- 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).
Greenhouse effect and Global Warming
- A greenhouse is a structure whose roof and walls are 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’.
Importance of Natural 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 are 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 Gases (GHGs)
- Atmospheric gases like carbon dioxide, methane, nitrous oxide (N2O), water vapour, and chlorofluorocarbons are capable of trapping the out-going infrared radiation from the earth’s surface thereby causing greenhouse effect.
- Hence these gases are known as greenhouse gases and the heating effect is known as greenhouse effect.
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.
- 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. increased incidence of El Nino), thus leading to increased melting of polar ice caps as well as of other places like the Himalayan snow caps.
Cryosphere: The cryosphere is the frozen water part of the Earth water system. Polar regions, snow caps of high mountain ranges are all part of cryosphere.
- 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.
|Gas||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 (N2O)||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).
Nitrous Oxide (N2O)
- N2O or Nitrous Oxide is a greenhouse gas.
- 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 GHGs.
- Carbon monoxide is a short-lived greenhouse gas (it is less dense 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 (explained in Geography > Climatology > Polar Vortex).
- 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 aluminium production and the manufacturing of semiconductors.
- Like HFCs, PFCs generally have long atmospheric lifetimes and high global warming potential.
- Sulphur hexafluoride is also a greenhouse gas.
- Sulphur hexafluoride is used in magnesium processing and semiconductor manufacturing, as well as a tracer gas for leak detection.
- Sulphur hexafluoride is used in electrical transmission equipment, including circuit breakers.
Black Carbon or Soot
- Black carbon (BC) is a solid particle or aerosol (though not a gas) that 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.
Among GHGs, only water vapor has the ability to absorb both incoming (UV) and outgoing (infrared) radiation.
|GHG ProtocolGHG Protocol is developing standards, tools and online training that helps countries, cities and companies track progress towards their climate goals.GHG Protocol establishes frameworks to measure and manage greenhouse gas (GHG) emissions from private and public sector operations, value chains and mitigation actions.GHG Protocol arose when World Resources Institute (WRI) and World Business Council for Sustainable Development (WBCSD) recognized the need for an international standard for corporate GHG accounting and reporting in the late 1990s.Q4. What is ‘Greenhouse Gas Protocol’? (2016)It is an international accounting tool for government and business leaders to understand, quantify and man-age greenhouse gas emissionsIt is an initiative of the United Nations to offer financial incentives to developing countries to reduce green-house gas emissions and to adopt eco-friendly technologiesIt is an inter-governmental agreement ratified by all the member countries of the United Nations to reduce greenhouse gas emissions to specified levels by the year 2022It is one of the multilateral REDD+ initiatives hosted by the World BankAnswer: a)|
Global Warming Potential (GWP) & Lifetime of Green House Gases
|Gas||GWP (100-year)||Lifetime (years)|
|Hydrofluorocarbons (HFCs)||140 -11,700||1-270|
|Sulphur hexafluoride (SF6)||23,900||3,200|
Global Warming – Impacts
Melting of the ice caps
- 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 neighbouring land. Ground water in such regions will become useless.
- Populous cities lying on the coasts will be submerged under the sea.
- 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.
Extreme Climatic Events
- 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. 2015 Chennai floods, 2018 Kerala floods) will severely impact agriculture.
Rising Health Related Issues
- 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.
No Food Security
- 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.
Deterioration of Carbon sinks
- 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.
- In the 1970s the tundra was a carbon sink, but today, it is a carbon source, all because of global warming. (global warming leads to more global warming).
Sea Level Change
- Sea level change means the fluctuations in the mean sea level over a considerably long period of time.
Reducing Carbon in the Atmosphere to fight Climate Change
- Clean coal technology, Carbon capture and storage Carbon Sink and Carbon Sequestration.
Clean coal technology to reduce CO2 in atmosphere
- Half of the world’s electricity is generated by burning coal.
- Coal will remain a dominant energy source for years to come.
- 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 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 sulphur dioxide, nitrogen oxides and particulates.
- Electrostatic precipitators remove particulates 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 sulphur dioxide, a major cause of acid rain, by spraying flue gas with limestone and water.
- Low-NOx (nitrogen oxides) burners reduce the creation of nitrogen oxides, a cause of ground-level ozone, by restricting oxygen and manipulating the combustion process.