claim: Globally averaged thermometers show two periods of warming since 1900: a half-degree from natural causes in the first half of the 20th century, before there was an increase in industrial carbon dioxide that was enough to produce it, and another half-degree in the last quarter of the century.
evidence: In terms of dollars, the World Bank has estimated that the size of the carbon market was US$11 billion in 2005, $30 billion in 2006, and $64 billion in 2007.