What is Climate? The Basics of Climate & Climate Change
Weather vs Climate
• Weather: short term (day-to-day) variations in the atmosphere
• Climate: long term (annual, multi-annual or longer) statistical properties of the atmosphere
o World Meteorological Organisation (WMO) defines the “classical” time period as 30 years
o More than 30 years or so of data it is climate change
• “Weather is your mood, climate is your personality”
Systems
• Inflows change the content of the stock (e.g. mass and material inside the stock)
• The small T on each flow signifies a faucet (e.g. control inflow of CO2)
• Cloud like shape at the beginning and end are outside of the system (extrinsic). They stand for wherever
those flows come in or go from.
o Whatever that occurs outside are not of relevant interest, we focus on the inside.
• Allows us to join different subsystems into larger systems; can be simple to complex.
What is the stock of climate? (aka what is the atmosphere made of?)
• Permanent gases: nitrogen (78%), oxygen (21%), argon
o Long residence time (millennial)
• Variable gases: CO2, CH4 (methane), O3 (ozone)
o Volume changes over space & time in the short term
o Each of them have very specific impacts on the atmosphere
What are the flows in the system? (how they change the quantity of the stock?)
• Material & Energy: without energy, there is no climate
o Energy from the Sun, Materials are the permanent & variable gases
• Three main physical processes help to alter or drive the flows within a system:
o Conduction: transfer of energy through the physical contact of molecules
o Convection: molecules of a fluid can transfer energy vertically
o Radiation: transfer of energy through the electromagnetic spectrum through radiation waves;
no medium required
• Flows within a system – in the long run, inputs into the system have to be balanced by the outputs,
otherwise things will overheat or get too cold
• Sun emits short wave radiation, once it is absorbed by earth and cools down, it is emitted as long wave
radiation.
,• Flow of energy through the arrows quantified by numbers
• Processes of how it is absorbed by gases or reflected by gases or absorbed by the surface/ozone layer
• About 45/100 units of energy from the Sun absorbed by Earth’s surface; about 31/100 units reflected
back into space as short wave radiation (how wide clouds are, how reflective surface is); about 21/100
units absorbed by the atmosphere.
• Over the long run, 45 units + 21 units re-radiated back into space (with 3 from ozone)
o Add this up to the short wave component we get 100 units
• In summary, energy that comes from the Sun has to be balanced by the energy that goes out from the
Earth, atmosphere, gases, stock back into space. This allows for the climate system to happen.
Greenhouse Effect
• Natural occurrence, prevent radiation from the surface to escape into the atmosphere, i.e. slows down
how much energy goes out
o Warms the atmosphere and the earth’s surface as well (radiation bounces back)
o Blanket analogy (blanket traps heat to make you feel comfortable) – normal greenhouse effect
• Issue: enhanced greenhouse effect, makes it warmer (more heat trapped)
o Adding/subtracting “blankets” results in changes in the system (processes, flow & stock)
o Water vapour is also a fantastic greenhouse gas
• Parts of the Earth’s system that acts as sinkholes to try to remove CO2 from the atmosphere
o Trees (absorb CO2 in order to develop and grow in size)
o Oceans (dissolve CO2 and keep it in ocean to store it away from atmosphere)
o Soil & terrestrial surfaces (absorb CO2)
• Basically understand where the stocks and flows are, how the processes affect the quantity of the stock
and quality in terms of rate of change of the stock in the system
, Feedbacks
1
1
• Refers to how the components within the system respond or are affected to a change
o Specific term if “forcing”, how it forces the system to react that either enhances or diminishes
the forcing.
§ Negative feedback cycle: inhibits further changes; adding a process doesn’t lead to a
change or further change drops.
§ Positive feedback cycle: magnifies initial changes
• When systems become more complex, accounting for these feedback mechanisms becomes more
challenging, especially for climate.
