How much has the amount of carbon dioxide in the atmosphere increased since 1750?

Data for the past 2000 years show that the atmospheric concentrations of CO2, CH4, and N2O - three important long-lived greenhouse gases - have increased substantially since about 1750. Rates of increase in levels of these gases are dramatic. CO2, for instance, never increased more than 30 ppm during any previous 1,000-year period in this record but has already risen by 30 ppm in the past two decades.