Lecture 22: Climate Flashcards
-Forcing and Feedback -Natural Variability -Shifting Continent and Tectonics Affect Long-Term Climates -Solar and Orbital Forcing -Milankovitch Cycles
What controls Earth’s climate?
A complex interaction between all the “spheres”, changed and controlled through a myriad of complex forcings and feedbacks.
What is a forcing?
When something causes an imbalance between the absorption of solar radiation and energy emitted by the top the Earth’s atmosphere.
What is a feedback?
The reaction of the climate system to the forcings, which can lead to a change in the forcing that started it. Can be positive or negative.
What is weather?
The state of the atmosphere at any given place and time.
What is climate?
The average state of the weather on time scales of seasons and much more. Often expressed as 30 year averages.
What is a negative feedback?
A feedback that diminish the mechanism of change.
-Ice-albedo feedback
What is a positive feedback?
A feedback that amplify the mechanism of change.
-Water-vapor feedback
What are some external forcings?
- Tectonic
- Orbital
- Solar
- Volcanism
- Anthropogenic changes
What are some of the internal forcings?
- Greenhouse gases
- Aerosols
- Albedo
- Ocean-atmospheric circulation patterns
What is natural variablility?
It refers to how climate has varied through time due to natural external and internal forcings.
What are the two states of the Earth climates?
Greenhouse and Icehouse
What is the quaternary?
The current and most recent of the three periods in the geological time scale.
What is the holocene?
The period that started after the last ice age.
How does tectonic forcing change basic feedback cycles?
- It alters the distribution of land masses/oceans and thus the distribution of surfaces with different heat capacities and albedo.
- It affects global and regional climate patterns
- -Affects weathering rates and thus the concentration of Carbon Dioxide in the atmosphere.
What does solar forcing cause?
A change in the total solar irradiation (TSI) received at the top of the atmosphere.
What is the very long term time scale of solar forcing?
The Sun increasing in strength through time.
What is the short term time scale of solar forcing?
The non-cyclical variations in TSI on centennial scales.
What is the very short time scale of solar forcing?
The sunspot cycles.
-The lower the sunspot activity the lower the TSI and vise versa
What are the three orbital forcings/Milankovitch cycles and what are their periods?
- Eccentricity (~100,00 period)
- Tilt (~41,000 period)
- Precession (~23,000 period)
What is eccentricity and how does it affect the Earth?
It is a measure of Earth’s orbit’s departure from circularity. It changes the distance between the Sun and the Earth.
-The only orbital parameter that changes the amount of TSI
What is tilt and how does it affect Earth?
The Earth’s tilt varies between ~24.6° and 21.6°
-Controls the strength of seasons
What is precession and how does it affect the Earth?
Tilt direction rotation relative to elliptical orbit.
- Effects distribution of TSI on the surface
- Changes the timing of the solstices and equinoxes
What is an interglaciaion climate mode?
When the ocean conveyor system is ‘operational”.
What is a glaciation climes mode?
When the ocean conveyor system has shifted.
