Download SNC 2DI: Climate Change

SNC 2DI: Climate Change
Note 1: Terminology
The sun is the driving force of our weather systems. It provides the
energy that produces wind, rain, and other factors of climate. There
are several factors that affect the climate and weather of any given
region.
Definitions:
Weather – is the environmental conditions such as wind, pressure,
temperature, amount of precipitation, etc. in a specific place at a
specific time. Eg. the weather in Cambridge at 5:00 am Jan 6 is cold
and windy with a temperature of – 9 °C and some light snow.
Climate – is the characteristic pattern of weather conditions within a
region, including average monthly temperatures, precipitation, wind
velocity and other conditions averaged over a long period of time
(years). Eg. southern Ontario has cool wet springs, hot humid
summers, cool windy falls and wet cold winters. Temperatures range
from – 30 °C to 30 °C.
Factors that affect Weather and Climate
Solar Activity – the amount of radiation the Earth receives from the
sun is not constant. These variations in solar radiation may have an
affect on the Earth’s climate.
Figure 1: Solar Activity
Earth’s Rotation and Orbit around the Sun
Seasons – produced by the combination of the Earth’s orbit around
the sun and the tilt of the Earth on its axis of rotation of 23.5 °.
Figure 2:
Seasons
The Earth’s orbit, tilt and rotation vary slightly in repeating cycles
over time.
Eccentricity – the fluctuation of the Earth’s orbit around the sun
due to the gravitational attraction to other planets. Over a cycle of
100,000 years the Earth’s orbit changes from being almost circular to
more elliptical. This has an affect on the length and intensity of the
seasons (the amount of solar radiation varies less throughout the
year when the orbit is circular).
Figure 3:
Eccentricity
Tilt – the tilt of the Earth on its axis changes by approximately 2.4°
over a period of 41,000 years. The greater the tilt, the greater the
temperature differences between summer and winter.
Figure 4: Earth’s tilt
and Wobble
Wobble – because the Earth is not a perfect sphere it wobbles on its
axis. This affects the amount and intensity of solar energy by the
northern and southern hemispheres of the planet.
Latitude – since the Earth’s surface is curved, a beam of light
illuminates different sized areas at different latitudes. Therefore the
solar energy absorbed per square metre is different at different
latitudes with the equator absorbing more energy and the poles
absorbing less.
Figure 5:
Effect of latitude
on the angle of
light ray
Albedo – the fraction of incident light or electromagnetic radiation
that is reflected by the surface of an object, such as from Earth back
into space. It is the object’s ability to reflect light.
In general, light-coloured surfaces reflect energy and dark surfaces
absorb energy.
Ocean surface – reflects 7 % of the solar energy
Field of fresh snow – reflects 80 to 90 % of the solar energy
PUT THESE SUBSTANCES IN ORDER OF HIGHEST TO LOWEST
ALBEDO: dirty snow, clean snow, ocean water, evergreen
forest
Tectonic Plates:
Figure 6: Tectonic plates on Earth
The lithosphere (Earth’s solid crust) is composed of massive
sections of solid rock. These sections are known as tectonic
plates. Every year these plates move a few centimetres. This
causes changes to both land and water masses which in
turn, affects air and water circulation. Changes in air and
water circulation affect weather patterns.
Volcanic Eruptions – tectonic plate movement is
responsible for volcanic activity. When volcanoes erupt, they
spew ash and particulate matter into the atmosphere. These
particles called aerosols reflect solar radiation and thus have
a cooling effect on the global climate.
Figure 7: Aerosols in the atmosphere after a volcanic eruption (45 days after)
The Atmosphere:
The atmosphere is a thin layer of gases that surround a planet or
moon. The thickness of the atmosphere of Earth in comparison to the
planet can be compared to the skin of an apple with the rest of the
apple.
Figure 8a, 8b: Thin layer of the atmosphere
Gases of Earth’s Atmosphere
The Earth’s atmosphere consists primarily of nitrogen (approx. 78%),
and oxygen (approx. 21%), as well as smaller concentrations of other
gases. Water and carbon dioxide are two other important gases in
the atmosphere. Note that other than argon and water all other
gases make up much less than 1% of the atmosphere.
