KAKATIYA UNIVERSITY, WARNAGAL
ENGLISH FOR EXCELLENCE
UG CBCS SEMESTER-4 TEXTS
UNIT 2: ECO SYSTEMS AND
ENVIRONMENTAL POLLUTION
ABOUT THE AUTHOR:
Michael Shafer is
a teacher, consultant and author who now manages Warm Heart, a community
development organisation set up in Thailand. Warm Heart focuses on climate
mitigation and poverty reduction through social entrepreneurship.
TEXT (LESSON)
Climate change
refers to significant, long-term changes in the global climate. global climate
is the connected system of sun, earth and oceans, wind, rain and snow, forests,
deserts and savannas, and everything people do, too. The climate of a place,
say New York, can be described as its rainfall, changing temperatures during
the year and so on.
But the global
climate is more than the average of the climates of specific places.
A description of
the global climate includes how, for example, the rising temperature of the
Pacific feeds typhoons which blow harder, drop more rain and cause more damage,
but also shifts global ocean currents that melt Antarctica ice which slowly makes
sea levels rise until New York will be under water.
It is this
systemic connectedness that makes global climate change so important and so
complicated.
What is Global Warming?
Global Warming is
the slow increase in the average temperature of the earth's atmosphere because
an increased amount of the energy (heat) striking the earth from the sun is
being trapped in the atmosphere and not radiated out into space.
The earth's
atmosphere has always acted like a greenhouse to capture the sun's heat,
ensuring that the earth has enjoyed temperatures that permitted the emergence
of life forms as we know them, including humans.
Without our
atmospheric greenhouse the earth would be very cold. Global warming, however,
is the equivalent of a greenhouse with high-efficiency reflective glass
installed the wrong way around.
Ironically, the
best evidence of this may come from a terrible cooling event that took place
some 1,500 years ago. Two massive volcanic eruptions, one year after each
other, placed so much black dust in the upper atmosphere that little sunlight
could penetrate. Temperatures plummeted. Crops failed. People died of
starvation and the Black Death started its march. As the dust slowly fell to
earth, the sun was again able to warm the world and life returned to normal.
Today, we have
the opposite problem. Today, the problem is not that too little sun warmth is
reaching the earth, but that too much is being trapped in our atmosphere.
So much heat is
being kept inside that the temperature of the earth is going up faster than at
any previous time in history. NASA provides an excellent course module on the
science of global warming.
How does Global Warming Drive Climate Change?
Heat is energy,
and when you add energy to any system, changes occur. Because all systems in
the global climate system are connected, adding heat energy causes the global
climate as a whole to change.
Much of the world
is covered in oceans which heat up. When oceans heat up, more water evaporates
into clouds. Where storms like hurricanes and typhoons are forming, the result
is more energy-intensive storms. A warmer atmosphere melts glaciers, mountain
snow peaks, the Polar ice cap, and the great ice shield jutting off of
Antarctica, thereby raising sea levels.
Changes in
temperature change the great patterns of wind that bring the monsoons in Asia
and rain and snow around the world, making droughts and unpredictable weather
more common.
This is why
scientists have stopped focusing just on global warming and now focus on the
larger topic of climate change.
Causes of Global Warming
There are three
positions on global warming: (1) that global warming is not occurring and so
neither is climate change; (2) that global warming and climate change are
occurring, but these are natural, cyclic events unrelated to human activity;
and (3) that global warming is occurring as a result primarily of human
activity and so climate change is also the result of human activity.
The claim that
nothing is happening is very hard to defend in the face of masses of visual,
land-based and satellite data that clearly shows rising average sea and land
temperatures and shrinking ice masses.
The claim that
observed global warming is natural or at least not the result of human carbon
emissions focuses on data that shows that world temperatures and atmospheric
CO2 or carbon dioxide levels have been equally high or higher in the past. They
also point to the well-understood effects of solar activity on the amount of
radiation striking the earth and the fact that in recent times the sun has been
particularly active.
In general, climate
scientists and environmentalists either (1) dispute the data based on, for
example, new ice core data or (2) suggest that the timing issue-that is, the
rapidity with which the globe has warmed and the climate changed simply do not
fit the model of previous natural events. They note also that compared to other
stars the sun is actually very stable, varying in energy output by just 0.1%
and over a relatively short cycle of 11 to 50 years quite unrelated to global
warming as a whole. The data strongly suggests that solar activity affects the
global climate in many important ways, but is not a factor in the systemic
change over time that we call global warming.
