Lecture 8 - Climate Change and environement

Environment & Ecology
Class No. 8
Climate Change
UPSC Prelims

Climate Change
Environment & Ecology by Dr. Shivin Chaudhary Click Here to Learn More
● Climate change refers to long-term shifts in temperatures and weather (rainfall, snow,
and wind) patterns attributed directly or indirectly to human (anthropogenic) activity
that alters the composition of the global atmosphere causing natural climate variability
observed over comparable periods (hundreds of years).
● Climate change encompasses global warming, but refers to a broader range of changes
(due to variability in temperature, rainfall, wind and water patterns), such as rising sea
levels, shrinking mountain glaciers, accelerating loss of cryosphere (melting of ice caps of
mountains and polar regions), ocean acidification, etc.

Climate Change
● Global warming refers to long-term warming (rise in global temperatures) of the planet,
which is only one aspect of climate change.
● Throughout its evolutionary history, earth has experienced episodic climate change events
involving global warming and global cooling (glaciation events).
● Global temperature shows a well-documented rise (global warming) since the early 20th
century & most notably since the late 1970s.

Greenhouse Gas Effect
● A greenhouse is a structure whose roof & 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. It is absorbed by the floor, earth, and contents, which
become warmer and re-emit the energy as longer-wavelength infrared
radiation.

● A greenhouse is a structure whose roof & 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. It 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 infrared radiation 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 greenhouse effect is a natural process that occurs in the Earth's
atmosphere, which helps to maintain a stable temperature on the planet's
surface.
● It is caused by certain gases in the atmosphere, known as greenhouse gases,
which trap some of the sun's heat and prevent it from escaping back into
space. This process keeps the Earth's temperature at a comfortable level for
living things.
● 95 % of the greenhouse effect is caused by water vapour and small water
particles in the atmosphere.

Importance of Natural Greenhouse Effect
● The greenhouse effect is a natural phenomenon 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 per cent of total greenhouse
warming.
● Average global temperatures are maintained at about 15°C due to the natural
greenhouse effect. Without this phenomenon, average global temperatures might
have been around -17°C, and at such low temperatures, life would not be able to
exist.

Greenhouse Gases
● Atmospheric gases like Carbon Dioxide (CO2), Methane (CH4), Nitrous
Oxide (N2O), Water Vapour, and Chlorofluorocarbons (CFCs) can trap the
out-going infrared radiation from the earth’s surface.
● Hence these gases are known as greenhouse gases (GHGs), and the heating
effect is known as the greenhouse effect.
● Worldwide, since 1880, average temperature has risen 1°C relative to the
baseline.
● This increased temperature can lead to deleterious environmental changes
and result in odd climatic changes like the elnino, increased melting of
cryosphere, rise in sea level, coral bleaching etc.

Greenhouse Gases
● Global warming potential
● It is a measure of how much energy the emissions of 1 ton of a gas will absorb
over a given period of time, relative to the emissions of 1 ton of carbon dioxide
(CO2).
● The larger the GWP, the more that a given gas warms the Earth compared to CO2
over that time period.
● The time period usually used for GWPs is 100 years.
● GWPs provide a common unit of measure, which allows analysts to add up
emissions estimates of different gases (e.g., to compile a national GHG
inventory), and allows policymakers to compare emissions reduction
opportunities across sectors and gases

Greenhouse Gases
Gas Global warming potential (100 years) Lifetime (years)
Carbon dioxide (CO2) 1 50-200
Methane (CH4) 21 12
Nitrous oxide (N2O) 310 120
Hydrofluorocarbons (HFCs) 140-11700 1-270
Perfluorocarbons (PFCs) 6500-9200 800-50000
Sulphur hexafluoride (SF6) 23900 3200

Greenhouse Gases
Gas Sources
Carbon dioxide (CO2) Burning of fossil fuels, deforestation, etc.
Carbon monoxide (CO) Iron ore smelting, burning of fossil fuels, burning e-waste.
Methane (CH4) Growing paddy, excreta of cattle and other livestock, termites,
burning of
fossil fuel, wood, landfills, wetlands, fertiliser factories, etc.
Nitrous oxide (N2O) Burning of fossil fuels, wood and crop residue; fertilisers.
Chlorofluorocarbons (CFCs) Refrigeration, solvents, insulation foams, aero propellants, industrial
and commercial uses.
Hydrofluorocarbons (HFCs) Semiconductor manufacturing, other industries
Perfluorocarbons (PFCs) Same as HFCs plus aluminium smelting
Sulphur hexafluoride (SF6) Electrical transmission systems, magnesium and aluminium
production

Greenhouse Gases
Source- IPCC AR6

Greenhouse Gases
● Carbon Dioxide (CO2)
● It is a meteorologically important gas as it is transparent to incoming solar radiation
but opaque to outgoing terrestrial radiation.
● Being an efficient absorber of infrared radiation (heat), it absorbs a part of
terrestrial radiation and reflects some of it towards the earth’s surface.
● It is mainly responsible for the greenhouse effect and heat energy budget.
● Its concentration is greater close to the earth’s surface as it is denser than air.
● Atmospheric carbon dioxide measured at NOAA’s Mauna Loa Atmospheric
Baseline Observatory (Hawaii) peaked for 2021 in May at a monthly average of
419 ppm.

Greenhouse Gases
● Total carbon
estimation
● 1.85 Billion Gigatons
(Gt) of total carbon
on Earth
Below the surface Above the surface
1.845 Billion Gt of the total carbon
on Earth is below the surface.
43,500 Gt of the total carbon on Earth is
above the surface.
Of this, 315 Million Gt of carbon is
in continental and oceanic
lithospheres.
1. 37,000 Gt in the deep ocean (85.1 %)
2. 3,000 Gt in marine sediments (6.9%)
3. 2,000 Gt in terrestrial biosphere (4.6%)
4. 900 GT in the surface ocean (2%)
5. 590 Gt in the atmosphere (1.4%)

Greenhouse Gases
● Ozone
● Ozone is another important greenhouse gas.
● Ozone (O3) forms less than 0.00005% by volume of the atmosphere and is
unevenly distributed.
● It is formed naturally in the stratosphere (good ozone — formed due to the
interaction between O2 and UV light) and absorbs harmful ultraviolet rays of the
sun.
● However, at the ground level (bad ozone), it is a pollutant (short-lived greenhouse
gas) with highly toxic effects.
● At ground level, pollutants like Carbon Monoxide (CO), Nitrogen Dioxide (NO2)
and Volatile Organic Compounds (VOC) convert O2 to tropospheric ozone (O3) in
the presence of sunlight.

Greenhouse Gases
● Ozone
● Ground level ozone is not released directly. Some of it is transported from the
stratosphere. Rest is formed by a chemical reaction
● At ground level, pollutants like Carbon Monoxide (CO), Nitrogen Dioxide (NO2)
and Volatile Organic Compounds (VOC) convert O2 to tropospheric ozone (O3) in
the presence of sunlight.

Greenhouse Gases

Ground Level Ozone.

Greenhouse Gases
● Tropospheric Ozone
● Tropospheric ozone formation reactions
1. Carbon Monoxide reacts with the hydroxyl radical (-OH) to produce hydroperoxy
radical (HO2).
2. Volatile Organic Compounds react with hydroxyl radical (-OH) to produce peroxy
radical (RO2).
3. Hydroperoxy radicals react with Nitrogen Oxide (NO) to form NO2 & hydroxyl
radical (OH) / alkoxy radical (RO).
4. NO2 gives O3 via photolysis (molecule seperation by light).

Greenhouse Gases
● Harmful Effects of Ozone
● Ozone at ground level is a harmful air pollutant and one of the main ingredients of
smog.
● Ozone makes our eyes itchy and watery. It lowers our resistance to colds and
pneumonia.
● Asthma patients are at the most significant risk from breathing air containing
ozone.
● Elevated ozone exposure can affect sensitive vegetation and ecosystems, including
forests, especially during the growing season.
● Ozone is most likely to reach unhealthy levels on hot sunny days. It can also be
transported long distances by wind, so even rural areas can experience high O3
levels.

