Climate as a Global Challenge

Scientists had measured rising carbon dioxide since 1958, and by the 1980s they warned that burning fossil fuels was warming the planet. In 1988 the UN set up the Intergovernmental Panel on Climate Change, and the 1992 Rio Earth Summit produced a framework convention to tackle it. The 1997 Kyoto Protocol set binding targets for rich nations, but the US never ratified it, and fast-growing countries like China, which became the largest emitter in the 2000s, had no targets.

The 2015 Paris Agreement took a different approach: nearly every country set its own pledges, with the shared aim of limiting warming to well below 2°C. Climate shows why global problems are hard to solve. Costs fall unevenly, benefits are shared, and countries argue over fairness: poorer nations note that rich countries emitted most historic carbon, while rich nations point to today's emissions. The Cold War offers a hopeful precedent, since rivals agreed in 1987 to protect the ozone layer.