Environment Quiz: Climate Change |21 Apr, 2021

Methane (CH4) is emitted by natural sources such as wetlands, as well as human activities such as leakage from natural gas systems and the raising of livestock.

Smaller sources include termites, oceans, sediments, volcanoes, and wildfires.

Source: Shankar

Fluorinated gases are emitted through a variety of industrial processes such as aluminum and semiconductor manufacturing & Substitution for Ozone-Depleting Substances.

· Many fluorinated gases have very high global warming potentials (GWPs) relative to other greenhouse gases. Fluorinated gases are well-mixed in the atmosphere, spreading around the world after they’re emitted.

· Fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere. In general, fluorinated gases are the most potent and longest lasting type of greenhouse gases emitted by human activities.

Source: Shankar

Black carbon (BC) is a solid particle or aerosol, (though not a gas) contributes to warming of the atmosphere.

· Black carbon, commonly known as soot, is a form of particulate air pollutant, produced from incomplete combustion.

· It consists of pure carbon in several linked forms. Black carbon stays in the atmosphere for only several days to weeks.

· Thus, the effects of BC on the atmospheric warming and glacier retreat disappear within months of reducing emissions.

Source: Shankar

Coastal waters are also affected by excess nutrient inputs, mostly nitrogen, from agriculture, fertilizers and sewage.

The resulting eutrophication leads to large plankton blooms, and when these blooms collapse and sink to the sea bed the subsequent respiration of bacteria decomposing the algae leads to a decrease in sea water oxygen and an increase in CO2 (a decline in pH).

Source: Shankar

UPWELLING: Surface Coastal regions periodically experience upwelling events where deeper ocean water circulates onto continental shelves and near-shore areas.

· This exposes the productive upper ocean ecosystems to colder water containing more nutrients & more CO2.

· As ocean acidification makes the upper oversaturated layer of sea water shallower each year, these natural upwelling events will more often cause under-saturated water to well up and flow to the shore.

· Coastal marine organisms that form shells are unaccustomed to such events, and periodic exposures to these significantly different conditions may affect these communities.

Source: Shankar

Deep, cold ocean waters are naturally under saturated with carbonate ions causing the shells of most calcifying organisms to dissolve.

· Surface waters are over saturated with carbonate ions and do not readily dissolve shells of calcifying organisms.

· The saturation horizon is the level below which calcium carbonate minerals undergo dissolution.

· Those organisms that can survive below the saturation horizon do so due to special mechanisms to protect their calcium carbonate from dissolving.

· As ocean acidification causes this horizon to rise vertically in the water column so more and more calcifying organisms will be exposed to under saturated water and thus vulnerable to dissolution of their shells and skeletons.

· The saturation horizon of calcite occurs at a greater ocean depth than that for aragonite, but both horizons have moved closer to the surface presently when compared to the 1800s.

Source: Shankar

Ozone is a natural gas; it is an allotrope of oxygen consisting of three atoms of oxygen bound together in a non-linear fashion. The chemical symbol of ozone is O3.

· It is found in two different layers of the atmosphere. Ozone in the troposphere is “bad” because it dirties the air and helps to form smog, which is not good to breathe.

· Ozone in the stratosphere is “good” because it protects life on Earth by absorbing some of the sun’s harmful Ultra Violet (UV) rays.

· The ozone layer is very important because the configuration of the ozone molecule and its chemical properties are such that ozone efficiently absorbs ultraviolet light, thus acting like a sun-screen.

Source: Shankar

CFCs molecules are made up of chlorine, fluorine and carbon. They are used as refrigerants, propellants in aerosol sprays, foaming agents in plastic manufacturing, fire extinguishing agents, solvents for cleaning electronic and metallic components, for freezing foods etc.

Two-thirds of CFC is used as refrigerants while one-third is used as blowing agents in foam insulation products.

Source: Shankar

The Umheher technique is the most common measure of total ozone abundance is the Dobson unit (named after the pioneering atmospheric physical Gordon Dobson) which is the thickness of the ozone column (compressed at Standard Temperature and Pressure (STP)) in milli-centimeters.

At STP one Dobson unit is equal to 2.69×1020 molecules per square meter.

Source: Shankar