What activity plays the biggest role in increasing greenhouse gases

Carbon dioxide accounts for most of the nation's emissions and most of the increase since 1990. Electricity generation is the largest source of greenhouse gas emissions in the United States, followed by transportation.

In 2010, global greenhouse gas emissions from the agricultural sector totaled 4.7 billion tons of carbon dioxide (CO₂) equivalent, up 13 percent over 1990. Agriculture is the third largest contributor to global emissions by sector, following the burning of fossil fuels for power and heat, and transportation. May 8, 2013