European researchers track world emissions BRUSSELS, July 19 (UPI) -- Global emissions of carbon dioxide, the main cause of global warming, increased to an all-time high of 34 billion tons in 2011, European researchers said. As part of a global increase of 3 percent last year, emissions in China reached 7.2 tons per capita, putting that country in the company of the major industrialized countries, whose emissions vary from 6 to 9 tons per capita, the European Commission Joint Research Center said in a release Thursday. Of the industrialized countries, the United States remains one of the largest emitters of CO2, with 17.3 tons per capita despite a decline due to the recession in 2008-2009, high oil prices and an increased share of natural gas, the researchers said. In the European Union CO2 emissions dropped by 3 percent to 7.5 tons per capita, they said. The 3 percent increase in global CO2 emissions in 2011 is above the past decade's average annual increase of 2.7 percent, the researchers said. However, they said, this is being mitigated by the expansion of renewable energy supplies, especially solar and wind energy and biofuels, with so-called modern renewables -- which does not include hydropower -- growing with increasing speed, and quadrupling from 1992 to 2011.