Global Dimmng
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Introduction
It can be strange when reading this; you will believe that the scientists are more and more crazy. First they say that the climate is warming up and now they have the theory that the Earth is cooling off. But the truth that is that Global Dimming is a completely valid theory, since it is solidly supported, with the exception that the international organisms are not taking it very seriously.
The Theory top
The condition that requires the Global Dimming to happen is that something reflects the light of the sun, so that this does not arrive at the Earth. Here is where enter the greenhouse effect, who is more is used to promote the theory of the global warming. But there is emptiness in that theory that was not taken into revision: When existing great amounts of gases located in the atmosphere, this is denser, so the clouds that form there. The clouds at the moment have greater amount of polluting agents than in the past, which causes that these are white and flat, which, ironically, reflects the light that come from the Sun, not allowing its entrance to the Earth. In general the global cooling comes from a very complex process that does not have very certain patterns more than the named previously. It varies according to the geographic place, reason why in the Earth is possible to be cooling in some zones while in another one there is warming. Another factor that influences is that at night, when the Earth releases the accumulated heat during the day, the heat cannot leave the atmosphere, because it is cached generally in the troposphere. However, according to those who postulate the theory, the biggest problem is that the sunlight can't enter to Earth. It is much more dangerous compared with the rays that cannot leave. One of the greater factors than is inducing to the global dimming is the flights of the airplanes, which in their step are leaving polluting agents everywhere.
The studies top
An afternoon at the end on the 60's, a scientific, Ivanovich Budyko, was investigating the ice. He discovered that this very positive for the Earth because it reflected great part of the heat that produced the global warming. He deduced that while greater ice existed, greater would be the amount than it would be created, because the temperatures would lower and would make snow more. Budyko was not the unique one in studying the global dimming; there are some studies that they indicate that the Earth could return at the age of ice if there is a volcanic eruption that emits much CO2. In the 80's, a geographer called Atsumu Ohmura discovered something that almost leaves him in shock: he discovered that the solar amount of energy that arrived at the Earth had diminished in a 10% with respect to the three previous decades.
In September 12th of 2001, a day after the terrorist attacks to the city of New York , there was a prohibition of any civil flight in all United States . That caused that no airplane flew in three days. For the scientist David Travis this was in some form a wonder, because it allowed him to study skies without airplane, that is, without anything of contamination. "While it went in way to my work, I noticed the clear thing that the sky was. Later I thought a little it and I occurred that was unusual", said in an interview for the BBC. The truth is that was unusual, since in those days without aeronautics the temperature got to rise one degree Celsius, to return to lower to the day in which they returned the airplanes. According to the doctor, a degree sounds a very small change, but from the climatic perspective is enormous. However, taking the two previous scientists, there was one before who noticed this fact; an English which he lived in Israel , call Gerry Stanhill. He had to make studies of the amount of sun that arrives at the Earth, to know the amount of water that is have to be provided to the agriculture to water the plants. Twenty years after his first investigation, in the 80's, Gerry decided to return to make its study, and something hit to him. From its measurements that had begun to collect from 1950 to 1960, compared with those of 1980, the solar light had gotten to lower in a impressive 22%. A reduction of 22% in the solar light is something massive. According to the study Israel would have to be under ice, but we all know that it is not (at least at the time of writing this site). This produced that the study happened unnoticed, something that Doctor Gerry in his interview even admits. But he was not the only scientist in realizing this, began to appear other diverse studies. All those focused in the down of percentage of sunlight that enters to the Earth.
The scientists who study the Global Dimming generally say "If million of dollars are spent in studding global warming, and then a few scientist stat saying that now it is happening all the contrary, nobody will take into account to us". That is one of the greater problems when studying the Global Dimming: it is very difficult to convince to the world that now, instead of which the Earth is being warmed up, is cooling off. Including in my personal case, when I told my parents that there is a theory that it indicated that the Earth could be cooling off, they ended up thinking that now there is a "Global Stability", and in fact, according to the studies on the global cooling, this it could be decreasing the effects of the Global Warming.
Another fact that sustains the theory of the global dimming is the evaporation of the water of sea. Australian biologists discovered that the percentage of water evaporation has decayed. This is a paradox, because most of the scientists thought that the Earth, when having greater temperatures, greater amount of water was going away to evaporate. However, the percentage of evaporation has diminished considerably. The explanation that gives scientists is that the temperature is not the main factor for water evaporation, but also is the wind and the sun, being this the most important one in the evaporation process. That means that, at smaller amount of heat than it arrives from the Sun at the Earth, minor will be the percentage of water that evaporates.
The Cause of Everything top
Planes produce this kind of pollution, a possible cause to global dimming.
Conclusion top
We said that this section was not going to have conclusion, but at least the part of the global cooling deserves one. We learned that now the Earth can reflect the solar light and instead of forming a greenhouse effect, passes all the opposite: the heat does not enter the Earth. Although a global heating can be disastrous, much more disastrous could be a global cooling, dice to that everybody is prepared for a heating, not a cooling.
Sources
http://en.wikipedia.org/wiki/Global_dimming
http://en.wikipedia.org/wiki/Climate_Change
http://es.wikipedia.org/wiki/Oscurecimiento_global
http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_trans.shtml : Documental of the BBC about Climate Change