Transcript Y11GeUC7.7 Climate change PPwk16

The greenhouse effect and
global warming
What are they?
The causes, effects,
impacts and responses
Key Idea – only the one
• Environmental abuse has serious
consequences. Its causes need to be
tackled to ensure a more sustainable
future.
• But there are still 3 sections to study …..
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Section 3 part 1
• Causes of global warming and climate
change: deforestation; use of fossil fuels;
air pollution; agricultural change; CFCs.
• Consequences: rising sea levels; more
hazards; ecosystem changes; new
employment opportunities; changing
settlement patterns; health and well being.
• A case study of the threats posed by global
warming and climate change to one country
(eg Bangladesh, the Maldives).
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Please visit
• http://news.bbc.co.uk/1/shared/spl/hi/sci
_nat/04/climate_change/html/greenhouse
.stm
• I tried downloading it but it wouldn’t
• I am aware some of you cannot access BBC
sites but those who can it is worth a look I
• In the meanwhile …..
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THE NATURAL GREENHOUSE
EFFECT
• The atmosphere has a number of gases,
often in tiny amounts, which trap the heat
given out by the Earth.
• To make sure that the Earth's
temperature remains constant, the balance
of these gases in the atmosphere must not
be upset.
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The GREENHOUSE GASES are very
important and are mainly:
• water vapour
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occurs naturally in the atmosphere.
carbon dioxide
produced naturally when people and animals breathe.
Plants and trees absorb carbon dioxide to live. Volcanoes
also produce this gas. Carbon dioxide is not the same as
carbon monoxide
methane
comes from cattle as they digest their food. The gas also
comes from fields where rice is grown in paddy fields.
nitrous oxide
when plants die and rot, nitrous oxide is produced.
ozone
occurs naturally in the atmosphere.
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THE ENHANCED GREENHOUSE
EFFECT
• Because there are more and more
greenhouse gases in the atmosphere, more
heat is trapped which makes the Earth
warmer. This is known as global warming.
• A lot of scientists agree that man's
activities are making the natural
greenhouse effect stronger. If we carry
on polluting the atmosphere with
greenhouse gases, it will have very
dangerous effects on the Earth.
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What are the causes of
rises in Greenhouse gases
THE ENHANCED GREENHOUSE
EFFECT
• Some of the activities of man also produce greenhouse
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gases. These gases keep increasing in the atmosphere.
The balance of the greenhouse gases changes and this
has effects on the whole of the planet.
Burning fossil fuels - coal, oil and natural gas - releases
carbon dioxide into the atmosphere. Cutting down and
burning trees also produces a lot of carbon dioxide.
A group of greenhouse gases called the
chlorofluorocarbons, - which are usually called CFCs,
because the other word is much too long! - have been
used in aerosols, such as hairspray cans, fridges and in
making foam plastics. They are found in small amounts in
the atmosphere. They are dangerous greenhouse gases
because small amounts can trap large amounts of heat.
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Methane is x 30 more effective than
CO2 Where does methane come
from? (3 places)
Some greenhouse
gases
X 300 more
effect on global
warming than
CO2 Man-made
sources of
nitrous oxide
include nylon
and nitric acid
production, the
use of fertilisers
in agriculture,
cars with
catalytic
converters and
the burning of
organic matter.
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CO2 and temperature rise
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Two ways of looking at causes
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The effects
Global Warming – some effects
Since 1970, rise in:
 Global surface temperatures
 Tropospheric temperatures
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
 (air closest to ground level)
Decrease in:
Snow extent
Arctic sea ice
Global Sea Surface Temperatures Glaciers
Global sea level
Cold temperatures
Water vapor
Rainfall intensity
Precipitation
Hurricane intensity
Drought
Extreme high temperatures
Heat waves
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Global mean temperatures are rising faster with time
Warmest 12 years:
1998,2005,2003,2002,2004,2006,2001,1997,1995,1999,1990,2000
Period
Rate
150 0.0450.012
Years /decade
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Global mean temperatures are rising faster with time
Period
Rate
100 0.0740.018
150 0.0450.012
Years /decade
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Global mean temperatures are rising faster with time
Period
25
50
100
150
Rate
0.1770.052
0.1280.026
0.0740.018
0.0450.012
Years /decade
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Land surface temperatures are rising faster than SSTs
Sea Surface T
Land
Annual anomalies of global average SST and land surface air
temperature
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Land precipitation is changing significantly over broad areas
Increases
Decreases
Smoothed annual anomalies for precipitation (%) over land from
1900 to 2005; other regions are dominated by variability.
