FACTBOX: US, China key to climate change challenge

July 12 (Reuters) - Cooperation between the United States and China is considered essential for the world to reduce heat-trapping gas emissions blamed for global warming.

U.S. Energy Secretary Steven Chu and Commerce Secretary Gary Locke will travel to Beijing this week to promote clean energy technology trade and other ways the two countries can work together to fight climate change.

Here are some climate change facts about the two countries:

U.S., CHINA BIGGEST GREENHOUSE GAS EMITTERS

* China's rapid growth has pushed it into first place as the world's leading source of carbon dioxide emissions. But the United States, the number two emitter, still has spewed the most heat-trapping gases into the air over time.

* From 1998 to 2006, China's annual carbon dioxide emissions doubled to more than 6 billion metric tons, according to the U.S. Energy Information Administration. Over the same period, U.S. carbon dioxide emissions grew much less rapidly, from 5.6 billion metric tons to 5.9 billion.

* The United States and China's greenhouse gas emissions are driven by their huge appetite for fossil fuels. The United States consumes more oil and natural gas than any other country and is second only to China in coal consumption. The United States and China are number one and two, respectively, in electricity generation.

* The United States, with 5 percent of the world's population, is responsible for about 30 percent of the world's cumulative carbon dioxide emissions. China, with one-fifth of the world's population, accounts for about 8 percent of the emissions already in the atmosphere.

* The average American accounts for 20 metric tons of carbon emissions per year, compared to 10 for the average European and around 5 for the average Chinese.