Climate Change- 1 | Environment for UPSC CSE PDF Download

What is it?

• Climate Change is the defining issue of our time and we are at a defining moment. From shifting weather patterns that threaten food production, to rising sea levels that increase the risk of catastrophic flooding, the impacts of climate change are global in scope and unprecedented in scale. Without drastic action today, adapting to these impacts in the future will be more difficult and costly.
• “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.
• However, when today people talk about ‘climate change’, they mean the climate changes over the last 100 years which is caused predominantly by human activity. 
• The change in Jammu’s winters' pattern from the normal winter pattern represents an epitome of climate change.
• Climate change is the measurable effects of the continual warming trend. Climate change is usually measured in major shifts in temperature, rainfall, snow, and wind patterns lasting decades or more.
• Humans create 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).

Global Warming

• Earth has warmed at an unprecedented rate over the last hundred years, particularly over the last two decades. Since 1992, each year has been one of the warmest years on record. 2016 was 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 temperature of the atmosphere near the Earth’s surface and in the troposphere, which can contribute to changes in global climate patterns. Global warming can occur from a variety of causes, both natural and human induced. In common usage, “global warming” often refers to the warming that can occur due to increased emissions of greenhouse gases from human activities.”

Global Warming - Impacts

• Rise in Sea level 
• Changes in rainfall pat terns.
• Increased likelihood of extreme events such a s heat wave, flooding, hurricanes, etc.
• Melting of the ice caps. 
• Melting of glaciers.
• Widespread vanishing of animal populations due to habitat loss.
• Spread of disease (like malaria, etc).
• Bleaching of Coral Reefs.
•  Loss of Plankton due to warming of seas.

Greenhouse effect

• The greenhouse effect is a naturally occurring phenomenon that blankets the earth lower atmosphere and warms it, maintaining the temperature suitable for living things to survive.
• Just as greenhouses, that keeps the air warm inside its chamber, water vapor and green house gases 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 green house effect, the earth surface's average temperature would be -19°C instead of present value of 15°C and the earth would be a frozen lifeless planet.

Green House

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 green house even when the outside temperature remained low. It protects plants from frost.

What is the Greenhouse Effect?

The greenhouse effect (similar to green house) is 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 transmit ted 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 Sun’s energy is reflected directly back into space by the atmosphere, clouds, and Earth's surface. The rest of the Sun’s energy is absorbed into the Earth’s system.
• 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
• In the atmosphere, greenhouse gases absorb much of the long-wave energy (infrared radiation) 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
  (i) The atmospheric concentration of greenhouse gases has increased significantly over the past two centuries, largely due to human-generated carbon dioxide emissions from burning fossil fuels, deforestation.
  (ii) This increase has amplified the natural greenhouse effect by trapping more of the Earth's energy emitted. This change causes Earth’s surface temperature to increase.

Green House Gases

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

(a) Water vapour

• Water vapour is the biggest contributor to the greenhouse effect. Humans are not directly responsible for emitting this gas in quantities sufficient to change its concentration in the atmosphere. However, CO₂ and other greenhouse gases increase the amount of water vapour in the air by boosting the rate of evaporation.
• Unlike CO₂, which can persist in the air for centuries, water vapour cycles through the atmosphere quickly, evaporating from the oceans and elsewhere before coming back down as rain or snow.
• Since the evaporation rate rises with temperature, the amount of water vapour 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.

(b) Carbon Dioxide

• Carbon dioxide (CO₂) 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 alter the carbon cycle by adding more CO₂ to the atmosphere and reducing the natural sinks, like deforestation, to remove CO₂ from the atmosphere.
• While CO₂ emissions come from various natural sources, human-related emissions are responsible for the increase in the atmosphere since the industrial revolution.

➤ The main sources

• The combustion of fossil fuels to generate electricity. 
• The combustion of fossil fuels such as gasoline and diesel used for transportation.
• Many industrial processes emit CO₂ through fossil fuel combustion.
• Several processes also produce CO₂ emissions through chemical reactions that do not involve combustion, such as the production and consumption of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals.