Greenhouse Gases
● Photochemical Smog
● Photochemical smog is also known as summer smog or Los Angeles smog.
● It occurs most prominently in urban areas with high vehicular emissions.
● It forms when nitrogen oxides & volatile organic compounds react together in the
presence of sunlight to form ozone (a secondary pollutant).
● The resulting smog causes a light brownish colouration of the atmosphere, reduced
visibility, plant damage, irritation of the eyes, and respiratory distress.
● The atmospheric pollution level of Los Angeles, Beijing, Delhi, etc. is increased by
inversion that traps smog near the ground.
● It is highly toxic to humans and can cause severe sickness and shorten life.
● Temperature inversions are accentuated, and precipitation is reduced due to smog.

Greenhouse Gases
Chemical reaction involved in photochemical smog

Greenhouse Gases
● Ozone Depletion
● There is a steady decline in the total ozone volume in Earth's stratosphere. A much
more significant decrease in stratospheric ozone is observed around Earth's polar
regions.
● The unique cocktail of the powerful polar vortex and low temperatures generates
stratospheric clouds that react with CFCs and other ozone-depleting substances and
destroy the Ozone layer in the process.
● Remember : Chloride ion causes depletion of ozone layer in the stratosphere.

Greenhouse Gases
● Stratospheric Ozone Depleting Substances (ODS)
● ODS are human-made gases that release chlorine and bromine atoms on exposure
to UV rays and destroy stratospheric ozone (good ozone). They include:
1. chlorofluorocarbons (CFCs)
2. hydrochlorofluorocarbons (HCFCs)
3. hydrobromoflurocarbons (HBFCs)
4. halons (halocarbon gases were used in fire extinguishers)

Greenhouse Gases
5. methyl bromide (was used as a fumigant for pest control — suffocating pests with
poison)
6. carbon tetrachloride (formerly widely used in fire extinguishers, refrigerants & as
cleaning agents)
7. methyl chloroform (aerosols, solvent for organic compounds; used for cleaning
metals & circuit boards).
• ODS have been used as refrigerants in air conditioners and refrigerators, foam-
blowing agents, components in electrical equipment, industrial solvents, solvents
for dry cleaning, aerosol spray propellants and fumigants.

Greenhouse Gases
Ozone hole at South Pole

Greenhouse Gases
● Process
● Depletion of ozone is due to increased halocarbons in the atmosphere.
● Halocarbons are compounds in which the hydrogen of a hydrocarbon is replaced by
halogens — a group of reactive non-metallic elements like fluorine, chlorine,
bromine, iodine, etc.
● Halogen Atoms Like Chlorine Destroy Ozone
● Photodissociation (under the influence of sunlight) of ozone-depleting substances
(CFCs, HCFCs, carbon tetrachloride and trichloroethane, freons, halons) like
halocarbon refrigerants, solvents, propellants, and foam-blowing agents creates free
chlorine atoms that destroy ozone.

Greenhouse Gases
● PSCs or nacreous clouds contain water, nitric acid and sulfuric acid. Cl-
catalysed ozone depletion is enhanced in the presence of polar stratospheric
clouds.
● PSCs convert reservoir compounds into reactive free radicals (Cl and ClO),
thereby significantly increasing the reactive halogen radicals.
● These free radicals accelerate the depletion of ozone.
● Polar Stratospheric Clouds (PSCs) are nacreous clouds that extend from 12-
22 km above the surface. They are formed mainly during the polar vortex
event in winter, more intense at the south pole.

Greenhouse Gases
● Role of Polar Vortex and Polar Stratospheric
clouds
● Polar vortex (circumpolar vortex) is a polar cyclone.
It gives rise to Polar Stratospheric Clouds (PSCs).
● Polar Vortex Acts as a Transporter for Halogens
● Polar Stratospheric Clouds (PSCs) are nacreous
clouds that extend from 12-22 km above the
surface.
● They are formed mainly during the polar vortex
event in winter, more intense at the south pole.
● Nacreous clouds are rare clouds in the frigid regions
of the lower stratosphere.

Greenhouse Gases
● Polar Stratospheric Clouds (PSCs) are nacreous clouds that extend from
12-22 km above the surface. They are formed mainly during the polar
vortex event in winter, more intense at the south pole.
● Polar vortex is a polar cyclone that gives rise to Polar Stratospheric Clouds.
● PSCs or nacreous clouds contain water, nitric acid and sulfuric acid. Cl-
catalysed ozone depletion is enhanced in the presence of polar stratospheric
clouds.
● PSCs convert reservoir compounds into reactive free radicals (Cl and ClO),
thereby significantly increasing the reactive halogen radicals.
● These free radicals accelerate the depletion of ozone.

Greenhouse Gases
● Impact of Nanoparticles (NPs)
● The hydroxyl radical (OH) is the most important oxidant in the troposphere and
lower stratosphere.
● OH initiates the removal of stratospheric ozone-depleting compounds such as
hydrochlorofluorocarbons (HCFCs).
● NPs being very reactive, bind with OH and ultimately result in its reduction of OH
radicals, maintaining the concentration of ozone-depleting substances.

Greenhouse Gases
● Ozone hole over Antarctic vs Arctic:
● Ozone holes are most commonly found over the Antarctic region (experiences
strong polar vortex).
● They are comparatively rare & small over the Arctic (because the polar vortex here
is comparatively weak and temperatures are relatively high).

Greenhouse Gases
Tropical Ozone Hole :
● Recently, a large, year-round ozone hole was discovered in the lower stratosphere
over the tropics. It has been in the tropics since the 1980s but was discovered
recently.
● The tropical Ozone Hole is an all-season ozone hole compared to the Antarctic
Ozone Hole, which is pre- dominantly visible during springtime. It is seven times
greater in area than the Antarctic ozone hole, and the depth of both is almost the
same.

Greenhouse Gases
● Short-lived climate pollutants
● They are powerful climate forcers that remain in the atmosphere for a much shorter
period of time than carbon dioxide (CO2), yet their potential to warm the
atmosphere can be many times greater.
● Certain short-lived climate pollutants are also dangerous air pollutants that have
harmful effects for people, ecosystems and agricultural productivity.
● The short-lived climate pollutants- black carbon, methane, tropospheric ozone, and
hydrofluorocarbons are the most important contributors to the man-made global
greenhouse effect after carbon dioxide, responsible for up to 45% of current global
warming.
● Black carbon is the second-largest contributor to warming the planet behind carbon
dioxide (CO2).

Greenhouse Gases
● Methane (CH4)
● Characteristics:
● Colourless and odourless gas.
● Primary component of natural gas.
● Powerful GHG: Lifespan in atmosphere: 20 years (fewer than CO2).
● Global Warming Potential: more than 80 times greater than that of CO2.
● Responsible for:
● More than 25% of global warming.
● ~1/2 of the growth in tropospheric ozone formation.
● India among the top 5 methane emitters in world.

Greenhouse Gases
● ‘Global Methane Assessment: 2030 Baseline Report’
● Released by Climate and Clean Air Coalition (CCAC) and United Nations
Environment Programme (UNEP), launched at Climate and Clean Air ministerial
meeting at COP 27 to the UNFCCC.
● Examines baseline projections of methane emissions over the coming decade and
implications for Global Methane Pledge (GMP) target.
● Key findings:
● Amount of Methane in the atmosphere is 260% of pre-industrial levels.
● Human-driven methane emissions are responsible for nearly 45% of current net
warming.
● 2021 saw the largest annual increase recorded.

