Climate Change and Global warming [UPSC]
Climate Change

Climate Change and Global warming [UPSC]

Climate Change and Global warming

Climate change

Climate change – a change in global or regional climate patterns, in particular a change
apparent from the mid to late 20
th century onwards and attributed largely to the
increased levels of atmospheric carbon dioxide produced by the use of fossil fuels.

Global warming (GW)

The formation of ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole?
(a) Presence of prominent tropospheric turbulence; and inflow of
(b) Presence of prominent polar front and stratospheric clouds; and inflow of
(c) Absence of polar front and stratospheric clouds; and inflow of methane and
(d) Increased temperature at polar region due to global warming
Prelims 2011

Which of the following can be threats to the biodiversity of a geographical area?
1. Global warming
2. Fragmentation of habitat
3. Invasion of alien species
4. Promotion of vegetarianism
Select the correct answer using the codes given below:
(a) 1, 2 and 3 only
(b) 2 and 3 only
(c) 1 and 4 only
(d) 1, 2, 3 and 4
Prelims 2012

Global Warming is the increase of Earth’s average surface temperature due to effect of
greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from
deforestation, which trap heat that would otherwise escape from Earth.


Increased extinction of many plant and animal species.
Shifts in patterns of agriculture
Rising sea levels.
Increase in concentrations of carbon dioxide, methane, and nitrous oxides in the
Increase in extreme events like floods, heat wave etc.
Melting of glaciers

Spread of disease
Bleaching of coral reefs.

Difference between climate change and global warming

In simple words GW is just increase in temperature while Climate change means
change in climate i.e. temperature + precipitation + winds etc.
Global warming is related to the more general phenomenon of climate change, which
refers to changes in the totality of attributes that define climate.
In addition to changes in air temperature, climate change involves changes to
precipitation patterns, winds, ocean currents, and other measures of Earth’s climate.
Normally, climate change can be viewed as the combination of various natural forces
occurring over diverse timescales
The term global warming is used specifically to refer to any warming of near-surface air
during the past two centuries that can be traced to anthropogenic causes.
Climate change had led to the global warming (think) because first climate had changed
and then it led to GW.

Causes of global warming

  • Greenhouse effect – The trapping of the sun’s warmth in a planet’s lower atmosphere,due to the greater transparency of the atmosphere to visible radiation from the sunthan to infrared radiation emitted from the planet’s surface.
  • Solar radiation is often called “shortwave” radiation because the frequencies of theradiation are relatively high and the wavelengths relatively short—close to the visibleportion of the electromagnetic spectrum.
  • Terrestrial radiation, on the other hand, is often called “longwave” radiation becausethe frequencies are relatively low and the wavelengths relatively long—somewhere inthe infrared part of the spectrum.
Solar radiation
  • Just as greenhouses, that keeps the air warm inside its chamber, water vapor and
    greenhouse gases warms the Earth.
    Greenhouse gases play an important role in the
    balance of Earth’s cooling and warming.
  • In the absence of naturally occurring greenhouse effect, the average temperature of the earth surface would be -190°C instead of present value of 150°C and the earth would be a frozen lifeless planet.
  • Human-generated greenhouse gas emissions had upset the natural balance and lead to increased warmth.

Radiative forcing

Radiative forcing or climate forcing is defined as the difference of insolation (sunlight)
absorbed by the Earth and energy radiated back to space. Typically, radiative forcing is
quantified at the tropopause in units of watts per square meter of the Earth’s surface.
A positive forcing (more incoming energy) warms the system, while negative forcing
(more outgoing energy) cools it.
Causes of radiative forcing include changes in insolation and the concentrations of
radioactively active gases, commonly known as greenhouse gases and aerosols.
Atmospheric aerosols include volcanic dust, soot, particles from burning forests and
mineral dust.

The influences of human activity on climate

Human activity has influenced global surface temperatures by changing the radiative
balance governing the Earth on various timescales and at varying spatial scales.
The most profound and well-known anthropogenic influence is the elevation of
concentrations of greenhouse gases
in the atmosphere.
Humans also influence climate by changing the concentrations of aerosols and ozone
and by modifying the land cover of Earth’s surface.

Greenhouse gases

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

1. Water vapor

Most potent of the greenhouse gases in Earth’s atmosphere, but its behaviour is
fundamentally different from that of the other greenhouse gases.
Primary role of water vapour is – not as a direct agent of radiative forcing but rather as
climate feedback—that is, as a response within the climate system that influences the
system’s continued activity.
This distinction arises from the fact that the amount of water vapour in the atmosphere
cannot, in general, be directly modified by human behaviour but is instead set by air
The warmer the surface, the greater the evaporation rate of water from the surface. As
a result, increased evaporation leads to a greater concentration of water vapour in the
lower atmosphere capable of absorbing longwave radiation and emitting it downward.

2. Carbon dioxide

Primary greenhouse gas emitted through human activities.
It is naturally present in the atmosphere as part of the Earth’s carbon cycle.
Human activities are changing the carbon cycle both by adding more CO2 to the
atmosphere and by reducing the ability of natural sinks, like forests, to remove CO2
from the atmosphere.

The main sources
Combustion of fossil fuels
Emission of CO2 by Thermal power plants and industries.
Several processes also produce C02 emissions through chemical reactions that do not
involve combustion. E.g. the production and consumption of mineral products such as
cement, the production of metals such as iron and steel, and the production of
chemicals, etc.

