Table of Contents
- Increased human activity, urbanization, industrialization have led to rapid deterioration of the environment. This has severely affected the life supporting system.
The important global environmental issues are:
- biodiversity loss
- depletion of ozone layer
- acid rain
- oil spills
- dumping of hazardous wastes
- Climate change due to greenhouse effect and global warming
- Climate is the long-term average of a region’s weather events. The Earth’s climate is not static. Over the billions of years of earth’s existence, it has changed many times in response to natural causes like sun spot, ice age glaciations, etc.
- “Climate change” means a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods (100 years).
- Climate change is usually measured in major shifts in temperature, rainfall, snow, and wind patterns lasting decades or more.
- Humans are creating climate change by burning large amounts of fossil fuels (coal, oil, natural gas), deforestation (when forests are cut down or burned, they can no longer store carbon, and the carbon is released to the atmosphere).
- A greenhouse is a structure with walls and roof made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions are grown.
- In a greenhouse, the incident solar radiation (the visible and adjacent portions of the infrared and ultraviolet ranges of the spectrum) passes through the glass roof and walls and is absorbed by the floor, earth, and contents, which become warmer and re-emit the energy as longer-wavelength infrared radiation (heat radiation).
- Glass and other materials used for greenhouse walls do not transmit infrared radiation, so the infrared cannot escape via radiative transfer.
- As the structure is not open to the atmosphere, heat also cannot escape via convection, so the temperature inside the greenhouse rises. This is known as the ‘greenhouse effect’.
- The green-house effect is a natural phenomenon and has been occurring for millions of years on the earth.
- Life on the earth has been possible because of this natural greenhouse effect which is due to water vapour and small particles of water present in the atmosphere.
- Together, these produce more than 95 percent of total greenhouse warming.
- Average global temperatures is maintained at about 15°C due to natural greenhouse effect.
- Without this phenomenon, average global temperatures might have been around –17°C and at such low temperature life would not be able to exist.
Greenhouse Effect And Global Warming Due to Greenhouse Gases
- Atmospheric gases like carbondioxide, methane, nitrous oxide (N2O), water vapour, and chlorofluorocarbons are capable of trapping the out-going infrared radiation from the earth’s surface. Thus, the temperature of the global atmosphere is increased.
[Oxides of Nitrogen with general formula NOx – NO, NO2 – Nitrogen oxide, Nitrogen dioxide etc. are global cooling gasses while Nitrous oxide (N2O) is a greenhouse gas]
- As this phenomenon of increase in temperature is observed in green houses, in the botanical gardens these gases are known as greenhouse gases and the heating effect is known as greenhouse effect.
- If greenhouse gases are not checked, by the turn of the century the temperature may rise by 5°C.
- Scientists believe that this rise in temperature will lead to deleterious changes in the environment and resulting in odd climatic changes (e.g. El Nino effect), thus leading to increased melting of polar ice caps as well as of other places like the Himalayan snow caps.
- Over many years, this will result in a rise in sea level that can submerge many coastal areas and lead to loss of coastal areas and ecosystems like swamps and marshes (most important ecosystems from the point of ecological services), etc.
Sources and Causes
|Carbon dioxide (CO2)||Burning of fossil fuels, deforestation|
|Chlorofluorocarbons (CFCs)||Refrigeration, solvents, insulation foams, aero propellants, industrial and commercial uses|
|Methane (CH4)||Growing paddy, excreta of cattle and other livestock, termites, burning of fossil fuel, wood, landfills, wetlands, fertilizer factories.|
|Nitrogen oxides (N20)||Burning of fossil fuels, fertilizers; burning of wood and crop residue.|
|Carbon Monoxide (CO)||Iron ore smelting, burning of fossil fuels, burning e-waste.|
- Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation.
- It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the greenhouse effect.
- Its concentration is greater close to the earth’s surface as it is denser than air.
- Ozone is another important greenhouse gas. But it is in very small proportions at the surface.
- Most of it is confined to the stratosphere where it absorbs the harmful UV radiation.
