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Human impacts on the environment
• Lesson outcomes
At the end of the lesson you must be able to:
 Define Climate change, greenhouse effect, and global warming
 Describe the causes of climate change
 Critically evaluate the possible impacts of an increased greenhouse effect.
 Observe one example of a human impact on the environment and compile and report on the specific example.
 Argue whether certain human activities are justified despite their impact on the environment

Key terminology/ Terms to look out for
 Climate change refers to any change or disturbance to an established climate pattern. This
has happened in the past and is occurring now
 greenhouse gases (GHGS) ,gases which trap heat in the atmosphere: the two main GHGS
are carbon dioxide and methane
 the greenhouse effect, warming of the surface of the earth by greenhouse gases trapping
heat in the atmosphere
 global warming ,the rise in earth’s average temperature as a result of the enhanced
greenhouse effect
 carbon footprint the amount of carbon dioxide released into the air because of individual or
group energy needs

Gaseous composure of the atmosphere
Earth’s atmosphere is a critical mixture of gases which sustain life,
with 78% nitrogen (N2)
 21% oxygen (O2)
 1% – all remaining gases, mainly carbon dioxide (CO2) and other small
(trace) amount

Greenhouse gases: Carbon dioxide sources
• Carbon dioxide (CO2) emissions are produced by:
 cellular respiration when CO2 is exhaled
 decomposition of dead plants and animals
 The burning of fossil fuels as an energy source for electricity
 chemical reactions in the cement industry and the production of fertilisers
Can you think of another way in which Carbon dioxide can be emitted?

Greenhouse gases: Methane emissions
• Methane is the second largest contributor to the enhanced greenhouse effect,
and as the planet warms up so its contribution increases even faster.
 Human activities are responsible for over 60% of total methane in the
atmosphere.
CH4 emissions are produced by:
natural anaerobic decomposition of organic materials, e.g. in wetlands
melting ice in polar regions and permafrost releasing trapped CH4 bubbles

Methane continued
Intensive agriculture:
 decomposing dung and
compost for fertilising
 gas being released by
ruminants (animals with
two stomachs – mostly
cattle)

Other greenhouse gases
Water vapour is the largest volume of greenhouse gas warming the planet naturally.
Nitrous oxide, ozone and CFCs (chlorofluorocarbon) all contribute to global
warming as greenhouse gas pollutants.
Nitrous oxide (N2O) N2O is released by the burning of wood and fossil fuels
Ozone (O3) is either helpful or harmful , The ozone produced by vehicle emissions
that accumulates close to the Earth is a pollutant and a harmful greenhouse gas.
Ozone can however also be helpful as serves to protect life on Earth by absorbing
the sun’s ultraviolet radiation.
CFC’s CFC’s (chlorofluorocarbons) are found in aerosol sprays, solvents, fridges
and foams used for fast food packaging.

Greenhouse effect
• The importance of these greenhouse gases is
that: These gases act as an insulating blanket in
Earth’s atmosphere keeping temperatures evenly
warm at a range that supports life on Earth. If
there were no greenhouse gases, the atmosphere
would have a temperature of -18°C. This
temperature would be unable to sustain life.

The problem? The enhanced greenhouse effect
• An increase in the concentration of greenhouse gases due to human
activities, leads to an enhanced greenhouse effect. This results in a significant
rise in the average temperatures
• The enhanced greenhouse effect is responsible for global warming.

Global warming
• The effects of global warming:
 Sharply rising temperatures result in increasing numbers of heat waves.
 Rising sea levels cause coastal flooding. Many coastal cities will vanish.
 Droughts periods are increasing leading to more frequent fires, soil erosion
and desertification.
 Food production is decreasing. Crops die as they cannot adapt to the
changing seasons. Food insecurity increases.

How can we reduce climate
change? Global warming and
enhanced greenhouse effect.
The power is in your hands and your change in behaviour

Check list: What have you learnt today
• Are you able to:
 Define Climate change, greenhouse effect, and global warming
 Describe the causes of climate change
 Critically evaluate the possible impacts of an increased greenhouse effect and suggest ways to
reduce global warming
 Describe the various greenhouse gases including their sources

Preparation
for the next
lesson
Deforestation
Carbon footprint
Ozone depletion
Water availability
Farming practices

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Human impacts on the environment

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Human impacts on the environment