Global Dimming

Global warming is a concept that I am aware of since my college days; however, I was unaware about Global Dimming, till I got an opportunity of coming across this concept in an article. The article has described the concept vividly and the person who has coined the name.

Environmental scientists, through their research and studies have inferred that the sun is dimming. The earth’s surface is experiencing less sunlight nowadays compared to recent past. From late 1950s to the early 1990s, at least a 10 percent drop in sun light reaching the earth surface was recorded. In some regions like Asia, the United States, and Europe, the drop was found to be more severe.

This stunning phenomenon was first noticed by Atsumu Ohmura, a researcher of Swiss Federal Institute of Technology in 1989, which was later confirmed by Gerald Stanhill who was involved in Israel's Agricultural Research Organization in 1992. The Global dimming was also coined by him.

Ohmura noticed the phenomenon while he was doing his research on global warming. He was checking, as a part of his studies, climate and atmospheric radiation, levels of sunlight recorded around Europe, in this process he discovered the phenomenon. Gerry Stanhill, on the other hand, was designing irrigation schemes in Israel. His task was to measure how strongly the sun shines over Israel. Stanhill collected his first set of data sometimes in 1960s. In the 1980s, he decided to repeat his measurement, when he discovered the dimming phenomenon of the sun.

Like global warming, global dimming is also the outcome of fossil fuel burning. When fossil fuel burns, it emits greenhouse gases in the air and releases particulate matters, such as soot and ash in the atmosphere. These particulate matters, by changing the properties of clouds, create global dimming. Clouds are formed when water droplets are seeded by air-borne particles. Now as a result of fossil-fuel burning, more and more particles are gathering in the atmosphere. Hence, large number of water droplets is also forming. These water droplets clusters together to form larger size droplets. The formation of water droplets in the atmosphere results in reflection of sunlight back into the space, this act of reflection increases with the increase in size of the water droplets.

Recently, another important cause has been discovered responsible for global dimming. This was the vapor (contrails) released from high-flying planes, also reflect sunlight significantly.

The immediate effect of global dimming is the change of temperature on the earth surface. The particulate matters in the air works in two ways, firstly, it reflects sunlight back to the space, and secondly, the heat radiation of the earth back to the planet itself. Therefore, during the day, global dimming gives us a cooling effect and at night it slows down the heat process of the earth’s surface.

Global dimming has also resulted in increasing the rate of photosynthesis in plants and trees. The sun rays are getting scattered because of global dimming. Through scientific research, it has been found out that in some cases photosynthesis increases with increasing in diffused or broken sunlight lights.

Another effect of global dimming is low rainfall. Less sunlight into the earth’s surface results in decreasing the rate of evaporation from the hydrosphere. The outcome of this is low rainfall and drought.