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Story Publication logo September 27, 2019

Attribution Science and Impossible Heatwaves

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A sign next to a newly repaved road in Kumagaya explains how lighter asphalt reflects solar radiation and lowers temperatures in the city center. During the 2018 Heatwave, Kumagaya City recorded the highest-ever temperature in Japan at 41.1 degrees Celsius (106 degrees Fahrenheit), and its residents and government are adapting to the hotter world. Image by Daniel Merino. Japan, 2019.
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In summer 2018, much of East Asia experienced an extreme heat wave that broke records across the...

High schoolers hiding from the late summer heat in Kashiwa, Chiba, Japan. Image by Daniel Merino. Japan, 2019. 
High schoolers hiding from the late summer heat in Kashiwa, Chiba, Japan. Image by Daniel Merino. Japan, 2019.

After a few days in Tokyo, I was headed back out into the countryside by train. The system is wildly efficient, fairly cheap, and certainly environmentally friendly when compared to driving.

About an hour and a half Northeast of Tokyo is the Kashiwa Campus of the University of Tokyo, and there I was scheduled to meet with two Japanese climate scientists, Dr. Yukiko Imada and Dr. Masahiro Watanabe. They are collaborators and leading experts in a young type of climate analysis called event attribution science and their most recent study is why I am here in Japan.

The heatwave that affected much of Northeast Asia in July and August of last year was really bad. In Japan alone, more than 1,000 people died due to the extreme heat and tens of thousands where hospitalized. The all-time temperature record in Japan was broken when a weather station in Kumagaya, a suburb 40 miles northeast of Tokyo, recorded a high of 41.1 Celsius (106 degrees Fahrenheit) on July 23.

Unfortunately, the extreme heat and severe loss of life are not what made that event unique. What sets it apart from other heatwaves and extreme weather events is what Imada and Watanabe found in a paper published in May 2019.

The walk from the train station to the campus was about a mile and took me through an orchard and agricultural research area belonging to the University of Chiba. There were some trees that had recently fallen over, and I wondered if the Typhoon that ripped through Chiba the week before was the cuase. I also wondered if climate change had helped fuel that typhoon. It was a hot and sweaty walk, humid and probably north of 85 degrees Fahrenheit. Fitting, considering the circumstances. Along the way were people with umbrellas, sun hats, and fans, all trying to stay cool in what seemed like some of the last days of another hot summer.

The title of the paper published by Imada and Watanabe sounds more like a news headline than a scientific paper. "The July 2018 high temperature event in Japan could not have happened without human-induced global warming."

Imada did not hedge her statements in person either. "We would have never seen such an extreme without global warming. That is a very sensational message for me because human impact made a new phenomenon in the climate."

I asked if that was she really meant. Her english is good but wondered if "sensational" and "phenomenon" had perhaps been lost in translation. She acknowledged the unusually strong language, especially coming from a scientist, but meant what she said.

"Human activity has created a new phase of the climate."

I have read the paper quite a few times (it's actually an easy read as far as scientific articles go) and knew what findings were. The heatwave was found to have a Factor of Attributable Risk equal to 1 (FAR=1), meaning it was so extreme that it could never have happened in a world without climate change. Scientists knew this would happen as the world warmed so the result isn't surprising really, but to hear it in person from the very woman who did the analysis left me speechless. A line has been crossed and there is no going back.

I asked what the public thought about climate change and the heatwave of last year, and Watanabe said that, "Generally, the people are convinced by the official story that global warming is affecting the frequency of heatwaves, it is accepted."

But thoughts are different than discussion and far from action and Watanabe had a pessimistic view of how the public reacted to the news of the study.

"I have an inclination that people remember what happens a year before, but will forget what happened five years ago. The memory is shorter than the timescale of nature."

But what about all of the solar panels? Aren't people adapting and changing their ways?

As Imada and Watanabe explained to me, that change happened not due to climate change, but another semi-man made tragedy, the 2011 earthquake and Fukushima Daiichi nuclear disaster, which Imada simply referred to as, "the big disaster in 2011." Japan underwent a big shift away from nuclear energy in the wake of 2011 and the government started buying electricity from individual solar producers at high prices. This triggered a boom in solar panels across the country.

When it comes to mitigation or adaptation, in spite of the broad knowledge and acceptance of the science, Imada and Watanabe agree that much more needs to be done.

While walking back to the train station, I ended up in the midst of a large group of uniformed middle schoolers. One thing that Watanabe said to me came to mind.

"The FAR is one indicator of human influence on weather. Based on that probabilistic measure, we have nothing more to say once FAR equals 1. We need to devise some other measure of human influence."

I wondered what measures were going to be needed when these kids grew up.

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