''Scientists in Australia and Canada say that pollution from western countries may have caused the droughts which ravaged Africa's Sahel region in the 1970s and 1980s. Millions died in the droughts, which hit Ethiopia hardest in 1984.

[....]

[The scientists] ran a simulation of global weather including the interaction between sulphur dioxide emissions and cloud formation.

Sulphur emissions from power stations and factories prevent cloud formation, cooling the Earth below.

As this pollution mainly happened in the industrialised north, the Northern Hemisphere became relatively cooler than the south.

This caused the rain belt to move south - away from the Sahel.

[....]

During the past few years, rainfall has increased in the Sahel. Mr Rotstayn explains this improvement by the "clean air" laws introduced in North America and Europe. This legislation reduced sulphur dioxide emissions in response to another environmental crisis - acid rain. ''

- BBC.co.uk