- Natural (Physical) causes - Human (Anthropogenic) causes

1. 1. NATURAL FACTORS 2. HUMAN FACTORS
(A) Variation in solar
output
(B) Large volcanic
eruptions (causes
cooling effect)
(A) Burning of fossil fuels
(B) Deforestation
(C) Changing land use due to:
(i) Agriculture & cattle farming
(ii) Industrial activities
(iii) Urbanisation
Causes of Climate
Change

2. (A) Variation in solar output
(B) Large volcanic eruptions

3. (A) Variation in solar
output
• Sunspots are cooler regions on the sun’s surface that
appear as dark spots.
• When the number of sunspots increases, it causes higher
solar radiation.

4. (A) Variation in solar
output
• This is because the areas surrounding the sunspots
radiate more energy to compensate for lower
temperatures of the sunspot areas.
• Thus, higher sunspot activity results in higher amount of
solar radiation received by earth, which coincides with
higher global temperatures.

5. (B) Large volcanic
eruptions
• During a volcanic eruption, for example Mount Pinatubo
which erupted in the Philippines in 1991, 17 million
tonnes of carbon dioxide, water vapour, sulphur dioxide,
dust and ash were released into the atmosphere.

6. (B) Large volcanic
eruptions
• Sulfur dioxide reacts with water to form sulphur based
particles in the atmosphere, which spread around the
earth in two weeks.
• Together with dust and ash particles, the sulphur based
particles reflects solar energy back into space.
• Thus, lesser solar energy is able to reach earth’s surface,
leading to a temporary lowering of global temperatures.
After the 1991 Mount Pinatubo eruption, temperatures
in the northern hemisphere cooled by as much as 0.6°C
for around two years.

7. (A) Burning of fossil fuels
(B) Deforestation
(C) Changing land uses

8. (A) Burning of Fossil
Fuels
• Countries like China, the USA, Canada
and the UK burn fossil fuels to produce
large amounts of energy for agricultural,
industrial and other human activities.
• But, due to the high carbon content, fossil fuels produce
large amounts of carbon dioxide when it is burnt.
• The world’s usage of fossil
fuels has increased in recent
years, releasing billions of
tonnes of carbon dioxide
into the atmosphere yearly.

9. • CO2 is a greenhouse gas that is a good absorber of
longwave radiation.
• A higher concentration of
greenhouse gases in the
atmosphere means that
more longwave radiation is
being absorbed. This causes
more heat trapped in the
atmosphere, resulting in the
enhanced greenhouse effect.
• This causes earth’s temperatures to rise
and leads to global warming.
(A) Burning of Fossil
Fuels

10. (B) Deforestation
• Deforestation is the loss of forests due to removal or
clearance of trees in forested areas.
• Between 2000 and 2010, 52,000 km2 of forests was lost
every year. In particular, the greatest loss of forests
comes from South America and Southeast Asia.
• Trees are felled for wood to make products such as
furniture and paper.
Trees are also removed
to clear the area for
cattle ranching,
soya bean production
and mining.

11. (B) Deforestation
• But, trees absorb billions of tonnes of carbon dioxide
every year via photosynthesis, thus taking in a significant
amount of global greenhouse gas emissions.
• With deforestation, there are
fewer trees and other plants
to absorb carbon dioxide,
leading to an increase in the
atmospheric CO2 levels.
• As a result of deforestation,
there are more CO2 greenhouse gas in the atmosphere
which traps heat and increases earth’s temperatures.

13. (C) Changing Land Uses
(i) Agricultural activities – Cultivation of rice
• In countries like India & Thailand,
tractors are used on padi fields
when growing rice, and these
tractors release CO2.
• The use of inorganic fertilisers
increases the amount of
nitrous oxides in the soil.
Nitrous oxide is then released when soil is ploughed or when rain
flows through the soil.
• Decomposition is very rapid in the rice fields due to the very moist
soil and this causes methane to be released into the atmosphere.
• CO2, nitrous oxides and methane are greenhouse gases which trap
heat in the atmosphere and increases earth’s temperatures.

14. (i) Agricultural activities – Cattle farming
• Cattle farming contributes to greenhouse gas emissions because
cattle release methane as a waste gas.
• With more fast food chains around the world, the demand for beef
has increased. As one of the world’s biggest beef producers,
Argentina rears more than 55 million cows. This has contributed to
more than 30% of the country’s total greenhouse gas emissions.
(C) Changing Land Uses

15. (ii) Industrial activities
• To manufacture goods and services, large amounts of fossil
fuels are burnt, which results in more greenhouse gas
emissions.
• For example, to manufacture
a mobile phone, 60kg of CO2
is produced.
• As a result, countries with many industries emit a lot of
greenhouse gases into the atmosphere, which causes more
heat to be trapped and this increases earth’s temperatures.
(C) Changing Land Uses

16. (iii) Urbanisation
• With an increasing number of
people living in cities, large
amounts of fossil fuels are burnt
to provide energy for urban
household activities such as
heating, cooking and lighting.
• The high concentration of cars,
buses and other forms of
transportation also contribute
to the amount of greenhouse
gases emitted in urban areas.
(C) Changing Land Uses

17. (iii) Urbanisation
• Constructing infrastructure and
producing construction materials
also releases greenhouse gases
into the atmosphere.
• The use of air con also requires
the burning of fossil fuels for
electricity.
• As a result, higher emission of
greenhouse gases cause more
heat to be trapped in our
atmosphere. This increases
earth’s temperature and leads to
global warming.
(C) Changing Land Uses

18. 1. NATURAL FACTORS 2. HUMAN FACTORS
(A) Variation in solar
output
(B) Large volcanic
eruptions (causes
cooling effect)
(A) Burning of fossil fuels
(B) Deforestation
(C) Changing land use due to:
(i) Agriculture & cattle farming
(ii) Industrial activities
(iii) Urbanisation
Leads to
Enhanced Greenhouse Effect
& Global warming
Causes of Climate Change

19. 19

20. Sun
Earth’s SurfaceAtmosphere
1) Incoming shortwave
radiation from the sun
passes through the GHG
found in the atmosphere.
2) Some of the shortwave
radiation is reflected by the
earth and the atmosphere.
LESS heat escapes back to space.
3) Most of the shortwave
radiation from the sun is
absorbed by the earth’s surface.
4) The earth’s surface warms up
and emits longwave radiation to
the atmosphere.
GHG
5) HIGHER concentration of greenhouse
gases in the atmosphere absorb MORE
longwave radiation, thus warming earth’s
atmosphere rapidly. This leads to a rise in
global temperatures and global warming.
Enhanced Greenhouse Effect (TB pg.103)
Human activities cause greenhouse
gases
(e.g. CO2, methane, nitrous oxides etc)
to be emitted to the atmosphere at a
far greater rate