➤ Emissions and Trends

• Changes in CO₂ emissions from fossil fuel combustion are influenced by many factors, including population growth, economic growth, changing energy prices, new technologies, changing behavior, and seasonal temperatures.
• Between 1990 and 2010, 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 (CO₂) emissions is to reduce fossil fuel consumption. Other strategies include Energy Efficiency, Energy Conservation, Carbon Capture and Sequestration.

(c) Methane

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

Source

(i) Natural sources

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

(ii) Human induced

• Agriculture: Domestic livestock such as cattle, buffalo, sheep, goats, and camels produce large amounts of CH₄ as part of their normal digestive process. Also, when animals’ manure is stored or managed in lagoons or holding tanks, CH₄ is produced. Because humans raise these animals for food, the emissions are considered human-related. Globally, the Agriculture sector is the primary source of CH₄ emissions.
• Industry: Methane is the primary component of natural gas. Some amount of CH₄ is emitted to the atmosphere during the production, processing, storage, transmission, and distribution of crude oil & natural gas.
• Waste from Homes and Businesses: Methane is generated in landfills as waste decomposes and from wastewater treatment.

(d) Nitrous Oxide

• Nitrous oxide (N₂O) is naturally present in the atmosphere as part of the Earth’s nitrogen cycle, and has various natural sources.
• However, human activities such as agriculture, fossil fuel combustion, wastewater management, and industrial processes increase the amount of N₂O in the atmosphere.

Sources

(i) Natural sources

• Natural emissions of N₂O are mainly from bacteria breaking down nitrogen in soils and the oceans.

(ii) Human induced

• Agriculture. Nitrous oxide is emit ted 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 emissions in 2010.
• Transportation. Nitrous oxide is emit ted when transportation fuels are burned.
• Industry. Nitrous oxide is generated as a byproduct during the production of nitric acid, which is used to make synthetic commercial fertilizer and adipic acid, which is used to make fibers, 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.

(e) Fluorinated Gases

• They 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.
• There are three main categories of fluorinated gases
  (i) hydrofluorocarbons (HFCs),
  (ii) perfluorocarbons (PFCs), and
  (iii) sulfur hexafluoride (SF6). 

➤ Substitution for Ozone-Depleting Substances

• Hydrofluorocarbons are used as refrigerants, aerosol propellants, solvents, and fire retardants. These chemicals were developed as a replacement for chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) because they do not deplete the stratospheric ozone layer.
• Unfortunately, HFCs are potent greenhouse gases with long atmospheric lifetimes and high GWPs, and they are released into the atmosphere through leaks, servicing, and disposal of equipment in which they are used.

➤ Industry

• Perfluorocarbons are compounds produced as a byproduct of various industrial processes associated with aluminum production and semiconductors' manufacturing.
• Like HFCs, PFCs generally have long atmospheric lifetimes and high GWPs.
• Sulfur 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 HCFC-22 production.

➤ Transmission and Distribution of Electricity

• Sulfur hexafluoride is used in electrical transmission equipment, including circuit breakers.

(f) Black Carbon

• 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.

Source

• biomass burning,
• cooking with solid fuels, and
• diesel exhaust, etc.

➤ 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. Besides, 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 mountain glaciers melting such as the Hindu Kush-Himalayan glaciers.

➤ Life time

• 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.

➤ How far India contributes to globe?

• According to estimates, bet ween 25 and 35 percent 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 coal to heat homes.

➤ Government Measures

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

(g) Brown Carbon

• Brown carbon is a ubiquitous and unidentified component of organic aerosol which has recently become the forefront of atmospheric research.
• Light-absorbing organic matter (other than soot) in atmospheric aerosols of various origins, e.g., soil humics, humic-like substances (HULIS), tarry materials from combustion, bioaerosols, etc.

➤ 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.