Transcript Earth and its Climate System

Earth and its Climate System
Starting Point:
What is the
difference
between weather
and climate?
Weather: Set of
environmental and
atmospheric conditions
encountered at a
specific place on a dayto-day basis (ShortTerm)
Climate: Set of
environmental and
atmospheric conditions
for a large area
averaged over many
years (Long-Term)
Temperature and Climate
• The Earth is
surrounded by an
envelope of gases
called the
atmosphere.
• Without an
atmosphere, the
days would be too
hot and the nights
would be too cold.
• So how is heat
energy
transferred?
– Always move from
hotter object to
colder object
Heat Energy Transfer
1. Radiation: Heat transfer by
electromagnetic waves through
space and can transfer its heat to an
object.
2. Convection: Heat transfer through
movements of particles in a liquid or
gas.
–
As a gas/liquid is heated, it expands
and rises because it is less dense. As
it rises and expands, it cools and falls.
This creates convection currents.
3. Conduction: Heat transfer through
collision of particles (direct contact
with one another)
Earth’s Climate System
• The biosphere is the global sum
of all biological components.
• Made up of three spheres:
1. Atmosphere – air
2. Hydrosphere – water
3. Lithosphere – rocks, soils,
minerals
•
What powers this system?
The sun!
•
The interaction of these
components and the sun
produces climate zones!
Factors that Affect Climate
What are some factors that cause different climates
in different areas?
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Sun
Latitude & axial tilt of Earth
Large bodies of water
Air and ocean currents
Land formations (eg. mountains, volcanoes)
Altitude
Solar Energy
• The most important factor that affects climate is the sun
• Earth’s climate systems are driven by radiation energy received from
the sun. Heat produces winds, rain & other features of climate.
• The intensity of the energy that reaches Earth’s surface affects the
temperature of air, water and land.
– Earth absorbs different wavelengths from the sun, heats up and gains
thermal energy. It then emits this as infrared radiation which returns to the
atmosphere and back into space.
– Earth’s global temperature stays constant (for the most part).
Changes in Solar Activity
• When the number of sunspots is high, the Sun emits
higher amounts of solar radiation.
• Some scientists believe that changes in solar output
are the main cause of climate change in the past. But
many argue that the phenomenon is too weak of a
correlation with climate change.
The Atmosphere
• Layers of gases surrounding the Earth. It acts
as a blanket, conserving thermal energy to
keep Earth warm.
• Reflects, absorbs and radiates or transfers
energy.
• Also shields Earth from dangerous radiation.
• 78% nitrogen, 21% oxygen
• Other gases: argon, CO2, helium, hydrogen,
ozone
• In the stratosphere (50 km
up), ozone absorbs
dangerous UV radiation.
• In the last few decades, a
hole in the ozone layer
has been apparent
(Antarctica), allowing
radiation and heat to get
through. Causes?
Ozone (O3)
– Human-made
chlorofluorocarbons
(CFCs) thins the ozone
layer (found in spray cans,
refrigerators, A/C). It was
banned in 1987.
– Montreal Protocol in 1989
(treaty for protection)
• Is the ozone recovering?
– New NASA research:
Maybe not until 2070!
http://www.ryot.org/full-recoveryozone-layer-wont-happen2070/499477
Wind
• Atmospheric factor that affects
climate = movement of air
from areas of high pressure to
areas of low pressure
• Caused by uneven heating of
the Earth’s surface
– Air moves as wind transfers
thermal energy around the
world from warm areas to
cooler areas
– Movement of air affects
More on
precipitation patterns and this later!
ocean currents.
• Winds blow in fairly constant
directions around the world
(prevailing winds)
Hydrosphere
• Consists of liquid water, water vapour and ice
• Reflects, absorb and emit, or transmits energy
from the sun
• Water Cycle (driven primarily by the Sun)
– Energy is absorbed when water evaporates →
cools surroundings
– Energy is released when water vapour condenses
into clouds → warms surroundings
Large Bodies of Water
• Water absorbs and stores more thermal energy than
land. It also heats up and cools down more slowly than
land. Temperatures of regions near oceans or a large
lake:
– Summer: Cooler
– Winter: Warmer
• Regions downwind from large bodies of water have
more snow (“lake-snow effect”) such as the Great
Lakes area.
Specific Heat Capacity
• Water acts as a “heat reservoir” and
influences climate due to this. Therefore,
water has a large specific heat capacity
compared to other substances.
– Specific heat capacity: The amount of heat
required to raise the temperature of 1 g of a
substance by 1°C.
– In other words, for 1 g of water, it takes more heat
to raise its temperature by 1°C compared to other
substances.
• The higher the heat capacity, the longer it take to warm
the substance up and the slower the substance loses its
heat.
• Water’s high specific heat capacity means a land mass
near a large body of water will have its temperature
“moderated” by the water – it will warm up more slowly
in the summer and cool down more slowly in the winter
compared to a land mass further from the water.
– Eg. Vancouver versus Ottawa climates
The water will warm and cool more slowly
than the beach
25 degrees
20 degrees
Ice
• 2% of the Earth’s water is
frozen.
• Most ice is located at the
two poles.
• Sea ice: thins and floats on
the ocean.
• Ice sheets: enormous areas
of permanent ice stretching
over land.
• Surfaces covered in ice and
snow reflect more radiant
energy than land (explains
why the poles are so cold).
Albedo Effect
Albedo: Measurement (%)
of how much light an object
reflects
The higher the %, the more
light that is reflected by the
object.
Contributes to the
maintenance of global
temperature but with the
disappearance of the ice
caps, what will happen?
Revolution & Axial Tilt of Earth
• Earth revolves around the sun
and completes its orbit every
365 days. The Earth is tilted at
23.5° so a different
hemisphere is pointed towards
the sun throughout the year.
This explains the changes in
seasons.
• When Northern Hemisphere is
tilted towards the sun =
SUMMER but Southern
Hemisphere experiences
WINTER during same time and
vice versa.
• Contributes to distribution of
heat around Earth
Latitude
• Sunlight striking the earth
perpendicular to the
surface is very
concentrated.
• Sunlight striking an angled
surface is more dispersed
and less effective.
• Thus higher latitudes tend
to be cooler than those
closer to the equator.
• This creates temperature
differences around the
world.
Mountain Climate & Altitude
• Mountain chains (due to movement of continental plates)
affects the patterns of wind & precipitation around the world.
• Mountains receive more rainfall than low-lying areas because
the temp. on the top of the mountains is lower.
– As altitude ↑, air is less dense (less pressure) so it expands and cools.
– Warm air from water body evaporates & rises, cools and condenses.
This moisture falls as rain on the windward side of mountain. The
other side of the mountain gets less rain. This effect is called the rain
shadow. The higher the mountain peak, the more pronounced this
effect becomes.
Volcanic Eruptions
• Related to continental plate
movement as well.
• During a volcanic eruption,
particles called aerosols
(such as ash) are released
into the atmosphere.
• Aerosols reflect solar
radiation, having a cooling
effect on the global climate,
and scatter light
• Some volcanic eruptions can
raise global temperatures by
releasing greenhouse gases.
• Forest fires have a similar
effect as well.
• https://www.youtube.com/watch?v=lrPS2HiY
Vp8