Written by : Energy Digital staff

GREENHOUSE GASES , GLOBAL warming , climate change and carbon footprints : these terms coexist as a result of carbon dioxide emissions . The main source of carbon dioxide ? The combustion of fossil fuels , primarily through electricity , transportation and industry according to the EPA . Cut back on these three man-made areas of activity , and rates of those terms all decline . Cities are the best starting place to do so , and some of the world ’ s largest cities have determined measures they are taking , or should be taking , in the battle to bat down carbon emissions .

Carbon Emissions Trading Emissions trading , or cap-and-trade , has been around since the 1980s . As discussed in the Smithsonian , this outlandish concept of trading pollution rights originated from Reagan administration attorney C . Boyden Gray . Today , emissions trading is a global phenomenon under the guise of the Kyoto Protocol . It is also the main way that major urban centers manage to offset advancing levels of pollution .

By trading emissions credits , the cities with the biggest carbon footprints are able to sell off their pollution to other not-so-polluted

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