Opinion: Climate change is a fact – but to prove it, scientists are bogged down in a | Basic Computer Hubb

An Austrian glaciologist explores a natural cavity of the Jamtalferner glacier in the eastern Alps this past October. Exploring the caves, which have appeared in glaciers and accelerated their melting process, is part of a worldwide effort to understand the effects of climate change.Lisi Niesner/Reuters

Viviane Fairbank is a writer based in Montreal. She is a former editor and head of research at The Walrus and is currently creating a guide for fact-checking journalism in the post-truth era.

In early May, 2017, torrential rain fell on the Ottawa River Basin, a watershed that stretches from eastern Ontario to Montreal. It poured for days, the water combining with snow and frozen soil, and by the end of that week, the watershed had reached its highest level in more than 50 years. All around the region, the river overflowed, seeping into people’s homes and causing more than $220-million worth of insured damages; several cities in Quebec declared a state of emergency, issuing mandatory evacuations. Near the south shore of the St. Lawrence, a 37-year-old man and his daughter were pulled by a current and drowned.

Within a week, the water retreated, and life slowly returned to normal. But a feeling of dread lingered: Residents had never experienced this degree of flooding before. “We can’t say that the [specific] flooding events we’re seeing is a result of climate change,” an environmental writer told the Montreal Gazette at the time, “but we can say that because of climate change, these types of episodes and catastrophes are becoming more and more frequent.” In short, scientists suspected the climate crisis was implicated, but they couldn’t say exactly how.

People look out at the swollen Ottawa River in May, 2017, as heavy rain flooded the watershed.Justin Tang/The Canadian Press

That same week, Laxmi Sushama, a civil engineer and specialist in sustainability at McGill University, was hosting a workshop focused on improving computer models of the Canadian climate. Her research team had spent the past few years refining the resolution and accuracy of regional climate models, such as the ones used by Environment and Climate Change Canada to understand weather patterns. Some of the team’s members were dealing with effects of the inundation in their own neighbourhoods, and so they decided to try to use their models to answer the question everyone had been asking: Had climate change caused the devastating flood?

For 40 days straight that summer, on one of the largest supercomputers in Canada, Dr. Sushama and her colleagues ran nearly 1,000 simulations of the climate over the Ottawa River Basin. The resulting study, which was published the following year, pinned down what the environmentalist in the Gazette had suggested: Anthropogenic (human-influenced) global warming had made the flood two to three times more likely to occur.

It was one of the first examples in Canada of event attribution (more formally known as extreme-event attribution), a recent innovation in the broader field of climate-attribution science, which is the study of the causes and effects of climate change.

Back in the 1970s and ‘80s, scientists wanted to determine whether the planet really was heating abnormally, and whether this was primarily because of human activity. To do this, they ran historical data about metrics such as temperature and carbon dioxide levels through computer models that simulated the earth’s climate over long periods of time. This helped them understand how the climate might change when certain variables (such as burning fossil fuels) were introduced. If a model ran several times with all the possible variations, and a change (such as rising temperatures) happened only when the model included greenhouse gas emissions, then it was reasonable to attribute that change to human activity.

Attribution science, in short, is how we now know that climate change is happening, and that people, and not just natural phenomena, are causing it.

Traditional attribution science is concerned with the climate, which is a broad description of what it’s like on the planet, averaged over 30-year periods. But in terms of day-to-day life, that kind of research is highly abstract: we don’t experience the climate, per se – we experience weather, which is the state of the climate at a given place and time. Unlike the climate, weather changes from day to day (even minute to minute). New event-attribution research, then, tries to understand the impact of human activity on those day-to-day happenings.

The message of event-attribution research is simple and concrete: Climate change has altered the weather you experienced today. Event attribution “makes climate change seem more real to people,” says Nathan Gillett, a researcher for the Canadian Centre for Climate Modeling and Analysis (CCCMA) in Victoria, B.C. “It helps to motivate people to do something about it.”

Thick smoke obscures the sun in Monte Lake, B.C., this past August after the White Rock Lake wildfire swept through.Darryl Dyck/The Canadian Press

Thanks to some of the latest event-attribution studies, we know that anthropogenic emissions are a cause not just of general warming in Canada, but of the heightened risk of fires and heatwaves in Western Canada, the increased frequency of flooding near Canadian coasts, and the reduction of small ice caps and shelves in the Canadian Arctic, most of which will be completely gone by 2100.