- At ground level, pollutants like NO2 react with volatile organic compounds in the presence of sunlight to produce ozone (tropospheric ozone).
- Water vapour is also a variable gas in the atmosphere, which decreases with altitude. Water vapour also decreases from the equator towards the poles.
- In the warm and wet tropics, it may account for four per cent of the air by volume, while in the dry and cold areas of desert and polar regions, it may be less than one per cent of the air.
- One unique feature about this greenhouse gas is that it absorbs both incoming (a part of incoming) and outgoing solar radiation.
- Methane is the most important greenhouse gas after carbon dioxide.
- It is produced from decomposition of animal wastes and biological matter.
- The emission of this gas can be restricted by using animal wastes and biological matter to produce gobar gas (methane).
- NOx and N2O are Different. N2O or Nitrous Oxide is a greenhouse gas.
- NOx[NO and NO2 (nitric oxide or nitrogen oxide and nitrogen dioxide)] emissions cause global cooling through the formation of (OH) radicals that destroy methane molecules, countering the effect of greenhouse gases.
- Carbon monoxide is a short-lived greenhouse gas (it is less denser than air).
- It has an indirect radiative forcing effect by elevating concentrations of methane and tropospheric ozone through chemical reactions with other atmospheric constituents (e.g., the hydroxyl radical, OH.) that would otherwise destroy them.
- Through natural processes in the atmosphere, it is eventually oxidized to carbon dioxide.
- CFCs were phased out via the Montreal Protocol due to their part in ozone depletion.
- This anthropogenic compound is also a greenhouse gas, with a much higher potential to enhance the greenhouse effect than CO2.
- Hydrofluorocarbons are used as refrigerants, aerosol propellants, solvents, and fire retardants.
- These chemicals were developed as a replacement for chlorofluorocarbons (CFCs).
- Unfortunately, HFCs are potent greenhouse gases with long atmospheric lifetimes.
- Perfluorocarbons are compounds produced as a by-product in aluminum production and the manufacturing of semiconductors.
- Like HFCs, PFCs generally have long atmospheric lifetimes and high global warming potential.
- Sulfur hexafluoride is also a greenhouse gas.
- Sulfur hexafluoride is used in magnesium processing and semiconductor manufacturing, as well as a tracer gas for leak detection.
- Sulfur hexafluoride is used in electrical transmission equipment, including circuit breakers.
- 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
- Soot is a form of particulate air pollutant, produced from incomplete combustion.
- 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.
- 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.
- Brown carbon is a ubiquitous and unidentified component of organic aerosol.
- Biomass burning (possibly domestic wood burning) is shown to be a major source of brown carbon
- “Brown carbon” is generally referred for greenhouse gases and “black carbon” for particles resulting from impure combustion, such as soot and dust.
The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs
- the water vapour of the air and retains its heat.
- the ultraviolet part of the solar radiation.
- all the solar radiations.
- the infrared part of the solar radiation
Answer: d) the infrared part of the solar radiation (outgoing radiation).
Among GHGs, only water vapor has the ability to absorb both incoming (UV) and outgoing (infrared) radiation.
|Gas||GWP (100-year)||Lifetime (years)|
|Carbon di oxide||1||50-200|
|Hydrofluorocarbons (HFCs)||140 -11,700||1-270|
|Sulfur hexafluoride (SF6)||23,900||3,200|
- Melting of the ice caps and glaciers will lead to rise in sea level. Thermal expansion also contributes to sea level rise.
- Fertile agricultural lands on the coast will be submerged and saline water intrusions will degrade the neighboring land. Ground water in such regions will become useless.
- Populous cities lying on the coasts will be submerged under the sea.
- The Himalayan glaciers are a source of fresh water for perennial rivers, in particular the Indus, Ganga, and Brahmaputra river systems.
- There is evidence that some Himalayan glaciers have retreated significantly since the 19th century.
- Flooding in Himalayas and Ganga plains in wet season and drought in dry season will severely affect the country.
- As a result of thawing of snow, the amount of arable land in high-latitude region is likely to increase by reduction of the amount of frozen lands.
