The amount of CO2 emissions from fuel combustion has doubled over the past 30 years. In 1971, the world-wide average emission was of 14095 million tonnes. In 2007, it was of 28962 million tonnes. Predictions for the year 2030 estimate an average of 40226 million tonnes of CO2 emission.
Source: OECD Factbook 2010, Economic, Environmental and Social Statistics, Chap. Emissions of Carbon Dioxide