Most people know that China and the United States are the world's top two carbon-producing nations. But researcher Richard Heede of the Climate Accountability Institute in Colorado dug deeper and found that 90 companies around the world have caused nearly two-thirds of all global greenhouse gas emissions since the beginning of the Industrial Age. (Half of those emissions were produced in the last 25 years or so.) All are oil, gas, or coal producers, except for seven cement manufacturers. The list, reported in the journal Climatic Change, can help activists hold individual carbon emitters' feet to the fire. There are thousands of oil, gas, and coal facilities in the world, Heede told the Guardian, "but the decision makers--the CEOs, or the ministers of coal and oil--they could all fit on a Greyhound bus or two."