Climate Change Made Canada's July Wildfires Twice as Likely, WWA Study Finds

Human-caused climate change made this summer's severe fire weather in Canada about twice as likely, a new World Weather Attribution (WWA) study found, with the Guardian reporting on August 6 that the human-driven climate crisis is fueling Canada's deadly wildfires. The analysis, covered by Eos and CBC, focused on July fire conditions in Ontario and the Northwest Territories, where detected fire activity ran from July 1-18.

Quantifying the Fingerprint

The team analyzed the Daily Severity Rating (DSR), a measure of how difficult a fire is to suppress once it ignites, and used climate models to test how often similar conditions would occur in a world without human-caused warming. The sustained severe DSRs in Ontario and the Northwest Territories were made about twice as likely, while the worst fire-weather week in the Northwest Territories was made roughly 27 times more likely, according to the researchers.

From Rare to Routine

In a world without climate change, similar extreme fire seasons would be expected about every 40 years. Today, they are expected every 2-6 years in the Northwest Territories and every 6-15 years in Ontario, the study found. While a doubling may sound small, a small change makes a huge difference for an ecosystem and a community, said Frederike Otto, scientific lead of WWA, noting the fires are incredibly hard to suppress with available people power and technology.

Why It Matters

The attribution results land in the middle of a political fight: President Trump has blamed management failures for the fires, while the study points to climate change, The Hill reported. With communities facing displacement in repeated fire seasons, Theodore Keeping, a climate scientist at Imperial College London and coauthor of the report, said the findings show the impacts of climate change are very real and can be quantified — a crucial input for fire policy, suppression budgets and evacuation planning across Canada.