Energy Balance lecture 4................................ppt

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ENVIROMENTAL ENERGY
RESOURCES
INSTRUCTOR
DR. M. MAZUNGA 11st DECEMBER 2019

LECTURE CONTENT
 Radiation from the sun
 Earth energy balance
 Radiative forcings
 Changes of the earth energy balance
 Manmade climate forcings
 Particulate matter (PM)
 Greenhouse effect
 Climate change and global warming
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“Our civilization runs by burning the remains of humble creatures who inhabited the Earth hundreds of
millions of years before the first humans…”
- Carl Sagan
 Earth's Energy balance
describes how the incoming
energy from the sun is used
and returned to space.
 If incoming and outgoing
energy are in balance, the
earth's temperature remains
constant

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Energy from the sun radiates through
space as electromagnetic wave.
The amount of solar radiation received
by the earth is ~340 W/m² every year
 This total amount of energy received at
the top of the earth's is measured in
Watts and is given by the solar constant
times the cross-sectional area of the
earth.

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 Received radiation is unevenly
distributed over the earth, because
the Sun heats equatorial regions
more than polar regions.
 Areas near the equator receive
more sunlight
 Sunlight received near poles is
not as strong as at the equator

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Tilt of Earth Causes Seasons
 Uneven heating of Earth is why we
have seasons
 Always warm at equator because sun is
nearly directly overhead
 Big variation in temps at poles because
angle of sunlight varies greatly over the
year
 These variations in heating drive
Earth’s climate and weather

 Different parts of Earth’s surface receive
different amounts of sunlight.
 The Sun’s rays strike Earth’s surface
most directly at the Equator. This focuses
the rays on a small area.
 Near the poles, the Sun’s rays strike the
surface at a slant. This spreads the rays
over a wide area.
 The more focused the rays are, the more
energy an area receives, and the warmer
it is. 7

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Overheating?
 If Earth is receiving so much
solar energy, why aren’t we
heating up like an oven
 Because there is a balance
between incoming solar heat
and outgoing solar heat.

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There’s a Balance!
Some solar radiation is
reflected/absorbed by atmosphere
before it reaches Earth.
Solar radiation (short wavelength)
warms the earth. Earth radiates
some of that energy (long
wavelength) back towards space.
Incoming energy must equal
outgoing energy to keep things in
balance.

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Atmosphere is absorbing Radiation
 If the radiation emitted by Earth
just escaped back into space,
Earth’s surface would be very,
very COLD!
The atmosphere is absorbing
some of that radiation and keeping
Earth comfortably warm. This is will
be discussed in the Greenhouse Effect.

 Incoming solar radiation is short wave
radiation, which is visible light and
ultraviolet. Shortwave radiation contains a lot
of energy than longwave radiation.
 Longwave radiation is usually defined as
outgoing infrared energy leaving the planet.
 Heat energy is transported to the atmosphere,
via evaporation, surface radiation,
conduction/convection.

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Earth's energy budget
 Earth's energy budget accounts
for the balance between the
energy that Earth receives from
the Sun and the energy the Earth
radiates back into outer space.
 Incoming solar radiation 100%
• Absorbed by atm. And clouds 19%
• Absorbed by the earth’s surface 51%
• Reflected by atmosphere 6%
• Reflected by clouds 20%
• Reflected from surface 4% Sometimes called “The energy cycle of the Earth”

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If the incoming energy flux is not equal to the
outgoing energy flux, net heat is added to or lost
by the earth
 On a global scale, the atmosphere's circulation
and weather is an attempt to balance differences
in solar energy that the earth receives across the
globe.
 Currents in wind and ocean water carry energy from the tropics toward the
poles to help balance out the energy differences across the globe.
A change in the incident radiated portion of the energy budget is referred to
as a radiative forcing.

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 Radiative forcing is the difference between insolation (sunlight)
absorbed by the Earth and energy radiated back to space.
 Changes to Earth's radiative equilibrium, that cause temperatures to rise or
fall over certain period are called climate forcing.
 Positive radiative forcing means Earth receives more incoming energy from
sunlight than it radiates to space. This net gain of energy will cause warming.
 Negative radiative forcing means that Earth loses more energy to space
than it receives from the sun. This net gain of energy will cause cooling.