As for the final
position that global warming and climate change result from human activity (are
'anthropogenic), scientists attribute current atmospheric warming to human
activities that have increased the amount of carbon-containing gases in the
upper atmosphere and to have increased amounts of tiny particles in the lower
atmosphere. Specifically, gases released primarily by the burning of fossil
fuels and the tiny particles produced by incomplete burning trap the sun's
energy in the atmosphere. Scientists call these gases 'greenhouse gases (GHGs)
because they act like reflective glass facing the wrong way in our global
greenhouse.
Scientists call
the tiny particles 'black carbon" (you might call it soot or smoke) and
attribute their warming effect to the fact that the resulting layer of black
particles in the lower atmosphere absorbs heat like a black blanket.
Scientists date
the beginning of the current warming trend to the end of the 18th or
beginning of the 19th century when coal first came into common use.
This warming
trend has accelerated as we have increased our use of fossil fuels to include
gasoline, diesel, kerosene and natural gas, as well as the petrochemicals (plastics,
pharmaceuticals, fertilisers) we now make from oil.
Scientists
attribute the current warming trend to the use of fossil fuels because using
them releases into the atmosphere stores of carbon that were sequestered
(buried) millions of years ago. The addition of this 'old' carbon to the
world's current stock of carbon, scientists have concluded, is what is heating
our earth and causing global warming.
Greenhouse Gases (GHGs)
The most common
and most talked about greenhouse gas is CO2 or carbon dioxide In fact, because
it is so common, scientists use it as the benchmark or measure of things that
warm the atmosphere.
Methane, another
important GHG, for example, is 28-36 times as warming a CO2 when in the upper
atmosphere, therefore, 1 ton of methane is 28-36 tons eCO2 or CO2 equivalents:
Common Greenhouse Gases
1. CO2 or carbon
dioxide is produced any time something is burned. It is the most common GHG,
constituting by some measures almost 55% of total long-term GHGs. It is used as
a marker by the United States Environmental Protection Agency, for example,
because of its ubiquity. Carbon dioxide is assigned a GWP or Global Warming
Potential of 1.
2. Methane or CH4
is produced in many combustion processes and also by anaerobic decomposition,
for example, in flooded rice paddies, pig and cow stomachs, and pig-manure
ponds. Methane breaks down in approximately 10 years, but is precursor of
ozone, itself an important GHG. CH4 has a GWP of 28-36.
3. Nitrous oxide
(laughing gas), NO/N20 or simply NOx is a by-product of fertiliser production
and use, other industrial processes and the combustion of certain materials
Nitrous oxide lasts a very long time in the atmosphere, and at the 100-year
point of comparison to CO2, its GWP is 265-298.
4. Fluorinated
gases were created as replacements for ozone-depleting refrigerants, bur have
proved to be both extremely long-lasting and extremely warming GHGs. They have
no natural sources, but are entirely man-made. At the 100 year point of
comparison, their GWPs range from 1,800 to 8,000 and some variants top 10000.
5. Sulphur
hexaflouride or SF6 is used for specialised medical procedures, but primarily
in what are called dielectric materials, especially dielectric liquids. These
are used as insulators in high voltage applications such as transformers and
grid switching gear. SF6 will last thousands of years in the upper atmosphere
and has a GWP of 22,800.
Black Carbon Global Warming
Black carbon (BC)
is tiny particles of carbon released as a result of the incomplete i combustion
of fossil fuels, biofuels and biomass. These particles are extremely small,
ranging from 10 pm (micrometres, PM10, the size of a single bacterium) to less
than 2.5 pm (PM2.5, one-thirtieth the width of a human hair and small enough to
pass through the walls of the human lung and into the bloodstream).
Although BC-think
of the plume of smoke from a chimney or a fire-falls out of the lower
atmosphere in days, while it is suspended in the air, it absorbs the sun's hear
millions of times more effectively than CO2. When wind carries BC over snow,
glaciers or ice caps, where it falls on the white, normally reflective surface,
it is particularly damaging because it contributes directly to melting. BC is
the second biggest contributor to global warming after CO2,
Sources of Green House Gases and Black Carbon?
Fossil fuel and
related uses of coal and petroleum are the most important sources of GHGs and
black carbon (power generation, industry, transportation, buildings).
