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GLOBAL WARMING

Earth has warmed at an unprecedented rate over the late hundred years and particularly over the last two decades. Since 1992, each year has been of the warmest years on record. 2016was the hottest year on record, Worldwide.  An upsurge in the amount of extreme weather events, such as wildfires, heat waves, and strong tropical storms, is also attributed. 

“Global warming is an average increase in the atmosphere near the earth’s surface and in the troposphere, which can contribute to change in global climate patterns. Global warming can occur from a variety of cause both natural and human induced. In common usage, “global warming often refers to the warming that can occur as a result of increased emissions  of greenhouse gases from human activities”.

GLOBAL WARMING – IMPACT

Rise in sea level Changes in rainfall patterns Increased likelihood of extreme events such as heat wave, flooding, hurricanes, etc. Melting of the ice caps Melting of glaciers Widespread vanishing of animal population due to habits loss Spread of disease like malaria, etc.Bleaching of coral reefsLoss of plankton due to warming of seas

GREENHOUSE EFFECT

The greenhouse effect is a naturally occurring phenomenon that blankets the earth’s lower atmosphere and warms it, maintaining the temperature suitable for living things to survive. 

Just as greenhouse, that keeps the air warm inside its chamber, water vapour and green house warms the earth. Greenhouse gases play an important role in the balance of earth’s cooling and warming. According to one estimate, in the absence of naturally occurring greenhouse effect, the average temperature of the earth surface would be -19C instead of present value of 15C and the earth would be a frozen lifeless planet.

A greenhouse/glasshouse is a building made of glass chambers in which plants are grown in cold countries or in cold climate areas. There is a continued increase in temperature in greenhouse even when the outside temperature remained low. It protects plants from frost.

What is the Greenhouse Effect ?

The greenhouse effect is a process (similar to greenhouses)caused by greenhouse gases, which occur naturally in the atmosphere. This process plays a crucial role in warming the earth’s surface, making it habitable. However, human-generated greenhouse gas emissions upset the natural balance and lead to increased warmth.

According to one estimate in the absence of naturally occurring greenhouse effect, the average temperature of the earth surface would be -19C instead of present value of 15’C and the earth would be a frozen lifeless planet.

The greenhouse effect is a process(similar to greenhouse)caused by greenhouse gases, which occur naturally in the atmosphere. This process plays a crucial role in warming the earth’s surface, making it habitable. 

However, human-generated greenhouse gas emissions upset the natural balance and lead to increased warmth.

Incoming energy

The sun emits energy that is transmitted to earth. Because the sun is very hot, the energy is emitted in high energy short wavelengths that penetrate the earth’s atmosphere.

Absorption

About 30% of the Earth’s is reflected directly back into space by the atmosphere, clouds, and surface of the earth. The rest of the sun’s energy is absorbed into the earth’s surface

Emission

The earth re-emits energy back into the atmosphere because the earth is cooler than the sun, the energy is emitted in the form of infrared radiation, at wavelengths longer than the incoming solar energy.

Role of greenhouse gases

Greenhouse gases in the atmosphere absorb much of the long-wave energy emitted from the earth’s surface, preventing it from escaping from the earth’s system. The greenhouse gases then re- emit this energy in all directions, warming the earth’s surface and lower atmosphere.

Human role

The atmospheric concentration of greenhouse gases has increased significantly over that past two centuries, largely due to human-generated carbon dioxide emissions from burning fossil fuels, deforestation.

This increase has amplified the natural greenhouse effect by trapping more of the energy emitted by the earth. The change causes earth’s surface temperature to increase.

GREENHOUSE GASES 

Greenhouse gases mean those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorbs and re-emit infrared radiation.

Water vapour

Water vapour is the biggest overall contributor to the greenhouse effect and humans are not directly responsible for emitting this gas in quantities sufficient to change its concentration in the atmosphere . however, CO2 and other in the air by boosting the rate of evaporation.

Unlike CO2 which can persist in the air at any one time (and the amount of warming it causes) is strongly related to the amount of other greenhouse gases in the air.

CARBON DIOXIDE 

• Carbon dioxide is the primary greenhouse gas emitted through human activities. Carbon dioxide is naturally present in the atmosphere as part of the earth’s carbon cycle (the natural circulation of carbon among the atmosphere, oceans, soil, plants, and animals)
• Human activities are altering the carbon cycle both by adding more CO2 to the atmosphere and by reducing the natural sinks, the deforestation, to remove CO2 from the atmosphere.

While CO2  emissions come from a variety of natural sources, human- related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.

The main sources 

1. The combustion of fossil fuels to generate electricity
2. The combustion of fossil fuels such as gasoline and diesel used for transportation.
3. Many industrial processes emit CO2 through fossil fuel combustion.
4. Several processes also produce CO2 emission through chemical reaction that do not involve combustion for example, the production and consumption of mineral products such as cement, the production of metals such iron and steel, and the production of chemical, etc.

Emission and trends 

• Changes in CO2 emission from fossil fuel combustion are influenced by many actors, including population growth, economic growth changing energy prices, new technologies, changing behaviour and seasonal temperatures.
• Between 1990 and 20110 the increase in CO2 emissions corresponded with increased energy use by an expanding economy and population.

Reducing carbon dioxide emissions 

• The most effective way to reduce carbon dioxide emissions is to reduce fossil fuel consumption. Other strategies include energy efficiency, energy conservation, carbon capture and sequestration.

