“Climate change presents a unique challenge for economics: it is the greatest and widest-ranging market failure ever seen.” -- Nicholas Stern, Leading climate economist; former World Bank chief economist.

“The ultimate commons problem of the twenty-first century—global climate change.” -- Robert Stavins, Harvard environmental economist and climate-policy expert.

“Climate change, an externality that is unprecedentedly large, complex, and uncertain.” -- Richard Tol, Prominent economist specializing in climate-change impacts.

“Climate change is a global public-goods externality whose formal resolution requires an unprecedented degree of international cooperation and coordination.” -- Martin Weitzman, Harvard economist; pioneering scholar of climate risk.

“Climate change is the Colossus of all global public goods.” -- William Nordhaus, Nobel laureate and pioneer of climate economics.

“The problem with climate change is that there’s a market failure.” -- Joseph Stiglitz, Nobel laureate and former World Bank chief economist.