For fuck’s sake. Global Dimming? I thought global warming was bad enough but global dimming? I heard about global dimming from a TV show on ABC TV Australia called Four Corners. This show has been running on the government funded channel since the 1960’s (I think). They only have one story that goes for 40 minutes, so they take a fairly good look at a subject.
Before we tackle Global Dimming what is Global Warming? Basically when you generate energy from fossil fuels such as mineral oil, natural gas and coal; you are burning it. When you burn something in an oxygen atmosphere it releases CO2 (carbon dioxide), amongst other gases. These gases mix with the atmosphere and change it. The energy (heat) from the sun cannot escape back out into space and is trapped in the atmosphere, which warms. This effects the natural flow of the atmosphere. Weather patterns that have evolved over a long period of time to keep the atmosphere in balance are disturbed.
So what is Global Dimming? Four Corners explained it was all about clouds. Clouds form when dust particles in the air attract water. More and more water clumps together until they become heavy enough to defy gravity and we get rain. Clouds reflect some of the sunlight back into space.
Global Dimming theory says that the very fine particles released when burning fossil fuels also attract water in the air. As there are many tiny particles attracting water, these clouds are denser and reflect more sunlight than normal clouds back into space. How do they know this? Some scientists analysed the results of many years of water evaporation readings taken each day. The results showed less water being evaporated as global temperatures increased. How could this be? If the atmosphere is warmer shouldn’t water being evaporating more? They found sunlight is the biggest factor in water evaporation, more than air temperature. Less sunlight was hitting the water so it evaporated less. At the same time the atmosphere has gotten warmer.
How does the World Trade Centre’s destruction come into this? Airplane vapour trails. When airplanes fly they leave a vapour trail (burnt fuel). This forms long thin clouds which block the sunlight. From September 12th to 14th most airplanes were grounded in the USA. A scientist who was studying vapour trail effects seized the chance to see what happens when there’s no vapour trails to block sunlight. What he found was a big jump in temperature for those 3 days when the airplanes were grounded.
So here’s the scary part. Global Dimming is hiding the true effects of Global Warming. If we stop emission of fine particles but still emit gases that warm the atmosphere the global temperature will increase even more than it has so far.
So basically; we’re fucked. Thanks for coming.