Donald Trump says Canada is poisoning American cities with wildfire smoke. He has told Prime Minister Mark Carney to get the fires under control, demanded compensation and threatened tariffs because smoke from Canadian fires crossed into the United States. The smoke did come from trees burning in Canada. That establishes the immediate source of the pollution, but says very little about the larger causes of the conditions producing fires of this scale. The border tells us where the forests caught fire. It does not allocate responsibility for the hotter and drier conditions that have made North American wildfire seasons longer, larger and harder to control. Trump is treating the location of the burning trees as though it settles the climate question. It does not. From 1850 through 2024, the United States produced about 24% of cumulative global fossil CO₂ emissions. The current EU27 produced about 16%, China 15% and India 4%. The United States has held the largest cumulative national total since 1917. A separate peer-reviewed assessment of national contributions to warming from historical CO₂, methane and nitrous oxide also puts the United States first. China now emits more CO₂ annually, a comparison frequently used to divert attention from the cumulative nature of carbon dioxide. The climate influencing current wildfire conditions was not created by emissions from the latest reporting year. It was built over generations. The United States industrialized early, consumed fossil fuels on an exceptional scale, organized transport and land use around oil, and received enormous economic benefits from doing so. No individual country contributed more to the accumulated warming now affecting forests across the continent. The fires are in Canada. The climate conditions affecting them are not exclusively Canadian, and the United States has contributed more to those conditions than any other country. Climate attribution science does not claim that carbon dioxide starts individual fires. It examines how warming changes the conditions in which fires start and spread. Higher temperatures dry vegetation and soils, intensify drought, lengthen fire seasons and increase the probability that fires will grow beyond the capacity of suppression systems. Climate change does not have to increase the number of ignitions dramatically to produce much greater damage. It can do so by increasing the area capable of sustaining large fires and extending the period during which they can burn. The peer-reviewed attribution analysis of Canada’s catastrophic 2023 fire season found that human-caused climate change more than doubled the likelihood of an area burned that large in eastern and southwestern Canada. It made an exceptionally long fire season more than five times as likely and increased the likelihood of simultaneous extreme fire weather across widely separated regions. Canada did not experience a record number of ignitions. The exceptional outcome came from fires becoming unusually large, persistent and geographically widespread. There is not yet an event-attribution study assigning a precise climate fraction to the fires burning this week. That means a precise fraction should not be invented. It does not mean the established relationship between warming and severe Canadian wildfire conditions should be ignored until a paper addressing this exact event is published. Scientific caution about a particular percentage is not evidence that the broader causal relationship is uncertain. Trump’s compensation demand therefore reverses the more important responsibility. The United States is not merely an uninvolved neighbour receiving pollution produced entirely by another country’s choices. It is the largest historical national contributor to the warming that has increased the likelihood and severity of this class of disaster. Under any serious system of transboundary climate accountability, the United States would face far larger claims arising from its historical emissions than it could plausibly make against Canada for wildfire smoke. The American responsibility is not confined to emissions released by people who died generations ago. The United States continues to make political choices that protect fossil fuel production and weaken climate policy. In 2016, the Electoral College installed Trump despite his losing the popular vote. In 2024, Americans returned him to office with 312 electoral votes and 49.8% of the national popular vote after having already seen his approach to climate science, environmental regulation and fossil fuel development. There was little room for misunderstanding the second time. Americans had watched repeated megafires, smoke emergencies, heat waves, floods and billion-dollar disasters. They had seen Trump withdraw the United States from the Paris Agreement during his first term. They knew he opposed greenhouse gas regulation, promoted expanded fossil extraction and treated climate policy as an obstacle to economic growth. Many voters ranked immigration, inflation, cultural grievance, partisan loyalty or gasoline prices above climate stability. That is their democratic right. It does not remove responsibility for the foreseeable climate consequences of the government they selected. Elections produce governments with entire policy programs, not individually chosen menu items. A voter may not have supported Trump because of his climate policies, but those policies were neither concealed nor incidental. Enough Americans approved of them, accepted them or considered them unimportant enough to overlook that Trump returned to power. Since then, his administration has again withdrawn the United States from the Paris Agreement. His EPA has rescinded the 2009 greenhouse gas Endangerment Finding and repealed federal greenhouse gas standards for light-, medium- and heavy-duty vehicles. The federal government is weakening measures intended to reduce future climate risk while blaming Canada for failing to contain one of its consequences. This does not make every American equally responsible. Children with asthma did not vote for the administration. Millions of Americans voted against it. Noncitizens could not vote, and lower-income households with poor access to filtration will often suffer more than wealthier people with greater political influence and better protection from smoke. Those inequities matter, but they do not eliminate collective political responsibility. Governments act in the name of countries, national emissions accumulate regardless of internal political disagreement, and elections determine which policies will be pursued. Americans who opposed Trump’s climate agenda can accurately say they fought against it. The United States as a political community cannot claim that the choice was never made. Canada deserves no general climate absolution. It is a wealthy, high-emitting fossil fuel producer whose governments have protected oil and gas production while repeatedly missing climate targets. Canadian emissions in 2024 were still 685 MtCO₂e, only 10.3% below 2005 and 12.6% above 1990. Oil and gas emissions were 5.1% higher than in 2005, while Canada’s own projections show current policies falling well short of its 2030 commitment. Canada also has direct responsibility for protecting communities, improving evacuation systems, funding firefighting capacity, using Indigenous-led cultural fire where appropriate and managing fuels around settlements. Some losses will reflect inadequate preparation, poor land management or delayed responses by Canadian governments. Those failures do not make the two countries equally responsible for climate change, and they do not turn the United States into an innocent downwind victim. Canada’s smaller population does not excuse its high per-capita emissions or fossil fuel expansion. Equally, Canada’s failures do not erase the much greater absolute historical contribution of the United States. Nor can Canada extinguish every fire across the boreal forest simply because smoke is moving toward American cities. Canada contains millions of square kilometres of forest, much of it remote and sparsely populated. Lightning storms can create many simultaneous fires, including fires that become very large before crews can reach them. Attempting to suppress every remote fire would be physically impossible, ecologically damaging and extraordinarily expensive. The relevant questions concern preparation, priorities and protection of communities, not the fantasy that a national government can prevent a continental forest system from burning. Trump’s argument depends on treating the border as decisive when smoke moves south and irrelevant when greenhouse gases move north. The atmosphere recognizes neither distinction. American emissions spread globally, contributed substantially to continental warming and helped intensify the conditions in which Canadian forests now burn. Canadian smoke is returning through that same shared atmosphere. The United States is breathing smoke from Canadian fires. It is also experiencing a climate risk that it did more than any other country to create and that its voters have again chosen not to treat as a governing priority. Blaming Canada may be politically convenient, but it does not survive contact with the emissions record, attribution science or the policies Americans knowingly put back into office. Previously published on TFIE Strategy Briefing.
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