The amount of sunshine we have depends on latitude and how much cloud there is in the sky. In some of the world’s deserts the number of sunshine hours is very high, more than 3,600 hours each year. In the Eastern Sahara desert, the sun is covered by clouds for less than 100 hours a year.
Hours of sunshine are usually recorded on a simple machine called a parheliometer also known as a Campbell-Stokes recorder. It works by using a glass ball to focus the sunlight and rays onto a strip of card. As the sun moves round during the day, the card is scorched creating a record of how many sunshine hours there were.