In order to understand the arguments involving climate change, we must first understand what human products are believed to cause climate change and how they effect that change. These gases are collectively called greenhouse gases.
The information presented here comes from the IPCC Technical Summary on Climate Change 2007: The Physical Science Basis and Understanding and Responding to Climate Change by the NAS.
There is no question that the current levels of carbon dioxide (CO2) in the atmosphere are much higher than levels measured in the last 650,000 years. How do we measure levels of CO2? CO2 and other gases are trapped in layers of ice in the Arctic and Antarctic. As ice and snow accumulate over time, newer layers build on top of old ones.