How do we know levels of Carbon Dioxide and other Greenhouse Gases are increasing in the atmosphere?
Since the late 1950’s we have been directly measuring the amounts of carbon dioxide in the atmosphere. We can also measure amounts from previous eras using ice core samples and other techniques. There is no scientific doubt that carbon dioxide levels have been increasing. According the IPCC’s third assessment, the atmospheric concentration of carbon dioxide (CO2) has increased by 31% since 1750. The current CO2 concentration has not been exceeded during the past 420,000 years, and most likely was not exceeded during the last 20 million years. The atmospheric concentration of methane (CH4), a potent greenhouse gas, has increased by 151% since 1750, and continues to increase.
