Earth's Energy Balance Flashcards
What is the first law of thermodynamics?
Conservation of energy- energy cannot be created or destroyed only changed from one form to another.
What is entropy?
• Entropy is a measure of the unavailability of a
system’s heat energy for conversion to other
forms of energy
• Lower entropy – more energy the system has
for conversion to other forms of energy
• Higher entropy – more disorganized system
What is the second law of thermodynamics?
– entropy increases with time so the system becomes
more disorganized
Distinguishing between temperature and heat
- Temperature – measure of the mean kinetic energy (speed) per molecule of an object (internal energy)
- Heat – measure of total kinetic energy of all the molecules of an object
Distinguishing between sensible and latent heat
• Sensible heat – heat acquired by transfer from
an object of higher temperature
• Latent heat – heat acquired when a body
changes to a higher state (solid to liquid or liquid
to gas). Heat added at the change of state
doesn’t raise the temperature
Heat transfer Processes- Conduction
Conduction – molecular impact without the
transfer of matter itself (heat transfer in solids)
Heat transfer Processes- Convection
Convection – involves the movement of large
volumes of the substance itself (mode of heat
transfer in fluids)
Heat transfer Processes- Radiation
Radiation – electromagnetic emission from a
body
Radiation
• Does not require a medium to travel through
• Has both a wave structure and a particle (photon) structure
• Spectrum of wavelengths
• Radiation laws – show that the amount of radiant energy emitted by an object is much greater as temperature
increases and is wavelength dependent
Global radiation receipt
Sum of all short-wave radiation received from
direct solar radiation and indirect diffuse radiation
Reflects astronomical factors and the distribution
of clouds
Shows a strong diurnal variation in intensity
Albedo
A measure of the reflecting power of a
surface (reflectivity)
The Natural Greenhouse Effect
• Water vapour, CO2 and other trace gases absorb
long-wave radiation emitted by the Earths surface
– re-emitting some back to Earth
• Without the natural Greenhouse Effect, the Earth
would be much colder
Radiative forcing of climate- forcing
Forcing – Processes acting as external agents to the
climate system that change the energy balance – e.g.
loading of the atmosphere with aerosols (particles)
Give examples of forcing
– Such forcing can occur naturally after volcanic eruptions or wildfires for example
– Aerosols scatter/reflect radiation and act as condensation nuclei promoting cloud formation
– Tropospheric sulphate aerosols slightly increase the atmospheric albedo – slight cooling effect (negative feedback)
Radiative forcing of climate- feedback
Feedback – Internal agent acting in response to forcing
agents (either negative or positive)
What is absolute zero?
As temperature decreases and the molecules are at complete rest where there is no internal energy, it is known as absolute zero.
How does radiation travel?
Radiation does not require any medium through which to travel and so it can pass through a vacuum with the speed of light.
What is a black body?
One that absorbs all the radiation falling on it and that emits, at any temperature, the maximum amount of radiant energy.
Why is albedo important?
It determines the fraction of the incoming solar radiation that is absorbed by the surface.
The greater the albedo, the less solar radiation is absorbed.
What is net radiation?
The difference between the total incoming and the total outgoing radiation.
What is the effect of thermal inertia?
To delay the atmospheric and oceanic response to various climate forcings.
What does the presence of thermal inertia imply?
That still greater climate changes will be in store for present increased atmosphere CO2 levels, which may be difficult or impossible to avoid.
What is the primary symptom of the climate system’s thermal inertia, in the presence of increasing greenhouse gas concentrations?
An imbalance between the energy absorbed and emitted by the planet.
What did Hansen (2005) discover?
Using a climate model, driven mainly by increasing human-made greenhouse gases and aerosols, among other forcing that the sun is now absorbing 0.85 +/- 0.15 W m-2 more energy from the sun than it is emitting to space.
What is the imbalance between the energy absorbed and emitted by the planet confirmed by?
Precise measurements of increasing ocean heat content over the past 10 years.
This implies an expectation of additional global warming of about 0.6oC without further change of atmospheric composition.
IPCC Working Group 1, Fourth Assessment Report (2007a) estimated that..
a further 0.6oC unavoidable warming by the end of the century relative to 1980-1999 even if atmospheric greenhouse levels remain at 2000 levels.
IPCC Working Group 2, Fourth Assessment Report (2007b) commented that…
this leads to the conclusion that there are some impacts for which adaptation is the only available and appropriate response.
What is lost and gained in terms of radiation in the atmosphere?
The atmosphere loses more heat to space in the form of long wave radiation than it gains from the absorption of short wave radiation, and this is the equivalent to a cooling of 1 or 2 degrees per day.
What is the majority of the heat lost to space in long term radiation?
The latent heat released by atmospheric water vapour that has evaporated from the surface, condensing to form precipitation.
What maintains the mean equilibrium atmospheric temperature?
A balance between radiative cooling and condensational heating.
Radiation has
a wave and a particle structure
Incoming radiation from the sun is predominantly
shortwave
• Radiation laws –
show that the amount of radiant energy emitted by an object is much greater as temperature increases and is wavelength dependent
