Climate Change Trends: Carbon Emissions GiantsClimate Change Trends: Carbon Emissions Giants Right now, 10 countries — including the U.S., China and Russia — are responsible for 80 percent of the world's carbon dioxide emissions. The United States is the world's second largest emitter (China ranks no. 1), sending around 5.8 million metric tons of CO2 into the atmosphere a year. That's the equivalent to a year's worth of greenhouse gas emissio
