the greenhouse effect and the thinning of the ozone layer

8/8/2019 The Greenhouse Effect and the Thinning of the Ozone Layer

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GREENHOUSE EFFECT


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WHY DOWE CALL IT THE GREENHOUSE

EFFECT?


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y The "greenhouse effect" often gets a bad rap

because of its association with globalwarming, but the truth is we couldn't live

without it.

y Life on earth depends on energy from the sun.

About 30% of the sunlight that beams toward

Earth is deflected by the outer atmosphereand scattered back into space. The rest

reaches the planet's surface and is reflected

upward again as a type of slow-moving energy

called infrared radiation.

What Causes the Greenhouse

Effect?


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y The heat caused by infrared radiation is absorbed

by "greenhouse gases" such as water vapor, carbondioxide, ozone and methane, which slows its escape

from the atmosphere.

yAlthough greenhouse gases make up only about 1

percent of the Earth's atmosphere, they regulateour climate by trapping heat and holding it in a

kind of warm-air blanket that surrounds the planet.

y This phenomenon is what scientists call the

"greenhouse effect." Without it, scientists estimatethat the average temperature on Earth would be

colder by approximately 30 degrees Celsius (54

degrees Fahrenheit), far too cold to sustain our

current ecosystem.


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How Do Humans Contribute to the

Greenhouse Effect?

y The problems begin when human activities distortand accelerate the natural process by creating

more greenhouse gases in the atmosphere thanare necessary to warm the planet to an idealtemperature.

y Burning natural gas, coal and oil

y Some farming practices and land-use changes

y Many factories produce long-lasting industrialgases

y Deforestation

y Population growth


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y Ultimately, more greenhouse gases means more

infrared radiation trapped and held, whichgradually increases the temperature of the

Earth's surface and the air in the lower

atmosphere.

y During the entire 20th century, the averageglobal temperature increased by about 0.6

degrees Celsius (slightly more than 1 degree

Fahrenheit).

y Using computer climate models, scientistsestimate that by the year 2100the average

global temperature will increase by 1.4 degrees

to 5.8 degrees Celsius (approximately 2.5

degrees to 10.5 degrees Fahrenheit).


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GLOBAL WARMING


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y Definition : increase in the averagetemperature of Earths near-surface air and

ocean.

y Caused : increasing concentrations of

greenhouse gases, which results from human

activity such as the burning of fossil fuels and

deforestation.

y The global surface temperature is likely to risea further 1.1 C - 6.4 C during the 21st century.

y temperature rose by 0.18 C over the period

19062005.


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y Temperature changes vary over the globe.

Since 1979, land temperatures have increasedabout twice as fast as ocean temperatures

(0.25 C per decade against 0.13 C perdecade).

y Ocean temperatures increase more slowly thanland temperatures because of the larger effectiveheat capacity of the oceans and because the oceanloses more heat by evaporation.

y The Northern Hemisphere warms faster than theSouthern Hemisphere because it has more landand because it has extensive areas of seasonal

snow and sea-ice cover.


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Effects of global warming

y

Although more greenhouse gases are emitted inthe Northern than Southern Hemisphere this doesnot contribute to the difference in warmingbecause the major greenhouse gases persist long

enough to mix between hemispheres.

y Increased in air and ocean temperature

y Rising of sea level

y Melting of ice


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THE THINNING OF THE OZONELAYER


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y The ozone layer is a region in the stratosphere

(situated between and 25 km above the earthsurface second layer of atmosphere, above

troposphere).

y The thinning of the O3 (OZONE) layer has been

recorded since 1970s.y 1985, it was reported that the stratospheric ozone

concentrations (over the Antarctica) has declined

by 40% (since 1977). Ozone hole is caused by

atmosphere in Antarctica has very lowconcentrations.

y Ultraviolet radiation has risen 7% in the

northern hemisphere and in southern

hemisphere has increase by 10%.


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A satellite image

of the Antarctic

ozone hole. Thedark region on the

image is actually

an ozone hole.


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y The causes ?

1. Is mainly due to the increasing levels ofchlorofluorocarbons (CFCs) in the

atmosphere.

