18CEO406T - GLOBAL WARMING AND CLIMATE CHANGE

UNIT – 1 [S1 to S3]

S1 : Introduction to earth system – Hydrosphere, lithosphere,

cryosphere, atmosphere and biosphere

Introduction to earth Climate

The climate of a place may be defined as a "composite" of the long-term

prevailing weather that occurs at that location. In a sense, climate is
"average weather". Climate can be measured quantitatively by calculating
the long term averages of different climate elements such as temperature
and rainfall. Extremes in the weather however, also help us define the
climate of a particular area.

We can study climate on a range of geographical scales.

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 1. Local climate
2. Regional climate
3. Global climate

Local climate:

At the smallest scale, local climates influence areas maybe only a few miles
or tens of miles across. Examples of local climatic phenomena include sea
breezes and urban heating.

Regional climate:

At larger scales, regional climates provide a picture of particular patterns of

weather within individual countries, or within climate zones that exist at
different latitudes on the Earth. Climate zones include tropical,
subtropical, desert, Savannah, temperate and polar climates. Different
climate zones reveal variable patterns of temperature and rainfall

Global climate

The term "global climate" is used to refer to the general state of the world's
climate. Whilst different climate zones may be identified, with different types
of weather in different parts of the world, climatologists sometimes like to
study the general climate of the whole Earth, for example when investigating
evidence for climate change.

The simplest means of assessing the state of the global climate is to

measure the global average temperature of the Earth's surface and
atmosphere in contact with it

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Climate system

The climate system is a complex, interactive system consisting of the

atmosphere, land surface, snow and ice, oceans and other bodies of water,
and living things. The atmospheric component of the climate system most
obviously characterises climate; climate is often defined as 'average
weather'.

The key to understanding global climate change is to first understand what

global climate is, and how it operates. At the planetary scale, the global
climate is regulated by how much energy the Earth receives from the Sun.
However, the global climate is also affected by other flows of energy which
take place within the climate system itself. This global climate system is
made up of the atmosphere, the oceans, the ice sheets (cryosphere), living
organisms (biosphere) and the soils, sediments and rocks (geosphere),
which all affect, to a greater or less extent, the movement of heat around
the Earth's surface.

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Earth's climate arises from the interaction of five major climate
system components:

1. Atmosphere (air),
2. Hydrosphere (water),
3. Cryosphere (ice and permafrost),
4. Lithosphere (earth's upper rocky layer) and
5. Biosphere (living things)

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Atmosphere:

The atmosphere plays a crucial role in the regulation of Earth's climate. The
atmosphere is a mixture of different gases and aerosols (suspended liquid
and solid particles) collectively known as air. Air consists mostly of nitrogen
(78%) and oxygen (21%). However, despite their relative scarcity, the so-
called greenhouse gases, including carbon dioxide and methane, have a
dramatic effect on the amount of energy that is stored within the
atmosphere, and consequently the Earth's climate. These greenhouse gases
trap heat within the lower atmosphere that is trying to escape to space, and
in doing so, make the surface of the Earth hotter. This heat trapping is called
the natural greenhouse effect, and keeps the Earth 33°C warmer than it
would otherwise be. In the last 200 years, man-made emissions of
greenhouse gases have enhanced the natural greenhouse effect, which may
be causing global warming.

The atmosphere however, does not operate as an isolated system. Flows of

energy take place between the atmosphere and the other parts of the
climate system, most significantly the world's oceans. For example, ocean
currents move heat from warm equatorial latitudes to colder polar latitudes.
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Heat is also transferred via moisture. Water evaporating from the surface of
the oceans stores heat which is subsequently released when the vapour
condenses to form clouds and rain. The significance of the oceans is that
they store a much greater quantity of heat than the atmosphere. The top
200 metres of the world's oceans store 30 times as much heat as the
atmosphere. Therefore, flows of energy between the oceans and the
atmosphere can have dramatic effects on the global climate.

Fig: Earth climate (Atmosphere)

Cryosphere:

The world's ice sheets, glaciers and sea ice, collectively known as the
cryosphere, have a significant impact on the Earth's climate. The cryosphere
includes Antarctica, the Arctic Ocean, Greenland, Northern Canada, Northern
Siberia and most of the high mountain ranges throughout the world, where
sub-zero temperatures persist throughout the year. Snow and ice, being
white, reflect a lot of sunlight, instead of absorbing it. Without the

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cryosphere, more energy would be absorbed at the Earth's surface rather
than reflected, and consequently the temperature of the atmosphere would
be much higher.

