Assessing a collapse

One of the coolest things about science is the cross-fertilization that happens between disciplines.

I'm always impressed when I see examples of this, and my reaction is usually, "How did you even think of doing that?"  It is, at its core, a highly creative process.  The best science involves looking at a problem from a different angle, drawing in data or methods from other disciplines, and putting the whole thing together in such a way that the answer is clear.  (Or at least, a piece of it is clearer than it was before.)  As Hungarian biochemist Albert von Szent-Györgyi put it, "Discovery consists of seeing what everyone has seen, and thinking what no one has thought."

The creative aspect of science struck me while I was reading an article yesterday in Ars Technica about a some new research into a historical puzzle: the sudden collapse of the Shang Dynasty in China, about three thousand years ago.  The Shang were in power for nearly six centuries -- a pretty long time for a single dynastic regime -- and had made some significant accomplishments, the most notable of which were the first recorded writing system for Chinese, and amazing advances in pottery making and bronze casting.  Then -- over a very short period, perhaps only a few years -- Shang rule imploded.  A rival group called the Zhou took advantage of the chaos to defeat the Shang in a bloody battle, then scattered the remaining Shang supporters throughout the land to assure they'd never be able to rise again.

Now, researchers at Nanjing University, led by meteorologist Ke Ding, have drawn on a variety of disparate fields -- meteorology, climatology, geology, archaeology, paleontology, and analysis of extant historical records -- to try to create a complete picture of the causes behind the Shang Dynasty's sudden demise.

Their conclusion: the collapse of the Shang was the consequence of a long line of dominoes that started with a series of prolonged and powerful El Niño events, thousands of kilometers away.

Paleontologists analyzing fossil remains in strata off the coast of Peru dating to around 1000 B.C.E. note a shift from cold-water species to those that favor warmer water.  The fact that there wasn't an oscillation back and forth, but a replacement by warm-water species that lasted perhaps a century, suggests that rather than the usual pendulum swing of El Niño/La Niña conditions -- the former causing a warmup of the surface waters off the west coast of South America, the latter a corresponding cooldown -- in the years before the Shang collapse, the climate seems to have switched over to a semi-permanent El Niño.  What would be the outcome of such a shift in the ENSO (El Niño Southern Oscillation)?  This is where the meteorologists and climatologists took over; they estimated the degree of warmup, and let their computer models predict what effects that would have.

One thing that popped out of the models was a drastic increase in the strength of Pacific typhoons, and a significant change in their paths.  The warmup shifted wind patterns, tracking large storms away from Australia (thus the droughts and wildfires in Australia and Indonesia that usually accompany El Niño years), and northward into China.  Typhoons, though, usually fizzle once they cross over from ocean to land; and the capital of the late Shang Dynasty was Zhaoge, in Henan Province, far away from the coast.  So how would typhoons have affected an inland city so drastically?

But the models showed that the altered wind direction didn't just shove storms toward China, it also fed warm, moist air inland -- atmospheric rivers.  These air currents flow until they meet a mountain range, and the humid air masses experience adiabatic cooling as they rise in elevation, causing them to dump their moisture as rain or snow on the windward sides of mountains.

In other words, the rain shadow effect.  The outcome; suddenly northern and central China were way wetter than they had been.

Now, enter the archaeologists.  One of the most common items in Shang-age archaeological sites are oracle bones -- usually the scapulae of ox, horses, or deer that are thrown into a fire, and the resulting cracks and scorch marks read by a shaman.  But fortunately for us, the shamans -- recall the Shang's development of the first Chinese writing system -- also recorded on the oracle bones what questions had been asked, and what the shaman's assessment of the results had been (i.e., the answer to the question).

And in the last fifty years of the Shang Dynasty, just about all of the oracle bones have to do with the weather.  A lot of them basically ask, "When the hell is it going to stop raining?"

A Shang Dynasty oracle bone [Image licensed under the Creative Commons Orakelknochen, CC BY-SA 3.0]

At the same time as this, the archaeologists also note the abandonment of village sites near riverbanks, an increase in burial of sites under riverine sediments, and the relocation of towns onto higher ground.

What Ke Ding and his colleagues concluded is that the Shang were weakened by years of floods, probably accompanied by poor harvests and resulting famine.  This set the stage for the Zhou rebellion, and the destruction of a dynasty that had ruled China for six centuries.

Now, here's the kicker.  The researchers caution that we're seeing a similar pattern today -- anthropogenic global warming is increasing oceanic surface temperatures, and the Pacific Ocean is seeing extended and more powerful El Niño events.  As Mark Twain observed, "History doesn't repeat, but it often rhymes."

Oh, except that noted climate scientist Donald Trump has evaluated the available data, and decided that global warming is a hoax, and the climatologists are big fat poopyheads.  So there's that.

Anyhow, it's a fascinating and elegant piece of research, and shows how creative the scientific enterprise can be.  Collaboration is the heart of discovery, and here we have an entire team of experts from disparate fields pitching in together to solve a historical puzzle.  One that, despite Trump's pronouncements, we had damn well better pay attention to today.