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Earth Albedo
Albedo is a measure of how much light that hits a surface is reflected without
being absorbed.
 Something that appears white reflects most of the light that hits it and has
a high albedo, while something that looks dark absorbs most of the light
that hits it, indicating a low albedo.
 An increase in global temperature causes
snow and ice to melt again, which decreases
the extend to which they cover the surface
which then decrease earth’s albedo.
This decrease in earth albedo means more energy is absorbed which cause
further warming and in turn causes more melting.
 Black carbon also causes ice and snow to
melt and causes global warming

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 The balance between absorbed and radiated energy determines the
average global temperature.
 The radiation balance is altered by
several factors such as;
 The intensity of solar energy
 Reflectivity of clouds or gases
 Absorption by various greenhouse
gases or surfaces
 Heat emission by various materials.
 Any such alteration is a radiative forcing and changes the balance.

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Climate forcings are different factors that affect the Earth's climate. These "forcings"
drive or "force" the climate system to change.
Natural climate forcings are
 Changes in the Sun’s brightness
 Variations in Earth’s orbit and tilt
 Large volcanic eruptions
– Add particles to atmosphere
Manmade climate forcings are
 Emission of Particulate Matter
– Changes how radiation reflected/absorbed
 Land use change (deforestation)
– Changes how radiation reflected/absorbed
 Emission of greenhouse gases
 Injection of Chemical Pollutant

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Manmade climate forcings
These manmade climate forcing causes climate changes;
 Particle pollution
Particle pollution, also called particulate matter or PM, small particle of
solids, liquid droplets and aerosols floating in the air.
Particles come in a wide range of sizes.
1. Particles less than or equal to 10 micrometers in diameter are so small that
they can get into the lungs
2. Coarse dust particles (PM10) are 2.5 to 10 micrometers in diameter.
3. Fine particles (PM2.5) are 2.5 micrometers in diameter can only be seen by
electron microscope.

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Particulate matter originates from many sources, among
which are:
 Combustion (e.g. coal dust, fly ash, carbon, soot)
 Automobile exhaust (especially diesel)
 Windblown dust (fugitive dust) from roadways,
fields, soil erosion and construction sites
 Detonation of nuclear weapons of megaton size
Sources of Particle Pollution
Components of particulate matter
Major components of particulate matter are
 Geological material
 Methane
 Ground level ozone
 Nitrate
 Ammonium,
 Sodium chloride,
 Sulfate
 Black carbon.

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The majority of energy for industry, domestic use, and transport is provided
by fossil fuel combustion.
Energy use and Particulate Matter
 Combustion of fossil fuels releases a variety of pollutants into the atmosphere,
sulfur oxides (SO2 and SO3), nitrogen oxides (NO and NO2), carbon monoxide
(CO) and particulate matter (PM).
 Fumes from diesel engines contain up to 100 times more particulate matter
than ordinary gasoline engines.
 The particulate matter is so tiny that any filtering device in our own respiratory
system does not catch it.
 The matter is inhaled in great quantities deep into the lungs, right into the
alveoli

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Health Effect of Particle Pollution
Particle pollution exposure to a variety
of health issues, including:
 Irritation of the eyes, nose and throat
 Coughing, chest tightness and
shortness of breath
 Reduced lung function
 Irregular heartbeat
 Asthma attacks
 Heart attacks
 Premature death in people with heart
or lung disease
Particle pollution can:
 Increase acidity in water bodies or change the flow of nutrients
 Reduce visibility (haze)
 Deplete the soil and damage forests and crops

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Particulate matter and climate change
Particulate matter can impact climate change, conversely Climate change can
impact particulate matter.
Particulate matter can impact climate change by affecting the amount of incoming
light that is reflected or absorbed by the atmosphere, with some others PM warming
and others cooling the earth.
 Burning fuel with CO2 emissions
may reduce the ozone content and
altering cloud cover and of general
changes in net radiation reflected
and absorbed by the earth.
Black carbon and methane are
among the top contributor of global
warming after CO2.
Black carbon, originating from
domestic heating or particles emitted by
traffic, either directly from the exhaust
or by wear of tires or brakes.

