Since measurements began in the 1950s, scientists have discovered that there has been a decline of sunlight reaching the Earth; they called it global dimming.

But according to a paper published in the journal Science, the dimming did not continue into the 1990s and indeed since the 1980s scientists have observed a widespread brightening. What caused the dimming to go down and what effect will it have, if any, on climate change?

The film explores the theory that pollution is shielding the oceans from the full power of the Sun, and disrupting the pattern of the world-s rainfall. There is evidence that dimming caused the droughts in sub-Saharan Africa which claimed hundreds of thousands of lives in the 1970s and 1980s.

It reveals that we may have grossly underestimated the speed at which our climate is changing. At its heart is a deadly new phenomenon. One that until very recently scientists refused to believe even existed. Alarmingly the dimming continues today, and Asia, home to half the world-s population is currently under threat.