Figure 10: Percentages of Atmospheric Gases
Gas Name
Nitrogen
Oxygen
*Water
Argon
*Carbon
Dioxide
Neon
Helium
*Methane
Hydrogen
*Nitrous Oxide
*Ozone
Chemical
Formula
N2
O2
H2O
Ar
Percent
Volume
78.08%
20.95%
0 to 4%
0.93%
CO2
0.0360%
Ne
He
CH4
H2
N2O
O3
0.0018%
0.0005%
0.00017%
0.00005%
0.00003%
0.000004%
Nitrogen and oxygen do not absorb infrared radiation, and
therefore do not contribute to the “natural” greenhouse
effect that keeps our planet warm enough for life. Gases
that absorb and re – emit infrared radiation are known as
greenhouse gases.
Layers of the Atmosphere: The
atmosphere has been divided into 5
sections: the troposphere,
stratosphere, mesosphere,
thermosphere and exosphere.
Weather occurs mainly in the
troposphere and lower
stratosphere.
Greenhouse Effect
The process by which gases build up thermal energy in the
atmosphere by absorbing infrared radiation from the Earth’s surface
is called the Greenhouse Effect. In effect the Earth’s atmosphere
works like a greenhouse does for plants.
Natural Greenhouse gases: water vapour, carbon dioxide,
methane, nitrous oxide and ozone. (Note: there are two sources of
ozone – ground level that contributes to greenhouse gases, and
stratospheric ozone that protects us from UV rays.)
Man – made Greenhouse gas: chlorofluorocarbons (CFC’s),
Release of excess carbon dioxide from the burning of fossil fuels.
Anthropogenic Greenhouse Effect
Human activities have greatly accelerated the production of carbon
dioxide and other greenhouse gases. This has caused a significant
increase in the overall global average temperature. The increase in
global average temperature, as a result of an increase in greenhouse
gases due to human activities, is known as the anthropogenic
greenhouse effect.
Wind – is the movement of air from an area of high pressure to an
area of low pressure. The uneven heating of the Earth’s surface due
to such things as latitude, season, type of ground cover, mountains,
hills, etc. contribute to varying high pressure and low pressure
areas.
COPY FIGURE 7.8 FROM THE TEXTBOOK INTO YOUR NOTES
NOW  Include the caption to the right of the figure.
[p273]
Wind affects both the movement of ocean currents and precipitation
patterns.
Prevailing winds – winds that blow in fairly constant directions
(covering large areas) around the world. Eg. Polar easterlies,
northeast trade winds, southwest trade winds, mid – latitude
westeries.
SEE FIGURE 7.9 P274
Jet streams – high- altitude winds that travel long distances at very
high speeds. Jet streams may carry warm, moist air or dry, cool air.
Canada’s weather is very much influenced by the polar jet stream.
The energy from this movement of air (wind) is transferred to the
surface of water causing water to move. As water moves it
distributes the heat held by the water.
Heat reservoirs:
Water can store more heat than air. Water has a large specific heat
capacity. Therefore water heats up slowly and releases heat slowly.
This has a great effect on the climate. Water acts as a buffer to
temperature changes in the atmosphere. Land heats and cools more
quickly than water. Land masses near large bodies of water are
warmer in the winter than more inland areas. In summer, they are
cooler than inland areas.
The Sun’s Energy
Solar energy travels through space as electromagnetic radiation.
There are different types of electromagnetic radiation. Infrared
radiation keeps our planet and the things on it, warm.
SEE P314 – TABLE 8.1 – TYPES OF ENERGY TRANSFER
Radiation – transfer of energy, including thermal energy, as
electromagnetic radiation. This energy can travel through a vacuum.
It can be absorbed, reflected, or refracted.
Conduction – is the transfer of thermal energy between two objects
that are in direct physical contact. Thermal energy always moves
from a region of higher temperature to a region of lower
temperature. Thermal energy is the energy an object has because of
the motion of its molecules.
Convection – the transfer of thermal energy by highly energized
molecules moving from one place to another. This movement can
occur in liquids and gases but not solids.
Climatographs
A climatograph is a graph that shows the average monthly
temperatures and precipitation for a particular region on a single
graph. Average measurements are taken over several years.
The horizontal axis of a climatograph indicates the 12 months of the
year. The right vertical axis indicates the temperature ( in °C) and
the left vertical axis indicates average rainfall (in mm). The average
precipitation is represented by a bar graph, while the average
temperature is represented by a line graph.
Climatographs help scientists classify and compare the climates of
various regions.
P269 -
READ 7.1 P269 - 277