Biosphere:

All land plants make food from the photosynthesis of carbon dioxide and
water in the presence of sunlight. Through this utilisation of carbon dioxide
in the atmosphere, plants have the ability to regulate the global climate. In
the oceans, microscopic plankton utilise carbon dioxide dissolved in seawater
for photosynthesis and the manufacture of their tiny carbonate shells. The
oceans replace the utilised carbon dioxide by "sucking" down the gas from
the atmosphere.

Fig: Earth climate (Biosphere)

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LITHOSPHERE
It is believed the lithosphere evolved about 4.6 billion years ago. The
lithosphere refers to the solid, rocky crust that covers the entire planet. This
solid, rocky crust is composed of a number of different rocks that have been
hrouped into three categories based on how they are formed. These three
groups include:

 Metamorphic rocks – Metamorphic rocks are formed by heat and / or

pressure from pre-existing rocks.
 Igneous rocks – igneous rocks are formed by the cooling of hot molten
rock also known as magma. When the hot magma cools it begins to
harden meaning once it had fully cooled it create what is known to be
an igneous rock.
 Sedimentary rocks – sedimentary rocks are formed from pre-existing
rocks. When rocks erode and mix with other dirt, clay and particles
then settle together the mix together to form a sedimentary rock.

The lithosphere includes a various number of different landforms such

as mountains, valleys, rocks, minerals and soil. The lithosphere is
constantly changing due to forces and pressures such as the sun,
wind, ice, water and chemical changes.

The earth’s surface is composed into two types of lithospheres. There

are known as the oceanic and continental lithospheres.

The oceanic lithosphere includes the uppermost layers of mantle which

is topped with a thin yet heavy oceanic crust. This is where the
hydrosphere and lithosphere meet.

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 The continental lithosphere include the uppermost layers of mantle
which is topped with a thick yet light continental crust. This is where
the atmosphere, biosphere and hydrosphere meet the lithosphere.

HYDROSPHERE -
The hydrosphere refers to the most important resource which I water. The
hydrosphere includes all forms of water in the Earth’s environment. The
forms of water include things such as the ocean, lakes, rivers, snow and
glaciers, water underneath the earth’s surface and even the water vapour
that is found in the atmosphere. The hydrosphere is always in motion as
seen through the movement and flow of water in rivers, streams and the
ocean (beach). Plant and animal organisms rely on the hydrosphere for their
survival as water is essential. The hydrosphere is also home to many plants
and animals and it believed that the hydrosphere covers approximately 70%
of the earth’s surface

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S1 : Earth system-hydrological cycle and carbon cycle

Hydrologic cycle

• Water exists on earth in all three states, liquid, solid and gaseous state
and various degrees of motion. The various aspects of water related to
the earth can be explained in terms of cycle known as hydrologic
cycle.

• Except for deep ground water, the total water supply of earth is in
constant circulation from earth tot atmosphere and back to the earth.

• The earth’ water circulatory system is known as hydrologic cycle. It is

the process of transfer of moisture from atmosphere to earth in the

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 form of precipitation, conveyance of precipitated water by streams and
rivers to oceans and lakes and evaporation of water back to the
atmosphere.

• The group of numerous arcs which represents the different path

through which water in nature circulates and is transformed is known
as hydrological cycle.

• These arcs penetrates into three parts of total earth system,

Atmosphere, Hydrosphere and lithosphere.

• Hydrological cycle can be represented in many different ways in

pictorial or diagrammatic forms.

• The hydrological cycle has no beginning or end as the water in nature

is continuously kept in cyclic motion.

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Thus the hydrologic cycle may expressed by the following equation as

Precipitation [P] = Evaporation [E] + Runoff [R]

Provided adjustment is made for the moisture held in storage at the

beginning and end of the period.

Precipitation [P]

• Precipitation may be defined as fall of moisture from atmosphere

to the earth surface in any form.
• The precipitation reaching the ground surface after meeting the needs
of infiltration and evaporation moves down the natural slope over the
surface and through rivers and streams to reach the oceans.
• Precipitation may be two forms
i. Liquid Precipitation – Rainfall
ii. Frozen Precipitation – Snow, Hail, sleet, freezing rain

Measurement of Precipitation
It can be measured by rain gauge. The rain gauge may be
i) Recording type rain gauge [ Weighing bucket, Tipping bucket, Floating
type]
ii) Non- recording type rain gauge[ Symon’s Raingauge]

Evaporation [E]
• Evaporation from the surfaces of ponds, lakes, reservoirs. ocean
surfaces, etc. and transpiration from surface vegetation i.e., from plant
leaves of cropped land and forests, etc. take place. These vapours rise
to the sky and are condensed at higher altitudes by condensation
nuclei and form clouds, resulting in droplet growth.

