Our climate is changing at a grossly under-estimated speed. Almost everything we do to create energy causes pollution. Burning fuel not only produces the invisible greenhouse gases which cause global warming but also visible pollution, tiny airborne particles of soot and other pollutants.

In the past five decades, the total solar irradiance is decreasing — the sunlight reaching the earths surface is falling by alarming levels. The effect varies by location, but worldwide it is of the order of a 5 percent reduction over the three decades (1960-1990). This trend has reversed during the past decade.

Global dimming

Global dimming creates a cooling effect that may have partially masked the greenhouse gases effect on global warming.

The effect was first spotted by Gerry Stanhill, an English scientist working in Israel. There was a staggering 22 percent drop in sunlight over Israel, with sunlight falling by 10 percent over the USA, nearly 30 percent over Soviet Union, and even by 16 percent in parts of the British Isles. Although the effect varied greatly from place to place, overall the decline amounted to one to two percent globally per decade between the 1950s and the 1990s. Jerry called the phenomenon global dimming and published his research in 2001, which hardly created a splash amongst the social scientists. Only recently his research is confirmed by Australian scientists and climate scientists around the world woke up to the reality that was global dimming.

Global dimming appears to have been caused by suspended particles in earths atmosphere; clouds are formed around pollen or sea salt particles around which water droplets can condense. The visible air pollution due to the burning of fossil fuels reflects sunlight back into space, preventing it reaching the surface. But the pollution also changes the optical properties of clouds since the particles seed the formation of water droplets. Recent research shows that this makes them more reflective than they would otherwise be, again reflecting the Sun’s rays back into space.

The ‘dimming’ effect may have caused large scale changes in weather patterns. Climate models speculatively suggest that this reduction in sunshine at the surface may have led to the failure of the monsoon in sub-saharan Africa during the 1970s and 1980s, together with the associated famine such as the Sahel Draught caused by Northern hemisphere pollution cooling the Atlantic. Because of this, the tropical rain belt may not have risen to its northern latitudes causing an absence of seasonal rains.

It is also concluded that the imbalance between global dimming and global warming at the surface leads to weaker turbulent heat fluxes to the atmosphere. This means globally reduced evaporation and hence precipitation occur in a dimmer (and warmer world), which could ultimately lead to a more humid atmosphere in which it rains less. Just burn oil and coal more cleanly. And in Europe we’ve already made a start: scrubbers in power stations, catalytic converters in cars and low sulphur fuels as examples.