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The Greenhouse Effect
The greenhouse effect is a natural process that keeps
the planet's climate warm enough to support life.
It is named for the effect that keeps greenhouses
warm enough to support plants.
 When sunlight passes through the glass windows
of the greenhouse, some of it is reflected by the
ground and some is absorbed and later released in
the form of heat waves.
 The reflected energy and heat waves are trapped
by the glass, warming the greenhouse.

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Instead of glass, our atmosphere contains greenhouse gases such as carbon dioxide
and water vapor that trap some of the energy from the sun.
 Without them, the Earth would be too cold to support life.
 Greenhouse effect is thus the natural
phenomena on earth.
This effect is now intensified by the
emission of greenhouse gases into the
atmosphere due to human activities
leading to the global warming
The Earth Greenhouse Effect

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Step 1: Solar radiation reaches the Earth’s
atmosphere – some of this is reflected back
into space.
Step 2: The rest of the sun’s energy is
absorbed by the land and the oceans, heating
the Earth.
Step 3: Heat radiates from Earth towards
space.
Step 5: Human activities such as burning fossil fuels, agriculture and land clearing are
increasing the amount of greenhouse gases released into the atmosphere.
Step 6: This is trapping extra heat, and causing the Earth’s temperature to rise.
Step 4: Some of this heat is trapped by greenhouse gases in the atmosphere, keeping the Earth
warm enough to sustain life.
Steps for greenhouse effect

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The Greenhouse Gases
The greenhouse gases
include
 Water vapor,
 CO2,
 Methane,
 Nitrous oxide,
 Ozone
 Chlorofluorocarbons
(CFCs) (halogenated
compound)

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Enhanced Green House Effect
Enhanced greenhouse effect is
caused by human activities like
 Uncontrolled burning of
fossil fuels (coal, oil and
natural gas),
 Agriculture and
 Land clearing.
 Enhanced Greenhouse effect refers to increase in the earth’s temperature due
to increase in concentration of greenhouse gases.

 Simply refers to the increase in overall
temperature of the earth.
The average temperature of the earth’s
surface has increased by 1.6×2 degree
Fahrenheit since 19th century
 The primary cause of global warming is
1. Burning fossil fuels
2. Deforestation
3. Farming (Livestock create methane gas
which is also a greenhouse gas)
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Global warming is the effect of the greenhouse gases

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Climate Change
Climate is the average weather conditions that persist over multiple decades
or longer. Weather can change in minutes or hours.
Climate change refers to the change observed over a time period of decades
to centuries or longer.
 Climate change encompasses both increases and decreases in temperature
as well as shifts in precipitation, changing risks of certain types of severe
weather events, and changes to other features of the climate system.
 Climate change affects all aspects of life
 It is the effect of the global warming

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Some effects of the global warming are as follows
Impacts due to weather events
 Global warming results to some extreme weather events, such as extreme precipitation,
flooding, droughts, and storms
Food and nutrition
 Extreme weather events such as extreme temperature drought, unpredicted rainfall, etc
has direct effect on the food productivity
 Availability of safe food and drinking water is affected
 Climate change increases the risk of illness through increasing temperature, more frequent
heavy rains and runoff, and the effects of storms.
 People at the coastal area, involved in fishery, horticulture are directly are affected financially

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Relation between Greenhouse Gases, Global Warming and Climate Change:
 Greenhouse gases are increased tremendously by the human actions. These
gases in the atmospheres creates the imbalance in the heat absorbing and
reflecting process.
 More heat are absorbed which result in overall increase in the temperature of
the planet known as the global warming
 Global warming overall alters the pattern of the rain, snowfall, temperature
change and then results in overall change in the climate pattern
 These three are interconnected. They have cause to effect kind of relationship
 Greenhouse effect is the cause and the climate change is the effect

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Mitigation strategies for reducing global warming
 Reduce the use of substances or
technologies that emits the greenhouse gases
 Eco-friendly approach
 Save and use clean energy
 Encourage the afforestation
 Set and adapt the climate policy
 Aware the people using medias and raise the
issue of the global warming
 Multi-approach and cooperation among the
nations to address the issue of the global
warming

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END OF LECTURE #4
THANK YOU

Energy Balance lecture 4................................ppt

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Energy Balance lecture 4................................ppt