UNIT 4
(TEXTBOOK UNIT 7)
PREPARED BY:
MS. SHEULI MITRA,
FACULTY, DEPT OF ARCHITECTURE
ENVIRONMENTAL CONCERNS
GLOBAL WARMING
Definition

Global warming is the phenomenon of increase in the
average temperature of the air near the Earth's
surface and oceans since the mid-20th century and its
projected continuation.
GLOBAL WARMING
GLOBAL WARMING
Key Facts
 Global
surface temperature increased 0.74 ±
0.18 °C (1.33 ± 0.32 °F) – around a centigrade,
during the last century. The average worldwide nearsurface temperature is about 14 °C.
 An increase of around 1°C
in the average
temperature near the earth’s surface makes it warmer
than it was in the past 1000 years, at least.
 In 1995
IPCC (International Panel on Climate
Change) predicted that global surface temperature
will probably rise a further 3.5 – 10 °C during the
twenty-first century, if present trends continue.
GLOBAL WARMING
Main Causes
 Fossil fuel burning and deforestation are responsible for
most of the observed temperature increase since the
middle of the 20th century, as they cause an increase in
concentration of green house gases in the atmosphere,
which in turn trap heat.
Other causes:
 Solar radiation variations, volcanic eruptions were some
causes of temperature increase in the pre-industrial era,
but do not account for the extent of continuous
temperature change resulting in global warming today.
GLOBAL WARMING
Green-house effect:
 The greenhouse effect is the heating of the surface of
earth (or any other planet) due to the presence of an
atmosphere containing gases that absorb and emit
infrared radiation.
 Incident Solar radiation is largely in the visible spectrum
and has small proportions of Ultra violet and infra Red
rays and passes through the atmosphere surrounding the
earth.
 The earth absorbs about 50% of solar radiation but emits
it back partially as infrared radiation (heat)
 The infrared radiations emitted by the earth are absorbed
by some gases in the atmosphere and re-emitted back as
heat in all directions including towards the earth’s surface.
GLOBAL WARMING
Green-house effect:
 Without an atmosphere and the greenhouse effect it
creates, the Earth's average surface temperature of 14 °C
would be as low as −18 °C and life would not be
supported on the surface of the earth.
 Green house effect in the context of Global warming, is
the phenomenon of a recent increase in warming of the
Earth's lower atmosphere as evidenced by the abnormal
rise in global mean temperature.
 This is believed to be the result of an "enhanced
greenhouse effect" mainly due to human-produced
increased concentrations of greenhouse gases in the
atmosphere.
GLOBAL WARMING
GLOBAL WARMING
Green-house effect:
Which gases mainly cause the green house effect?

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Water vapor, which contributes 36–70%
Carbon dioxide, which contributes 9–26%
Methane, which contributes 4–9%
Ozone, which contributes 3–7%
The major non-gas contributor to the Earth's
greenhouse effect, clouds, also absorb and emit
infrared radiation.
GLOBAL WARMING
What are the Causes?
 Increase in CO2 in the atmosphere due to increase in
human activities producing CO2 like burning of fossil fuel
for generation of electricity, and other industrial processes.
 Cutting of trees for urbanization and deforestation have
resulted in more CO2 in the atmosphere.
 Increase in amounts of Methane released from marshes
and bogs and animal excreta.
 The 2005 levels of in the atmosphere (375 ppm) are
higher than the highest recorded in the last 800,000
years (in the range of 270 ppm in post industrial era)
GLOBAL WARMING
Adverse Effects of global warming:
An increasing global average temperature causing multiple
secondary effects which in turn trigger a chain of reactions:
 Changes in patterns of precipitation
 Increased extreme weather events


altered patterns of agriculture,

the expansion of the range of tropical diseases,
Melting of ice caps and rising sea levels


Threat to coastal settlements
Change in the pH balance of sea water, affecting
marine life
GLOBAL WARMING
Responses to global warming:

