Topic 2

Question 1

Radiative Forcing, Q’

Answer 1

Net downward radiative flux change [Wm^-2] caused by external drivers of climate state

Question 2

Radiative Feedback, lambda

Answer 2

Net downward radiative flux change per kelvin [Wm^-2K^-1]

Question 3

Forcings

Answer 3

• Greenhouse gases such as CO2. Mostly from industry, warms the Earth.
• Sulphate aerosol particles that reflect sunlight. Produced by industry and volcanoes. Cool the Earth.
• Other aerosols, Black carbon, that absorb radiation. Mostly from industry and biomass burning. Generally warm the Earth.
• Changes in solar input. Warm and cool the Earth.

Question 4

Longer Timescale Forcings

Answer 4

• Orbital. Various kinds with periods of 10,000 to 100,000 years.
• Positions of continents. Significant time scares of millions of years and beyond.

Question 5

Planck Feedback, lambda(p)

Answer 5

The basic response. Increasing temperatures cool the system by causing more radiative and emission to space. Cools the Earth.

Question 6

Water Vapour Feedback, lambda(q)

Answer 6

Increasing atmospheric H2O traps outgoing radiation from the surface and the lower atmosphere. Warms the Earth.

Introduced by de/dTs = +gamma

Question 7

Lapse Rate Feedback, lambda(LR)

Answer 7

Changes in upper tropospheric temperatures are different than changes in surface temperature. In general, the troposphere warms more than the surface, cooling the Earth overall.

Introduced by adding a flux, F, at the surface

Question 8

Surface Albedo Feedback, lambda(SA)

Answer 8

Melting ice and snow cover increase surface absorption of solar radiation. Warms the Earth.

Introduced by dA/dTs = -alpha

Question 9

Shortwave Cloud Feedback, lambda(CLA)

Answer 9

Probably causes warming through the loss of low clouds.

Introduced by dA/dTs = -alpha

Question 10

Negative Components

Answer 10

Cause net upward radiation and cooling.

Question 11

Positive Components

Answer 11

Cause net downward radiations and warming.