Nearly 200 nations agreed last December to the most ambitious deal to slow climate change ever. It looks very likely that the requisite number of countries will actually ratify the deal this week to make it official. That will set in motion the difficult process of making sure both rich and poor countries deliver on their promises to cut emissions of greenhouse gases.
The European vote to ratify it effectively ends debate over the climate deal. Once the EU turns over paperwork to the U.N. later this week, the plan will officially come into force.