The reason that global CO2 levels rise and fall in response to the global temperature is because cold water is capable of retaining more CO2 than warm water. That is why carbonated beverages loose their carbonation, or CO2, when stored in a warm environment. We store our carbonated soft drinks, wine, and beer in a cool place to prevent them from loosing their fizz, which is a feature of their carbonation, or CO2 content. The earth is currently warming as a result of the natural Ice Age cycle, and as the oceans get warmer, they release increasing amounts of CO2 into the atmosphere.