Google "Vostok ice cores".
Should give you graphs of temperature and carbon dioxide from previous 400,000 years. There were ancient warming periods with high levels of carbon dioxide --- not caused by humans.
Thank you for the links. Regarding ice cores and other measures, I do not doubt there have been other warm periods, that were not caused by man. However, this does not prove or disprove that man is having an influence on this warming period. Regardless of whether we are or are not causing warming, our resources are finite, and we should conserve as much as is reasonable. I for one switched to CFL lights about 12 years ago and have already saved almost $2,000 because of it.