Words by Katie Puckett
“Attribution science is a huge game-changer. Without it, fossil fuel companies could sow uncertainty about the role of climate change in certain events. But now we can say: this percentage of this impact is because of climate change”
In May 2021, a Dutch court ruled that Royal Dutch Shell must cut the carbon emissions from both its operations and the oil and gas it sells by 45% by 2030, relative to 2019 levels — a global first, but likely not the last, thanks to rapid advances in the fields of attribution science and climate litigation. L Delta Merner leads the Science Hub for Climate Litigation at the Union of Concerned Scientists, a non-profit science advocacy organization based in the US. She provides evidence to inform legal cases that hold fossil fuel companies accountable for climate-related damage. UCS evidence has been cited in more than 70% of US climate damages and fraud cases to date.
What are the scientific advances that allow us to quantify the impact of climate change with such confidence?
Climate attribution has been around for about two decades now, which makes it an incredibly new science. But while the science is new, the concepts are not. There are two major areas — event attribution and source attribution — and there have been really important advances in both over the last five years.
The area that’s generally talked about most is extreme event attribution, which can tell us how climate change may have added to the severity of an event. It’s about understanding the role of climate change versus natural weather patterns or random climate variability. Studies can now tell us how much hotter a heatwave is or how much greater the intensity of a downpour is during a hurricane or any other rainfall event because of climate change. We also see connections by understanding sea-level rise. Sea level is impacted by things external to climate change as well, but you can isolate the role of climate change and then understand how that’s changed a storm surge from a hurricane, for example. So these all fall under event attribution.
One of the things that’s been exciting is that we can now attribute changes to specific emission sources. This work started in 2013 with a publication by Richard Heede, which found that nearly two thirds of industrial carbon emissions from the Industrial Revolution onwards can be traced to the 90 largest fossil fuel and cement producers — so ExxonMobil, BP, Chevron, Royal Dutch Shell, to name a few. One of the first studies to make the connection with global warming was published in 2017 by some of my colleagues at UCS. They found that emissions from these 90 major fossil fuel producers and cement manufacturers contributed to around 42-50% of all global temperature rise.
I think so often we get caught in thinking of climate change as something that’s global, that’s abstract, that’s hard to address. But here we see that there’s clear connections between specific actors. Global temperature rise is scientifically the easiest to look at, but another more recent UCS study found that 26-32% of global sea-level rise was tied to the products of just these 90 carbon producers.
Right now, the majority of the models that we’re looking at are global. So the next steps are about better connecting attribution work to local models. This is a scale that is much more beneficial for people, communities and businesses, so that they can better understand the impacts for their local environment. A study that was released in May looked at economic damage from Hurricane Sandy related to human-caused sea-level rise. Again, they did extensive scientific work to isolate the human-caused sea-level rise that was from climate change, and used that number to estimate that there was approximately US$8.1 billion of damages that were just attributable to climate-change-induced sea-level rise. This is just one small sliver of climate change impacting one individual storm, but these events are happening globally and impacting cities across the world.