saying they are still actively debated.  From there he discusses how those pillars are not seen, but rather inferred, through an “intricate veil” of oceanic carbonate chemistry.  Then it was on to conflicting interpretations of the same evidence and other problems that a new paper might resolve, Wing hopes.

His last paragraph stresses the value of the narrative.  While he asserts that the authors of a new paper provide a “quantitive footing,” it implies that everything prior has been qualitative.  That’s a lot of faith to put on one paper.  Even if the footing is solid, it means that scientists are only at the doorstep:

Despite its clear importance to extreme Earth-system events like the end-Permian and the Marinoan snowball Earth, examination of the initial arbiter of geologic trends in atmospheric CO2 and O2—global biospheric productivity—has remained mostly qualitative, inspired inferences from the fossil record notwithstanding. The paper by Cao and Bao places these examinations on quantitative footing and opens the door for new understanding of the coevolution of life and Earth.

If one is only at the door of understanding, in other words, he does not yet have that understanding.  The pursuit of understanding is worthwhile, but when the understanding is always beyond the threshold of a door, one could ask if the right door has been chosen.

This is no different than giving idle scriptwriters a new plot to play with.  One stands up and says, “What if the earth were once like a big snowball?”  The others pipe in, “Cool idea!  I love snowballs.  I like it, man.  What can we do with it?”  The others start thinking of ideas: “Once upon a time, ice covered the whole earth!”  When?  “Uh, let’s say 635 million years ago… that doesn’t hurt the dinosaur script.”  Someone asks, “But how did the snowball start?”  They furrow their brows for a few minutes on that one, then somebody offers a “Maybe this” type of clever solution.  Another asks, “How did it end?”  More furrowed brows for a few minutes as they realize how difficult it is to get a frozen earth to melt again.  “Maybe elevated carbon dioxide did it.  You know, like global warming.”  Everyone thinks that’s great.  “We can even tie this in with Darwinian evolution, claiming that melting ice created an explosion of new life!”  Cheers go up.  “We have a script!”

The fact-checkers report back with numerous problems.  Data are hard to come by, and require interpretations that experts disagree on.  The scriptwriters, eager to maintain their plot line, come up with “clever calibrations” and “creative solutions” for each impossibility or conflict.  One of them says that they could “release the constraints of geochemical uniformitarianism” just this one time for the sake of the project.  Stretching timescales, special pleading, and ad hoc scenarios are liberally sprinkled into the plot to keep the narrative going.  They run to the press, touting, “Snowball Earth is a Fact!”  The artists and animators go to work.  Snowball Earth enters the public consciousness as a Fact of Science, while behind the scenes, the scriptwriters continue an “active debate” about it to look busy.

Meanwhile, the sulfides and ice cores just sit there, silently, meaning only what some human being interprets them to mean.

Anyone taught to respect science for its presumed “Scientific Method” that supposedly guarantees Truth about the natural world should be appalled at what “historical science” has become.  It’s job security for storytellers.  The game is to become ensconced as a member of the accepted consensus, swear allegiance to Naturalism, then whale away.  The media will love you for keeping them gainfully employed.  As scientists parade by in triumph, only perceptive outsiders regret that Truth gets trampled in the streets under the chariot wheels of Imagination.

 

 

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