User:Popsie~enwiki

Did you know that there is another disastrous event aside from global warming? It is called global dimming.Global dimming is the gradual reduction in the amount of global hemispherical irradiance (or total solar irradiance) at the Earth's surface, observed since the beginning of systematic measurements in 1950s. The effect varies by location, but worldwide it is of the order of a 5% reduction over the three decades from 1960–1990. This trend has reversed during the past decade. Global dimming creates a cooling effect that may have partially masked the effect of greenhouse gases on global warming.

It is currently thought that the effect of global dimming is probably due to the increased presence of aerosol particles in the atmosphere. Aerosol particles and other particulate pollutants absorb solar energy and reflect sunlight back into space. The pollutants can also become nuclei for cloud droplets. It is thought that the water droplets in clouds coalesce around the particles. Increased pollution, resulting in more particulates, creates clouds consisting of a greater number of smaller droplets, which in turn makes them more reflective, therefore bouncing more sunlight back into space.

Clouds intercept both heat from the sun and heat radiated from the Earth. Their effects are complex and vary in time, location and altitude. Usually during the daytime the interception of sunlight predominates, giving a cooling effect; however, at night the re-radiation of heat to the Earth slows the Earth's heat loss.

Early reports of "global dimming" attracted little interest, perhaps because the term itself had not yet been coined. The earliest reports seem to be by M. Budyko: "The effect of solar radiation variations on the climate of the Earth" in 1969, published in Tellus. From the late 1980s onwards, scientists independently began working on solar radiation datasets and discovered declining trends worldwide; Atsumo Ohmura Secular variation of global radiation in Europe in 1989; Vivii Russak in 1990 "Trends of solar radiation, cloudiness and atmospheric transparency during recent decades in Estonia", and Beate Liepert in 1994 "Solar radiation in Germany - Observed trends and an assessment of their causes". Gerry Stanhill who studied these declines worldwide in many papers coined the term "dimming". Dimming exists in sites all over the Former Soviet Union.

Independent research in Israel and the Netherlands in the late 1980s showed an apparent reduction in the amount of sunlight, despite widespread evidence that the climate was actually becoming hotter. The rate of dimming varies around the world but is on average estimated at around 2–3% per decade, with the possibility that the trend reversed in the early 1990s. It is difficult to make a precise measurement, due to the difficulty in accurately calibrating the instruments used, and the problem of spatial coverage. Nonetheless, the effect is almost certainly present.

The effect is due to changes within the Earth's atmosphere; the value of the solar radiation at the top of the atmosphere has not changed by more than a fraction of this amount.