Greenhouse Gases
● Earlier report titled “Global Methane Assessment: Benefits and Costs of Mitigating
Methane Emissions” concluded that reduction of anthropogenic methane emissions
by 45% would prevent a rise in global warming by up to 0.3 degrees Celsius by
2045. Also released by Climate and Clean Air Coalition along with UNEP.
● Global methane budget : By global carbon project.
● Agriculture and waste > Wetlands > Fossil Fuel.
● Flooded rice cultivation has been identified as one of the leading global agricultural
sources of anthropogenic methane (CH4) emissions

Greenhouse Gases
● Global Methane Pledge (GMP)
● Launched at COP26 of UNFCCC in 2021 to catalyse action to reduce methane
emissions.
● Led by: United States and European Union.
● Aim: To collectively reduce methane emissions by at least 30% below 2020 levels
by 2030.
● Membership: More than 100 country participants, together responsible for 45% of
global human-caused methane emissions.
● India did not sign the pledge because of its concerns over the impact on trade, on
the country's vast farm sector, and the role of livestock in the rural economy.

Greenhouse Gases
● International Methane Emissions Observatory (IMEO)
● According to a report by IMEO, cutting methane emissions is fastest way to tackle
climate change in short-term.
● It is An initiative by UNEP, launched in 2021, with support from European
Commission
● Aim: To catalyse reduction of methane emissions, starting with fossil fuel sector.
● Core implementing partner of Global Methane Pledge

Greenhouse Gases
● Global Energy Monitor (GEM)
● As per GEM, just 30 fossil fuel companies account for nearly half of the planet-
warming methane emitted by the world’s energy sector.
● A non-profit organization which aims to develop and share information in support
of the worldwide movement for clean energy.

Tropospheric Ozone

Black Carbon (Soot)
● Black carbon warms the earth by reducing albedo (the ability to reflect sunlight) when
deposited on snow.
● It is the strongest absorber of sunlight (a lot more than carbon dioxide) and heats the air
directly.
● Black carbon is said to be one of the largest contributors to climate change after CO2. But
unlike CO2, which can stay in the atmosphere for years together, black carbon is short-
lived and remains only for days to weeks before it descends as rain or snow.

Black Carbon (Soot)

Black Carbon (Soot) and COVID-19
According to a study conducted by the Indian Institute of Tropical Meteorology:
● The COVID-19 infection count increase corresponded with an increase in black carbon in
the atmosphere and decreased simultaneously with the decrease in black carbon in the
atmosphere.
● The COVID-19 death count increased with an increase in black carbon in the atmosphere
and decreased when there was a decrease in black carbon in the atmosphere.
Read at: https://www.downtoearth.org.in/blog/air/black-carbon-particles-contribute-to-
increasing-covid-19-cases-78130
Remember : prelims question : vectors for virus are biological only. (wrong)

Fluorinated Gases
Chlorofluorocarbons (CFCs)
● CFCs were phased out via the Montreal Protocol due to their part in ozone
depletion. These anthropogenic compounds are also GHGs, with a much higher
potential to enhance the greenhouse effect than CO2.
Hydrofluorocarbons (HFCs)
● HFCs are used as refrigerants, aerosol propellants, solvents, and fire retardants.
These chemicals were developed as a replacement for CFCs. Sadly, HFCs are
potent GHGs with long atmospheric lifetimes.

Fluorinated Gases

Fluorinated Gases
Perfluorocarbons or Fluorocarbon (PFCs)
● PFCs are a group of human-made chemicals composed of carbon and fluorine
only.
● They are produced as a by-product in aluminium production and the
manufacturing of semiconductors (as alternatives to CFCs).
● Like HFCs, PFCs generally have long atmospheric lifetimes and high GWP.
Sulphur Hexafluoride (SF6)
● Sulphur hexafluoride is also a GHG.
● It is used in magnesium processing and semiconductor manufacturing, as well as a
tracer gas for leak detection.
● It is used in electrical transmission equipment, including circuit breakers.

Nitrous Oxide (N2O)
● Nitrous Oxide (N2O)
● It is a GHG (300 times more potent than carbon). It is also the only remaining
threat to the ozone layer as it can live in the atmosphere for up to 125 years (long-
lived, just like CO2).
● N2O emissions have increased by 30 per cent between 1980 & 2016. It has the
third-highest concentration after CO2 and methane in our atmosphere among
GHGs responsible for significant global warming.
● 43% of the total emissions of N2O came from human sources, a significant
portion of it from the agricultural sector (nitrogen-based fertilisers).
● Most N2O emissions have come from emerging countries like India, China &
Brazil. Agriculture accounts for over 70% of all nitrous oxide emissions in the
Indian environment, of which fertilisers, mostly urea, contribute 77%

Nitrous Oxide (N2O)
● Nitrogen Oxide (NO), Nitrogen dioxide (NO2) are global cooling gasses.
● Nitrous Oxide (N2O) is a greenhouse gas.
● They all fall under the general category of oxides of nitrogen (NOx)

Nitrous Oxide (N2O)

Carbon monoxide
● Carbon monoxide (less dense than air) is a short-lived, very weak direct GHG.
Through natural processes in the atmosphere, it is eventually oxidised to carbon
dioxide (GHG).
● It has an indirect radiative forcing effect by elevating concentrations of methane
(GHG) and tropospheric ozone (GHG).

Carbon monoxide: In News
● Carbon monoxide plumes from the wildfires in California, United States spread
across the other side of the country in the East coast and across the Great Lakes and
Canada, showed data from NASA.
● The plumes were carried by the atmospheric jet stream that blew the carbon
monoxide plume eastward across the US and over the Atlantic Ocean, according to
the US National Weather Service.

Greenhouse Gases
● Water Vapour
● It is one of the most variable gaseous substances in the atmosphere – constituting
between 0.02% and 4% of the total volume (in cold, dry and humid tropical
climates, respectively).
● Water vapour is also a variable gas in the atmosphere, which decreases with
altitude. 90% of moisture content in the atmosphere exists within 6 km of the
earth’s surface.
● Water vapour also decreases from the equator towards the poles.
● Like carbon dioxide, water vapour plays a significant role in the insulating action,
of the atmosphere.
● It absorbs not only the long-wave terrestrial radiation (infrared radiation or heat
emitted by the earth during the night), but also a part of the incoming short-wave
solar radiation (visible and UV radiation).

Greenhouse Gases
● Carbon Footprint
● Carbon footprint is a measure of the impact of one’s activities have on the amount
of CO2 produced through the burning of fossil fuels and is expressed as the weight
of CO2 emissions produced in tons.
● It is measured during the course of a year & can be associated with an individual,
organisation, product etc.
● For example- India has pledged to reduction by 45% in the emissions intensity
(carbon footprint) of its economy by 2030 compared to 2005 levels.

Greenhouse Gases
AFLOU- Agriculture, forestry and other land use (AFOLU)
Source-
https://w
ww.ipcc.c
h/report/a
r6/wg3/do
wnloads/r
eport/IPC
C_AR6_
WGIII_Ch
apter02.p
df
Pg 28

Greenhouse Gases
Source-
https://w
ww.ipcc.c
h/report/a
r6/wg3/do
wnloads/r
eport/IPC
C_AR6_
WGIII_S
PM.pdf
Pg 14

Greenhouse Gases
Source-
3rd BUR
Page 169
Emission by sector- India Emission by GHG- India

Greenhouse Gases
● Carbon Bomb
● A Carbon Bomb is “a coal, oil or fossil gas project with a potential to emit over a
Gigaton of CO2 emissions over its lifetime.”
● A network named “Leave It In the Ground Initiative (LINGO)” has identified 425
of them around the world. According to LINGO, Carbon bombs' potential
emissions exceed a 1.5°C carbon budget by a factor of two.
● China, the United States, Russia, & Saudi Arabia have the highest number of
Carbon Bombs.
● Some listed carbon bomb projects include:
● Carmichael Coal Project (coal mine in Queensland, Australia & owned by the
Adani Group)

Greenhouse Gases
● Gevra Coal Mines in Chhattisgarh by Coal India.
● Rajmahal Coal Mines in eastern Jharkhand is owned by Eastern Coalfields.
● About LINGO
● LINGO is a think tank with a mission to “leave fossil fuels in the ground & learn to
live without them.”
● It envisions a world powered by 100% renewable energy & advocates a circular
economy.
● LINGO aims to gain ground support for protesting such projects & challenge them
through litigation.

