Followers of Shintoism have been tracking ice since the 1400s, long before anybody was worried about global warming...
One of the pesky things about climate change is tracking down reliable data about what the Earth was like decades and centuries ago, before scientists began tracking all the environmental markers they could. That's what makes the presentation of new climate change data out of Japan so stunning: It comes from Japanese monks who have been monitoring ice levels consistently since 1443.
Shintoism, the ethnic religion of Japan, has no founder or official texts. However, it generally holds to the belief in kami, the spiritual presence tied to natural elements. The myth of omiwatari, or God's Footstep, at Lake Suwa is a perfect example. After the god Takeminakata lost the first sumo match in history, he fled to Lake Suwa. Every year, he would walk across the ice to see his wife. His footsteps would cause large, elevated cracks in the ice, rising as high as six feet and spreading over 1,000 feet while creating beautiful shards. The cracks would come to symbolize both good luck and the severity of winter. As there was no set date on Takeminakata's journey, monks began to document and mark each time. They've now been doing it for more than five centuries.
There is a scientific explanation for omiwatari, of course. There is a natural hot spring under Lake Suwa. When the lake freezes over in the winter, the warmer waters eventually come into contact with the frozen surface, resulting in pressure ridges. The event rarely occurs these days, the last time being in 2012, and it's long been known that global warming was the culprit. Average temperatures in Suwa have risen over the years, and only an "unusually cold" winter can cause the event now, says Tokio Okino, a professor emeritus at Shinshu University and an expert on Lake Suwa's natural environment.
The monks' recordings therefore offer fascinating data about climate change. For the first 250 years of recording, there were only three instances of omiwatari not occurring—a condition known as akenoumi. Akenoumi increases as the Industrial Revolution begins in 1750. During the period of 1955 and 2004 there were twelve instances, and from 2005 and 2014, there were five. When omiwatari does occur, it hass gotten pushed back further and further.
Scientists have looked at older texts, like Thoreau's Walden Pond, to examine how nature existed in an earlier time. A Finnish merchant named Olof Ahlbom began recording ice levels in 1693. These measurements by the monks are 250 years older and may be the oldest we know of. All of these efforts come from the same place: a desire to better contextualize the world. But the Shintoist monks of Lake Suwa, who still practice to this day, deserve special recognition.