2194/02 Elective Geography: Weather and Climate slides on global warming and climate change. ICT lesson to be done together with handout.

1. Causes of climate change

2. http://tinyurl.com/qyy26vu
 Today’s objectives:
-we will be able to define key terms in Gateway
2
-we will be able to explain the various causes of
climate change

3. Buzzfeed
What comes to mind when you hear the term
climate change?

4. Temperature Anomaly
It is a departure from a reference value or a
long term average.
A positiveanomaly indicates that the observed
temperature was warmer than the reference value,
while a negative anomaly indicates that the
observed temperature was cooler than the
reference value.

5. How has global climate
changed?
Source: http://climate.nasa.gov/news/index.cfm?NewsID=249

6. Global Warming
The
increase in
global temperatures
over a long period of

7. Global Cooling
The
decrease in
global temperatures
over a long period of

8. Global dimming
The gradual
reduction in the
amount of sunlight
reaching earth

9. Hence, climate
change is not just
about global
warming.

10. Global Climate Change
 Variation in global climate in the long term
General
increasing
trend
Fluctuations in
between, and
decreases in certain
years

11. Global Climate Change
Increase in global
temperatures over a long
period of time  GLOBAL
WARMING
Decrease in global
temperatures over a
long period of time 
GLOBAL COOLING

12. Is global climate
change natural?
Or caused by
humans???

13. Climate change in the past 150
years
 Significant but irregular temperature rise of 0.3 to
0.6℃ since 1881
 Global cooling recorded after WWII for several
decades because of industrial pollution and volcanic
activity
 Amount of sunlight that reaches earth’s surface is
reduced because of large amount of particles in the
atmosphere  low temperature
 Also known as global dimming
 Global warming over last century: world warming on
an average of 0.74℃ especially since 1970s

14. Watch the video below to find out
more about climate change
 https://www.youtube.com/watch?v=8YQIaOldD
U8

15. WHY?
Climate
change
Natural
causes
Variation in
solar output
Volcanic
eruptions
Human
causes
Burning fossil
fuels
Deforestation
Changing
land use

16. Variations in solar output
 Sun emits solar radiation at different rates
due to changes in magnetic field
 An increase in magnetic activity  increase in solar
radiation.
 Magnetic activity of the sun has a cycle that lasts
about 11 years.
 Through the study of sunspots, the solar activity
cycle was discovered
 Many sunspots  indicates high solar activity &
higher temperature

17. Watch the video below to find out
about the causes of climate
change
 You have to fill in the handout based on what
you watched. You can also use the following
slides below to help you with your handout.
 You can also look at your textbook 103-108 for
the answers.
 https://www.youtube.com/watch?v=RHrFBOUl
6-8

18. Volcanic Activity
 Produces large volumes of carbon dioxide, water
vapour, ash and dust
 Sulphur dioxide + water  sulphur-based particles in
atmosphere that reflect solar energy back into space
 Results in a reduction in amount of sunlight that
reaches earth’s surface: also known as global dimming
 E.g. When Mount Pinatubo in Philippines erupted in
1991, 17 million tonnes of sulphur dioxide was released
into atmosphere. The sulphur-based particles reflected
solar energy back into space & lowered temperature in
northern hemisphere by 0.6℃.

19. Volcanic Activity evaluation
 Usually have few long-term effects on
climate
 Because temporary global cooling effect
will cease once the volcanic dust & ash
settle
 E.g. Global climate returned to original
state 2 years after Mount Pinatubo
eruption. The large volume of carbon
dioxide released by volcanoes was still 100

21. Greenhouse Effect
 Incoming shortwave radiation from the sun
passes through the greenhouse gases found
in atmosphere
 Some shortwave radiation is reflected back to
space
 Most shortwave radiation is absorbed by the
earth’s surface which then heats up as a result
 The warmed surface of earth emits longwave
radiation to the atmosphere
 Greenhouse gases absorb longwave radiation,
warming the atmosphere

22. ENHANCED Greenhouse Effect
 Increase in the concentration of greenhouse
gases in atmosphere  rise in global
temperatures
 Happens when human activity causes
greenhouse gases to be released at a far
greater rate than natural emission of
greenhouse gases
 Increase in concentration of carbon dioxide
usually the greatest amongst the greenhouse

23. Burning fossil fuels
 Fossil fuels: coal, oil, natural gas
 Large amount of fossil fuel burnt for industries,
transportation, electricity etc.  gives out
large amount of greenhouse gases, esp.
carbon dioxide
 Greater amount of greenhouse gases  traps
more heat  temperature increase

24. Deforestation
 Forests cleared for development, agricultural
and commercial activities like cattle ranching,
commercial logging etc.
 Forests absorb billions of tonnes of carbon
dioxide each year via photosynthesis,
absorbing a significant amount of global
greenhouse gas emission.
 With deforestation  lesser trees to absorb
carbon dioxide  larger concentration of CO2 in
atmosphere

25. Deforestation
 Soil: very large source of carbon because
carbon is accumulated through decay of
organic matter like dead leave and animals
 Exposes soil to sunlight
 Increases soil temperature and rate of carbon
oxidation
 Causes carbon dioxide to be released from soil
into atmosphere

26. Changing land use- Agriculture
Agriculture
 Population increases  need for more food
 More land used for agriculture (practice of
cultivating land, producing crops & raising
livestock)
 But such activities release a lot of greenhouse
gases into atmosphere!

27. Changing land use
Cattle Ranching Rice Cultivation
Cattle release methane as
waste gas
Requires the use of tractors
which run on fossil fuel and it
releases carbon dioxide
Methane is a greenhouse gas Use of fertilisers increases
nitrous oxide in soil and is
eventually released when rain
flows through soil
Dead leaves and manure
(organic matter) releases
methane when they
decompose.

30. Changing land use-
Industrialisation
Industrialisation
 A lot of carbon dioxide is produced when fossil
fuels are burnt for manufacturing industries
 E.g. manufacturing a mobile phone releases
60kg of carbon dioxide.
 Countries like China and India are contributing
more to global carbon dioxide emissions in
recent years due to rapid industrialisation

31. Changing land use-
Urbanisation
Urbanisation
 Process by which an increasing number of
people live in urban areas such as
cities/towns.
 Large amount of fossil fuels burnt to provide
energy for household activities like cooking,
lighting
 High concentration of cars, buses  increase
amount of greenhouse gases