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Regions
of disproportionate
changes
in heavy in
Proportion
of heavy rainfalls:
increasing
th) precipitation
(95th) and very heavy
(99
most
land
areas
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Projected Patterns of Precipitation Change
2090-2100
Precipitation increases very likely in high latitudes
Decreases likely in most subtropical land regions
This continues the observed patterns in recent
trends
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Sea level is rising:
from ocean expansion and melting glaciers
Since 1993
•Global sea level has
risen 41 mm (1.6
inches)
• 60% from
expansion as ocean
temperatures rise,
• 40% from melting
glaciers
Steve Nerem
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Evidence for reality of climate change
Glaciers melting
Muir Glacier, Alaska
1909
Toboggan
Glacier
Alaska
2000
1900
2003
Alpine glacier, Austria
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Global mean temperatures are rising faster with time
Period
25
50
100
150
Rate
0.1770.052
0.1280.026
0.0740.018
0.0450.012
Years /decade
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The
impacts
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Impacts on living things
• If the sea-levels are rising then – what might
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the effects be? And on people and the
ecosystems?
If there are more climatic hazards – what might
they be? What is the impact? Where might be
affected the most?
Changes in rainfall – what might be the effects
on the earth? On the human welfare?
Rises in temperature – what would be the
effects? What are the impacts on the different
groups? That is the sea as well? Warming seas
with more CO2 in ( that is an acid by the way)?
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Impacts on living things
• Ecosystem changes –
 which would be most affected?
 What would be the impacts on the world as a
whole?
 On people?
 On ecosystem populations?
• Agricultural production: all bad or maybe
some good?
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One of the impacts is on human health –
why?
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Case
study:
Bangladesh
Notice all the rivers that come down
from the Himalayas – when is there the
highest flow in these?
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75% of
Bangladesh is
at or below
just 10 metres
in height.
Before we go
further, what do
you know about
Bangladesh?
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Projected climate change impacts
• Many of the projected impacts of climate change will
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reinforce the baseline environmental, socio-economic and
demographic stresses already faced by Bangladesh.
Climate change is likely to result in:
i. Increased flooding, both in terms of extent and
frequency, associated with sea level rise, greater
monsoon precipitation and increased glacial melt
ii. Increased vulnerability to cyclone and storm surges
iii. Increased moisture stress during dry periods leading
to increased drought
iv. Increased salinity intrusion
v. Greater temperature extremes
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So what are the issues?
• The ice caps in the Himalayas are melting so the
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spring flood carrying sediments to re-enrich the
soils are slowly reducing.
The storms seem to be becoming more intense
The sea level is rising due to snow melt and
thermal expansion.
The mangrove swamps, the Sundarbans, are the
largest in the world, will disappear is the sea
levels rise by a mere 45cm.
Without mangroves to protect the coastal
behind them, much land will be washed away in
storms, leaving millions homeless.
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So what are the issues?
• More salt water infiltration is likely, which will make more of
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the land that is still above sea level, useless for growing rice, so
putting more pressure on more to people to migrate.
Saltwater from the Bay of Bengal already penetrates 100
kilometres inland during the dry season , and climate change is
likely to exacerbate this.
Pressure from an increasing population (rising at 2% pa) and
rising demand for groundwater further reduces the availability
of freshwater supplies for domestic and industrial purposes
If sea levels rises up to one metre this century, Bangladesh
could lose up to 15 per cent of its landmass and up to 30 million
Bangladeshis could become climate refugees .
In these areas, agriculture, industry, infrastructure, livelihoods,
marine resources, forestry and biodiversity, human health, and
utility services will all suffer. Such a scenario could lead to a
decline in GDP of between 27 and 57 per cent . ( It is currently
US$ 700)
Given the high population density (954 per sq km) of the country
as a whole, this could lead to mass climate emigration – where
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could they go?