1. “We are getting out.”

The United States, the largest carbon polluter in history, will withdraw from the Paris climate deal, President Trump announced at the White House.

Ignoring the pleas of business leaders, climate activists and members of his own staff, Mr. Trump argued that the goal of reducing carbon emissions would cost the economy too much.

Withdrawing from the accord could take up to four years, meaning a final decision could be left to voters in the next presidential election.