It is a fact that the amount of solar radiation reaching the earth’s surface has been reduced gradually and globally, up to 10% due to air pollution, with unforeseeable consequences for the Earth. This phenomenon has been called Global Dimming.
It is a real phenomenon that, despite having been clearly observed and studied for two decades, very little known to the public, governments and even by the scientific community.
The combustion of fossil fuels like coal and oil, not only generates waste carbon dioxide or other gas responsible for the greenhouse effect, but also released into the atmosphere small particles of ash, soot and compounds of sulfur that reflect sunlight back into space, diminishing in their journey to reach the earth’s surface, causing what is known as “mirror effect” and causing a cooling effect.
This air pollution has been reduced by 10% during the past 50 years, solar radiation Earth, directly affecting photosynthesis, behavior, training and composition of clouds and implicitly promoting drought, and most serious of all: its cooling effect has offset global warming, covering it up, which has led us to underestimate and understate the impact of greenhouse effect and the true extent of global warming in general.
The diverse background described below, show how the findings of different scientists in different parts of the world, with completely different methods of measurement and without knowing each other, have reached the same conclusion.
Atsumu Ohmura, a Japan Climatologist, was the first to intuit the global dimming in 1989, based on solar radiation and energy balance of the earth. He formed a group of researchers from the global climate, and the results were partly the basis of a report showing the late ’80s, the existence of a considerable decrease in sunlight reaching the planet’s surface over the level of 1960, as a result, some scientists were given the task of finding the possible causes.
The comments of Gerry Stanhill in 1992, a specialist in irrigation on Israel has been striking: observed the phenomenon on the basis of a significant reduction in the rate of evaporation in the tank, ie the amount of water evaporating from a tank in the sun has progressively declined. Contrary to what might be expected due to global warming, as the evaporation of water depends on the temperatures have increased on the planet or the humidity, but depends on the sunlight it receives, because they are the photons of light, that when it struck the water, providing enough energy so that they become detached from the rest of molecules which are linked by hydrogen bonds. Therefore, the only possible explanation for such measurements, is that every time we receive less solar radiation.
The same trend was observed and supported by farmers and meteorologists from around the world, albeit with variations in each zone, reducing evaporation was clear and progressive.
Other studies would further strengthen these conclusions, by way completely different. Experiments at the archipelago of the Maldives, comparing the climate of the islands located in the north to the south, showed that the polluting effects of the atmosphere at the time, from the north from India, produced approximately a 10% of sunlight reaching the surface in the area under the cloud contaminated (which means a reduction much greater than expected by the mere presence of particle pollutants). Before undertaking such investigations, predictions indicate that the anthropogenic aerosols (particulate matter pollutants) only contributed between 0.5% and 1% to effect. The enormous variation observed against the prediction is because the formation of clouds contaminated particles act as condensation nuclei of a larger number of drops though smaller, creating new clouds, which are more effective at reflecting light back into space.
On the other hand, a group led by Martin Wild at the Federal Institute of Technology Swiss in Zurich, home to the archive BSRN (Baseline Surface Radiation Network), started a research through a survey of measurements and calculations conducted by the Program Measurements Atmospheric Radiation, which was crucial as it reveals that the planet’s surface has increased its brightness by 4% over the last decade. This upward trend of brightness planetary is supported by various data, including several analysis by satellite.
This corroborates that the pollution of suspended particles in the clouds do they reflect much more sunlight than clouds clean back to space, increasing the brightness of the planet.
credit to: Piero Zanatta
photo source: http://isiria.files.wordpress.com/
