You wouldn't think that a Japanese monk and a merchant from Finland would have much in common, but it turns out they do: Climate change.
The men — and others — kept meticulous records dating back almost 700 years, and are now providing scientists with the earliest evidence of global shifts in the environment.
The data has been crunched and more details are now available in the journal Nature Scientific Reports.
Sapna Sharma is a professor at York University in Toronto, Canada, and John Magnuson is a professor emeritus of limnology and zoology at the University of Wisconsin, Madison. They authored the report, and Magnuson joined host A Martinez to tell more about what they found.
How the records were discovered:
"Well in the 1990s, NSF (National Science Foundation) sponsored a workshop that we did in which we gathered scientists from lake areas around the northern hemisphere that had long ice records... and one of the records was this record from Lake Suwa, and Dr. Arai brought that record, and another record was from River Torne, and then we've stayed with these scientists and interacted with them, and updated them, so that we could do this paper using the most current data."
On the original purpose of these records:
"The Japanese priests were keeping the records as part of a legend in the Shinto religion in which they had tried to explain these ridges that would form across the lake, ice ridges which we call them, they called them omiwatari... and it was a god, one of the male gods, would cross the lake when the lake was frozen to visit the female god on the other side of the lake, and the steps caused this ridge to form. Also those early Shinto priests were probably the intelligentsia of those communities, and they were trying to use these records to see if they could predict whether the rice crop would be good the next year. In the case of Finland, the gentleman who started the records was a businessman, and when the river was frozen, there weren't any bridges at that time, all of a sudden you could get across the river, it was important to commerce and trade, and when he no longer made the records, other people carried it on for the same reason."
What these records tell us about climate change:
"Basically what we did is we had records with human observers that went to before the Industrial Revolution began. And so we thought that a reasonable thing for us to do would be to analyze how fast the ice dates were changing for the period of time we had before the start of the Industrial Revolution, and then the period after the start of the Industrial Revolution. And in both systems what we found is that the recent records after the Industrial Revolution, the ice dates were moving towards a warmer condition, meaning the lake froze later and the river broke up earlier in the case of the Finnish one. And so in both cases, the ice dates after the Industrial Revolution started were changing more rapidly than before the Industrial Revolution began. I thought this was a pretty key finding."