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
Adaptation - dealing with the effects of global
warming,
Mitigation - reducing carbon emissions,
Geo-engineering- directly intervening to modify the
climate
GLOBAL WARMING
Adaptation to Global warming
 Initiatives and measures to reduce the vulnerability of
natural and human systems against actual or
expected climate change effects.
 Construction of flood defenses
 Abandoning of settlements affected by rising sea
levels
 Water conservation
 Adjustments to agricultural yield abnormalities
 Protection of threatened species
GLOBAL WARMING
Mitigation of Global warming
 Global average temperatures would continue to rise if
human activities producing increased green house gases
are not controlled.
 Several measures are being taken across the globe to
reduce green house emissions – individual, community
and regional measures.
 International treaties to implement reduction in emissions:


Rio de Janeiro Earth Summit, 1992
Kyoto Protocol
GLOBAL WARMING
International treaties:
Rio de Janeiro “Earth Summit” 1992
 The United Nations Framework Convention on Climate
Change (UNFCCC) is an international treaty agreed at
the Rio de Janeiro "Earth Summit" in 1992.
 It acknowledges the ‘climate justice principle’ that
developed countries alone should take initial
responsibility for the reduction of greenhouse gas
emissions.
 These countries are known as Annex 1 countries
GLOBAL WARMING
International treaties:
Kyoto Protocol
 Negotiated in 1997, it postulates that Annex 1 countries
are subject to legally binding targets of reduction of
green house emissions.
 The Kyoto Protocol was a supplement to the UNFCC and
was eventually ratified in February 2005.
 Kyoto target: the Annex 1 countries should achieve in
aggregate a 5% reduction in their green house gas
emissions of 1990 by the year 2012.
GLOBAL WARMING
Geo-engineering
 Geo-engineering is the planned modification of the
earth's natural environment on a large scale to suit
human needs.


Solar radiation management
Removal of green house gases from the atmosphere
Large scale geo-engineering projects have not yet
been implemented but are in the research stage.
ACID RAIN



Definition
Acid rain is rain or any other form of precipitation that is
unusually acidic (Ph value significantly less than 7)
When chemicals from burned fossil fuel mix with moisture in
the atmosphere and fall to the ground as rain, snow, sleet,
etc., acid rain occurs.
‘Acid deposition’ is a more precise name than acid rain
because acid can fall to the ground as not only rain but any
form of precipitation and is called ‘wet deposition’
It can also combine with dry particulate matter and fall to
the ground and is then called ‘dry deposition’.
ACID RAIN
ACID RAIN
Composition of Acid Rain


