In “Unsafe Climates,” Elizabeth Kolbert writes about this week’s summit, where world leaders must confront the destabilizing consequences of global warming.

In “ISIS After Paris,” Steve Coll writes that a study of insurgencies offers lessons in the aftermath of the attacks on the French capital.

In “Still Standing,” George Packer argues that, by the close of the fourth Republican debate, the outlines of the battle for the Party’s nomination were becoming clear.

In “Harsh Talk,” Margaret Talbot writes about Latino voters and the G.O.P.

In “Powerful Gestures,” George Packer writes about Rosalynn Carter’s visit to the Thai-Cambodian border, and the Obama Administration’s inaction in response to the Syrian refugee crisis.

In “Powerful Gestures,” George Packer writes about Rosalynn Carter’s visit to the Thai-Cambodian border, and the Obama Administration’s inaction in response to the Syrian refugee crisis.