Climate Sensitivity
● Carbon sensitivity refers to the sensitivity of the Earth's climate to changes in
atmospheric carbon dioxide (CO2) concentrations. It is a measure of how much the
Earth's temperature would change in response to a certain increase or decrease in
atmospheric CO2.
● The concept of carbon sensitivity is usually expressed in terms of "climate sensitivity,"
which is defined as the equilibrium global mean surface temperature change that
would result from a doubling of atmospheric CO2 concentrations above pre-industrial
levels.
● This value is typically estimated to be between 1.5°C and 4.5°C, with a most likely
value of 3°C.

Climate Feedback
● Climate feedback refers to the interactions between the various components of the
Earth's climate system that either amplify or dampen the effects of an initial climate
forcing, such as an increase in greenhouse gas concentrations. These feedback
mechanisms can either accelerate or slow down climate change, and are an important
factor in determining the overall sensitivity of the climate system to external
perturbations.
● One of the most well-known examples of a positive climate feedback is the ice-albedo
feedback. As global temperatures rise, ice and snow melt, exposing darker surfaces
that absorb more solar radiation, further warming the Earth and causing more ice and
snow to melt. This feedback loop amplifies the initial warming, leading to even more
ice loss and warming.

Climate Feedback
● On the other hand, negative feedback mechanisms can act to reduce the effects of a
climate forcing. For example, as atmospheric CO2 concentrations increase, plants may
grow more rapidly, absorbing more carbon and reducing the atmospheric CO2
concentration.
● Other examples of climate feedbacks include changes in cloud cover, ocean
circulation, and the release of greenhouse gases from permafrost or ocean sediments.
● Permafrost melts : earth releases stores of greenhouse gases from melting permafrost
and the temperature rises, creating a positive feedback.
● Water vapour : world warms, water vapour in atmosphere increases and so does the
temperature.

Effect of Clouds on Climate Change
● Clouds have a dual effect on our climate,
1) they reflect part of the sunlight back into space, which decreases temperatures
(negative feedback), and
2) they trap part of the heat reflected from the earth’s surface, which increases
temperatures (positive feedback). The net effect depends on the type of cloud.

● A warmer and wetter atmosphere will affect cloud cover. Clouds that contain more
water droplets are optically thicker and more effective at blocking sunlight than those
composed mainly of ice crystals (cirrus clouds).
● Low clouds are “strong coolers” since they reflect a large part of solar radiation
(sunlight) and absorb little heat from the ocean and land. On the other hand, very thin,
high clouds such as cirrus clouds reflect little sunlight, but they are very efficient at
absorbing thermal radiation (heat), making them “strong warmers”.

● Meanwhile, a shift in sun-blocking clouds (due to global warming) from
the tropics towards the poles, here the incoming sunlight is less intense,
would decrease their power to block sunlight.
● All this means the global net effect of cloud feedback is complex and hard
for scientists to model precisely.

Impact of Global warming
● Increased Frequency and Severity of Heat Waves
● A heat wave is a period of excessively hot weather. India Meteorological
Department (IMD) declares heat waves when the actual maximum temperature
remains 45°C or more, regardless of the normal maximum temperature.
● Example- British Columbia (South-Western Canada) & neighbouring Washington
and Oregon states (North-Eastern US) in 2021, Australia (2019-20), California
(2020), and Siberia.
● Heat waves are caused due to shifting of Jet Streams (meandering Rossby Waves in
the temperate region case Heat Domes), hot local winds like loo (affects Gangetic
Plains Region), and anthropogenic causes like global warming.
● **read from Geography

● Communities close to coastal environments, small island nations, polar areas and
high mountains are particularly vulnerable to changes, such as rising sea levels and
shrinking glaciers.
● Communities in other areas are affected by extreme weather events exacerbated by
ocean warming
● Statistics
● Marine heat waves have become twice more frequent in the past four decades and
are lasting longer.
● The report finds that human activities are responsible for 84 to 90 per cent of the
marine heat waves that occurred in the last decade.
● By 2081, the frequency of marine heat waves could jump by 20 to 50 times.

● Marine Heat Waves
● Marine heatwaves occur when ocean temperatures for a particular oceanic location
are unusually extremely warm for an extended period and time of year.
● They can occur in summer or winter
● IPCC Special Report on the Ocean and Cryosphere in a Changing Climate
(SROCC) on Marine Heat Waves
● Today’s oceans are experiencing unprecedented conditions with increased
temperatures, further ocean acidification, marine heatwaves and more frequent
extreme El Niño and La Niña events.

● Impact of marine heatwaves
● Marine productivity
● They have resulted in large-scale coral bleaching, which takes more than 15 years
for corals to recover from.
● Marine heat waves reduce the mixing between water layers and, consequently, the
supply of oxygen and nutrients for marine life.
● The Pacific Ocean, which had seen such unusually warm water, had boosted the
growth of toxin-producing algae and suppressed the growth of small organisms at
the base of the ocean food chain.

● Impact on weather patterns
● A more pronounced effect of marine heat waves would be on global wind circulation
and ocean currents.
● IPCC report indicates, the Atlantic Meridional Overturning Circulation (which ensures a
northward flow of warm, salty water in the upper layers of the Atlantic and a southward
flow of colder, deep waters) has already weakened which could have cascading effects.
Please READ AMOC from geography.
● More severe cyclonic storms
● IPCC says there is emerging evidence of an annual increase in the percentage of
category 4 and 5 storms.
● These storms sustain their strength further by feeding on the moisture over warm ocean
waters.

● Urban Heat Islands
● An urban heat island is an urban or an industrial area that has temperatures
considerably higher than its surrounding rural areas (both share the same climate)
primarily due to anthropogenic reasons.
● Causes
● Heat-trapping concrete and asphalt (have very low albedo or low reflectivity)
replace natural vegetation and water (reduced evaporation and evapotranspiration).
● High-rise buildings that offer more surface area for heat absorption.
● High vehicle density and heat released from their engines.

● High pollution levels and high concentrations of GHGs like CO2 (thermal power
plants and vehicles).
● GHGs, aerosols, particulate matter, etc., are good at absorbing outgoing infrared
radiation.
● Cooling appliances like air conditioners release heat into the surroundings.
● Bad monsoons because of less evaporation of water from vegetation
(evapotranspiration) and soil.
● Heat islands at night: Cities used to cool down during the night, but nowadays, they
are trapping this heat overnight. ACs, pollution and a close & dense networks of
buildings are the primary reason for the Urban heat islands at night.

● Albedo of a surface is the proportion of sunlight that the
surface can reflect back into space.
● Fresh snow has the highest albedo (reflects back 80-
90% of the incident sunlight). Dark asphalt used to road
construction and in the roofing of buildings has very
low albedo (~5%).

● Increased Incidence of Wildfires
● Increased incidence of wildfire creates a positive feedback
loop exacerbating global warming.
● In climate change, a feedback loop is something that speeds up
or slows down a warming trend. A positive feedback
accelerates a temperature rise, whereas a negative feedback
slows it down.
● Example- Australia’s Bushfires are Getting Severe

● Wildfires in Arctic
● Wildfires on permafrost in Siberia south of the Arctic are not uncommon.
● But in 2020, burning occurred well above the Arctic Circle (tundra), a region not
commonly known to support large wildfires.
● Reason- unprecedented drying up of the tundra vegetation like moss, grass & dwarf
shrubs.
● ‘Zombie fires’ are becoming more frequent in the once-frozen tundra — north of the
Arctic Circle.
● A zombie fire (holdover fire) is a fire from a previous growing season that can burn
slowly with smoke but no flame under the ground made of carbon-rich peat.
● Impact- The fires & record temperatures have the potential of turning the carbon sink
into a carbon source.

