After a week of tense negotiations, the 195 countries that met in Paris agreed to the text of a historic climate change agreement late Saturday. The accord is not itself an end game, but it lays out the road the world will have to travel in order to limit the harm of climate change.

The international agreement states that nations will aim to limit “the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels." International negotiations have long been focused on a 2°C limit, but the 1.5°C language was a surprise addition.

Rather than prescribe some common emissions target, the negotiations took a “bottom-up” approach, with nations each submitting their own emissions pledges. Current pledges are only good enough to limit 20th century warming to around 3°C. But a key part of the agreement is a framework for revisiting emissions pledges every 5 years, with the goal being that those pledges are ratcheted down over time. To that end, it states that nations will “aim to reach global peaking of greenhouse gas emissions as soon as possible” and reach net-zero emissions “in the second half of this century”. While the details remain to be filled in, the agreement also calls for transparent reporting of emissions to keep nations to their pledges.

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