In recent years, climate scientists tell me, they have experienced a hugely increasing demand from media and policy makers for event-attribution results. Indeed, as a journalist whose job includes communicating scientific facts to the public, I’ve found event-attribution research exceptionally helpful in understanding and communicating the consequences of climate change. Environmental journalists have long felt frustrated that their colleagues’ news coverage doesn’t “connect the dots” between the weather and climate. Last June, for example, one American journalist analyzed 149 local news stories about a record-breaking heatwave in Colorado and found that only 4 per cent had made “even the slightest reference to climate change.”

This finding, he tweeted, represented “just a total failure [on the part of journalists] to perform our basic function to tell people what’s happening, what’s important and why.” I’m inclined to agree: There’s something intuitively wrong about a journalist reporting on recent dangerous weather events (such as deadly hurricanes, floods, and wildfires) without including a reminder to readers that avoiding such problems (and worse) in the future will require some kind of admission of guilt about climate change.

Event-attribution research gives journalists the tools they need to rigorously connect the necessary dots: With an event-attribution study in hand, a journalist can report on a weather event, then tell readers how climate change is implicated in its happening (which it nearly always is).

Over time, however, I’ve come to realize that the scientific story about event-attribution research is not as simple as we journalists tend to make it out to be. It turns out that dramatic event-attribution findings often come with significant caveats; a calamity such as a deadly heatwave can never be directly and exclusively blamed on global warming.

Like attribution science in general, event-attribution science relies on statistical climate models. But a specific weather event is a much more difficult thing to pin down statistically than a broader climate pattern. Owing to their difference in scale, it is, practically speaking, impossible to connect a single weather event to a decades-long change in climate; all climate change can be blamed for is having increased or decreased the likelihood of the climate conditions that make such weather possible.

A protester at the U.S. Chamber of Commerce in Washington this past October.Jacquelyn Martin/The Associated Press

To understand the nuance of this distinction, I find it helpful to think of the stock market: Climate-attribution science is like looking at long-term trends in the stock market, whereas event-attribution research is like studying a temporary financial crash. Long-term analysis can help us gain a more accurate perspective on robust trends for the future of the financial market, but it certainly can’t explain short-term blips and anomalies along the way. Saying that a single flood was caused by climate change is no more reasonable than saying that the sudden crash in bitcoin during a couple hours in April was caused by its steady growth in price over the past decade. From a strictly theoretical scientific perspective, then, event-attribution results are not all that useful – or even intelligible.

Of course, in the years since attribution science was first developed, climate models have become vastly more intricate, incorporating clouds, aerosols, oceans, swamps, volcanic eruptions, vegetation and permafrost. The models are run on some of the most powerful supercomputers in the world; a typical program contains more than one million lines of code, enough to fill 18,000 pages of printed text. Even with such a rich base of information, however, there’s only so far science can take us: Any modelling research has an unavoidable degree of imprecision, and the more fine-grained we try to conduct our analysis of a broad region over time, the less certain we can be of our exact findings.

I see event-attribution science, then, as questioning the boundary in climate science between theoretical research (focused on the improvement of climate models and statistical analytical methods) and practical communication (focused on the dissemination of results that will resonate with the general public). Attribution scientists still don’t all agree on how the nuances and limitations of their work should be communicated to the public – and whether such work, when accompanied with all the necessary caveats, really can serve the purpose it’s meant to. For Francis Zwiers, the director of the Pacific Climate Impacts Consortium in Victoria, the inherent limitations of event-attribution research make some recent studies “not quite scientific anymore” – and even, depending on how their results are presented to the public, “irresponsible.” For Dr. Sushama, on the other hand, event-attribution work is crucially important, precisely because of its public-facing motivations. Climate change, after all, is a matter of life or death. “I didn’t need to study the Montreal flood: I wanted to do it to show people what is happening,” she says.

Dr. Zwiers and Dr. Sushama represent two different, and, I think, both reasonable, responses to the unusual set of challenges climate scientists face. Their findings, and how we choose to react to them, are helping determine the future of the planet. In order to get people to properly appreciate the severity of the thing that climate scientists are absolutely sure of – that humans are causing the climate to change, with disastrous consequences – some are increasingly motivated to conduct research that is, while less scientifically rigorous, more accessible to the general public.

This is made more problematic by the fact that the general public is largely out of touch with scientific practice, and thus misunderstands the level of certainty one can reasonably expect from scientific research. (The gap between public perceptions of science and actual practice was highlighted, most recently, during the COVID-19 pandemic, when ambiguous scientific results were published, criticized and revised in the public eye.) Many people interpret ambiguity and uncertainty, which are natural indicators of scientific research, as a sign of scientific failure. Denialists have noticed this same gap and exploited it in order to generate doubt among the public about climate science’s probabilistic results.

Thus,…

Opinion: Climate change is a fact – but to prove it, scientists are bogged down in a