● Shrinking Cryosphere
● The areas of snow or ice, which are subject to temperatures below 0°C for at least a
part of the year, compose the cryosphere.
● Continental ice sheets found in Greenland and Antarctica, ice caps, glaciers, areas of
snow (glaciers of Alps, Himalayas) and permafrost (Siberia), frozen parts of the
ocean, rivers, lakes, etc., are all part of the cryosphere.
● Glaciers from almost half of natural World Heritage sites- such as the Khumbu
Glacier in the Himalayas- may disappear entirely by 2100, if emissions continue at the
current rate, an IUCN study warns.
● The study predicts glacier extinction in 21 of the 46 natural World Heritage sites with
glaciers.

● Importance of cryosphere
● Snow and ice (have the highest albedo) reflect heat from the sun (heat budget). (refer
earlier slide)
● Supply freshwater to many parts of the world
● Cryosphere is most sensitive to climate shifts. Hence, it acts as the earth’s black box
(ice accumulates layer over layer) > Studying the vertical ice column helps understand
past global changes in climate

● Impact of shrinking cryosphere
● Water scarcity and water wars between nations.
● Loss of ecologically rich and important coastal wetlands.
● Distress migration of coastal inhabitants due to the submergence of major coastal
cities.
● Submergence of Small Island Developing States (first to suffer the consequences of
climate change).
● Reduced hydroelectric power generation due to the abnormal behaviour of glaciers
will further increase dependence on fossil fuels.

● Vegetation change- The tundra will return to swamps (> loss of forest > loss of
carbon sink), the permafrost is thawing (> exposing the subsurface carbon sinks).
● The Northern Sea Route (NSR) which would connect the North Atlantic to the North
Pacific through a short polar arc is slowly opening due to ice melting. Models predict
that this route could be ice-free in summer by 2050.
● Coastal flooding and reduction of arable land on coasts.

● The distance from Rotterdam to Yokohama will be cut by 40 per cent compared to the
Suez route.
● Unexplored oil & natural gas deposits are estimated to be 22% of the world’s
unexplored resources, mostly in the Arctic Ocean (Barents Sea Region).
● Mineral deposits including 25 per cent of the global reserves of rare earths are buried
in Greenland
● Issues
● Environmental risks.
● Unlike Antarctica, the Arctic is not a global common.
● There is no treaty that governs it, only the UN Convention of Law of the Sea
(UNCLOS) deals it.

● Arctic Amplification
● Arctic is heating up 4 times as fast as rest of world due to Arctic amplification (AA).
● It refers to enhancement of near-surface air temperature change over Arctic relative to
lower latitudes.
● Whenever there is change in net radiation balance, it is slightly higher in the arctic as
compared to tropical areas.
● Reasons
● Change in Albedo:
● Amplification is primarily caused by melting polar ice, which is increasing in the
Arctic at a rate of 13% per decade.
● Ice is more reflective of sunlight (high albedo) than land or ocean.

● When ice melts, it typically reveals darker areas, & this results in increased sunlight
absorption (low albedo) & associated warming.
● Melting sea ice also releases greenhouse gases from thawing permafrost & frozen
methane from the ocean bottom & further intensifies Amplification.
● Polar amplification stronger in Arctic than Antarctic as:
● Arctic is an ocean covered by sea ice, while Antarctica is an elevated continent
covered in more permanent ice & snow. In fact, the Antarctic continent has not
warmed in the past seven decades, despite a steady increase in the atmospheric
concentrations of GHGs.

● Impact of arctic amplification
● Sea-level rise globally.
● Zombie ice from massive Greenland ice sheet will eventually raise global sea level by
at least 10 inches.
● (Zombie ice- It’s the ice that is still attached to thicker areas of ice, but is no longer
getting fed by those larger glaciers because parent glaciers are getting less
replenishing snow)
● Arctic permafrost thaw releases carbon dioxide & methane, which has the potential to
cause even further warming (positive feedback).

● Impact of arctic amplification
● Impacts on mid-latitude climate, as well as the occurrence of extreme events by:
● Weakening of the tropospheric Jet Stream (will contribute to an increase in unusual &
extreme weather in the mid-latitudes).
● Weakening of the stratospheric polar vortex (which results in extreme weather events
in the mid-latitudes).
● Arctic Report Card 2022 (by US National Oceanic and Atmospheric Administration
(NOAA), annually since 2006)
● Key highlights of Report:
● Arctic continues to warm more than twice as fast as rest of globe.
● Persistent summer sea ice due to cooler surface waters and north winds at Chukchi
Sea.

Mains questions.
● How does the cryosphere affect global climate? (2017)
● Why is India taking keen interest in resources of Arctic Region? (2018)
● What is the economic significance of discovery of oil in the Arctic Sea & its
● possible environmental consequences? (2015)
● How do the melting of the Arctic ice and glaciers of the Antarctic differently affect
the weather patterns and human activities on the Earth? Explain. (2021)

Sea Level Change
● Sea level change means the fluctuations in the mean sea level over a considerably
long period of time. Commonly, seasonal variations of 5-6 cm are observed in a year.
Sea level change means the fluctuations in the mean sea level over a considerably
long period of time.

Processes that cause Change in Sea Level
Eustatic changes
● It occur when the volume of sea water changes due to factors such as global warming
and melting of ice sheets (rise in sea level) or ice ages (fall in sea level) and changes
in the volume of mid-oceanic ridges.
Tectonic changes occur due to a change in land level
● Isostatic changes take place due to addition or removal of load — during ice ages,
landmass subsided due to the load exerted by the glacial ice. On the other hand,
landmasses rise as the glacial ice is removed.
● Epeirogenic movement occurs due to broad scale tilting of continents which may
result in the rise of one part of the continent even as the other part may subside,
causing an apparent rise in sea level.
● Orogenic movement (mountain building) results in the formation of lofty mountains
and an apparent fall in sea level

Effects of Climate Change
Sea Level Rise and Coastal Flooding
● IPCC report warns that sea level rise
could reach 60 to 110 cm if emissions
continue to increase strongly.
● More than half the global population live
in cities, most of which are located on
low-lying islands and coasts & economic
losses due to extreme flooding will soar
166 times more by 2050.

● Biggest losers here are small island development states or SIDS.
● They are most vulnerable to climate change.
● At the UN conference on environment and development (1992 Earth Summit) they
were recognised as a distinct group of developing countries.
● Most of them are coral islands on shallow atolls.
● UN programme of action on sustainable development of SIDS is popularly referred to
as the Barbados Plan of Action (BPOA). It is the only internationally approved
programme specific to SIDS. (1994)
● Mauritius Strategy : 10 year comprehensive review of the BPOA in 2005.

Tropical Cyclones
● Tropical cyclones require a sea surface temperature (SST) of 26.5°C to form, while
the highest intensity storms require much warmer sea surface temperature (SST) of
28-29°C. The frequent high intensity storms have been tied to the very warm SST
(30°C+).
● Regions further from the equator are more regularly experiencing the threshold
temperature or 24-26°C widening the range of formation of tropical cyclones. These
conditions are exacerbated by global forcing mechanisms including El Niño, Indian
Ocean Dipole, Southern Annular Mode and Madden-Julian Oscillation (these in
turn are affected by global warming).

Tropical Cyclones
● The Arabian Sea is heating rapidly and driving more cyclones, and excessive rainfall
(excessive rainfall in sea less moisture in monsoon winds less rainfall on the mainland).
Climate models suggest that 64 per cent of the cyclone risk in the Arabian Sea was due
to climate change.
● Unusual timing of cyclones in the arabian sea. Ex : cyclone vayu in june 2019.
● Changing path of cyclones in the arabian sea. Ex : Tropical Cyclones restricted to
Gujarat earlier, but now affect kerala and karnataka too.