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History by proxy

In a new study from Proceedings of the National Academy of Sciences, we learn something simultaneously fascinating and a little alarming; humanity's fingerprint on the globe is so clear that it can even track our wars, famines, and plagues -- back twenty-five centuries or more.

The whole thing was done using proxy records, which involve using indirect sources of evidence about the past to infer what conditions were like.  A commonly-used one is using the constituents of air bubbles in amber and ice to make inferences about the global average air temperature at the time -- a technique that shows good agreement with the measurements of the same variable using other methods.

Here, in a team effort from the Desert Research Institute, the University of Oxford, the Norwegian Institute for Air Research, the University of Copenhagen, the University of Rochester, and the Alfred Wegener Institute for Polar and Marine Research, researchers studied ice cores from thirteen different locations in the polar northern hemisphere, and found that the levels of one contaminant in the ice -- lead -- was enough to parallel all of the major plagues and wars that occurred in Europe and northern Asia back to 800 B.C. E.

What they found is that lead concentrations in the ice rose when things were quiet and prosperous, probably due to an expansion of smelting operations for items like lead seams for stained-glass windows and impurities in silver ore processing.  The signature of wars was clear, but the signature from plagues was blatantly obvious; the years following the Plague of Justinian (541-542 C.E.) and the two spikes of the Black Death (1349-1352 and 1620-1666 C.E.) were two of the lowest points on the graph.

"Sustained increases in lead pollution during the Early and High Middle Ages (about 800 to 1300 CE), for example, indicate widespread economic growth, particularly in central Europe as new mining areas were discovered in places like the German Harz and Erzgebirge Mountains," said study lead author Joseph McConnell of the Desert Research Institute.  "Lead pollution in the ice core records declined during the Late Middle Ages and Early Modern Period (about 1300 and 1680 C.E.) when plague devastated those regions, however, indicating that economic activity stalled."

Silver smelting plant in Katowice, Poland, ca. 1910 [Image is in the Public Domain]

The authors write:

Lead pollution in Arctic ice reflects midlatitude emissions from ancient lead–silver mining and smelting.  The few reported measurements have been extrapolated to infer the performance of ancient economies, including comparisons of economic productivity and growth during the Roman Republican and Imperial periods.  These studies were based on sparse sampling and inaccurate dating, limiting understanding of trends and specific linkages.  Here we show, using a precisely dated record of estimated lead emissions between 1100 BCE and 800 CE derived from subannually resolved measurements in Greenland ice and detailed atmospheric transport modeling, that annual European lead emissions closely varied with historical events, including imperial expansion, wars, and major plagues.  Emissions rose coeval with Phoenician expansion, accelerated during expanded Carthaginian and Roman mining primarily in the Iberian Peninsula, and reached a maximum under the Roman Empire.  Emissions fluctuated synchronously with wars and political instability particularly during the Roman Republic, and plunged coincident with two major plagues in the second and third centuries, remaining low for >500 years.  Bullion in silver coinage declined in parallel, reflecting the importance of lead–silver mining in ancient economies.  Our results indicate sustained economic growth during the first two centuries of the Roman Empire, terminated by the second-century Antonine plague.

Of course, there's nowhere in the ice cores that has as high a level of lead contamination as recently-deposited ice does.  "We found an overall 250 to 300-fold increase in Arctic lead pollution from the start of the Middle Ages in 500 CE to 1970s," said Nathan Chellman, a doctoral student at the Desert Research Institute, and co-author on the study.  "Since the passage of pollution abatement policies, including the 1970 Clean Air Act in the United States, lead pollution in Arctic ice has declined more than 80 percent.  Still, lead levels are about 60 times higher today than they were at the beginning of the Middle Ages."

As an aside, the Trump administration has steadily rolled back regulations requiring industry to conform to reasonable pollution standards, including allowable levels of air pollution.  So look for the contaminants in ice -- and in your lungs -- to spiral upward once again.

But hey, it means the economy's good, so nothing to worry about, right?

Of course right.

So as I've pointed out (repeatedly), what we are doing does have a measurable, quantifiable effect on the environment, and studies like McConnell et al. should be a significant wake-up call.  And as I've also pointed out, it probably won't.  It's all too easy for people to say, "Meh, what do I care about a little lead in Arctic ice?  So it bothers a few seals and polar bears.  Too bad for them."  And continue with our throw-away, gas-guzzling, conspicuous-consumption lifestyles.

It's cold comfort knowing that when the aliens come here in a thousand years to find out why the Earth is barren, they'll be able to figure it out by looking at the traces we left behind in the ice, soils, rocks, and air.

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This week's Skeptophilia book recommendation is pure fun for anyone who (like me) appreciates both plants and an occasional nice cocktail -- The Drunken Botanist by Amy Stewart.  Most of the things we drink (both alcohol-containing and not) come from plants, and Stewart takes a look at some of the plants that have provided us with bar staples -- from the obvious, like grapes (wine), barley (beer), and agave (tequila), to the obscure, like gentian (angostura bitters) and hyssop (Bénédictine).

It's not a scientific tome, more a bit of light reading for anyone who wants to know more about what they're imbibing.  So learn a little about what's behind the bar -- and along the way, a little history and botany as well.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]