Focusing on global mitigation pathways masks key aspects of technical, political, and social feasibility, which play out at the country level. We illustrate the dilemma between a “carbon law” (halving emissions every decade) at the global level and the nationally determined contributions submitted at the country level. Our results suggest that even if the United States, European Union, China, and India could strengthen their nationally determined contributions by 2050, the rest of the world is required to immediately change from their current course to a very rapid decrease in emissions reaching almost zero emissions by 2030, to achieve the Paris 2015 goal. The greatest mitigation challenges lie in the developing world. Real progress toward the Paris Agreement goal awaits an effective commitment by leading countries to undertake breakthrough research and development of low‐, zero‐, or even negative‐carbon‐emissions energy technologies that can be deployed at scale in the developing world.