Global environmental problems
By
Dr. Ashraf Hussain
PhD, Com. Med.
Global Environmental Problems:
1. Global Warming
2. Ozone Layer Depletion
3. Acid Rain
4. Deforestation
5. Loss of biodiversity
6. Water polution
7. Desertification
8. Waste disposal
Global warming:
Global warming is a phenomenon of long-term rise in the average temperature of
the Earth's climate system.
This term commonly refers to the observed and continuing increase in average air
and ocean temperatures since 1900 caused mainly by emissions of greenhouse
gasses in the modern industrial economy.
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Concept of global warming
One of planet earth’s unique characteris cs is a warm average temperature of 57°
F(13.8°C) that enables it to support the flourishing life that exists today.
Global warming begins when sunlight reaches the Earth. The clouds, atmospheric
particles, reflec ve ground surfaces and surface of oceans then sends back about 30
% of sunlight back into the space, whilst the remaining is absorbed by oceans, air and
land.
This consequently heats up the surface of the planet and atmosphere, making life
feasible.
As the Earth warms up, this solar energy is radiated back by thermal radiation and
infrared rays, propagating directly out to space there by cooling the Earth.
However, some of the outgoing radiation is re-absorbed by carbon dioxide, water
vapours, ozone, methane and other gases in the atmosphere and is radiated back to
the surface of Earth.
These gases are commonly known as greenhouse gases due to their heat-trapping
capacity.
It must be noted that this re-absorption process is actually good as the Earth’s
average surface temperature would be very cold if there was no existence of
greenhouse gases.
The dilemma began when the concentration of greenhouse gases in the atmosphere
was artificially increased by humankind at an alarming rate since the past two
centuries.
Once released, these greenhouse gases stay in the atmosphere for decades or even
longer.
Gradual increase in the concentration of these gases lead to propagated rise in the
mean earth´s temperature
Each of the last 3 decades has been successively warmer than any preceding decade
since 1850.
Over the last 50 years, human ac vi es – particularly the burning of fossil fuels –
have released sufficient quantities of carbon dioxide and other greenhouse gases to
trap additional heat in the lower atmosphere and affect the global climate.
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As of 2004, over 8 billion tons of carbon dioxide was pumped
According to Intergovernmental Panel on Climate Change (IPCC), carbon dioxide and
methane levels have increased by 35 % and 148 % since the industrial revolu on of
1750.
Causes of global warming
I.
Green House Gases:
The first and foremost in the list is carbon dioxide. Excessive burning of fossil fuels
like coal and oil is the major factor for producing this gas.
Deforestation i.e. removal of trees for acquiring lands also causes large amount of
carbon dioxide in the atmosphere.
Cement manufacture also contributes carbon dioxide to atmosphere when calcium
carbonate is heated generating lime and carbon dioxide.
The second culprit gas is methane, commonly known as natural gas.
It is produced as a result of agricultural activities such as livestock digestion, paddy
rice farming and use of manure.
Methane is also produced due to improper management of waste.
The third is Nitrous oxides, generated mainly by fertilizers.
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Fourth are the Fluorinated gases such as chlorofluorocarbons (CFCs) which are
chiefly a result of various industrial processes and refrigeration.
II.
The second major cause of global warming is the depletion of ozone layer.
v
This happens mainly due to the presence of chlorine-containing source gases.
v
When ultraviolet light is present, these gases dissociate releasing chlorine
atoms which then catalyses ozone destruction.
III.
Aerosols present in the atmosphere are also causing global warming
Environmental Effects
Extreme high air temperatures exaggerate the process of evaporation from water
reservoirs as rivers, seas and oceans.
Extra water vapour formed in the atmosphere falls again as rain which leads to
floods in various regions of the world.
Floods contaminate freshwater supplies, heighten the risk of water-borne diseases,
and create breeding grounds for disease-carrying insects such as mosquitoes.
They also cause drownings and physical injuries, damage homes and disrupt the
supply of medical and health services.
Increasingly variable rainfall patterns are likely to affect the supply of fresh water.
On the other hand, Excess heat leads to drought in the regions where increased
evaporation process is not compensated by increased precipitation.
This will result in crop failure and famine particularly in areas where the
temperatures are already high.
The warmer climate will also leads to amplification in the severity of hailstorms and
thunderstorms.
Also Sea levels are rising, glaciers are melting and precipitation patterns are
changing.
Impact of climate change on health
Although global warming may bring some localized benefits,
such as fewer winter deaths in temperate climates and increased food production in
certain areas, the overall health effects of a changing climate are likely to be
overwhelmingly negative.
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1. In general, Climate change affects social and environmental determinants of
health – clean air, safe drinking water, sufficient food and secure shelter.
2. Extreme heat
Extreme high air temperatures contribute directly to deaths from cardiovascular and
respiratory disease, particularly among elderly people.
In the heat wave of summer 2003 in Europe for example, more than 70 000 excess
deaths were recorded
High temperatures also raise the levels of ozone and other pollutants in the air that
exacerbate cardiovascular and respiratory disease.
Pollen and other aeroallergen levels are also higher in extreme heat which can
trigger asthma in susceptible individuals.
Rising temperatures and variable precipitation are likely to decrease the production
of staple foods in many of the poorest regions.
This will increase the prevalence of malnutrition and undernutrition, which currently
cause 3.1 million deaths every year.
3. Patterns of infection
Climatic conditions strongly affect water-borne diseases and diseases transmitted
through insects, snails or other cold blooded animals.
Changes in climate are likely to lengthen the transmission seasons of important
vector-borne diseases and to alter their geographic range.
These include snail-borne disease schistosomiasis, also Malaria and dengue.
Who is at risk?
All populations will be affected by climate change, but some are more vulnerable
than others
Those are:
People living in small island developing states and other coastal regions, megacities,
and mountainous and polar regions are particularly vulnerable.
Areas with weak health infrastructure – mostly in developing countries – will be the
least able to cope without assistance to prepare and respond.
Children – in particular, children living in poor countries – are among the most
vulnerable and will be exposed longer to the health consequences.
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The health effects are also expected to be more severe for elderly people and people
with infirmities or pre-existing medical conditions.
2. Ozone layer Deple on
Depletion of Ozone Layer
Ozone depletion, gradual thinning of Earth’s ozone layer in the
upper atmosphere caused by the release of chemical compounds containing
gaseous chlorine or bromine from industry and other human activities.
The thinning is most pronounced in the polar regions, especially over Antarctica.
Ozone depletion is a major environmental problem because it increases the amount
of ultraviolet (UV) radiation that reaches Earth’s surface, which increases the rate
of skin cancer, eye cataracts, and genetic and immune system damage.
This global decrease in stratospheric ozone is well correlated with rising levels
of chlorine and bromine in the stratosphere from the manufacture and release of
CFCs and other halocarbons.
Halocarbons are produced by industry for a variety of uses, such as refrigerants
(in refrigerators, air conditioners, and large chillers), propellants for aerosol cans,
blowing agents for making plastic foams, firefighting agents, and solvents for dry
cleaning and degreasing.
Atmospheric measurements have clearly corroborated theoretical studies that
chlorine and bromine released from halocarbons in the stratosphere react with and
destroy ozone
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