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What is Climate Change?
Long term changes in the Earth’s heat
budget resulting from radiative inbalance
can result in a colder or warmer climate
Ice Ages
There have been many ice ages on Earth,
as well as many warm climate periods
What is an Ice Age?
• Ice ages are periods when glaciers grow to
cover large portions of continents
• Another term for this is continental glaciation
• Unlike alpine glaciers which are restricted to
valleys, continental glaciers advance along a
wide front and cover large areas.
• Currently, Greenland and Antarctica are the
sites of most of the world’s continental glaciation
~22,000
years ago,
Albany was
under more
than a mile of
ice
Glaciers
sculpted
much of New
York’s
landscape
What causes ice ages?
• There are several factors that contribute to
global climate change and glaciation events.
Among them are:
• Continental Drift
– Continents must be at or near poles
– Changes in oceanic and atmospheric circulation
• Mountain building
• Variations in the Earth’s orbit around the Sun
• Variations in the albedo of the earth’s surface
and atmosphere
• One of these factors is not enough; a
combination of factors favorable to glaciation
is required
Prior to relatively recent
Ice Ages, there were four
periods of major
glaciation or “icehouse”
times
Permian-Carboniferous
Late Ordovician
Late Proterozoic
Earliest Proterozoic
Continental Drift
• Plates can move from low latitudes to high
latitudes. Land at the poles helps promote
glaciation.
• Plate reorganization can also cause changes in
oceanic and atmospheric circulation that can
trigger significant global climate change. It is
essential that warm moist air be circulated
towards the poles.
• Mountain building events caused by plate
collisions can also help to trigger glaciation
Closure of the Isthmus of Panama
caused reorganization of major
oceanic currents and helped bring
on major Northern Hemisphere
glaciation over the last 3 million
years
The closure occurred about 4
million years ago. After a lag
of about 1million years, the
glaciations began
Ocean circulation & Climate
What causes changes in the heat
budget?
1) Changes in the sun’s energy output:
sunspots
What causes changes in the heat
budget?
2) Changes in the Earth’s orbit and tilt:
What causes changes in the heat
budget?
3) Volcanic eruptions: aerosols cause
cooling
What causes changes in the heat
budget?
4) Humans:
a) overgrazing causes desertification
What causes changes in the heat
budget?
4) Humans:
b) deforestation makes air drier
What causes changes in the heat
budget?
4) Humans:
c) urbanization
What causes changes in the heat
budget?
4) Humans:
d) burning fossil fuels makes greenhouse
gases, the current major cause of
GLOBAL WARMING
Global Warming
Greenhouse gases are:
Greenhouse Effect
Water vapor
Methane
Carbon dioxide
Reradiated from surface
Short wave light
Long wave
infrared
Summary
Short waves
Long waves
Scientists agree
that over the past few
decades the earth has
been heating up, primarily due to
human activities
This in turn could cause rises
in sea level by as much as 20
feet or higher, flooding much
of the worlds coastal areas
and many major cities.
A significant rise in world
Wide temperature could
Melt the Antarctic Ice Fields
The flood waters move in steadily
For example:
A rise in sea level
of 20 feet would
flood all of the
parts of Florida
that are green
Ok, we get the point,
Turn down the heat.
If temperatures are
increasing world wide
as a result of
greenhouse gases,
the effect is
known as
Global Warming
I’m wilting
The 800 degree temperatures
on Venus are the result
of a runaway greenhouse
effect
Venus has more than
1000 times more CO2
in it’s atmosphere
than earth