This document summarizes the key causes and effects of global warming. It explains that global warming is caused by an increase in greenhouse gases like carbon dioxide, methane, and nitrous oxide that are trapping more heat in the lower atmosphere. As a result, average surface temperatures have risen about 0.6 degrees Celsius over the past century. Some observed impacts include melting glaciers and ice, rising sea levels, and shifts in plant and animal ranges. The document focuses on the greenhouse effect and how certain gases like carbon dioxide, methane, and nitrous oxide released from human activities are enhancing this natural effect and causing the current global warming trend.

1. Done by:-JAHNAVI
Class:-3rd

2. INTRODUCTION
• Global warming is an average increase in the
temperature of the atmosphere near the Earth's
surface and in the troposphere, which can contribute
to changes in global climate patterns.
• The Intergovernmental Panel on Climate Change
(IPCC) reported that the 20th century saw an increase
in global average surface temperature of
approximately 0.6 °C (1.1 °F).
• Rising average temperatures are affecting the
environment. Some observed changes include
shrinking of glaciers, thawing of permafrost, later
freezing and earlier break-up of ice on rivers and lakes,
lengthening of growing seasons, shifts in plant and
animal ranges and earlier flowering of trees

3. CAUSES OF GLOBAL WARMING:
THE GREEN HOUSE EFFECT
 The greenhouse effect is the natural process by which the
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atmosphere traps some of the Sun's energy, warming the Earth
enough to support life.
It is the warming that results when solar radiation is trapped by
the atmosphere; caused by atmospheric gases that allow sunshine
to pass through but absorb heat that is radiated back from the
warmed surface of the earth
Without greenhouse warming the Earth’s average surface
temperature would be around –18°C (0°F) and unable to support
life.
Scientists believe a human-driven increase in "greenhouse gases" is
increasing the effect artificially.
Modern global warming is the result of an increase in magnitude
of the called greenhouse effect, a warming of Earth’s surface and
lower atmosphere caused by the presence of water vapour, carbon
dioxide, methane, and other greenhouse gases

4. GREEN HOUSE EFFECT

5. GREENHOUSE GASES
Greenhouse gases include water vapour, Carbon dioxide,
Methane, Nitrous oxide, Halogenated Fluorocarbons,
Ozone, Perfluorinated carbons, and Hydrofluorocarbons.
Greenhouse gases warm Earth’s surface by increasing the
net downward longwave radiation reaching the surface
Global warming is also caused by an increase in the levels
of these gases brought about by human activity. The
greatest impact on the greenhouse effect has come from
industrialization and increases in the amounts of carbon
dioxide, methane, and nitrous oxide.

6. SOME GREEN HOUSE GASES
WATER VAPOUR
Water vapour is the most important
greenhouse gas, but human activity doesn’t
have much direct impact on its amount in
the atmosphere.
 The primary role of water vapour is not as a
direct agent of radiative forcing but rather as
a climate feedback
Increased evaporation leads to a greater
concentration of water vapour in the lower
atmosphere capable of absorbing longwave
radiation and emitting it downward

7. CARBON DIOXIDE
Carbon dioxide (CO2) is is a colourless, odorless non-
flammable gas and is the most prominent Greenhouse gas
in Earth's atmosphere
Carbon dioxide is used by plants during photosynthesis to
make sugars
It is produced during respiration by plants, and by all
animals, fungi and microorganisms that depend either
directly or indirectly on plants for food
Carbon Dioxide is also produced by burning of fossil fuels
and deforestation

8. Methane (CH ) is the second most
METHANE
important greenhouse gas.
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Methane is a colourless, odorless,
flammable gas
Natural sources of methane include
tropical and northern wetlands, methaneoxidizing bacteria that feed on organic
material consumed by termites, volcanoes,
seepage vents of the seafloor in regions
rich with organic sediment
Methane is also released from rice
paddies, livestock farms and landfill sites

9. NITROUS OXIDES
Nitrous Oxide (N2O) is a colourless non-flammable
gas, with a pleasant, slightly sweet odor.
It is a significant Greenhouse gas
Nitrous oxide is emitted during agricultural and
industrial activities, as well as during combustion of
fossil fuels and solid waste.

10. FLUORINATED GASES
Hydrofluorocarbons, Perfluorocarbons, and Sulfur
Hexafluoride are synthetic, powerful greenhouse gases
that are emitted from a variety of industrial processes.
 Fluorinated gases are sometimes used as substitutes for
ozone-depleting substances (that is, CFCs, HCFCs, and
Halons).
These gases are typically emitted in smaller quantities, but
they are potent greenhouse gases

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