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, they release carbon in the form of carbon dioxide and methane.
● In the 1970s, the tundra was a carbon sink (takes more than it gives), but today, it is a
carbon source, all because of global warming. (Global warming leads to more global
warming positive feedback loop).

Carbon Dioxide Fertilization
● Earth’s vegetated lands have shown significant greening (an increase in leaves on
plants/trees) largely due to rising levels of atmospheric CO2 (increases photosynthesis).
● Carbon dioxide fertilization contributes to 70 percent of the greening effect. The second
most important driver is nitrogen, at 9 percent. The rest occurs due to land cover
changes, precipitation, sunlight changes, etc.
● Plants acclimatize to rising CO2 concentration and the fertilization effect diminishes
over time. That is, raising CO2 concentrations may be beneficial in the short run, but in
the long-run it is harmful due to climate change.
● Therefore, carbon fertilisation is increasing carbon sink on land temporarily.

Climate Migrants
● Environmental Migrants are people displaced due
to adverse changes to their local environment.
Climate migrants are migrants people displaced
due to climate change impacts such as sea level
rise (Sundarbans), floods (Ganges, Brahmaputra
basins), drought (central India, Vidarbha,
Telangana, Rayalaseema), etc.
● The 64th round of NSSO, in 2007-08, titled
Migration in India identified natural disasters
including floods and droughts as one of the major
reasons for migration

● Economic Losses
● Economic losses suffered involve money spent on adaptation to climate change (costs
involved in moving from submerging areas to higher ground), rebuilding post extreme
climatic event and money spent on climate change mitigation (like carbon
sequestration).
● The economic losses suffered due to the emission of one ton of carbon dioxide into the
atmosphere is termed the social cost of carbon. It is expressed as the dollar value of the
losses suffered.
● India’s country level social cost of carbon emission was estimated to be the highest at
$86 per ton of CO2.
● It means the Indian economy will lose $86 by emitting each additional ton of CO2. India
is followed by the US, where the economic damages would be $48 per ton of CO2
emissions.

● Ocean Deoxygenation
● Ocean deoxygenation is the expansion of oxygen minimum zones (OMZs) in the world's
oceans as a consequence of anthropogenic emissions of carbon dioxide.
● OMZs are found in areas where an interplay of physical (ocean stratification) and
biological (less photosynthesis) processes create a “pool” of water where oxygen
concentrations fall (anoxic zones).
● Warmer oceans cause deoxygenation both because oxygen is less soluble in warmer
water, and through temperature-driven stratification.
● The oxygen minimum zone ( OMZ ), sometimes referred to as the shadow zone, is the
zone in which oxygen saturation in seawater in the ocean is at its lowest.

Food and Health Security at Risk
● 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.
● Rising temperature would increase fertilizer requirement and result in higher
GHG emissions, ammonia volatilization (Ammonia volatilization results in a
net loss of nitrogen from the soil system) and cost of crop production.
● 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.
● Spread of diseases (like malaria, etc.) in the tropics will put more pressure on the
healthcare sector.

Climate Tipping Points
● Climate tipping points are points where any
small change could push the earth system into
abrupt or irreversible change.
● A new research highlighted that Antarctica is
approaching a climate tipping point by 2060-
when Antarctic ice could begin melting at a
runaway rate.
● Globally 9 climate tipping points including the
Antarctic Ice Sheet

Corals
● Coral reefs are made up of calcareous skeletons of thousands of tiny marine organisms
called coral polyps.
● Phylum: Cnidaria (Related to anemones and jellyfish (cnidarians)).
● Colors differs wrt the nature of the salts they are made of.
● Polyps are shallow warm-water organisms with soft bodies covered by calcareous
skeletons. The polyps extract calcium salts from seawater to form these hard, tubular
skeletons. Small marine plants (algae) also deposit calcium carbonate contributing to
coral growth.

Corals
● Polyps live in colonies on the seafloor as a cemented
calcareous rocky mass, collectively called corals.
● When the coral polyps die, they shed their skeleton
(coral) on which new polyps grow.
● The cycle is repeated for millions of years, leading to the
accumulation of layers of corals.
● The shallow layers of corals created by the depositions of
corals are called coral reefs.

Types of Corals in News
● Acropora corals
● A recent report stated that highest levels of coral cover,
within the past 36 years, have been recorded in northern
and central parts of GBR, fuelled largely by increases in
fast-growing Acropora corals.
● These fast-growing corals are also most susceptible to
environmental pressures such as rising temperatures,
cyclones, pollution etc.

● Black Corals (Deep Sea Corals)
● Researchers have discovered new species of black corals
living 2,500 feet below surface off the coast of Australia.
● They are all over the world and at all depths. However,
typically, they are known as deep-sea corals.
● They are rarely black, but rather vary in color from white
to red, green, yellow, or brown.
● They are filter feeders and eat tiny zooplankton.

● Azooxanthellate Corals
● Zoological Survey of India (ZSI) recorded four species of azooxanthellate corals from
waters of Andaman and Nicobar (A&N) Islands.
● Azooxanthellate corals are a group of corals that do not contain zooxanthellae and
derive nourishment not from the sun but from capturing different forms of plankton.
● They are deep-sea representatives, with the majority of species reporting from
between 200 m to 1000 m. Their occurrences are also reported from shallow coastal
waters.
● Pillar coral (Dendrogyra cylindrus)
● Habitat: Caribbean from the Yucatan Peninsula and Florida to Trinidad and Tobago.
● Moved from Vulnerable to Critically Endangered,

Coral Relief Features
● Fringing Reefs (Shore Reefs)
● Fringing reefs are reefs that grow directly from a shore.
They are located very close to land, and often form a
shallow lagoon between the beach and the main body of
the reef. (most common)
● Barrier Reefs
● Barrier reefs are extensive linear reef complexes that
parallel a shore and are separated from it by lagoon.
● Largest (in size, not distribution) of the three reefs
● Eg: Great Barrier Reef

Coral Relief Features
● Atolls
● An atoll is a roughly circular (annular) oceanic reef system surrounding a large (and
often deep) central lagoon.
● A large ‘number of atolls also occur in the Lakshadweep Islands.

Ideal Conditions for Coral Growth
● Stable climatic conditions: Highly susceptible to quick changes.
● Perpetually warm waters: Tropical waters (30°N to 30°S latitudes; temperature around
20°C) with narrow diurnal and annual temperature ranges. Coral reefs are absent on the
west coast of tropical continents (Cold Ocean Currents).
● Shallow water: Ideal depths are 45 m to 55 m below the sea surface, where enough
sunlight is available. Need good amount of sunlight to survive.
● Clear salt water: Clear salt water is suitable for growth, while freshwater & highly saline
water are harmful.

Ideal Conditions for Coral Growth
● Abundant Plankton: Adequate supply of oxygen and microscopic marine food (plankton)
is essential for growth. As the plankton is more abundant on the seaward side, corals
proliferate on the seaward side.
● Little or no pollution: Corals are highly fragile and are vulnerable to climate change and
pollution, and even a minute increase in marine pollution can be catastrophic.

Types of Corals
● Hard corals: primary reef-building
corals, extract calcium carbonate from
seawater to build hard, white coral
exoskeletons. (Hermatypic Corals)
● Soft Corals: flexible because they lack
solid skeleton (Ahermatypic Corals)

Hermatyphic Corals (Corals and
Zooxanthellae)
● Tropical Rainforests of the Oceans: Many invertebrates, vertebrates, and plants live in
close association with corals, with tight resource coupling and recycling, allowing coral
reefs to have extremely high productivity and biodiversity.
● Scleractinian corals (stony, hard corals) build skeletons of calcium carbonate sequestered
from the water. They receive their nutrient and energy resources in two ways.
a. They use the traditional cnidarian strategy of capturing tiny planktonic organisms
with their tentacles.
b. Having a symbiotic relationship with a single-cell photosynthetic alga known as
zooxanthellae.

