The Threat of Climate Change - Energy and Climate: How to Achieve a Successful Energy Transition - page 22

The greenhouse effect
The CO 2 emitted in the atmosphere behaves like a greenhouse gas,
according to the mechanism shown in Figure 3.1. The atmosphere is
transparent to the incident solar radiation transmitted in the visible light
spectrum, but some of the solar energy received by the Earth is reflected
back as infrared radiation. This radiation can be partly stopped by some
gases present in the atmosphere, the greenhouse gases, and returned to the
Earth whose surface warms up accordingly.
Carbon dioxide is not the only greenhouse gas. Other gases such as
methane, nitrous oxide and ozone produced by human activity contribute
to the thermal imbalance of the Earth.
Agricultural activities are also responsible for emissions of greenhouse
gases: in addition to CO 2 emissions due to the use of fossil energies, they
also produce methane (from cattle and paddy fields) and nitrous oxide.
Some industrial gases also participate in global warming, especially
halogenated gases such as carbon tetrafluoride and sulphur hexafluoride.
The contribution of these greenhouse gases depends on their global
warming potential (GWP), which measures the absorption of infrared
radiation emitted back into the atmosphere. Carbon dioxide, with a GWP
of 1, acts as reference. Methane has a GWP of 22, nitrous oxide 310 and
sulphur hexafluoride 23 900!
Figure 3.1 Greenhouse mechanism