UN say cities are green, need to be greener (pdf). Cities provide higher standards of living, and more economic opportunity with less energy, materials, and land use. They house 50% of the world’s people, but account for 60-75% of the world’s emissions, not because they’re inefficient, but because city dwellers are disproportionately rich. Interesting data points: Tokyo and Paris dwellers emit half as much carbon as New Yorkers or Londoners. São Paulo is as rich as Mexico City but with 1/3 the emissions. Delhi is 1/3 as rich as São Paulo, but with the same emissions.