Download Climate Change

EDU 711
Science and Technology
Education
Trimester 1
2014
Week 13
Lecturer : Mrs. Runaaz Sharma
Global Warming
Greenhouse Gases
and Climate
Is the climate becoming
warmer and warmer?
• According to the National Academy of Sciences, the
Earth's surface temperature has risen by about 1 degree
Fahrenheit in the past century, with accelerated warming
during the past two decades. There is new and stronger
evidence that most of the warming over the last 50 years is
attributable to human activities. Human activities have
altered the chemical composition of the atmosphere
through the buildup of greenhouse gases – primarily
carbon dioxide, methane, and nitrous oxide. The heattrapping property of these gases is undisputed although
uncertainties exist about exactly how earth's climate
responds to them.
(source: US-EPA)
The real greenhouse
These two
aspects make
the
greenhouse
warmer than
outside air
temperature
Another Example of the
Greenhouse Effect
The Sun’s energy passes
through the car’s
windshield.
This energy (heat) is
trapped inside the
car and cannot pass
back through the
windshield, causing
the inside of the car
to warm up.
Greenhouse Effect
Natural Greenhouse effect
The natural greenhouse effect causes the mean temperature
of the Earth's surface to be about 33oC warmer than it would
be if natural greenhouse gases were not present.
Enhanced greenhouse effect
When concentrations of greenhouse gases increase,
more infrared radiation is returned toward the earth
and the surface temperature rises.
Greenhouse Effect & Global Warming
• The “greenhouse effect” & global
warming are not the same thing.
– Global warming refers to a rise in the
temperature of the surface of the
earth
• An increase in the concentration of
greenhouse gases leads to an increase in
the magnitude of the greenhouse effect.
(Called enhanced greenhouse effect)
– This results in global warming
What are the major greenhouse
gases?
• H2O
• CO2
• CH4
• N2O
• O3
• CFCs
• SF6
What determines the contribution of a
greenhouse gas to global warming?
• Concentrations
▫ H2O and CO2 are the two biggest contributors
to the atmospheric warming because of their
higher concentrations.
• Lifetime
▫ The longer-live a gas is, the higher the
contribution. e.g. N2O contribution > CH4
• Effectiveness as an infrared absorber
▫ For example, CFC-11 and CFC-12
Greenhouse Gases
• The primary components of Earth’s atmosphere, N2 and O2
do not have absorption in the IR wavelength range, therefore,
do not have a significant role in setting the surface
temperature of the planet…
• Greenhouse gas are efficient in absorbing IR light…
The most important greenhouse gases are:
▫ H2O – Water vapor.
▫ CO2 – Carbon Dioxide
▫ CH4 – methane
The most abundant greenhouse gas in Earth’s
atmosphere is water vapor. Most of the
greenhouse heating of Earth’s atmosphere is due
to Water vapor absorption of IR radiation emitted
by Earth, and then transferring the energy to the
surrounding air molecule
Consequences of global warming
• Sea level rise
▫ Beach erosion
▫ Coastal wetland loss
▫ Loss of low-lying territories
• Water resources change
▫ Precipitation pattern shift
▫ Increases instances of heavy precipitation
▫ New burdens on water capture, storage and
distribution system to be expected.
• Effects on agriculture
▫ Changes in the length of growing season
▫ Growth of undesirable plant species
Consequences of global warming…
• Effects on air quality
▫ Increase in reaction rates and concentrations of certain
atmospheric species increase in O3 in urban areas
▫ More droughts widespread forest fire worsen air quality
▫ Change in how pollutants are dispersed.
• Impacts on human health
▫ Changes in patterns of sickness and death.
▫ Respiratory problems affected by air quality change
• Biodiversity
▫ Some species may grow too quick and overshoot their
reproductive period (e.g. reef corals)
▫ Forest could be devastated if the rate of climate change outpaced
the rate at which forest species could migrate.
• Change in the pattern of ocean current
Consequences of Global Warming
Rising Sea Level
Habitat Damage and
Species Affected
Increased Temperature
Changes in Water Supply
Melting ice and
rising sea level
Receding high mountain
glaciers
Ice shelves of the South
Pole have partly separated
and are collapsing. (NASA)
What’s the proof that global
warming is taking place?
Portage Glacier
• Alaska
1914
Photos: NOAA Photo Collection and Gary Braasch – WorldViewOfGlobalWarming.org
2004
Colorado River
June 2002
Dec 2003
Global Atmospheric Concentration of CO2
Not everybody is convinced of the
greenhouse gases - global warming theory
• At this point, it appears that
the warming itself is real – the
surface temperature indeed
becomes higher in the last few
decades.
