Thomas Becket, also known as Saint Thomas of Canterbury, was assassinated in 1170 by followers of Henry II, King of England, in Canterbury Cathedral. While that killing resulted in Becket quickly being canonized a saint, which only served to increase his influence posthumously, it also had a murderous effect of a slower yet just as deadly kind – lead poisoning. And not just on one person – on an entire country. This scourge of the 12th century was discovered recently as a consequence of a scourge of the 21st century — climate change and its melting of glaciers. How are all of those dots connected? The line starts at Thomas Becket.

“Will no one rid me of this turbulent priest?”

That inaccurate quote is attributed to Henry II and disputed by many historians, but it definitely illustrates his contempt in 1170 for his former friend and current archbishop – Thomas Becket. They became pals when Becket joined the king’s staff as his Lord Chancellor and began enforcing tax collections from all landowners. The friendship turned ugly quickly when Becket was named Archbishop of Canterbury and sought to build the power of the church. The rift hit the last straw when the Archbishop threatened to excommunicate the king and followed through with a number of his close associates. Some historians believe the oral history of the time twisted the later stories of Henry ordering Becket’s death, but dead is still dead and his fame and posthumous power elevated him to sainthood, devoted followers and a famous movie where he was played by Richard Burton (and Henry II by Peter O’Toole).

What does this have to do with climate change and glaciers melting?

“High-resolution analysis of the ice core from Colle Gnifetti, Switzerland, allows yearly and sub-annual measurement of pollution for the period of highest lead production in the European Middle Ages, c. AD 1170–1220. Here, the authors use atmospheric circulation analysis and other geoarchaeological records to establish that Britain was the principal source of that lead pollution.”

Note the date referenced in the opening to a new study published in the journal Antiquity and reviewed in Science Magazine – 1170. Scientist have long theorized that a rise in lead production, lead pollution and deaths and health problems from lead exposure in Europe came from the increased production by lead mines in Germany. However, archaeologist and lead author Chris Loveluck of the University of Nottingham and his team found earlier evidence in an unlikely location – the Colle Gnifetti Glacier in the Swiss Alps. Exposed by the warmth of climate change, they were able to extract a 72-meter-long ice core in 2013 which contained a 2000-year-old picture of fallout from pollution, volcanoes and dust storms. Using a laser, they were able to slice the core into 120-micron-thick slivers that represented just a few days of dust falling onto the Alps. Starting in 1170, they noticed a 50-year concentration of lead pollution – the highest levels until the Industrial Revolution began in the 1800s.

How does this involve King Henry II?

It’s complicated … and yet very simple. Churches and monasteries in the 12th century were made using a lot of lead, which meant a lot of smelting. The best method to track church building in those times was by studying tax records – during times of war or unrest when there was no tax collection, no churches were built. When the coffers filled again, building resumed. Archbishop Becket forced the reduction of tax collections, especially from the churches. After his death, Henry II tried to get back in good graces with the new religious leaders by building more churches and monasteries, thus increasing smelting and lead pollution. Loveluck’s team also look at wind records from the time and found that summer winds blew from Britain to Switzerland, carrying lead dust from mining and smelting. (You can see his graphs here.)

Case closed?

Well, yes … if you’re referring to blaming King Henry II for the severe lead poisoning cases of his reign and afterward. This new correlation of king-to-lead also occurred in 1193, the year Richard the Lionheart was jailed in Germany by Holy Roman Emperor Henry VI and lead mining increased to pay his ransom.

Would knowing this at the time have saved Thomas Becket from being assassinated?

Probably not. As the ruler played by Mel Brooks in “History of the World, Part I” liked to say, “It’s good to be the king.” And bad to be anyone who gets in his way.