[irresseni]

This is the natural process by which the Earth heats up and cools down over time. There is four stages to this process which are shown on the diagram below:

The diagram can be clicked on in order to skip to the paragraph on a particular part of normal global warming. The natural process of global warming occurs in four stages, we are currently in one now.

Firstly though I will explain the processes involved with the greenhouse gases. Greenhouse gases (CO2 is the example used in the diagram, although Ccl2f2 are often on exams) are found in the Troposphere of the Earths atmosphere. There is a table taken from Salters Advanced Chemistry Chemical Storylines book that shows most of the gases and their contributions to the effect, below. Greenhouse gases work very simply, the sun radiates electromagnetic radiation in a variety of wavelengths towards the Earth. The O-zone layer (which is also under threat from our CFC's) absorbs some of the high energy radiation and emits it to the Earths surface at a lower wavelength (often visible light). This hits the Earths surface and is absorbed again, and then emittedat a lower wavelength. This time the radiation is infra-red (heat). This infra-red radiation is intercepted by the greenhouses gases and emitted in all directions some of which returns to the surface for a second time. The more greenhouse gases there is in our atmosphere, the more ir radation will be returned to the Earths surface and so the hotter the surface will be. However it is important to know that this is a natural processes that keeps the Earth warming and leads to the occasional ice age. Click here to skip to the enhanced greenhouse effect!

http://www.restoringearth.co.uk/inde...nhouse-effect/