(4) Green plants Explanation: When it comes to greenhouse gases many of us think first of CO2. But a large proportion of global greenhouse gas emissions are actually other gases, such as N2O (nitrous oxide) and CH4 (methane). The emission of methane and nitrous oxide is largely the result of agricultural activities; nitrous oxide from fertilisers and methane mostly from cows. In peat pasture areas these emissions are particularly prevalent.