Corals and Zooxanthellae
● Zooxanthellae live symbiotically within the coral polyp
tissues.
● The symbiotic relationship allows the slow-growing
corals to compete with the faster-growing multicellular
algae. The corals feed by day through photosynthesis
(by zooxanthellae) and night through predation.
● The tissues of corals are inherently clear. The corals
receive their colouration from the zooxanthellae living
within their tissues.

Ahermatypic Polyps
● Corals which live w/o symbiotic relations & Zooxanthellaes.
● They DO NOT BUILD REEFS.
● It is not found in shallow waters but in ocean bottom floor. (Deep Ocean)
● It collects food directly from flowing water.
● It is found in cold, deep oceans. - Antarctica, Canada, Norway, US, UK, Japan, NZ.
● Fire Corals, Organpipe Corals, Black Corals (India)

Coral Bleaching
● Coral reef bleaching is a typical stress response of corals to various disturbances.
Bleaching occurs when the densities of zooxanthellae decline and/or the concentration of
photosynthetic pigments within the zooxanthellae fall (no longer helpful for the corals,
and the corals will bleach them).
● During bleaching, they commonly lose 60-90% of their zooxanthellae, and each
zooxanthellae may lose 50-80% of its photosynthetic pigments.
● If the stress-causing bleaching is not too severe and decreases in time: the affected
corals usually regain their symbiotic algae within several weeks or a few months.
● If zooxanthellae loss is prolonged: zooxanthellae populations do not recover, the coral
host eventually dies

Ecological Causes of Coral Bleaching
Temperature Changes
● Coral species (similar to most marine species) live within a relatively narrow temperature
range.
● Coral bleaching events have occurred mainly during the protracted warming periods
(summer seasons) and also during low wind velocity, clear skies, calm seas and low
turbidity.
● These conditions favour localised heating and high ultraviolet (UV) radiation — which
readily penetrates clear sea waters. (The corals contain UV-absorbing compounds, but
rising temperatures mean a reduction in their concentration.)

Ocean Acidification
● Acidification reduces corals’ calcifying ability.
Subaerial exposure
● It can be caused extreme low tides, ENSO-related sea level drops, or tectonic uplift.
● Results in consequent exposure to high or low temperatures and increased solar radiation.
Inorganic Nutrients
● Rather than causing coral reef bleaching, an increase in ambient elemental nutrient
concentrations (e.g., ammonia and nitrate) increases zooxanthellae densities 2-3 times.
● Although eutrophication is not directly involved in zooxanthellae loss, it could cause
secondary adverse effects such as lowering corals’ resistance to diseases.

Xenobiotics
● Xenobiotics are chemical substances that are foreign to animal life. When corals are
exposed to high concentrations of chemical contaminants like copper, herbicides and
oil, coral bleaching happens.
Epizootics
● Most coral diseases cause patchy or whole colony death due to sloughing (shedding) of
soft tissues, resulting in a white skeleton (not to be confused with bleached corals).

Great Barrier Reef
● The Great Barrier Reef, the world's largest reef system, is located in the Coral Sea, off
Queensland, Australia.
● It is the world’s most prominent single structure made by living organisms and can be
seen from outer space. The reef is a habitat of the dugong (sea cow) and green turtle. It
was selected as a World Heritage Site in 1981.
● According to IUCN, Australia’s Great Barrier Reef is in a “critical state and deteriorating”
as climate change warms up the waters in which it lies. Its IUCN conservation status has
been downgraded from “significant concern” to “critical” because of frequent mass
bleaching events (four in the past six years).
● An UN-backed mission recommended that the Great Barrier Reef be added to the list of
endangered World Heritage sites (not yet).

Great Barrier Reef
● A joint report by the IUCN and UNESCO’s World
Heritage Centre (WHC) has recommended that the
GBR “be inscribed on the List of World Heritage in
Danger”.
● Inscribing a site on the Danger List allows the WHC
to allocate immediate assistance from the World
Heritage Fund, while simultaneously gathering
international support and attention to the site.

Coral Reefs In India
● The three major types of coral reefs found in India are
fringing, barrier and atolls.
● Coral reefs in India are found in a lot of areas
including the Gulf of Kutch, Gulf of Mannar, Palk
Bay, Andaman & Nicobar and Lakshadweep Islands.
The Gulf of Kutch in the northwest has some of the
most northerly reefs in the world.
● Patches of coral reefs are also found in Ratnagiri,
Malvan and Redi, south Bombay and at the
Gaveshani Bank located in the west of Mangalore.

Biorock Technology for Coral Restoration

● The Zoological Survey of India attempted to restore coral reefs using biorock in the Gulf
of Kachchh. If successful, biorock technology could potentially help to restore the
degraded coral reefs.
● Biorock is the substance formed by mineral accretion or electro-accumulation of minerals
on steel structures that are placed on the seabed and are connected to a power source like
floating solar panels.

● The technology works by passing a small amount of electrical current through electrodes
in the water. When electric current flows between the anode (+ve) and cathode (-ve)
placed on the sea floor, calcium ions combine with carbonate ions and adhere to the
cathode as calcium carbonate (CaCO3). This electroaccumulated calcium carbonate is
termed biorock.
● Fragments of broken corals are tied to the biorock structure, where the coral larvae adhere
to the CaCO3 and grow faster as they need not spend their energy building their CaCO3
skeletons.

Cryomesh Technology
● Cryomesh Technology is to freeze and store coral larvae.
● Cryomesh method will help in building reefs threatened
by climate change.
● Mesh technology will help to store coral larvae at -196°C
● (-320.8°F).

Initiatives of India
● Coastal Zone Regulation
● Integrated Coastal and Marine Area Management (ICMAM)
● Coral reef areas: On the recommendations of the National Committee on Mangroves
and Coral Reefs following coral reef areas in the country have been identified for
intensive conservation and management since 1987:
1. Andaman & Nicobar Islands
2. Lakshadweep Islands
3. Gulf of Kutch (Gujarat)
4. Gulf of Mannar (Tamil Nadu)

Initiatives of India
● The Coral Bleaching Alert System(INCOIS since 2011): uses the satellite derived Sea
Surface Temperature (SST) in order to assess the thermal stress
● accumulated in the coral environs.
● National Coral Reef Research Centre has been established at Port Blair
● Blue flag Certification

Global Initiatives
● United Nations Environment Programme (UNEP) has included coral reef conservation
and restoration as an ecosystem based adaptation measure (EBA) for coastal
protection.
● International Coral Reefs Initiative (ICRI)
● Informal partnership between Nations and organizations India is a member of ICRI.
● The ICRI declared 2018 as the third International Year of the Reef (IYOR).
● Global Coral Reef monitoring network under ICRI: works to provide scientific
information and communication on the status of coral reef ecosystems
● Abu Dhabi Marine Restoration Initiative (by The Environment Agency – Abu Dhabi)
● Aim: To restore coral, mangrove and seagrass in Abu Dhabi, creating a refuge for the
dugong, a fast-disappearing aquatic mammal.

Global Initiatives
● International Coral Reef Action Network (ICRAN)
● It is a strategic alliance of private and public organizations that acts worldwide to
● address the management of coral reef ecosystems and the needs of the communities
that depend upon them. shares and promotes traditional knowledge, current
research, and best practices in order to strengthen reef management.
● Coral Triangle Initiative
● The six governments of the Coral Triangle – Indonesia, Malaysia, Papua New Guinea,
the Philippines, Solomon Islands, and Timor Leste have established partnership to
conserve coral reefs and the multitude of species and fisheries they support.

