Climate Change has
happened on
Earth several
times during its
entire history.
Climate change
lead to
extinction of
many plant and
animal species
and also
prompted the
evolution of new
species in both
plant and
animal kingdom
on Earth. Geologic data from past
climates proves that Earth had experienced
several periods of climate changes which resulted in
several Ice ages and warm periods. To
know about
various factors
which caused
Earth's Climate
change prior to
industrialization
Click here
...or Go to
Causes of
Climate Change
Page.
Climatologists
can reconstruct
the Earth's past
climate using
various kind of
data such as:
Biological
Data. past
climates and
their
variations
can also be
studied by
the analysis
of
fossilized
pollen and
other plant
macrofossils,
annual tree
rings, the
abundance
and
distribution
of insects
and other
organisms in
lake rives
and lake
sediments.Glacial
Marine
Sediments
(Fauna and
Flora ).
Climate
change can
also be
determined
by the
analysis of
fossilized
marine fauna
and flora
abundance, morpological
changes in
preserved
organisms,
coral
deposits,
and the
oxygen
isotopic
concentration
of marine
organisms.
Ice
Deposits.
Climate
Fluctuations
can be
found by
the
analyzing
the
ancient
ice
deposits
for the
gas
bubbles
which
can shed
a light
on the
state of
the
atmosphere
they
were
deposited.
Inorganic
Marine
Sediments.
This type of
data
includes
analysis of
clay, aeolian
terrestial
dust, and
ice rafted
debris etc.
Geomorphology
and
Geological
Data.
Study of
past glacial
deposits,
glacial erosional
features,
shoreline
features,
aeolian
deposits,
lake
sediments,
relict soil
deposits etc
can also
lead to
analysis of
past
climates.
Watch
Climate
Change
History of Earth
and
Climate
Fluctuations
Pleistocene
or Ice Age
(2,000,000 -
14,000 ).
During
Pleistocene
period which is
also called as
Ice Age, huge
glacial ice
sheets covered
much of the
Erath including
North America,
Europe, and
Asia. But this
was not the the
period when
Earth had only
Ice Age
throughout,
there were
periods when
there were
warmer
temperatures
which ,made the
ice sheets melt
followed again
by glaciations.
According to
historical
climatic models
for this periods
the average
Earth's
temperatures was
about 4 - 5
degrees Celsius
colder than
present day
temperature.
It is also
called the most
recent
glaciation
activity which
is still going
on which
frequently
changes into
warmer and
cooler climates.
The present
warming trend
began about
14,000 -15,000
years ago.
This
warming was
suddenly
interrupted by
cooling in
around 10,000 -
8500 BC, this
period is called
Younger Dryas.
Scientists
believe that
this cooling
happened because
there was a
sudden release
of fresh water
trapped in ice
sheets of
North America
which went into
North Atlantic
Ocean. As a
result this
altered the
vertical
currents in the
ocean which
exchanged
the heat energy
with the
atmosphere.
Warming of Earth
again
resumed during
8000 - 8500 BC.
About 5000 to
3000 BC Earth's
average
temperatures was
about 1 to 2
degrees Celsius
warmer than
today. This
period is called
Climatic Optimum
by
Climatologists.
But this from
3000 to 2000 BC
Earth
experienced
cooling trend
again.
Which resulted
in large drop in
sea level. It
also resulted in
emergence of
many islands
such as Bahamas
which still are
above the sea
level.
A short warming
trend took place
from 2000 to
1500 BC,
followed once
again by colder
conditions.
Colder
temperatures
from 1500 - 750
BC caused
renewed ice
growth in
continental
glaciers and
alpine glaciers,
and a sea level
drop of between
2 to 3 meters
below present
day levels.
Earth saw
warming up
during the
period from 750
BC - 800 AD up
to 150 BC.
Around 150 BC -
300 AD
cooling again
and lasted until
about 900 AD.
during this time
cooling caused
the Nile River
(829 AD) and the
Black Sea
(800-801 AD) to
freeze.
Then came the
period called
Little Climatic
Optimum.
It
was one of the
warmest climate
period. During
this period,
snow line of
Rocky Mountains
was about 370
meters higher
than today.
From 1550 to
1850 AD global
temperatures
were at their
coldest since
the beginning of
the Holocene.
Scientists call
this period the
Little Ice Age.
During the
Little Ice Age,
the average
annual
temperature of
the Northern
Hemisphere was
about 1.0 degree
Celsius lower
than today.
During the
period 1580 to
1600, the
western United
States
experienced one
of its longest
and most severe
droughts in the
last 500 years.
Cold weather in
Iceland from
1753 and 1759
caused 25% of
the population
to die from crop
failure and
famine.
Newspapers in
New England were
calling 1816 the
year without a
summer.
Figure 1
describes the
global
temperature
trends from 1880
to 2006.
Figure1
Near-global
annual-mean
temperature
change
for
the
period
1880
to
2006
(deviation
from
the
normal
period
1951-1980).
(Source:
NASA
Goddard
Institute
for
Space
Studies)
In the 1930s and
1950s, the
central United
States
experience two
periods of
extreme drought.
In the seventeen
year period from
1990 to 2006,
ten of the
warmest years in
the last 100
years and
possibly since
the Little
Climatic Optimum
have occurred.
Proxy and
instrumental
data indicate
that 2005 was
the warmest year
globally in 1200
years of Earth
history. Many
scientists
believe the
warmer
temperatures of
the 20th and
21st centuries
are being caused
by the human
enhancement of
the Earth's
greenhouse
effect.
Future Climate
Prediction:
Its hard to
predict
precisely how
future climate
would be with
today's
available tools.
But climate
scientists think
that they will be
able to predict
future climates
more accurately with new and
more powerful
computers in future.
Watch Video
about Future
Climate
Predictions:
References: 1) Earth's Climatic History". Fundamentals of Physical Geography, 2nd Edition: 2) NASA Goddard Institute for Space Studies - Global Temperature Trends
