Just four years after the adoption of the Paris Agreement, there are serious warning signs that the Agreement could unravel in the 2020s. Not only did President Trump’s 2017 withdrawal announcement damage the universality and reciprocity of the Agreement, but many parties are not on track to reach their own voluntary carbon reduction pledges.

This Article shows how and why the Paris Agreement could falter. I explore the recent stressors on the Agreement and challenge the dominant scholarly narrative that I call the “peer pressure proposition”—the view that international peer pressure will encourage parties to ramp up their pledges over time. Highlighting the flawed assumptions of the peer pressure proposition, I provide a more nuanced, pragmatic account of the prospects for cooperation under the Agreement in the 2020s.

While no outcome can be predicted with certainty, I argue that policymakers will plausibly face a Breakdown scenario in the next decade, where the Paris Agreement lapses into ineffectiveness, or even a Breakup scenario, where the Paris Agreement collapses and parties withdraw or disengage. Either scenario would be ecologically devastating, and I explore the implications of both scenarios for international law and the climate change regime.