The Earth is getting hotter. How heat domes, El Niño and greenhouse gases all play a part.

WASHINGTON, D.C. — What a difference a few days make. Rather than cutting the deal U.S. President Donald Trump hailed early last week, the United States and Canada entered an escalating tariff conflict over the weekend that threatens to become a full-blown trade war. Prime Minister Mark Carney pulled his negotiating team back from Washington late Friday and has threatened dollar-for-dollar retaliatory tariffs in response to the newly imposed 50 per cent Section 338 tariffs Washington placed on about $28 billion worth of Canadian exports to the U.S. on Saturday. The relationship “is...