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“Clean” or unpolluted rain has a slightly acidic pH of
about 5.2, because carbon dioxide and water in the
air react together to form carbonic acid (H2CO3), a
weak acid (pH 5.6 in distilled water)
Distilled water, which contains no carbon dioxide, has
a neutral pH of 7.
Acid rain has Ph between 2 and 5.5 and has
Sulphuric acid and Nitric acid content
ACID RAIN
Acid rain in Europe-1993, Hydrogen ion print in USA 1997
ACID RAIN
Causes of Acid Rain
 Acid rain forms in the atmosphere from chemicals
created by the burning of fossil fuels.
 When coal and oil are burned they release sulfur
dioxide (SO2) and two nitric oxides, nitric oxide (NO)
and nitrogen dioxide (NO2) designated by the
symbol NOX, which are the main components of smoke
emitted from factories and vehicle exhaust pipes.
 The sulfur dioxide and nitrogen oxides emitted, react
with other chemicals in the air, water vapor, and
sunlight to produce sulfuric and nitric acids, the acids
in acid rain. The more sulfuric and nitric acids present,
the higher the acidity of the rain.
ACID RAIN
Acid rain causing emissions from different sources in US
ACID RAIN
Adverse Effects of Acid Rain
On Surface waters and aquatic animals:
 Both the lower pH and higher aluminum concentrations
in surface water that occur as a result of acid rain can
cause damage to fish and other aquatic animals.
 At pHs lower than 5 most fish eggs can not hatch and
lower pHs can kill adult fish also.
 As lakes and rivers become permanently acidic
 Aquatic biodiversity is reduced as Acid rain has
already eliminated some insect life and fish species
ACID RAIN
Adverse Effects of Acid Rain
On Soils:
 Soil biology and chemistry can be seriously damaged
by acid rain.
 Some microbes are unable to tolerate changes to low
pHs and are killed. The enzymes of these microbes
are denatured (changed in shape so they no longer
function) by the acid.
 The hydronium ions of acid rain also mobilize toxins
such as aluminium, and leach away essential nutrients
and minerals such as magnesium.
ACID RAIN
Adverse Effects of Acid Rain
 On Forests and other vegetation
 High altitude forests are affected strongly as they
are often surrounded by clouds and fog which are
more acidic than rain.
 Other plants are also damaged by acid rain.
ACID RAIN
Adverse Effects of Acid Rain
On Human health
 Fine particles, a large fraction of which are formed
from the same gases as acid rain (sulfur dioxide and
nitrogen dioxide), have been shown to cause illness
and premature deaths such as cancer and other
diseases.
Other effects:
 The acid in rain corrodes the stones and cement in
buildings. Some buildings have been permanently
weakened beyond repair.
ACID RAIN
Preventive measures
Technical solutions
 Use of Fuel gas desulfurization (FGD) in many coalburning power plants to remove sulfur-containing gases
from their stack gases.
 Lime or limestone in slurry form is also injected into the
tower to mix with the stack gases and combine with the
sulfur dioxide present, to form calcium sulphate , which
may be even sold as commercial gypsum
 Automobile emissions control reduces emissions of
nitrogen oxides from motor vehicles.
ACID RAIN
International Treaties
Sulphur Emissions Reduction Protocol under the
Convention on Long-Range Transboundary Air Pollution
(CLRTAP).
It is intended to protect the human environment against air
pollution and to gradually reduce and prevent air pollution,
including long-range transboundary air pollution.
The convention opened for signature on 1979 and entered
into force on 1983
ACID RAIN
International Treaties
Sulphur Emissions Reduction Protocol under the
Convention on Long-Range Transboundary Air Pollution
(CLRTAP).
 The aim of the Convention is that countries shall endeavour to
limit and, as far as possible, gradually reduce and prevent
air pollution including long-range transboundary air
pollution.
 Countries develop policies and strategies to combat the
discharge of air pollutants through exchanges of information,
consultation, research and monitoring.
OZONE DEPLETION
The Ozone Layer
 The ozone layer is a layer in Earth's atmosphere which
contains relatively high concentrations of ozone (O3).
 About 90% of the ozone in our atmosphere is contained in
the stratosphere, mainly in its lower portion, from
approximately 10 km to 50 km above Earth, though the
thickness varies seasonally and geographically
 The significance of the Ozone layer is that this layer absorbs
93-99% of the sun's high frequency ultraviolet light, which is
potentially damaging to life on earth.
OZONE DEPLETION

