Dec 11, 2014
Carbon dioxide (CO2) is the main contributor to climate change. In 2013, the global combustion of fossil fuels and the production of cement resulted in the emission of 36.1 billion tons of CO2, which was 61 percent over 1990 levels. (In terms of carbon, the emissions totaled 9.8 billion tons in 2013.) According to the most recent estimates, emissions in 2014 are projected to be 2.5 percent over 2013 levels. In physical terms, this translates into the release of 37 billion additional tons of CO2 in the atmosphere. It is estimated that to keep the rate of Earth's warming below the 2 degrees Celsius threshold believed to be the temperature increase that will have severe and irreversible global environmental effects, total future emissions cannot exceed 1,200 billion tons.