Agriculture is the second most important source (animals-cows and pigs). feed
production, chemical-intensive food production, and flooded paddy-rice
production, as well as deforestation driven by the desire to expand cultivated
areas. Natural sources of GHGs and black carbon include forest fires, savannah
fires and volcanoes.
What Evidence do we have of Climate Change?
The most
compelling evidence scientists have of climate change is long-term data
detailing atmospheric CO2 levels and global temperature, sea levels, the
expanse of ice, fossil records and the distribution of species.
This data, which
goes back millions of years, shows a strong correlation between CO2 levels and
temperature. Recent data shows a trend of increasing temperature and rising CO2
levels beginning in the early 19th century.
Because all parts
of the global climate are connected, scientists have been able to create models
of how changes caused by heating should work their way through the entire
system and appear in different areas, for example, sea level, intemperate
weather, the movement of fish species in the ocean. [...]
The Impact of Climate Change
Because the
global climate is a connected system, climate change impacts are felt everywhere.
Among the most important climate change impacts are:
Rising sea levels
Climate change
impacts sea levels. The average sea level around the world has risen by about 8
inches (20 cm) in the past 100 years; climate scientists expect it to rise more
and more rapidly in the next 100 years as part of climate-change impacts.
Coastal cities such as New York are already seeing an increased number of
flooding events and by 2050 many such cities may require seawalls to survive.
Estimates vary, but conservatively sea levels are expected to rise 1 to 4 feet
(30 to 100 cm), enough to flood many small Pacific island states (Vanatu),
famous beach resorts (Hilton Head) and coastal cities (Bangkok, Boston). [...]
Melting ice
Projections
suggest the following climate change impacts within the next 100 years, if not
sooner: the world's glaciers will have disappeared, as will the Polar ice cap,
and the huge Antarctic ice shelf, Greenland may be green again, and snow will
have become a rare phenomenon at what are now the world's most popular ski
resorts.
Torrential downpours and more powerful storms
While the
specific conditions that produce rainfall will not change, climate change
impacts the amount of water in the atmosphere and will increase producing
violent downpours instead of steady showers when it does rain. Hurricanes and
typhoons will increase in power, and flooding will become more common. [...]
Heatwaves and droughts
Despite downpours
in some places, droughts and prolonged hearwaves will become common. Rising
temperatures are hardly surprising, although they do not mean that some parts
of the world will not 'enjoy' record cold temperatures and terrible winter
storms. (Heating disturbs the entire global weather system and can shift cold
upper air currents as well as hot dry ones. Single snowballs and snowstorms do
not make climate change refutations.) Increasingly, however, hot, dry places
will get hotter and drier, and places that were once temperate and had regular
rainfall will become much hotter and much drier. The string of record high
temperature years and the record number of global droughts of the past decade
will become the norm, not the surprise that they have seemed.
Changing ecosystems
As the world
warms, entire ecosystems will move. Already rising temperatures at the equator
have pushed such staple crops as rice north into once cooler areas, many fish
species have migrated long distances to stay in waters that are the proper
temperature for them. In once colder waters, this may increase fishermen's catches;
in warmer waters, it may eliminate fishing [...].
Reduced food security
One of the most
striking impacts of rising temperatures is felt in global agriculture, although
these impacts are felt very differently in the largely temperate developed world
and in the more tropical developing world. Different crops grow best at quite
specific temperatures and when those temperatures change, their productivity
changes significantly. [...] The productivity of rice, the staple food of more
than one third of the world's population, declines 10% with every 1° C increase
in temperature. Past climate-induced problems have been offset by major
advances in rice technology and ever larger applications of fertiliser;
expectations are that in Thailand, the world's largest exporter of rice,
however, future increases in temperatures may reduce production 25% by 2050. At
the same time, global population models suggest that the developing world will
add 3 billion people by 2050 and that developing world food producers must
double staple-food-crop production by then simply to maintain current levels of
food consumption.
Pests and disease
Rising
temperatures favour agricultural pests, diseases and disease vectors. Pest
populations are on the rise and illnesses once found only in limited, tropical
areas are now becoming endemic in much wider zones. In Southeast Asia, for
example, where malaria had been reduced to a wet-season-only disease in most
areas, it is again endemic almost everywhere year around. Likewise, dengue fever,
once largely confined to tropical areas, has become endemic to the entire
region. Increased temperatures also increase the reproduction rates of microbes
and insects, speeding up the rate at which they develop resistance to control
measures and drugs (a problem already observed with malaria in Southeast Asia).
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