For the first time, science has directly linked human-induced climate change to extreme weather events using the emerging field of attribution science.
Words By Daniel Merino
Photo by Scott. L.
For decades, scientists did not believe it was possible to blame a specific weather or climate event on climate change. They were almost positive a link existed – trends, models and logic all suggested as much – but no one knew a way nor had the tools to show a direct connection between climate change and a particular event.
That has now changed. A young branch of climate science is using high-resolution weather data and powerful climate modeling to prove the formerly unprovable. So-called attribution science can now link extreme weather and climate events to anthropogenic climate change, and for the first time, science has shown that events happening our world today were only possible because of the effect of climate change.
“Recently,” said Friederike Otto, Director of the Environmental Change Institute at the University of Oxford, “there were three studies of events where the likelihood of them happening in a non-anthropogenically warmed world was zero.”
Since 2012, the Bulletin of the American Meteorological Society has put out an annual review of attribution studies titled Explaining Extreme events From a Climate Perspective, and the 2016 review, published in January 2018, contained the three studies mentioned by Otto.
These three events were the record high global average temperature, a record-breaking and deadly heat wave in Asia, and a marine heatwave off the Alaskan coast.
The report contained studies on 34 events in total, of which 25 were found to have been influenced by climate change, and 9 of which no influence was found or it was uncertain what role climate change played.
The events in the 2016 report that were affected by climate change spanned the globe and ranged from droughts to extreme rainfall events and even ecological catastrophes including two massive coral bleaching events and the collapse of a salmon fishery in western North America. One study found that extremely dry conditions related to wildfires in western North America summers are five times (500%) more likely now than in a pre-climate change world, while another found that extreme rain events over the Yangtze River are 17%-59% more likely. These increases have real-world impacts. “Even if climate change only doubled the likelihood, in the world we live in today, the risks have increased a lot,” says Otto.
In order to calculate an increased likelihood using an attribution study, scientists look at a real-world event, a drought for example, and calculate the chances of it happening again in today’s climate-changed world. Then, scientists calculate the likelihood of a similar drought happening in a computer modeled world without any anthropogenic climate change. If the likelihood of an extreme weather event happening in our world is higher than the likelihood in the simulated, climate change-free world, then climate change played a role
“Attribution science becomes really important to inform our understanding of these events and how closely they are linked to climate change,” says Emily Boyd, director of the Lund University Center for Sustainability Studies. “It’s a kind of a step change in thinking. If we can start to say this event is related specifically to climate change, then it has massive implications.”
Dr. Kristian Lauta, head of the Copenhagen Center for Disaster Research, believes those implications will first be felt in the courts. “From pretty early on, people have been trying to make a legal claim against climate change. But you need damages,” he says. “The future potential loss of livelihood is not specific enough for law.”
Attribution science will, in Lauta’s eyes, allow damages to be directly connected to climate change by “making the whole chain of causality accessible to us, from emitter to victim.” Who is specifically to blame is a question to be answered by the courts, and lawsuits like Juliana v US, otherwise known as the Children’s Climate Change Lawsuit, may soon have answers, but for now, proving the link is where the focus lies. “The link between climate change, a disaster, and who is really affected, that is what we want to work on,” says Boyd. “It can be really powerful if we can manage to do that.”
Beth Daley, Director of Strategic Growth with InsideClimate News, believes the legal ramifications of attribution science are still far in the future. “I think it is a beginning step and I think it is important, but attribution science is really young,” she says. “Once there are some really good studies that can attribute X to Y, then you can blame someone.” But Daley does see attribution science having an impact in the world of public perception. “I think as more events happen, as there is more linking of the dots, I think the public will start to realize that these extreme events they are seeing are not something that climate change could look like, but are what climate does look like,” she says. Many people are already seeing the costs.
“It looked like Hell,” says Jordan Iskin, a botanist living Los Angeles who frequently surfs and hikes in the areas affected by the recent wildfires. “The fires are to be expected this time of year, but with the prolonged drought, there is no water out there. The stuff is just so dry. It felt like the whole city could burn down.” But it does seem the dots are getting connected at least. As Iskin says, “All the leadership and first responders are using the language ‘Climate change exacerbated this fire.’”
Attribution studies looking at the California drought of 2012-2014 found that climate change significantly increased the risk of California experiencing drought-related wildfires. It is too recent to tell if the fires and drought of this year were influenced by climate change, but now, thanks to attribution science, we have the ability to ask that question. Whether the homeowners of Malibu and Paradise will be suing anyone remains to be seen, but the damage has been done. Hopefully, lessons are being learned, because as Lauta puts it “Not only did we construct our cities to be destroyed by strong winds, we also contributed to strong winds.”