- At the same time arable land along the coast lines are bound to be reduced as a result of rising sea level and saline water inundations.
- Increased likelihood of extreme events such as heat wave, flooding, hurricanes, etc. will offset all the economic advancements made.
- Changes in rainfall patterns (E.g. Chennai floods) will severely impact agriculture.
- Reduced hydroelectric power generation due to abnormal behavior of glaciers will further increase dependence on fossil fuels.
- Widespread vanishing of animal populations due to habitat loss will add more species to the ‘threatened’ and ‘extinct’ list.
- Spread of diseases (like malaria, etc.) in tropics will put more pressure on the health care sector.
- It is anticipated that there will be an increase in the number of deaths due to greater frequency and severity of heat waves and other extreme weather events.
- Lack of freshwater during droughts and contamination of freshwater supplies during floods compromise hygiene, thus increasing rates diseases like cholera, diarrhoea etc..
- Loss of Plankton due to warming of seas will adversely affects marine food chain.
- Bleaching of Coral Reefs [Rain forests of the ocean] will cause great loss of marine biodiversity.
- Rising temperature would increase fertilizer requirement for the same production targets and result in higher GHG emissions, ammonia volatilization and cost of crop production.
- Rising temperatures will further affect the physical, chemical and biological properties of fresh water lakes and rivers, with adverse impacts on many individual fresh water species.
- Climate Change affects crops by impacting irrigation, insolation as well as the prevalence of pests.
- Increased frequencies of droughts, floods, storms and cyclones are likely to increase agricultural production variability.
- Moderate warming (increase of 1 to 3°C in mean temperature) is expected to benefit crop yields in temperate regions, while in lower latitudes the crops will take a hit. However, the natural calamities due to global warming can offset the benefits in temperature regions.
- In coastal areas, sea level rise will exacerbate water resource constraints due to increased salinization of groundwater supplies.
- High latitude forests store more carbon than tropical rainforests.
- One third of the world’s soil-bound carbon is in taiga and tundra areas.
- When the permafrost melts due to global warming, it releases carbon in the form of carbon dioxide and methane (Both are GHGs).
- In the 1970s the tundra was a carbon sink, but today, it is a carbon source, thanks to global warming. [global warming leads to more global warming]
- Half of the world’s electricity is generated by burning coal.
- Coal will remain a dominant energy source for years to come.
- Since CO2 contributes to global warming, reducing its release into the atmosphere has become a major international concern.
- CO2 and CO (carbon monoxide) are the major greenhouse gas which are released during burning of coal.
- Along with the above gases, nitrogen oxides (destroys ozone) and sulphur oxides (acid rains) are also released.
Clean coal technology
- Clean coal technology seeks to reduce harsh environmental effects by using multiple technologies to clean coal and contain its emissions.
- Some clean coal technologies purify the coal before it burns.
- One type of coal preparation, coal washing, removes unwanted minerals by mixing crushed coal with a liquid and allowing the impurities to separate and settle.
- Other systems control the coal burn to minimize emissions of sulfur dioxide, nitrogen oxides and particulates.
- Electrostatic precipitators remove particulates that aggravate asthma and cause respiratory ailments by charging particles with an electrical field and then capturing them on collection plates.
- Gasification avoids burning coal altogether. With gasification, steam and hot pressurized air or oxygen combine with coal in a reaction that forces carbon molecules apart. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then cleaned and burned in a gas turbine to make electricity.
- Wet scrubbers, or flue gas desulfurization systems, remove sulfur dioxide, a major cause of acid rain, by spraying flue gas with limestone and water.
- Low-NOx (nitrogen oxide) burners reduce the creation of nitrogen oxides, a cause of ground-level ozone, by restricting oxygen and manipulating the combustion process.
- Coal mined in India is a poor quality coal with less carbon, high ash (hard to dispose) and high moisture content (more gases; less fuel efficiency) [India’s coal is not Carboniferous Coal].
- To improve efficiency and reduce adverse effects, India should do away with its present sub-critical coal power plants and build more super-critical and ultra-super-critical ones (15-20% increase in efficiency).
