This week, the United Nations announced that industrialized nations around the world have agreed to cut CO2 emissions by at least 15-21 percent (relative to 1990 levels) by the year 2020.

Though the decrease falls a bit short of the original goal of a 25-40 percent cut, emissions should fall to between 10.71 and 9.86 billion metric tons of carbon dioxide in 2020, compared with 12.53 billion metric tons in 1990.

In the US President Obama has vowed to (only) cut emissions by 14 percent in the same time frame.

Read More: Rich Nations offer 15-21 percent CO2 cuts by 2020: U.N. (Reuters)