Most of the world's greenhouse gas (GHG) emissions come from a relatively small number of countries. The United States, China, and the European Union (EU-25) together accounted for about 50% of global emissions in 2004. The eight largest emitters - the United States, China, the European Union, Russia, India, Japan, Germany and Brazil - accounted for more than 70% of global emissions.
Links:
[1] http://pewclimate.org/facts-and-figures/international
[2] http://pewclimate.org/global-warming-basics/facts_and_figures