Greenhouse gases cause the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3).

Post

The two main gases responsible for the greenhouse effect are :- 1. Water vapour (H2O), 2. carbon dioxyde (CO2). There are others such gases, and even many others. Some of them are “natural”, which means that they were present in the atmosphere before the apparition of men, and other can be called “artificial”, in the sense that they are present in the atmosphere only because of us. Beyond water and CO2, the other important “natural” greenhouse gases are : methane (CH4), which is nothing else than the cooking gas we use in our stoves, Nitous oxyde (N2O), the scholarly name for….. laughing gas (which is not so much amusing here), ozone (O3), which molecule comprises 3 oxygen atoms (the molecules of the “regular” oxygen gas have only 2 atoms of oxygen). When we say that these gases are “natural”, it does not mean that men did not play a role in the amount we can find in the atmosphere today. It just means that there are also natural sources (or natural cycles). For these 3 above mentionned gases, humanity “simply” adds its part to natural emissions and therefore significally increases their concentration in the air. All these “natural” gases are taken into account in the international negociations (like the Kyoto Protocol, for example), except ozone, because as it has no direct emissions. Ozone results from a subtle chemistry taking place in the air, involving “precursors” which are regular pollutants – NOx, hydrocarbons – with the help of sun rays. Calculating – even roughly – the amount of ozone emitted by a country is today clearly very difficult.

Post