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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 external.
Internal processes are processes operating
on the global energy balance from within the Earth, while external
processes operate
from
outside planet
Earth.
External forcing processes
include:
-
variations in the amount of energy received from the Sun,
and
-
variations in the Earth’s orbit around the Sun
A third of the
UV energy from the Sun is believed to be reflected back into space after hitting Earth's upper
atmosphere, while two thirds gets through to the Earth. This ratio could
change however, due to variations in Sun’s characteristics from time to
time.
Changes in the tilt of the Earth’s axis,
changes in the shape of Earth's orbit (eccentricity) and the shifting of
the equinoxes (precession) play major roles in determining variations in
the amount of Sun’s energy reaching the Earth and hence the Earth’s
climate variations.
Internal climate forcing
processes include:
-
Oceans
-
The atmosphere
-
Water Cycle
-
Clouds
-
Ice and Snow
-
Land Surfaces
-
Impacts
of large volcanic eruptions and collisions with comets or meteorites
-
Man Made Pollution
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 of global climate and accounts for the variations.
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.
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.
Clouds reflect solar energy
(cooling the Earth) and by trap heat being radiated up from the surface
(warming the Earth).
The whiteness of ice and snow reflects heat out, cooling the planet.
When ice melts into the sea, this drives heat from the ocean.
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.
The Earth is not hit by large
comets or meteorites very often, perhaps every 20 to 30 million years or
so, and therefore their associated climate changes occur rarely throughout
Earth History.
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.
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