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 • It is the process by which water from liquid state passes into vapour
state under the action of sunrays.

• Transpiration is the process of water being lost from the leaves of

plants from their pores.

Thus total evaporation inclusive of transpiration consists of

i. Surface evaporation
ii. Water Surface evaporation [Rivers, oceans]
iii. Evaporation from plants and leaves [Transpiration]
iv. Atmospheric evaporation
A portion of water that reaches the ground enters the earth surface through
infiltration, enhance the moisture content of soil and reach the ground water
body.
Runoff [R]

• Runoff is the portion of precipitation that is not evaporated.

• When moisture falls to the earth surface as precipitation, a part of it is

evaporated from the water surface, soil and vegetation and through
transpiration by plants and remainder precipitation is available as
runoff which ultimately runs to the oceans through surface or sub-
surface streams.

Classification of run off

i. Surface run off

ii. Sub surface runoff
iii. Ground water flow or base flow

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Carbon cycle

The carbon cycle is most easily studied as two interconnected subcycles:

 One dealing with rapid carbon exchange among living organisms.[ Biological carbon
cycle]
 One dealing with long-term cycling of carbon through geologic processes.[ Geological
carbon cycle]

Fig: Carbon cycle

Biological carbon cycle

Carbon enters all food webs, both terrestrial and aquatic, through
autotrophs, or self-feeders. Almost all of these autotrophs are
photosynthesizers, such as plants or algae.
Autotrophs capture carbon dioxide from the air or bicarbonate ions from the
water and use them to make organic compounds such as glucose.

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Heterotrophs, or other-feeders, such as humans, consume the organic
molecules, and the organic carbon is passed through food chains and webs.
Carbon can cycle quickly through this biological pathway, especially in
aquatic ecosystems. Overall, an estimated 1,000 to 100,000 million metric
tons of carbon move through the biological pathway each year.

In the first step, through photosynthesis (the process by which plants

capture the sun's energy and use it to grow), plants take carbon dioxide out
of the atmosphere and release oxygen. The carbon dioxide is converted into
carbon compounds that make up the body of theplant, which are stored in
both the aboveground parts of the plants (shoots and leaves), and the below
ground parts (roots).

In the next step, animals eat the plants, breath in the oxygen, and exhale
carbon dioxide. The carbon dioxide created by animals is then available for
plants to use in photosynthesis. Carbon stored in plants that are not eaten
by animals eventually decomposes after the plants die, and is either
released into the atmosphere or stored in the soil.

Large quantities of carbon can be released to the atmosphere

through geologic processes like volcanic eruptions and other natural
changes that destabilize carbon sinks. For example, increasing temperatures
can cause carbon dioxide to be released from the ocean.

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Geological Process of carbon cycle

The geological pathway of the carbon cycle takes much longer than the
biological pathway described above. In fact, it usually takes millions of years
for carbon to cycle through the geological pathway. Carbon may be stored
for long periods of time in the atmosphere, bodies of liquid water—mostly
oceans— ocean sediment, soil, rocks, fossil fuels, and Earth’s
interior.
The level of carbon dioxide in the atmosphere is influenced by the reservoir
of carbon in the oceans and vice versa. Carbon dioxide from the atmosphere
dissolves in water and reacts with water molecules in the following
reactions:

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S2: Importance of earth system and climate
Earth System Science is a relatively new field of study that focuses on the
operation of the whole Earth, including the atmosphere, hydrosphere,
biosphere, and geosphere. These four spheres can be thought of as four
machines or systems that are connected together to make one larger
machine -- the whole Earth system. Earth System Science is especially
concerned with the interactions between these different spheres and how
these interactions control the global climate. This field of study incorporates
and integrates material from traditional geology, meteorology,
oceanography, ecology, atmospheric chemistry, and other fields.