- Should employ clean coal technology.
- Carbon capture and storage catches and sequesters (hide) carbon dioxide (CO2) from stationary sources like power plants.
- Capture: Flue-gas separation removes CO2 and condenses it into a concentrated CO2 stream.
- After capture, secure containers sequester the collected CO2 to prevent or stall its reentry into the atmosphere.
- The two storage options are geologic and oceanic (must hide the CO2 until peak emissions subside hundreds of years from now).
- Geologic storage involves injecting CO2 into the earth.
- Depleted oil or gas fields and deep saline aquifers safely store CO2 while coal seams absorb it.
- Ocean storage, a technology still in its early stages, involves injecting liquid CO2 into waters 500 to 3,000 meters deep, where it dissolves under pressure. However, this method would slightly decrease pH and potentially harm marine habitats.
- A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period.
- The process by which carbon sinks remove carbon dioxide (CO2) from the atmosphere is known as carbon sequestration.
- A carbon sink is anything that absorbs more carbon that it releases, whilst a carbon source is anything that releases more carbon than is absorb.
- Forests, soils, oceans and the atmosphere all store carbon and this carbon moves between them in a continuous cycle.
- This constant movement of carbon means that forests act as sources or sinks at different times.
- Carbon sequestration is the process of capture and long-term storage of atmospheric carbon dioxide (CO2)
- It has been proposed as a way to slow the atmospheric and marine accumulation of greenhouse gases
- Carbon dioxide is naturally captured from the atmosphere through biological, chemical, or physical processes.
- Forests are carbon stores, and they are carbon dioxide sinks when they are increasing in density or area.
- In Canada’s boreal forests as much as 80% of the total carbon is stored in the soils as dead organic matter.
- Tropical forests absorb about 18% of all carbon dioxide added by fossil fuels.
- In the context of climate change, the most important carbon stores are fossil fuel deposits as they have the unique benefit of being buried deep inside the earth, naturally separated from the carbon cycling in the atmosphere.
- This separation ends when humans burn coal, oil and natural gas, turning fossil carbon stores into atmospheric carbon.
- This release of carbon from fossil fuel has caused greenhouse gas (GHG) concentrations in the atmosphere to soar to levels more than 30 per cent higher than at the beginning of the industrial revolution.
- Because of this increase in atmospheric carbon, a lot of emphasis and hope has been put into the ability of trees, other plants and the soil to temporarily sink the carbon that fossil fuel burning releases into the atmosphere.
- Indeed, the Kyoto Protocol, the international communities’ main instrument for halting global warming suggests that the absorption of carbon dioxide by trees and the soil is just as valid a means to achieve emission reduction commitments as cutting carbon dioxide emissions from fossil fuels.
The scientific view is that the increase in global temperature should not exceed 2 °C above pre-industrial level. If the global temperature increases beyond 3°C above the pre-industrial level, what can be its possible impact/impacts on the world?
- Terrestrial biosphere tends toward a net carbon source
- Widespread coral mortality will occur.
- All the global wetlands will permanently disappear.
- Cultivation of cereals will not be possible anywhere in the world.
Select the correct answer using the code given below.
- 1 only
- 1 and 2 only
- 2, 3 and 4 only
- 1, 2, 3 and 4
Taiga and temperate forests act as an important carbon sink. Global warming by 3°C will turn these forests into carbon source.
Corals are very sensitive to temperature changes. 3°C rise in global temperature will lead to widespread coral mortality.
3°C rise in global temperature will lead to submergence of many low lying coastal wetlands (not all) due to rise in sea levels. Inland wetlands like Keoladeo Ghana National Park will not be effected (it is 100s of kilometers away from coast).
Because of the slow inertia, long response time for parts of the climate system, it has been estimated that we are already committed to a sea-level rise of approximately 2.3 metres (7.5 ft) for each degree Celsius of temperature rise within the next 2,000 years.
Cultivation of cereals in tropics will take a hit. But in temperate regions their production increases in the short run.