• Positive feedback cycle is more widespread in scale, it occurs planet-wide
• Negative feedback cycle tends to be concentrated in tropical areas, where more clouds tend to occur
and helps to reflect more shortwave radiation
• For instance, air-conditioning as a positive feedback cycle
Weather vs Climate
• Weather: short term (day-to-day) variations in the atmosphere
• Climate: long term (annual, multi-annual or longer) statistical properties of the atmosphere
o World Meteorological Organisation (WMO) defines the “classical” time period as 30 years
o More than 30 years or so of data it is climate change
• “Weather is your mood, climate is your personality”
Systems
• Inflows change the content of the stock (e.g. mass and material inside the stock)
• The small T on each flow signifies a faucet (e.g. control inflow of CO2)
• Cloud like shape at the beginning and end are outside of the system (extrinsic). They stand for wherever
those flows come in or go from.
o Whatever that occurs outside are not of relevant interest, we focus on the inside.
• Allows us to join different subsystems into larger systems; can be simple to complex.
What is the stock of climate? (aka what is the atmosphere made of?)
• Permanent gases: nitrogen (78%), oxygen (21%), argon
o Long residence time (millennial)
• Variable gases: CO2, CH4 (methane), O3 (ozone)
o Volume changes over space & time in the short term
o Each of them have very specific impacts on the atmosphere
What are the flows in the system? (how they change the quantity of the stock?)
• Material & Energy: without energy, there is no climate
o Energy from the Sun, Materials are the permanent & variable gases
• Three main physical processes help to alter or drive the flows within a system:
o Conduction: transfer of energy through the physical contact of molecules
o Convection: molecules of a fluid can transfer energy vertically
o Radiation: transfer of energy through the electromagnetic spectrum through radiation waves;
no medium required
• Flows within a system – in the long run, inputs into the system have to be balanced by the outputs,
otherwise things will overheat or get too cold
• Sun emits short wave radiation, once it is absorbed by earth and cools down, it is emitted as long wave
radiation.
,• Flow of energy through the arrows quantified by numbers
• Processes of how it is absorbed by gases or reflected by gases or absorbed by the surface/ozone layer
• About 45/100 units of energy from the Sun absorbed by Earth’s surface; about 31/100 units reflected
back into space as short wave radiation (how wide clouds are, how reflective surface is); about 21/100
units absorbed by the atmosphere.
• Over the long run, 45 units + 21 units re-radiated back into space (with 3 from ozone)
o Add this up to the short wave component we get 100 units
• In summary, energy that comes from the Sun has to be balanced by the energy that goes out from the
Earth, atmosphere, gases, stock back into space. This allows for the climate system to happen.
Greenhouse Effect
• Natural occurrence, prevent radiation from the surface to escape into the atmosphere, i.e. slows down
how much energy goes out
o Warms the atmosphere and the earth’s surface as well (radiation bounces back)
o Blanket analogy (blanket traps heat to make you feel comfortable) – normal greenhouse effect
• Issue: enhanced greenhouse effect, makes it warmer (more heat trapped)
o Adding/subtracting “blankets” results in changes in the system (processes, flow & stock)
o Water vapour is also a fantastic greenhouse gas
• Parts of the Earth’s system that acts as sinkholes to try to remove CO2 from the atmosphere
o Trees (absorb CO2 in order to develop and grow in size)
o Oceans (dissolve CO2 and keep it in ocean to store it away from atmosphere)
o Soil & terrestrial surfaces (absorb CO2)
• Basically understand where the stocks and flows are, how the processes affect the quantity of the stock
and quality in terms of rate of change of the stock in the system
, Feedbacks
1
1
• Refers to how the components within the system respond or are affected to a change
o Specific term if “forcing”, how it forces the system to react that either enhances or diminishes
the forcing.
§ Negative feedback cycle: inhibits further changes; adding a process doesn’t lead to a
change or further change drops.
§ Positive feedback cycle: magnifies initial changes
• When systems become more complex, accounting for these feedback mechanisms becomes more
challenging, especially for climate.
• Positive feedback cycle is more widespread in scale, it occurs planet-wide
• Negative feedback cycle tends to be concentrated in tropical areas, where more clouds tend to occur
and helps to reflect more shortwave radiation
• For instance, air-conditioning as a positive feedback cycle