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In addition to understanding how different parts of the Earth System affect
the global climate, it is important to understand how these different parts
are linked together &emdash; how they are interconnected. The graph below
represents these interconnections in the form of connecting arrows; each
arrow represents some set of processes that operate within one of the
Earth's four "spheres" that influences the "sphere" that the arrow points to

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S3: Atmosphere and its composition, different strata of atmosphere

and temperature profile

Atmosphere and its composition

The earth's atmosphere is a very thin layer wrapped around a very large
planet. The three major constituents of dry air are nitrogen (N2) oxygen
(02) and argon (Ar), which account respectively for 79 percent, 21
percent and 1 percent of the molecules.

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Different strata of atmosphere

Based on temperature, the atmosphere is divided into five layers:

i) Troposphere
ii) Stratosphere
iii) Mesosphere and
iv) Thermosphere
v) Exosphere

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 Fig: Different layers of Atmosphere

i) Troposphere
“Tropos” means change.
This layer gets its name from the weather that is constantly changing
and mixing up the gases, in this part of our atmosphere.This layer is the
closest to Earth's surface.
On average the troposphere extends, from the ground to about 12
kilometers or 7.5 miles high.The troposphere contains, about 75% of all of
the air in the atmosphere, and, almost all of the water vapor, which forms

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clouds and rain. In this layer, air is made up of approximately 78% nitrogen,
21% oxygen, and 1% argon with small amounts of additional gases,
including water vapor and, carbon dioxide.
(ii) Stratosphere
“Strat” means layer.
This layer of our atmosphere has its own set of layers. The boundary
between the stratosphere and the troposphere is called the tropopause. It is
the region where airplanes fly.
The Stratosphere layer, extends from the tropopause to about 50 kilometers
(32 miles) above the Earth’s surface.This layer contains a thin layer of ozone
molecules which forms a protective layer and absorbs harmful ultraviolet
radiation, from the Sun. The high-altitude weather balloons flying into the
stratosphere for monitoring atmospheric conditions and climate research.
(iii) Mesosphere
“Meso” means middle.
This layer is located above the stratosphere and below the
thermosphere. It is the third layer in our atmosphere which is 35 kilometers
(22 miles) thick. The transition boundary which separates the mesosphere,
from the stratosphere is called the stratopause. In the mesosphere fewer air
molecules to absorb incoming electromagnetic radiation from the Sun. Most
meteors burn up in this atmospheric layer.
(iv) Mesosphere
“Thermo” means heat.
This layer has extremely high temperatures, and located above the
mesosphere, and below the exosphere. The boundary between the
mesosphere, and the thermosphere atmospheric regions, is called
Mesopause. It is the coldest part of Earth's atmosphere. The thermosphere,
extends from the mesopause to 700 kilometers (435 miles) above the
surface of the Earth. The thermosphere is the thickest layer, in the
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atmosphere. Only the lightest gases, mostly oxygen, helium, and, hydrogen
are found here. The aurora, and satellites mostly occur in this layer.
(V) EXOSPHERE
“Exo” means outside.
The exosphere, represents the outermost layer of Earth’s atmosphere.
It extends, from the top of the thermosphere to 10,000 kilometers (6,214
miles) above Earth’s surface.
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Temperature profile

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Atmospheric Composition - affects Air Temperature:

Air temperature also changes as altitude increases. The temperature

differences result mainly from the way solar energy is absorbed as it moves
through the atmosphere.Some parts of the atmosphere are warmer because
they contain a high percentage of gases that absorb solar energy. Other
parts of the atmosphere contain less of these gases and are cooler

Heat and Temperture:

Temperature: Average energy of molecules or atoms in a material.

Heat: Total energy of molecules or atoms in a material.
It’s possible to have large amount of heat but low temperatures and high
temperatures but little heat.
The Arctic Ocean has a large amount of heat (because of large mass) even
though the temperature is low. Air in an oven at 500⁰F has high temperature
but little heat.
However if you touch anything solid in the oven you’ll get burned. Same
temperature but much larger amount of heat. The earth’s outermost
atmosphere is extremely “hot” but its heat content is negligible.
It takes time for things to warm up and cool off.

Temperature Scales Absolute Temperature

1) Fahrenheit Kelvin scale uses Celsius degrees and
a) Water Freezes at 32 F starts at absolute zero
b) Water Boils at 212 F
Absolute Zero specify
2) Centigrade or Celsius
a) Water Freezes at 0 C - 273⁰C / - 459⁰F.
b) Water Boils at 100 C
3) Two scales exactly equal at -40

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