GEO – Unit 2 Notes
2.1. Causes of global climate change
Atmosphere – consists of the mixture of solids, liquids and gases that are held to the earth by
the gravitational force – consists of weather and climate
Weather – the state of the atmosphere at a local level, usually on short-term timescale from
minutes to months – includes temperature, precipitation, atmospheric pressure, wind speed
and wind direction
Climate – the average weather condition of a place taken over a given period of time, usually
about 30 years – climatic data temperature, precipitation, atmospheric pressure, wind speed
and wind direction are used to predict elements of weather for daily, monthly or annually
averages
The Atmospheric System
o Air of our planet is composed of 79% nitrogen and under 21% oxygen – the rest is
carbon dioxide + other inert gases, e.g. argon
o Four layers of the atmosphere: troposphere, stratosphere, mesosphere and
thermosphere
Energy balance in the atmosphere
o Main source of earth’s energy is the sun
o The earth receives incoming energy in the form of short-wave radiation or solar
radiation
o The amount of energy received is determined by different factors; absorption,
reflection, scattering, transmission or refracted
Absorption
o Mainly by ozone, carbon dioxide, particles of ice or dust
Reflection
o Mainly by clouds and a bit the surface of the earth
o High clouds reflect (low ones give precipitation or trap long-wave radiation)
o Albedo – the proportion of solar radiation reflected by the Earth’s surface
Scattering
o Occurs when solar radiation is diverted
o Takes place in all directions + may reach the earth as diffuse radiation
o Diverted by particles of dust, molecules of gas, volcanoes and deserts
Transmission
o Occurs when both shortwave and longwave energy, instead of scattering, pass through
the atmosphere
, Refracted
o When energy moves from one type of space to another, e.g. from air to water
o As the energy moves, it changes its speed + direction when reacting with the particles
present in it
• Less than half of the solar energy actually reaches the Earth due to the combined effect
of the factors above
• When solar energy reaches the Earth, it is converted into heat energy – this energy is
needed to keep the earth warm
Long-wave or infrared radiation – the energy that is radiated from the surface of the earth back
into the atmosphere
o Over 90% of this energy is trapped by the ozone layer or absorbed by carbon dioxide,
clouds + water vapour
o This energy is then re-radiated and 6% is lost to space – this process is called the natural
greenhouse effect
o The natural greenhouse effect keeps the earth’s temperature at a level that makes it
possible for living things to survive on this planet
Horizontal heat transfers – horizontal movement of heat across the globe – done through wind,
hurricanes, depressions and ocean currents
Vertical heat transfers – vertical movement of heat into the atmosphere – achieved through
radiation, conduction, convection and latent heat
Change in global energy balance and the role of feedback loops
o External factors can also contribute to climate change in ways described as atmospheric
forcings – outside of earth, no human activity and can increase/decrease global
temperatures
Feedback loops
o In the atmospheric system, the input is short-wave radiation, and the output is long-
wave radiation from the earth
o The output of energy can be reinvested into the atmospheric system when long-wave
radiation is re-radiated to the earth – this is feedback loops (which can be positive or
negative)
Positive feedback – tends to amplify or enhance the initial system by changing its equilibrium
state
o E.g. increase in global temperature increase in the melting of ice in polar regions
may lead to decrease in glaciers and ice sheets reducing albedo (fresh snow reflects
solar radiation) increase in solar radiation increasing global temperatures
2.1. Causes of global climate change
Atmosphere – consists of the mixture of solids, liquids and gases that are held to the earth by
the gravitational force – consists of weather and climate
Weather – the state of the atmosphere at a local level, usually on short-term timescale from
minutes to months – includes temperature, precipitation, atmospheric pressure, wind speed
and wind direction
Climate – the average weather condition of a place taken over a given period of time, usually
about 30 years – climatic data temperature, precipitation, atmospheric pressure, wind speed
and wind direction are used to predict elements of weather for daily, monthly or annually
averages
The Atmospheric System
o Air of our planet is composed of 79% nitrogen and under 21% oxygen – the rest is
carbon dioxide + other inert gases, e.g. argon
o Four layers of the atmosphere: troposphere, stratosphere, mesosphere and
thermosphere
Energy balance in the atmosphere
o Main source of earth’s energy is the sun
o The earth receives incoming energy in the form of short-wave radiation or solar
radiation
o The amount of energy received is determined by different factors; absorption,
reflection, scattering, transmission or refracted
Absorption
o Mainly by ozone, carbon dioxide, particles of ice or dust
Reflection
o Mainly by clouds and a bit the surface of the earth
o High clouds reflect (low ones give precipitation or trap long-wave radiation)
o Albedo – the proportion of solar radiation reflected by the Earth’s surface
Scattering
o Occurs when solar radiation is diverted
o Takes place in all directions + may reach the earth as diffuse radiation
o Diverted by particles of dust, molecules of gas, volcanoes and deserts
Transmission
o Occurs when both shortwave and longwave energy, instead of scattering, pass through
the atmosphere
, Refracted
o When energy moves from one type of space to another, e.g. from air to water
o As the energy moves, it changes its speed + direction when reacting with the particles
present in it
• Less than half of the solar energy actually reaches the Earth due to the combined effect
of the factors above
• When solar energy reaches the Earth, it is converted into heat energy – this energy is
needed to keep the earth warm
Long-wave or infrared radiation – the energy that is radiated from the surface of the earth back
into the atmosphere
o Over 90% of this energy is trapped by the ozone layer or absorbed by carbon dioxide,
clouds + water vapour
o This energy is then re-radiated and 6% is lost to space – this process is called the natural
greenhouse effect
o The natural greenhouse effect keeps the earth’s temperature at a level that makes it
possible for living things to survive on this planet
Horizontal heat transfers – horizontal movement of heat across the globe – done through wind,
hurricanes, depressions and ocean currents
Vertical heat transfers – vertical movement of heat into the atmosphere – achieved through
radiation, conduction, convection and latent heat
Change in global energy balance and the role of feedback loops
o External factors can also contribute to climate change in ways described as atmospheric
forcings – outside of earth, no human activity and can increase/decrease global
temperatures
Feedback loops
o In the atmospheric system, the input is short-wave radiation, and the output is long-
wave radiation from the earth
o The output of energy can be reinvested into the atmospheric system when long-wave
radiation is re-radiated to the earth – this is feedback loops (which can be positive or
negative)
Positive feedback – tends to amplify or enhance the initial system by changing its equilibrium
state
o E.g. increase in global temperature increase in the melting of ice in polar regions
may lead to decrease in glaciers and ice sheets reducing albedo (fresh snow reflects
solar radiation) increase in solar radiation increasing global temperatures
