Climate researchers have found worldwide carbon emissions have grown sharply since 2000, despite growing concern of global warming. During the 1990s, carbon emissions grew by less than one percent per year. Since 2000, emissions have grown at a rate of 3.5 percent per year. No part of the world had a decline in emissions from 2000 to 2008. Climate scientist Christopher Field says the largest factor in this increase is the widespread adoption of coal as an energy source.