  One of the big problems of the age concerns 'Global Warming', and whether it
is 'man-made' or 'natural'. Most climatologists believe that it is very likely
to be the former but some scientists (mostly non-climatologists) subscribe to
the latter. Unsurprisingly, the population at large is often confused and and
is not convinced either way. Here we try to explain the principles of man-made
global warming in a simple way. Our purpose is to try to understand the story
which the climatologists are telling us through their rather complicated
general circulation models. Although the effects in detail are best left to the
climatologists' models, we show that for the Globe as a whole the effects of
man-made global warming can be demonstrated in a simple way. The simple model
of only the direct heating from the absorption of infrared radiation,
illustrates the main principles of the science involved. The predicted
temperature increase due to the increase of greenhouse gases in the atmosphere
over the last century describes reasonably well at least most of the observed
temperature increase.
