Apart from discussing industrial emissions, car exhaust levels and that kind of more obvious topics, there has recently been mention of more natural sources of CO2 inflation, in particular the lakes in the mountainous regions of northern Sweden.

A lake such as Vassijaure annually emits the equivalent of 165 car laps around the globe....and that's just one of many lakes in the north! Another comparison says the annual emissions of the lake are the equivalent of what one Sweden causes in 400 years....

The surrounding/underlying soil binds large quantities of CO2 or rather, has been binding them. As the permafrost increasingly thaws more and more CO2 is released into the lakes and from there into the atmosphere. According to the scientists involved in the study this contribution is not taken into consideration in the current set of climate models.

photo: http://www.emg.umu.se/research/natgeo/project1.htm