Global Initiatives
● Coral Triangle
● A marine area located in the western
Pacific Ocean. It includes the waters
of Indonesia, Malaysia, the
Philippines, Papua New Guinea,
Timor Leste and Solomon Islands.
● 200 varieties of reef fishes and
supports livelihood of 120 million
people.

Blue Flag Certification
● This Certification is accorded by an international agency “Foundation for Environment
Education, Denmark” based on 33 stringent criteria in four major heads i.e
○ Environmental Education and Information,
○ Bathing Water Quality,
○ Environment Management and Conservation and
○ Safety and Services on the beaches.
● It started in France in 1985 and has been implemented in Europe since 1987, and in
areas outside Europe since 2001 when South Africa joined.
● Spain tops the list with 566 such beaches; Greece and France follow with 515 and 395,
respectively.

Blue Flag Certification

PYQs: Q1
2022
Q. Consider the following statements :
1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
2. Low clouds have a high absorption of infrared radiation emanating from the Earth’s
surface and thus cause warming effect.
Which of the statements given above is/are correct ?
A. Only 1
B. Only 2
C. Both 1 & 2
D. Neither 1 nor 2

PYQs Q1
2022
Answer- D
Whether a given cloud will heat or cool the surface depends on several factors,
including the cloud’s altitude, its size, and the make-up of the particles that form the
cloud.
Statement 1 is incorrect: Low, thick clouds primarily reflect solar radiation and cool
the surface of the Earth.
Statement 2 is incorrect: High, thin clouds primarily transmit incoming solar radiation;
at the same time, they trap some of the outgoing infrared radiation emitted by the Earth
and radiate it back downward, thereby warming the surface of the Earth.

PYQs: Q2
2022
Among the following crops, which one is the most important anthropogenic source of
both methane and nitrous oxide?
[A] Cotton
[B] Rice
[C] Sugarcane
[D] Wheat

PYQs Q2
2022
Answer- B
Methane and nitrous oxide are important greenhouse gases. They contribute to global
warming. Important anthropogenic sources of biogenic methane are wet rice fields,
cattle, animal waste, landfills and biomass burning.
Flooded rice cultivation has been identified as one of the leading global agricultural
sources of anthropogenic methane (CH4) emissions. Furthermore, it has been
estimated that global rice production is responsible for 11% of total anthropogenic
CH4 emissions.
Paddies are a potential source of anthropogenic nitrous oxide (N2O) emission as well.
In paddies, both the soil and the rice plants emit N2O into the atmosphere. The rice
plant in the paddy is considered to act as a channel between the soil and the
atmosphere for N2O emission.

PYQs: Q3
2020
Which one of the following statements best describes the term ‘Social Cost of
Carbon’? It is a measure, in monetary value, of the
a) long-term damage done by a ton of CO2 emissions in a given year.
b) requirement of fossil fuels for a country to provide goods and services to its
citizens, based on the burning of those fuels.
c) efforts put in by a climate refugee to adapt to live in a new place.
d) contribution of an individual person to the carbon footprint on the planet Earth.

PYQs: Q3
Answer: A
● The economic losses suffered due to the emission of one ton of carbon dioxide
into the atmosphere is termed the social cost of carbon. It is expressed as the
dollar value of the losses suffered.

PYQs: Q4
2019
Why are dewdrops not formed on a cloudy night?
[A] Clouds absorb the radiation released from the Earth’s surface.
[B] Clouds reflect back the Earth’s radiation.
[C] The Earth’s surface would have low temperature on cloudy nights.
[D] Clouds deflect the blowing wind to ground level.

PYQs: Q4
2019
Answer- B
Because on a cloudy night, the clouds send the heat back to the ground so the ground
never gets cold enough for the dew to be formed.
Dew drops are formed due to condensation of water vapours. Air around us contains
water vapours which we call moisture or humidity. Hot air contains more moisture as
compared to cold air.
During the night when the hot air comes into contact with some cold surface due to the
reflection of earth radiation by clouds, water vapour present in it condenses on the cold
surface in the form of droplets. These tiny drops of water are called dew drops.

PYQs: Q5
2018
Which of the following statements best describes “carbon fertilization”?
a) Increased plant growth due to increased concentration of carbon dioxide in the
atmosphere
b) Increased temperature of Earth due to increased concentration of carbon dioxide in
the atmosphere
c) Increased acidity of oceans as a result of increased concentration of carbon dioxide
in the atmosphere
d) Adaptation of all living beings on Earth to the climate change brought about by the
increased concentration of carbon dioxide in the atmosphere

PYQs: Q5
Answer: A
● The carbon dioxide fertilization or carbon fertilisation is not only the cause of
plant growth but also contributes the greening effect.
● It is the phenomena that the increase of carbon dioxide in the atmosphere
increases the rate of photosynthesis in plants.

PYQs : Q6
2019
Consider the following:
1. Carbon monoxide
2. Methane
3. Ozone
4. Sulphur dioxide
Which of the above are released into the atmosphere due to the burning of
crop/biomass residue?
a) 1 and 2 only
b) 2, 3 and 4 only
c) 1 and 4 only
d) 1, 2, 3 and 4

PYQs Q6
Answer:
● O3 is not released directly. It is a secondary pollutant.
● Burning of biomass releases CO, CH4 and SO2.

PYQs: Q7
2011
The increasing amount of carbon dioxide in the air is slowly raising the temperature of
the atmosphere, because it absorbs
a) the water vapour of the air and retains its heat.
b) the ultraviolet part of the solar radiation.
c) all the solar radiations.
d) the infrared part of the solar radiation

PYQs: Q7
Answer: D
● Among GHGs, only water vapour can absorb both incoming (UV) and outgoing
(infrared) radiation.

PYQs: Q8
2011
Consider the following statements: Chlorofluorocarbons, known as ozone depleting
substances, are used
1. in the production of plastic foams
2. in the production of tubeless tyres
3. in cleaning certain electronic components
4. as pressurising agents in aerosol cans
Which of the statements given above is/are correct?
a. 1, 2 and 3 only
b. 4 only
c. 1, 3 and 4 only
d. 1, 2, 3 and 4

PYQs: Q8
2011
Answer: c)
Explanation:
• CFCs were used as refrigerants, pressurising agents (aerosol cans) & for cleaning
electronic equipment.

PYQs: Q9
2011
The formation of ozone hole in the Antarctic region has been a cause of concern. What
is the reason for the formation of this hole?
a)Presence of prominent tropospheric turbulence; and inflow of chlorofluorocarbons
b)Presence of prominent polar front and stratospheric clouds; and inflow of
chlorofluorocarbons.
c) Absence of polar front and stratospheric clouds; and inflow of methane and
chlorofluorocarbons.
d) Increased temperature at polar region due to global warming

PYQs: Q9
2011
Answer: B)
During the winter, temperatures inside the Antarctic polar vortex fall so low that water
vapour and several other types of molecules in the stratosphere condense into
extremely small icy particles. These icy particles, in turn, make up polar stratospheric
clouds (PSCs). When the sun sets in the Antarctic around the end of March each year,
its disappearance marks the beginning of a long, dark winter. Once the last rays of
sunlight have faded away, temperatures on land and in the air fall very quickly.
In the stratosphere, high-altitude winds that create the polar vortex begin to blow
around the continent. Isolated from warmer air outside the vortex, the air inside gets
colder and colder. Eventually, it is cold enough for PSCs to form.

PYQs: Q10
2011
The increasing amount of carbon dioxide in the air is slowly raising the temperature
of the atmosphere, because it absorbs
a) the water vapour of the air and retains its heat.
b) the ultraviolet part of the solar radiation.
c) all the solar radiations.
d) the infrared part of the solar radiation

PYQs: Q10
2011
Answer: d) the infrared part of the solar radiation (outgoing radiation).
Explanation:
• Among GHGs, only water vapour can absorb both incoming (UV) and outgoing
(infrared) radiation.

Lecture 8 - Climate Change and environement

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