Lecture 22: Climate

Question 1

What controls Earth’s climate?

Answer 1

A complex interaction between all the “spheres”, changed and controlled through a myriad of complex forcings and feedbacks.

Question 2

What is a forcing?

Answer 2

When something causes an imbalance between the absorption of solar radiation and energy emitted by the top the Earth’s atmosphere.

Question 3

What is a feedback?

Answer 3

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.

Question 4

What is weather?

Answer 4

The state of the atmosphere at any given place and time.

Question 5

What is climate?

Answer 5

The average state of the weather on time scales of seasons and much more. Often expressed as 30 year averages.

Question 6

What is a negative feedback?

Answer 6

A feedback that diminish the mechanism of change.

-Ice-albedo feedback

Question 7

What is a positive feedback?

Answer 7

A feedback that amplify the mechanism of change.

-Water-vapor feedback

Question 8

What are some external forcings?

Answer 8

• Tectonic
• Orbital
• Solar
• Volcanism
• Anthropogenic changes

Question 9

What are some of the internal forcings?

Answer 9

• Greenhouse gases
• Aerosols
• Albedo
• Ocean-atmospheric circulation patterns

Question 10

What is natural variablility?

Answer 10

It refers to how climate has varied through time due to natural external and internal forcings.

Question 11

What are the two states of the Earth climates?

Answer 11

Greenhouse and Icehouse

Question 12

What is the quaternary?

Answer 12

The current and most recent of the three periods in the geological time scale.

Question 13

What is the holocene?

Answer 13

The period that started after the last ice age.

Question 14

How does tectonic forcing change basic feedback cycles?

Answer 14

• 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.

Question 15

What does solar forcing cause?

Answer 15

A change in the total solar irradiation (TSI) received at the top of the atmosphere.

Question 16

What is the very long term time scale of solar forcing?

Answer 16

The Sun increasing in strength through time.

Question 17

What is the short term time scale of solar forcing?

Answer 17

The non-cyclical variations in TSI on centennial scales.

Question 18

What is the very short time scale of solar forcing?

Answer 18

The sunspot cycles.

-The lower the sunspot activity the lower the TSI and vise versa

Question 19

What are the three orbital forcings/Milankovitch cycles and what are their periods?

Answer 19

1. Eccentricity (~100,00 period)
2. Tilt (~41,000 period)
3. Precession (~23,000 period)

Question 20

What is eccentricity and how does it affect the Earth?

Answer 20

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

Question 21

What is tilt and how does it affect Earth?

Answer 21

The Earth’s tilt varies between ~24.6° and 21.6°

-Controls the strength of seasons

Question 22

What is precession and how does it affect the Earth?

Answer 22

Tilt direction rotation relative to elliptical orbit.

• Effects distribution of TSI on the surface
• Changes the timing of the solstices and equinoxes

Question 23

What is an interglaciaion climate mode?

Answer 23

When the ocean conveyor system is ‘operational”.

Question 24

What is a glaciation climes mode?

Answer 24

When the ocean conveyor system has shifted.