• The question is – Is the
warming caused by the
greenhouse gases (especially
CO2)?
• Some groups, especially the
IPCC members argue strongly
for it. But there are other
groups that are not convinced.
The summary to the right is
from Robinson et al. (1998).
You can get IPCC reports at http://www.ipcc.ch/
Summary
World leaders gathered in Kyoto, Japan,
in December 1997 to consider a world
treaty restricting emissions of
''greenhouse gases,'' chiefly carbon
dioxide (CO2), that are thought to cause
''global warming'' severe increases in
Earth's atmospheric and surface
temperatures, with disastrous
environmental consequences.
Predictions of global warming are based
on computer climate modeling, a branch
of science still in its infancy. The
empirical evidence actual measurements
of Earth's temperature shows no manmade warming trend. Indeed, over the
past two decades, when CO2 levels have
been at their highest, global average
temperatures have actually cooled
slightly.
You can get this from the following website
http://www.oism.org/pproject/review.pdf
Ozone Depletion
Ozone Layer
The ozone layer is found in the stratosphere
▫ It protects the Earth from ultraviolet
rays emitted by the sun.
▫ The wavelengths of ultraviolet
radiation are absorbed by the ozone
molecules.
Ozone
absorbs
uv-b
radiation
There is a natural cycle of
formation and depletion of ozone
What is the ozone layer?
• The ozone layer is a
layer of gas consisting
of O3 molecules, called
ozone, that forms
when free Oxygen
atoms bond to O2
molecules.
Ultra-Violet Radiation
• UV rays penetrate
the Earth’s
atmosphere at 3
slightly different
wavelengths called
UV-A, UV-B, and
UV-C rays.
So, why is the ozone layer important
to life on Earth?
• The stratospheric ozone
layer completely stops
the penetration of UV-C
rays and eliminates most
of the UV-B rays.
• Therefore, the ozone
layer protects life on
Earth from the harmful
effects of solar radiation
on a daily basis.
• Chlorofluoro carbons (CFC’s) and other
halogenated hydrocarbons contribute to the
destruction of stratospheric ozone.
• Just one chlorine and bromine atom can catalyze
the destruction of 100,000 ozone molecules
• CFC’s (chlorofluorocarbons)
• Other harmful compounds include
HCFCs, halons, methyl bromide,
carbon tetrachloride, NO2, and methyl
chloroform.
• CFCs were used in refrigerators, home
insulation, aerosols, plastic foam, and
throwaway food containers.
Note: Both chlorine and bromine from
halogenated hydrocarbons deplete the
ozone.
Ozone Depleting Chemicals
• Chlorofluorocarbons (CFCs)
• Methyl bromide
• Halons
• Methyl chloroform
• Hydrogen chloride
• Carbon tetrachloride
• Linked to skin cancer – a deadly cancer
• Linked to cataracts on the lens of the eye causing
blindness
So what might life be like without the
ozone layer?
UV light changes DNA in the skin, this can
cause tumors, and can lead to cancer
• Disruption of plant cycles
and food chains
▫ May limit plant growth
and change plant form,
how nutrients are
distributed,
• Lowers levels of surface
phytoplankton in the
ocean
• Damages the base of the
ocean food chain
•
•
•
•
•
•
•
Limiting the use of CFC’s is difficult
Ban the production and use of CFC’s
Use CFC substitutes such as HCFC’s and HFC’s
Recycling refrigerants
Alternatives to gas-blown plastics
Alternative propellants
Alternatives to methyl bromide, a fungicide
How does ozone depletion affect global
warming and ultimately climate
change?
• As ozone levels in the stratosphere are depleted,
more solar radiation penetrates the Earth’s
atmosphere.
• This affect results in an increase in solar radiation
reaching the Earth’s surface adding to an increase
in surface temperature.
• In turn, global warming actually results in a
warming of the troposphere, but a cooling of the
stratosphere, hindering the ozone layer’s natural
chemistry for repairs.
• Montreal Protocol (1987): 30 countries agreed to
reduce CFC, also encouraging other countries.
▫ Effectiveness: As a result of the Protocol, ozone-depleting
gases have been reduced in recent years. Expected to be
completely reduced by 2050.
▫ Countries are required to report annually on their
consumption and emission of ozone depleting substances to
the UNEP
• London Convention (1990)
• Copenhagen Protocol (1992)
• Kyoto Protocol (1997)
Research
• What is the impact of climate change on pacific
Island countries? How is Fiji affected? Has there
been any research done to measure its impact?
• Find out about :
▫
▫
▫
▫
Montreal Protocol
London Convention (1990)
Copenhagen Protocol (1992)
Kyoto Protocol (1997)
(Is Fiji part of these initiatives ?)