In 1997, most of the world agreed to an international treaty, known as the Kyoto Protocol, that required developed countries such as the United States to reduce greenhouse gas emissions by about 5 percent when compared with the baseline year of 1990. But countries that are still developing, including China and India, were not limited by how much carbon dioxide they expelled. The United States never ratified the treaty.
The latest pollution numbers, calculated by the Global Carbon Project, a joint venture of the Energy Department and the Norwegian Research Council, show that worldwide carbon dioxide levels are 54 percent higher than the 1990 baseline.
The 2011 figures for the biggest polluters:
1. China, up 10 percent to 10 billion tons.
2. United States, down 2 percent to 5.9 billion tons
3. India, up 7 percent to 2.5 billion tons.
4. Russia, up 3 percent to 1.8 billion tons.
5. Japan, up 0.4 percent to 1.3 billion tons.
6. Germany, down 4 percent to 0.8 billion tons.
7. Iran, up 2 percent to 0.7 billion tons.
8. South Korea, up 4 percent to 0.6 billion tons.
9. Canada, up 2 percent to 0.6 billion tons.
10. South Africa, up 2 percent to 0.6 billion tons.