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Global Warming has become a hot button issue over the last few years. A vision of huge hurricanes, ice sheet loss, and extreme drought are brought up frequently in the media as the true story of global warming. But to truly understand global warming we must analyze it through the larger scope of climate change, because it is only one mechanism at work in large machine which drives the world's atmosphere.
In 1993 a paper came out detailing how radiation from the sun had decreased by 0.33% yearly from 1967-1986 (Stanhill and Moreshet). This was a little understood phenomena and in the past 15 years has been dubbed "global dimming". Global dimming has the opposite effect of global warming. As pollutants such as Sulphur Dioxide, soot, and ash are released in the air they collect with clouds causing a dense mass to form and reflect much of the suns light. This in turn causes the oceans to cool a bit and changes weather patterns.
A large effect of this was seen in the 1990's in Africa as the waters which regularly evaporated from the Northern Atlantic and brought upon the rainy season on the Sahel in Northern Africa disappeared. In a January 15, 2005 BBC documentary titled Horizon a chilling conclusion was offered: "what came out of our exhaust pipes and power stations [from Europe and North America] contributed to the deaths of a million people in Africa, and afflicted 50 million more" with hunger and starvation.
Scientists believe that Asia may be hit soon with effects from dimming. Every year the Indian subcontinent and Southeast Asia receive nourishing rains from a "monsoon season". If the evaporative mechanisms which produce these rains are altered the irrigation and sustenance of not only farming ventures but wildlife reserves may be threatened.
Another mechanism affecting dimming is called the "Contrail Effect" where the "condensation trails" of jets are leaving behind remnants that form cirrus clouds which block sunlight but also trap heat. Studies have shown that contrails from just six aircraft can expand to shroud some 7,700 square miles. Just after September 11, 2001 scientists had an opportunity of a lifetime to study the contrail effect as all commercial flights were grounded due to the terrorist attacks. During those three days that commercial aircraft were grounded the days had become warmer and the nights cooler, with the overall range greater by about two degrees Fahrenheit. David Travis of the University of Wisconsin-Whitewater and two colleagues measured the differences and say the results suggest "that contrails can suppress both daytime highs (by reflecting sunlight back to space) and nighttime lows (by trapping radiated heat)."
In skies usually crosshatched with condensation trails, the only contrails seen in this image from September 12, 2001, were left by the plane returning President Bush to Washington from Nebraska and several escort fighters (image credit: NASA).
In this true-color satellite image shot above northwestern Europe, the contrast between skies with contrails and those without offers a striking sense of the influence these pseudo clouds might have on regional climate.
This phenomena of global dimming is not the hot new issue or the latest thinking about global climate change, it is simply a cog in the understanding of how our climate is shaped and what we are doing to alter its natural cycles. This is the same way we should consider global warming. Everything we throw into the atmosphere is going to have a different effect with secondary and tertiary cascading effects which we may not understand for another 20 years. There are going to be mechanisms discovered which will shift the way we think about global warming and dimming, and that in turn will shape what we know about climate.
Fire and brimstone fear induction should stop now. This is something that is serious and with enough research our scientists will begin to understand the complex workings of our climate. But it is important to realize that we are affecting the world around us and that everyone, whether you are rich or poor, or republican or democrat, needs to agree that right now the Earth provides for us very well and we have to make an effort to maintain our relationship with that equilibrium or be forced to adapt when our safety net of normality is shifted. The reality is that the public needs to be aware that we may face a global crisis very soon because of our interaction with the planet, for millions of years the Earth has shielded our fragile bodies from the harshest of conditions and let us tread on favorable ground. But now we must show the same respect and care that has been given to us, we are a powerful force with the overreaching ability to manipulate and alter our surroundings. Attention must be paid to how we tread and our minds must be open to new discoveries and a shift in the way we think.
March 18, 2008
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