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Causes of
Climate Change
The
Earth receives energy
solely
from the Sun, in the form of
light and ultraviolet (UV)
radiation, and releases energy back to space, in the form of infrared
heat. The Earth's climate is determined by the
"Earth's stored Energy" which is the
difference in the amount of
energy received from the Sun and the amount the Earth releases
back to Space.
That is:
Earth’s
“stored” Energy = Energy from Sun – Energy released to space
(The
Global Energy Balance)
Any process
or activity that
influences this global energy balance either by increasing or decreasing
the
"Earth’s
stored
Energy"
contributes to climate change and is qualified to be called a
"climate
forcing process".
Yes, Climate Changes are caused by several
climate forcing processes.
Climate forcing processes
could be internal and/or external.
Internal processes are processes operating
on the global energy balance from within the Earth, while external
processes operate
from
outside planet
Earth (e.g. influence on the sun on the
earth. These two processes and how they contribute to climate change are
discussed below:
A. The External Climate Forcing Processes:
1. variations in the amount of energy received from the Sun
About 30-40% of the UV energy from the Sun is believed to be reflected
back into space after hitting Earth's upper atmosphere, while the
remaining 60-70% gets through to the Earth. This ratio could change
however, due to variations in Sun’s characteristics from time to
time, thus leading to changes to the the global energy balance above and
hence changes in our climate
2.
variations in the Earth’s orbit around the Sun
Changes in the tilt of the Earth’s axis,
changes in the shape of Earth's orbit (i.e. eccentricity) and the shifting of
the equinoxes (i.e. precession) play major roles in determining variations in
the amount of Sun’s energy reaching the Earth and hence lead to variations
in the Earth’s
climate (i.e. Climate Change).
B.
The Internal Climate Forcing
Processes:
1. The Oceans
Oceans cover up to 70% of the Earth. Oceans are the key source of
moisture in the air through interactions with the atmosphere. Oceans also
store heat efficiently, transporting it thousands of miles thus
redistributing heat in time and space. The oceans and marine life also
consume huge amounts of carbon dioxide. These ocean based processes exert
tremendous influence on global climate and accounts for the variations.
2. Continental Drift
The surface of our earth
is mostly (3/4 th) covered by water. Our current day earth is made up of
7 continents (Australia, North America, South America, Asia, Africa,
Europe and Antarctica) - big landmasses separated apart by oceans. A
close look at the shape of the earth, one will think that the continents
look like the pieces of a jig-saw puzzle that fits into a solid mass
when brought together. Actually, scientists believe that several
millions of years ago, the whole earth consisted of 1 big continent
surrounded by a big ocean. Over time, it is believed that the big
landmass (earth) slowly broke up and take the current form it has today.
Scientists proofs for this theory are: similarity between plant and
animal fossils and broad belts of rocks found on the eastern coastline
of South America and western coastline of Africa, which are now widely
separated by the Atlantic Ocean. The discovery of fossils of tropical
plants (in the form of coal deposits) in Antarctica has led to the
conclusion that this frozen land at some time in the past, must have
been situated closer to the equator, where the climate was tropical,
with swamps and plenty of lush vegetation.
Scientists believe that the
our earth is still slowly drifting and constantly changing. This constant
drifting is believe to have impact on the climate because it changes the
physical features of the landmass, their position and the position of
water bodies. The separation of the landmasses changed the flow of ocean
currents and winds, which affects the climate.
3. The atmosphere
The atmosphere stores a lot of heat or energy which comes from the Sun.
This energy regulates the Earth's climate.
Furthermore, the atmosphere composes of small particles and several gases
such as oxygen, nitrogen, carbon dioxide. Some of the gases (e.g. carbon
dioxide vapour, carbon dioxide, methane and nitrous oxide) are known to
trap heat in the atmosphere thus increasing the net “energy” stored and
contributing to Earth warming. The later forms of gases are referred to as
“greenhouse gases (GHG)”. The Earth climate is also affected by the
particles in the atmosphere which tend to block sunlight reaching the
Earth.
4. Water Cycle
Higher air temperatures can increase water evaporation and melting of
ice. And while water vapour is the most potent greenhouse gas, clouds also
affect evaporation, creating a cooling effect.
5. The Clouds
Clouds reflect solar energy
(cooling the Earth) and thereby trapping heat being radiated up from the surface
(warming the Earth). Clouds variability contribute to climate change
6. Ice and Snow
The whiteness of ice and snow reflects heat out, cooling the planet. When
ice melts into the sea, this drives heat from the ocean causing
variability in climate.
7. Land Surfaces
Mountain ranges can block clouds, creating
"dry" shadows downwind. Sloping land allows more water runoff, leaving the
land and air drier. A tropical forest will soak up carbon dioxide, but
once cleared for cattle ranching, the same land becomes a source of
methane, a greenhouse gas.
8.
Volcanic Eruptions
A volcanic eruption, lasting for few days,
emits large volumes of sulphur dioxide (SO2), water vapour,
dust, and ash into the atmosphere that influence climatic patterns for
years. The gases and dust particles partially block the incoming rays of
the sun, leading to cooling (more details on: http://edugreen.teri.res.in/explore/climate/causes.htm)
9. Man Made Pollution (Human Causes)
Human industrial activities are believed to be adding to the amount of
"greenhouse gases" naturally present in the atmosphere. These gases trap heat that are otherwise supposed to be lost to the
space from the Earth and consequently warm up the Earth. Human activities in the Industry and the agricultural sectors are
believed to be responsible for the increasing quantities of carbon
dioxide, methane and other greenhouse gases in the atmosphere. For more
details go to - Greenhouse Gases
Other Sources of Information:
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