The thesis is divided thematically into two parts. The first one describes the state of gaseous carbon dioxide production, being considered the main cause of greenhouse effect or global warming. By the summary of many sources it is revealed how CO2 is produced, what influences its concentration in air the most and the CO2 level trends. The second part is focused on European Union and Czech emissions trading system, which is actual and widely discussed topic in the last few years. The main rules, mechanisms of the market and a model case of allowances trading is presented. The existence of the whole system and its positive and negative effects on the economy and environment are discussed