1 - Energy and Climate Flashcards
What is the difference between climate and weather?
Climate is the average weather conditions of a place, usually measured over one year or month – including temperature, rainfall and wind.
Weather is the day to day condition of the atmosphere, including temperature, rainfall and wind
What are the components of the climate system?
Atmosphere
Hydrosphere – oceans, lakes & rivers
Cryosphere – ice sheets, sea ice, glaciers, snow, permafrost
Geosphere – soil, mountains, volcanoes, plate tectonics
Biosphere – land, marine
What are the sources of energy for the climate system?
Solar radiation(providing 342 W/m2 on avg), geothermal energy, anthropogenic energy generation, radiation from a full moon, radiation from stars
How does solar radiation work?
Nuclear fusion in the Sun’s core creates radiation that is quickly absorbed in the Sun’s interior and cconverted to heat which then moves outward through conduction and convection.
From the Sun’s outer layer, radiation is emitted to space and the Earth intercepts a tiny fraction of this.
Describe the properties of radiation.
Oscillations of electric and magnetic fields
Characterised by frequency or wavelength
Moves with constant speed
Product of wavelength and frequency
Electromagnetic energy depends on frequency
How does Planck’s law describe the radiation of a black body?
The Planck function describes the intensity of radiation for a given wavelength and for a black body of a certain temperature - hotter objects emits more radiation at small wavelengths.
How does the Stefan-Boltzmann Law relate to Planck’s law?
It is the integral of Planck’s function over all wavelengths.
How does the Stefan-Boltzmann Law describe the relationship between the total energy emitted and the temperature of an object?
The hotter an object is the more total energy it emits per unit area - doubling temperature leads to sixteen fold increase in emitted energy as the formula is E = (Delta) x T(to the power of 4)
What is the solar constant?
The solar energy flux received by the Earth(outside its atmosphere) - it is approx 1360 W/m(sq)
It depends on total radiation emitted by the Sun & Sun-Earth distance.
How do changes in solar output occur?
Total radiation emitted by the Sun:
Geological time scales -radiation emitted by the Sun increases steadily over time(faint young Sun paradox)
Decadal/centennial time scales - sunspot activity(every 11 years) dominates changes in solar output
Sun-Earth distances:
Elliptical vs Spherical orbit - Milankovitch cycles
Why is Earth’s mean surface temperature 15C and not 5C as the Stefan-Boltzmann law would suggest?
- Earth is not a black body and has an albedo of around 0.3 - Earth’s average temperature should be -18C
- The Earth’s atmosphere acts as a blanket that raises surface temperatures on average by 33C and makes our planet habitable.
