Scientists predict dark future

Polluting particles that are slowing global warming by reflecting the sun's rays back into space are also acting as a global dimmer switch, gradually lowering the lights on Earth.

Earlier this month, scientists made the counter-intuitive claim that some pollutants actually had a silver lining, bouncing warming rays away from the Earth's surface, negating some effects of climate change (se related story).

But now an amendment to the theory points out that keeping the heat at bay is also losing us light.

The idea that the skies are getting darker is not a new one and was first brought to light by Swiss-based researcher Atsumu Ohmura in the late 80s.

But his findings were largely ignored by the scientific community, which remained sceptical even when Ohmura's theory was backed up by almost identical results from independent experiments carried out in Israel by researchers Gerald Stanhill and Shabtai Cohen in the late '90s.

The world has slowly come round to the idea that global dimming is a real phenomenon, however, and it is now generally accepted that the level of light we receive has been falling since the 1950s.

The estimates of how rapidly we are losing light vary wildly, and the effect seems to be dramatically different depending on where in the world measurements are taken.

Figures of around a 2% decrease per decade are often used as a realistic benchmark, though some research show, for example, the drop has been as high as 20% in parts of the former Soviet Union between 1960 and 1987.

The jury is still out on what the possible impact of global dimming is likely to be, but it has sent shivers down the spines of some of the advocates of solar power and could even affect photosynthesis in plants if it continues at its current rate.

The theory has been given a publicity boost this week as a team working for BBC Focus science magazine are set to publish an article highlighting the fact that as more is done to reduce the pollutants that reflect light and heat from the sun away from the Earth, we are likely to see climate change gather pace.

So while the lights may be turned back up in decades to come, it looks like the pay-off will be a rise in temperatures even faster than previously predicted.

By Sam Bond



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