Beyond national governments, more than 200 cities — such as Rio de Janeiro, Seoul and Philadelphia — now have strategies to reduce greenhouse gas emissions, with those locations' projected reductions estimated at 454 megatons of carbon dioxide by 2020. What's impressive is the cumulative estimated effect of those commitments. Cumulative emission savings by 2050 from those city efforts equal the combined current annual emissions of China and India, and annual savings equal current emissions in South Africa.