Ozone layer in atmosphere
OZONE DEPLETION
The Ozone Layer
 Ozone concentrations are greatest between about 20 and
40 km, - about 2 to 8 parts per million.
 The Dobson Unit is the unit of measurement of the amount of
Ozone in an air column overhead.
 Ozone in the earth's stratosphere is created by ultraviolet
light striking oxygen molecules (O2), splitting them into
individual oxygen atoms (atomic oxygen); the atomic oxygen
then combines with unbroken O2 to create ozone, O3. The
ozone molecule is also unstable and when ultraviolet light hits
ozone it again splits into a molecule of O2 and an atom of
OZONE DEPLETION
What is Ozone Depletion?
Ozone depletion describes two distinct, but related
phenomena:
 A slow, steady decline of about 4% per decade in the total
volume of ozone in Earth's stratosphere (ozone layer) since
the late 1970s
 A much larger, but seasonal, decrease in stratospheric ozone
over Earth's polar regions during the same period. This
phenomenon is commonly referred to as the ‘ozone hole’.
 There is also Tropospheric ozone depletion, which occurs
near the surface of the earth in polar regions during spring.
OZONE DEPLETION
Arctic Ozone depletion
Ozone Hole
Seasonal Variations in Arctic
Ozone Concentration
OZONE DEPLETION
Causes of Ozone Depletion
 The catalytic destruction of ozone is caused by atomic
chlorine and bromine.
 The main source of these halogen atoms in the stratosphere is
from chlorofluorocarbon (CFC) compounds, commonly called
Freons, and Bromofluorocarbon compounds known as Halons.
 These compounds are transported into the stratosphere after
being emitted at the surface and release free radicals of
chlorine and bromine on interacting with sunlight.
 Both mid altitude and polar ozone depletion mechanisms
increased with increase in emissions of CFCs and halons.
OZONE DEPLETION
Total Ozone in Atmosphere CFC Emissions in Atmosphere
OZONE DEPLETION
Correlating chlorine concentrations in Industry products with their ozone depleting potential
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The HCFCs and HFCs are considered environmentally superior to CFCs because they are
largely destroyed in the lowest region of the atmosphere.
The HFCs do not contain chlorine and have no potential to deplete ozone.
HCFCs, however, do contain chlorine, but only a small percentage of that chlorine can affect
the ozone layer;
Most of the HCFCs released at ground level are destroyed in the lower atmosphere before
they reach the stratospheric ozone layer.
OZONE DEPLETION
The Magnitude of the threat:
 Once in the stratosphere, every chlorine atom can destroy up
to 100 000 ozone molecules.
 The lifetime of some of these ozone depleting substances is
very long, and they may continue to deplete the ozone layer
long after their use has been phased out.

Aircraft emissions of nitrogen oxides and water vapour add
to this depletion effect by creating ice crystals that serve as
a base for ozone destroying reactions.
OZONE DEPLETION
Effect of Ozone Depletion
 Since the ozone layer prevents most harmful UVB
wavelengths (270–315 nm) of ultraviolet light (UV light)
from passing through the Earth's atmosphere, decreases in
ozone increases the penetration of UV rays through the
atmosphere significantly.
 A one percent loss of ozone leads to a two percent increase
in UV radiation.
 Disturbance of the thermal structure of the atmosphere may
result, probably causing changes in atmospheric circulation;
 Efforts to tackle ozone depletion may result in increased
OZONE DEPLETION
Harmful Effects of Exposure to UV radiation
 Continuous exposure to UV radiation affects humans,
animals, and can lead to:
 skin problems (ageing, cancer),
 depression of the immune system,
 and corneal cataracts (an eye disease that often leads to
blindness).
 Damage to plant life
 Increased UV radiation may also lead to a massive die-off
of photo plankton in the ocean (a CO2 "sink") and therefore
further increase atmospheric CO2 enhancing global warming
OZONE DEPLETION
Montreal Protocol
 The Montreal Protocol on Substances That Deplete the
Ozone Layer is an international treaty designed to protect
the ozone layer by phasing out the production of a number
of substances believed to be responsible for ozone
depletion. The treaty was opened for signature in 1987 and
entered into force in 1989
 Since then it has undergone seven revisions, the last being in
1999.
 It is widely accepted that if the international agreement is
adhered to, the ozone layer is expected to recover by 2050.
OZONE DEPLETION
Correlating chlorine concentrations in Industry products with their
ozone depleting potential

An index called the Ozone Depletion Potential (ODP) has been adopted for
regulatory purposes under the Montreal Protocol. The ODP of a compound
is an estimate of the total ozone depletion due to 1 Kg of the compound
divided by the total ozone depletion due to 1 Kg of CFC-11.