2. CFCs are a group of chemicals compound

that contain chlorine, fluorine and carbon.

3. These gases are used as coolants in air

conditioners, refrigerators, propellants in

aerosol cans and foaming agents in themaking of Styrofoam packaging.

4. These chemicals are stables, so they can

persist in the environment for as long 75 to

100 years.


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yATTENTION!!!

y EVERY 1% DROP IN OZONE

CONCENTRATIONS RESULTS IN A 2%

INCREASE IN THE INTENSITY OF THEMOST HARMFUL TYPE OF

ULTRAVIOLET RAYS (UV-B WILL CAUSE

SKIN CANCER, CATARACTS AND

SUPPRESSION OF THE IMMUNE SYSTEMWILL DECREASE)


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Some products which containCFC compounds.


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y The ozone layer protects the Earth from the

ultraviolet rays sent down by the sun. If the ozone

layer is depleted by human action, the effects on the

planet could be catastrophic.

y Ozone is present in the stratosphere. The

stratosphere reaches 30 miles above the Earth, and at

the very top it contains ozone. The suns rays areabsorbed by the ozone in the stratosphere and thus do

not reach the Earth.

y OZONE: a bluish gas that is formed by three atoms of

oxygen.y The form of oxygen that humans breathe in consists of

two oxygen atoms, O2. When found on the surface of

the planet, ozone is considered a dangerous pollutant

and is one substance responsible for producing the

greenhouse effect.


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y

Cause :1. Release of CFCs, chlorofluorocarbons

y Effects :

1. small amount of the ozone layer is lost, more

ultraviolet light from the sun can reach the Earth.2. Every time 1% of the ozone layer is depleted, 2%

more UV-B is able to reach the surface of the

planet. UV-B increase is one of the most harmful

consequences of ozone depletion because it can

cause skin cancer.

3. increase rates of malaria and other infectious

diseases. (such as cataract, etc)

4. environment will also be negatively affected.


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IMPACT OF GLOBALWARMING


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y Extreme weathery Warm spells or heat waves over most land area will

increase.

y Increased area will be affected by drought

y There will be increased intensed tropical cycloneactivity

y There will be increased incidences of extreme high

sea level (excluding tsunamis)

y Increased freshwater flowy Flow of freshwater into the ocean increases, partly

from melting of ice

y Increase in global freshwater flow based on data

from 1994 to 2006 was about 18%

1. Effects on weather


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y Local climate change

y Melting of ice, changing the hydrological cycle andchanging currents in the ocean.

y The first recorded South Atlantic hurricane,

"Catarina", which hit Brazil in March 2004.


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y

Mountain glaciers and snow cover had decreased inboth hemisphere which results in increases of sea level

y A map of the change in thickness of mountain glacierssince 1970. Thinning in orange and red, thickening inblue.

2. Glacier retreat and disappearance


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y

Oceans serve as a sink of carbon dioxide,CO2yAcidification

y Dissolving CO2 in seawater increases the

hydrogen ion, H+ concentration in the ocean and

decreases ocean pHy Oxygen depletion

yAmount of oxygen dissolved in the oceans may

declined

y Sea level risey Since 1961, global average sea level had risen at

an averagerate of 1.8 [1.3 to 2.3] mm/yr.

y Between 1993 and 2003, the rate increased above

the previous period to 3.1 [2.4 to 3.8] mm/yr.

3. Oceans


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y Temperature risey From 1961 to 2003, the global ocean temperature

has risen by 0.10 C from the surface to a depth of

700 m.

y Food supply

y Health

y Water resourcesMigration and conflict

yAggregate impact

4. Climate change will also effect:


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IMPACTS OF OZONE DEPLETION


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yIncreasedUV

y Biological effects

y Effects on human :

1. Skin cancer : - Basal and Squamous Cell Carcinomas

- Malignant Melanoma

2. Cortical Cataracts

y Effects on crops :

1. A number of economically important species ofplants, such as rice, depend on cyanobacteria

residing on their roots for the retention of nitrogen.

Cyanobacteria are sensitive to UV light and they

would be affected by its increase.

the greenhouse effect and the thinning of the ozone layer

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