How to reduce CO2 emissions?
Most effective way – reduce fossil fuel consumption.
Other strategies include Energy Efficiency, Energy Conservation; Carbon Capture and

3. Methane

Emitted by natural sources such as wetlands, as well as 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 –
Natural sources –
Wetlands largest source
Smaller sources – termites, oceans, sediments, volcanoes, and wildfires.
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 in tanks.
Industry – primary component of natural gas. Some amount is emitted during the
production, processing, storage, transmission, and distribution of crude oil and natural
Generated in landfills as waste decomposes and from the treatment of wastewater.

4. Nitrous Oxide

Natural sources
Emissions from breaking down of nitrogen in soils and oceans.
Human induced

Agriculture – emission during use of synthetic fertilizers. It is also emitted during the
breakdown of nitrogen in
livestock manure and urine.
Transportation – it is emitted when transportation fuels are burned.
Industry – It is generated as a byproduct during the production of nitric acid (used to
make synthetic commercial fertilizer), and in the
production of adipic acid (used to
make fibers like nylon, and other synthetic products)
Removal – It is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.

5. Fluorinated gases

Emitted through a variety of industrial processes such as aluminum and semiconductor
manufacturing & Substitution for Ozone-Depleting Substances.
High global warming potentials (GWPs) + longest lasting type of greenhouse gases
emitted by human activities.
Removal – only when they are destroyed by sunlight in the far upper atmosphere.
3 main categories –

  • o HFCs (Hydroflurocarbons)
    o PFCs (Perflurocarbons)
    o SF6 (Sulfur haxafluoride)

Substitution for Ozone-Depleting Substances
They are used as refrigerants, aerosol propellants, solvents, and fire retardants.
HFCs do not deplete the stratospheric ozone layer and so they were developed as a
replacement for chlorofluorocarbons (CFCs) and hydro chlorofluorocarbons (HCFCs)


Compounds produced as a by-product of various industrial processes associated with
aluminum production and the manufacturing of semiconductors.
Long atmospheric lifetimes
High GWPs


It 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.

6. Black Carbon

It is a solid particle or aerosol, contributes to warming of the atmosphere.
Commonly known as soot.
It is a form of particulate air pollutant, produced from incomplete combustion.
It consists of pure carbon in several linked forms.
Biomass burning,
Cooking with solid fuels, and
Diesel exhaust etc.

What does BC do?

Warms the Earth by absorbing heat in the atmosphere and by reducing albedo, (the
ability to reflect sunlight) when deposited on snow and ice.
Strongest absorber of sunlight and heats the air directly.
Leads to melting of ice and snow.
BC disrupts cloudiness and monsoon rainfall and accelerates melting of mountain
Life time
Stays in the atmosphere for only several days to weeks.
Effects of BC on the atmospheric warming and glacier retreat disappear within months
of reducing emissions.

Government measures

Project surya – reduce black carbon by introducing efficient stove technologies, solar cookers, solar lamps and biogas plants.

Global warming Potential (GWP)

Global warming potential describes the impact of each gas on global warming.
Two most important characteristics of a GHG –

  • o How well the gas absorbs energy
    o How long the gas stays in the atmosphere?

The Global Warming Potential (GWP) for a gas is a measure of the total energy that a
gas absorbs over a particular period of time (usually 100 years), compared to carbon
Higher GWP gases absorb more energy → Contribute more to warming earth.
Carbon dioxide (C02) has a GWP of 1 and serves as a baseline for other GWP values.
The larger the GWP, the more warming the gas causes.

  • o E.g. methane’s 100-year GWP is 21, which means that methane will cause 21
    times as much warming as an equivalent mass of CO2 over a 100-year time

Global emissions

Global emissions by source

Global emissions by source

Energy supply

  • 26% of GHG emissions
  • Source –burning of coal, natural gas, and oil


  • 19% of GHG emissions
  • fossil fuels burned on-site for energy
  • Emissions from chemical, metallurgical, and mineral transformation processes
    not associated with energy consumption.

Land Use, Land-Use Change, and Forestry

  • 17% of GHG emissions
  • deforestation, land clearing for agriculture, and fires or decay of peat soils.


  • 14% of GHG emissions
  • Management of agricultural soils, livestock, rice production, and biomass


  • 13% of GHG emissions
  • fossil fuels burned for road, rail, air, and marine transportation

Commercial and Residential Buildings

  • 8% of GHG emissions
  • Burning of coals and wood for energy requirements.

Waste and Wastewater

  • 3% of GHG emissions
  • Landfill methane, waste water methane, nitrous oxide.

Global emissions by Gas

Global emissions by Gas

Receding glaciers – a symptom of global climate change

Impact of glacial retreat

  • Rise in sea level – challenge for poor and low-lying countries.
  • Will affect water supplies
  • Variation in temperature and snowfall because water cycle balance changed
  • Loss of glaciers would impact to those countries’ human beings, animals and vegetation which are dependent on it.

Chain of events

•Computation of fossile fuels due to human activities
•Increase of GHG
•Global warming
•climatic changes
•Meeting of glaciers
•flooding/rise in sea level
•submergence of low-lying coastal lands
•large scale destruction of ecosystems and extinction of species

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