Global Dimming | Causes and Impact

Global Dimming
Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface. It is thought that global dimming is probably due to the increased presence of aerosol particles in the atmosphere caused by human action. Aerosols and other particulates absorb solar energy and reflect sunlight back into space. Increased pollution causes more particulates and thereby creates clouds consisting of a greater number of smaller droplets (that is, the same amount of water is spread over more droplets). The smaller droplets make clouds more reflective, so that more incoming sunlight is reflected back into space and less reaches the Earth's surface. Al first global dimming sounds like an ironic saviour for climatic changes including global warming.However, now its believed that global dimming has caused severe drought in several parts of the world as the northern hemisphere oceans were not warmed enough to form rainfall.
The concept of geoengineering (or climate engineering, climate remediation, and climate intervention) refers to the deliberate large-scale engineering and manipulation of the planetary environment to combat or counteract anthropogenic changes in atmospheric chemistry. Some geoengineering techniques are based on carbon dioxide removal (CDR). These techniques seek to reduce greenhouse gases in the atmosphere directly. These include direct methods (e.g. carbon dioxide air capture) and indirect methods (e.g. ocean iron fertilization). These techniques can be regarded as mitigation of global warming. The Intergovernmental Panel on Climate Change concluded in 2007 that geoengineering options, such as ocean fertilization to remove CO2 from the atmosphere, remained largely unproven.

Ocean Iron Fertilization or Ocean Nourishment
Ocean Nourishment is a type of geoengineering based on the purposeful introduction of nutrients (Iron, Nitrogen etc)to the upper ocean to increase marine food production and to reduce carbon dioxide from the atmosphere. Fertilization can also potentially create sulfur aerosols which reduce the rate of global warming. The marine food chain is based on photosynthesis by marine phytoplankton which combine carbon with inorganic nutrients to produce organic matter. The production of organic matter is limited in general by the availability of nutrients, most commonly nitrogen or iron. Ocean Nourishment offers the prospect of both reducing the concentration of atmospheric greenhouse gases with the aim of avoiding dangerous climate change and at the same time increasing the sustainable fish stocks. It promises to do this by increasing the ocean primary production.

Albedo or reflection coefficient is the reflecting power of a surface. The average overall albedo of Earth, its planetary albedo, is 30 to 35%, because of the covering by clouds, but varies widely locally across the surface, depending on the geological and environmental features.

Asian Brown Cloud
The Asian brown cloud is a layer of air pollution that covers parts of South Asia, namely the northern Indian Ocean, India, and Pakistan. Viewed from satellite photos, the cloud appears as a giant brown stain hanging in the air over much of South Asia and the Indian Ocean every year between January and March, possibly also during earlier and later months. The Asian brown cloud is created by a range of airborne particles and pollutants from combustion (e.g.woodfires, cars, and factories), biomass burning and industrial processes with incomplete burning. A 2002 study indicated nearly two million people die each year, in India alone, from conditions related to the brown cloud.