Political misinformation continues to swirl the climate change debate like a thick fog rolling in from a rising ocean. However, a wealth of government documents and reports from researchers and historians make it clear what scientists and government officials knew and when.    Scientists already figured out in the late 19th century that the greenhouse effect keeps the planet warm and that carbon dioxide produced by burning coal can amplify this effect. In the 1970s, researchers measured these emissions in the atmosphere and warned that the Earth's temperature could warm by 0.5 to 5 degrees Celsius by the middle of the 21st century. (Dinah Voyles Pulver)