Factors Affecting Climate Change
Climate: the characteristic pattern of weather conditions within a region,
including temperature, wind velocity, precipitation, and other features, averaged
over a long period of time. (ON Science 10)
The climate IS changing.
Evidence:
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Ice sheet depths are decreasing
Ocean levels are rising
Oceans are Acidifying
Average global temperatures have increased by 0.74 degrees celcius (1.4
degrees in Ontario)
 Wind patterns have changed over the past 50 years
 Precipitation patterns have changed over the past 50 years
So there is evidence that climate is changing. However, the Earth has
experienced periodic climate changes in climate before humans even existed.
Historic Global Temperatures and Natural Climate Variability
Earth's climate has always been affected by a range of natural factors and is
known to have changed significantly during recorded history, before gaseous
emissions from human activity could have posed any significant threat to
atmospheric or climatic conditions.
The graph below shows average global temperature changes plotted against a
scale for time increasing in powers of ten, from millions of years ago to the
present. Look CAREFULLY at the scale.
What do you notice?
Earth's temperature trends
A schematic representation of recent climate trends and future projections in
historical perspective. The 20th century is shown on a linear scale. Earlier
periods are shown in terms of increasing powers of ten years ago but are linear
within each period.
Source: Bureau of Meteorology, The greenhouse effect and climate change,
Bureau of Meteorology, 2003, p. 33.
Natural Causes of Climate Change (Global Warming or Cooling)
Extraterrestrial (NOT aliens!)
1. Changes in Solar Activity
 The amount of solar radiation fluctuates over time
 Sun spot activity
 Sun spots follow an 11 year cycle of activity showing variations in solar
output of approximately 0.1%
2. Movement of Earth in Space
 Seasons are caused by the Earth’s 23.5 degree tilt
 The Earth rotates and revolves constantly through space around the sun.
3. Changes in the Earth’s Rotation, Orbit and Tilt
 Milankovic, a Serbian Mathematician in the 1900s, proposed that changes
in the Earth’s movement affects global climate.
 These changes in movement or position can affect the intensity of solar
radiation on different parts of the planet.
Eccentricity: Orbit in space changes about a period of 100 000 years from
circular to elliptical.
Tilt: the Earth’s tilt varies between 22.1 and 24.5 degrees over a period of
41 000 years
Wobble: The Earth is not a perfect sphere which causes it to “wobble” slightly
as it rotates.
4. Latitude
 The varying intensity of solar radiation on different parts of the Earth
account for difference in climate between different parts of the world.
 This also affects the amount of solar radiation absorbed by different land
masses and oceans.
Interactions of Factors
Combinations of these factors have been responsible for cooling and warming
periods in the past.
Example: Little Ice Age
In the 16th and 17th century Europe experienced a cooling period.
A combination of the above factors combined with volcanic activity have been
used to explain the sudden change in climate.
However, computer modeling suggests that each individual factor or even a
combination of the above could account for some of the dramatic changes in
the Earth’s climate that have been recorded.
The above extraterrestrial factors should account for global variations in
temperature over many thousands of years, however what we have found in ice
cores disagrees with this because there is evidence of faster periods of cooling
and warming.
Atmospheric Factors
5. Greenhouse Gases
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Gases in the atmosphere that absorb thermal energy.
This helps the Earth to retain energy so that it does not fly off in to space
This process is called “the greenhouse effect”
Without it life on Earth would not be possible and would be frozen.
Examples of Greenhouse Gases:
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Carbon dioxide
Methane
Nitrous oxide
Ozone
Venus for example presently has an atmosphere of about 96% carbon dioxide
but is believed by many scientists to have once had a closer climate to that of
Earth.
Scientists have for many years theorized that greenhouse gases could account
for faster changes in temperature observed in ice cores.
Example of Impact of Greenhouse Gases in the Past:
Late Paleocene Thermal Maximum (LPTM, 55 million years ago)
Scientists have long known that there was a short, but dramatic period of
warming at the end of the Palaeocene era. This is now believed to have resulted
from several massive releases of methane from the sea floor, probably as a
result of continental drift, but possibly as a result of volcanic activity.
6. Convection Currents
Hot air rises, cold air sinks which creates wind patterns
7. Ocean Currents
 Oceans absorb and release energy
 Winds help to move ocean water
 Differences in temperature and salt concentration causes giant ocean
currents like rivers under the water
8. Precipitation Patterns
 Wind and air masses create jet streams which are high altitude winds.
 These impact where and when rain falls.
9. Heat Capacity of Water
Heat Capacity: the amount of energy required to increase the temperature of a
substance one degree celcius.
 Water absorbs lots of solar energy before it evaporates.
 Lakes and Oceans are heat reservoirs that can absorb and release energy
slowly.
10. Albedo
 Lighter objects reflect solar energy.
 Dark ones absorb it.
 Ice reflects solar energy, so it may explain how ice ages progress faster
and faster since more ice means more reflected solar energy.
Terrestrial Factors
11. Movement of Tectonic Plates
This can affect wind and ocean currents and also cause the release of
greenhouse gases.
12. Volcanic Eruptions
 Causes the release of aerosols (tiny particles) that reflect solar radiation
back in to space.
 They also release significant amounts of greenhouse gases.
 They can cause warming or cooling depending on the interaction of other
factors.
13. Anthropogenic (Human Caused) Factors
 Release of greenhouse gases, through the burning of fossil fuels.
 The release of carbon dioxide from storage on land and in the oceans.
Current Climate Change
The temperature of the planet is increasing. The controversy surrounding global
warming is due to the arguments regarding it’s cause, whether it be natural or
anthropogenic. Many scientists believe that we are enhancing the natural
warming cycle of the Earth by releasing more greenhouse gases into the
atmosphere.
Forcing agents: these are factors that work to force the change in a climate.
Natural or anthropogenic (human made). Scientists believe greenhouse gases
could be the forcing agent for modern climate change.
Homework:
Read p. 279 - 280 on climatographs and finish your climatograph from class.