METHANE

• Methane is emitted by natural sources such as wetlands as well as human activities such as leakage from natural gas system and the raising of livestock.
• Natural processes in soil and chemical reactions in the atmosphere help remove CH4 from the atmosphere.

Source 

Natural sources: 

·       Wetlands are the largest source, emitting CH4 from bacteria that decompose organic        materials in the absence of oxygen smaller source include termites, oceans, sediments   volcanoes and wildfires.

Human induced:

• Agriculture: domestic livestock such as cattle buffalo, sheep, goats, and camels produce large amount of CH4 as part of the normal digestive process. Also, when animals manure is stored or managed in lagoons or holding tanks, CH4  is produced because human raise these animals for food the emission are considered human-related. Globally the agriculture sector is the primary source of CH4 emission.
• Industry: methane is the primary component of natural gas. Some amount of CH4 is emitted to the atmosphere during the production processing , storge , transmission and distribution of crude oil and natural gas.
• Waste from homes and business: methane is generated in landfills as waste decomposes and from the treatment of wastewater.

NITROUS OXIDE

• Nitrous oxide is naturally present in the atmosphere as part of the earth’s nitrogen cycle and has a variety of natural sources. 
• However, human activities such as agriculture, fossil fuel combustion, wastewater management and industrial processes are increasing the amount of N2O in the atmosphere. 

Sources 

Natural source:

• Natural emission of n2o is mainly from bacteria breaking down nitrogen in soils and the oceans.

Human induced:

• Agriculture: nitrous oxide is emitted when people add nitrogen to the soil through the use of synthetic fertilizers. Nitrous oxide is also emitted during the breakdown of nitrogen in livestock manure and urine, which contributed to 6% of N2O emission in 2010.
• Transportation: nitrous oxide is emitted when transportation fuels are burned 
• Industry: nitrous oxide is generated as a by product during the production of nitric acid, which is use to make synthetic commercial fertilizer and in the production of atopic acid, which is use to make fibres, like nylon and other synthetic products.
• Removal: nitrous oxide is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.
• They are emitted through a variety of industrial processes such as aluminium and semiconductor manufacturing and substitution for ozone- depleting substance.

FLORINATED COMPOUNDS

• Many fluorinated gases have very high global warming potentials relative to other greenhouse gases. 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.
• There are three main categories of fluorinated gases-

1. Hydro fluorocarbons ( HFCs)
2. Per fluorocarbons (PFCs)
3.  sulphur hexafluoride (SFs)

Substitution for ozone- depleting substance 

• Hydro fluorocarbons are used as refrigerants, aerosol propellants, solvent, and fire retardants. These chemical were developed as a replacement for chlorofluorocarbon and hydro chlorofluorocarbon because they do not deplete the stratospheric ozone layer. 
• Unfortunately, HFCs are potent greenhouse gases with long atmospheric lifetime and high GWPs, and they are released into the atmosphere through leaks, servicing and disposal of equipment in which they are used.

Industry: 

·        Per fluorocarbons are compounds produced as a by-product of various industrial process associated with aluminium production and the manufacturing of semiconductors. 

·       Like HFCs, PFCs generally have long atmospheric lifetimes and high GWPs,

·       Sulphur hexafluoride is used in magnesium processing and semiconductor manufacturing, as well as a tracer gas for leak detection. HFC-23 is produced as a by-product of HFC-22 production.

Transmission and distribution of electricity 

·       Sulphur hexafluoride is used in electrical transmission equipment, including circuit breakers.

BLACK CARBON 

• Black carbon is a solid particle or aerosol, 9 though not a gas 0 contributes to warming of the atmosphere.
• Black carbon, commonly known as soot, is form of particulate air pollutant, produced from incomplete combustion. 

Source 

• Biomass burning,
•  cooking with solid fuels, and
• Diesel exhausted.

What does BC do?

• Black carbon warms the earth by absorbing heat in the atmosphere and by reducing albedo(the ability to reflect sunlight) when deposited on snow and ice.
• BC is the strongest absorber of sunlight and heats the air directly. In addition, it darkens snow packs and glaciers through deposition and leads to melting of ice and snow.
• regionally , BC disrupts cloudiness and monsoon rainfall and accelerates melting of mountain glaciers such as the Hindu kush-himalayan glaciers.

Lifetime

• Black carbon stays in the atmosphere for only several days to weeks.
•  Thus he effects of BC  on the atmospheric warming and glacier retreat disappear within months of reducing emission.

How far India contributes to globe

• According to estimates, between 25 and present of black carbon in the global atmosphere comes from china and India, emitted from the burning of wood and cow dung in household cooking and through the use of coal to heat homes.

Government measures.

• Project soya has been launched to reduce black carbon in atmosphere by introducing efficient stove technologies, solar cookers, solar lamps and biogas plants.

BROWN CARBON

• Brown carbon is a ubiquitous and unidentified component of organic aerosol which has recently come into the forefront of atmospheric research.
• Light- absorbing matter (other than soot) in atmospheric aerosols of various organs, e.g.; Soil humans,- like substance(HULIS) tarry materials from combustion such as soot and dust.

Possible sources of brown carbon are 

• Biomass burning (possibly domestic wood burning) is shown to be a major source of brown carbon.
• Smoke from agricultural  fires may be an additional source.
• Brown carbon is generally referred for greenhouse gases and black carbon for particles resulting from impure combustion, such as soot and dust.