Carbon dioxide is a greenhouse gas. When there is more CO2 in the atmosphere, global temperatures tend to rise. When there is less CO2, temperatures tend to be lower. By carefully studying temperature and CO2 levels from the past, scientists have been able to formulate a mathematical relationship between atmospheric CO2 concentration and average global temperatures. In general, whenever the carbon dioxide concentration in our atmosphere doubles, global temperatures rise by about 3° C (5.4° F). This is called the climate sensitivity, and there is evidence that it might be higher or lower than 3° C.
The simple calculator below allows you to play around with this relationship. The calculator starts with 2010 levels for carbon dioxide and temperature. Drag the slider to raise or lower the CO2 concentration. See how the temperature changes as a result. Change the climate sensitivity and see how the temperature is affected.