and Climate / Science / Travel

What comes around, goes around

“Drought occurred in 7th year of the Emperor Jiajing period, Ming Dynasty (the traditional Chinese calendar). Gui Jiang and Sishan Jiang came to Da’an town (the town where Dayu Cave is located) to acknowledge the Dragon Lake inside in Dayu Cave.”

Quotation from Dayu Cave, 1528 A.D. (Tan et al., 2015)

Working in science is a funny thing. The longer you work in the field, the more you realize how every little thing is connected, no matter how seemingly unrelated. This idea hit me full force this week as I was trying to come up with a blog topic. I was trawling twitter, various news websites, and recently published literature when I came upon a fresh off the press journal article in Scientific Reports by way of NY Times Science. At first I thought it was just a really cool article using historical cave writings and isotope analysis of stalagmites to link social unrest with drought conditions (more on this in a bit), but then I realized how this single journal article appeared to link all of my most recent blog posts (cue creepy scifi music now) and re-iterated how everything in science is connected.

Some of the writing in Dayou Cave. The red and yellow boxes indicate text that refers to the periodic droughts (Tan et al., 2015).

Some of the writing in Dayu Cave. The red and yellow boxes indicate text that refers to the periodic droughts (Tan et al., 2015).

But first, let’s review what the journal article was actually about. In a nutshell, a group of Chinese, Taiwanese, American, and British scientists used chemical isotope (δ18O, δ13C) and elemental analysis (Sr/Ca ratio) of stalagmites from a Chinese cave to infer past climate conditions (things like relative rainfall amount). The special thing about this cave is the cave writings lining the wall that detailed sporadic periods of drought between 1520-1920 A.D., allowing the scientists to use the anecdotal cave wall writings to corroborate the scientific data. Using the scientific data collected from the stalagmites, the cave writings, and historical events during the time period, the scientists were able to examine the relationship between societal unrest (things like the ending of a royal dynasty or a rebellion) with periods of limited rainfall (as measured from the isotope analysis and confirmed by the cave writings). The investigators were even able to predict periods of drought in Central China in the future. An interesting mix of history, social, and natural sciences (which is why I was interested in the piece to begin with).

Some data! The gray line is the actual 18O data measured from the stalagmite, the green line is the predicted 18O data from the model, and the dashed green line is future predictions. The purple circles indicate past drought events recorded in the cave and predicted severe drought events in the future (Tan et al., 2015).

Some data! The gray line is the actual δ18O data measured from the Dayu Cave stalagmite (the less negative the value, the less rainfall), the green line is the predicted δ18O data from the model, and the dashed green line is future predictions. The purple circles indicate past drought events recorded in the cave and the black circles are predicted severe drought events in the future (Tan et al., 2015).

It was amid the technical jargon about isotopic analysis (which still makes my head spin – one day I’ll tackle a blog post about that…), that it hit me. Science is insanely interconnected. Remember that post I did about the California Drought awhile back? The study in the Chinese cave highlights how natural climate cycles can have drastic and lasting affects on society just like how the California drought could lead to a decline in crop production and therefore economic impacts that ripple across the state (and even the entire country). Then there was that post about El Nino a few weeks back. Turns out the periods of drought versus rain in the Chinese cave correlated with El Nino cycles. Then don’t forget all the climate change stuff you’ve heard about. The scientists found that increased drought frequency was connected to warmer periods, as is predicted with climate change. And then of course, there’s the fact that I do research in China (which is another reason I was attracted to the journal article in the first place…). So just remember, everything you read and learn will come back to haunt you…in a ‘Casper the friendly ghost’ type of way (and I promise to take a break from droughts and China, too in my next blog posts!).

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