They point to the United States' huge historical emissions of heat-trapping gases from the burning of coal, oil and gas. Hazardous smoke spread across both the United States and Canada, choking large cities such as New York. When asked Sunday about punishing Canada, Trump on Air Force One told reporters he has decided one, adding “you'll find out about it soon.” That history shows that the United States contributed more than any other country,” said University of Victoria climate scientist Andrew Weaver. “President Trump is pointing at the smoke while ignoring America's fingerprints on the climate conditions behind it.”