The Economist - USA (2019-07-13)

ADBC

1,000

10,000

100,000

100

200 200 400 600 800 1000 1200 1400 1600 1800 2013

Logscale

Leaddepositsinglacialice-coresamples

Nanogramspersquaremetre,11-yearrollingaverage

Source:J. McConnelletal.,PNAS,July 2019

LeadtrappedinArcticicetracksEurope’smoneysupplyoverthepasttwomillennia

Beginningoflead

“phasedown”following

introductionofthe

CleanAirActintheUS

Joachimsthal

silvermines

established

inBohemia

Industrialera.

Coalovertakes

silverasmain

sourceof

leademissions

PaxRomana

Theheightofthe

RomanEmpire

CrisisoftheThirdCentury

50-yearRomancivilwar

Guelph-Ghibellinewars

ConflictsbetweenGerman

emperorsandthePapacy

Charlemagne ThirtyYearsWar

consolidatesFrankish

EmpireacrossEurope

Antonine

Plague

ravages

theRoman

Empire

TheFranks

adoptsilver

currency

TheBlackDeath

killsatleastonethird

ofEurope’spopulation

Lateantique

littleiceage

Medieval

warmperiod

Samplesfrom

NorthernGreenland

Sample

fromSiberia

→→

Theprocessofextractingsilver

fromleadorereleasedleadinto

theatmosphere.

Layersofglacialicebuiltupover

centuries.Theypreservea record

ofEurope’ssilverproduction.

Windscarriedleadparticlesfrom

EuropetotheArctic,whereit was

trappedintheice.

TheEconomistJuly 13th 2019 81

T

oday, jachymovis a small Czech town

nestling in a valley on the German bor-

der. In 1534, though, it was Joachimsthal,

the largest city in Bohemia apart from

Prague and home to the almighty thaler—a

weighty silver coin that became the de fac-

to currency of Europe and the New World.

The thaler lent an English version of its

name, “dollar”, to the money of the United

States and a score of other jurisdictions. Jo-

achimsthal’s silver rush began in 1512. By

the middle of the century the local mines

were the most prolific in Europe.

Joachimsthal’s mines left another lega-

cy, however: lead. Silver and lead often co-

mineralise, and refining silver from its ore

releases some of that lead into the atmo-

sphere, where winds can carry it far and

wide. Lead transported in this way to the

Arctic often ends up trapped in layers of

glacial ice. That is where a team of re-

searchers led by Joseph McConnell of the

Desert Research Institute, in Reno, Nevada

found it, in ice cores pulled from glaciers in

Greenland and Siberia.

In their new study, published in the Pro-

ceedings of the National Academy of Sciences,

Dr McConnell’s team used coring to ana-

lyse lead emissions and produce a record of

the European economy from Roman to

modern times. Moreover, by comparing re-

cords from Greenland and Siberia, Dr

McConnell could distinguish mines in

western and eastern Europe. Eastern mines

left more lead in Siberia than in Greenland,

and western ones the reverse.

The data illuminate the historical re-

cord. As Charlemagne conquered most of

western Europe, his mints turned out huge

quantities of new silver currency. After his

reign, his empire disintegrated and smaller

potentates took over minting. Silver pro-

duction rose gradually but steadily through

the prosperous medieval warm period.

Conflict punctuates the record, as combat-

ants fought over mining regions.

Disease, too, makes its terrible impact

plain. Major modern economic shocks,

like the Great Depression, have taken a dec-

ade or so to recover from. By comparison,

the Black Death halved lead levels, and it

took 100 years for them to recover after-

wards. The implication is that silver mines

were unprofitable—either because of a lack

of demand, or of a shortage of affordable la-

bour, or both—well into the Renaissance.

When plague recurred across Europe in the

late 16th and 17th centuries, growth in lead

emissions stalled as well.

After 1750, industrial processes over-

took silver production as the chief source

of lead pollution. Leaded gasoline, intro-

duced in the 1930s, sent lead levels still

higher. Starting in the 1970s, environmen-

tal policies in America and Europe decou-

pled lead pollution from economic growth.

Arctic lead levels have since fallen by more

than 80%—but they remain 60 times high-

er than in the medieval era. 7

Arctic lead levels reveal the impact of

climate and disease on Europe’s history

Plumbing the

glaciers

Graphic detailEurope’s economic history