lecture 2

Question 1

Why do the sun and earth have different spectral properties? wavelength reflects intensity of energy flux

Answer 1

No atmosphere, straight exchange
Values of energy in and out in Wm-2
Planet emits longer wavelength radiation

Question 2

Temperature of a radiating body definition

Answer 2

is a function of energy out (emissivity) and σ, the Stefan-Bolzmann contstant (5.67 x 10-8), and albedo

Question 3

Temperature of earth with no atmosphere

Answer 3

-18oC

Question 4

Abundant atmospheric gases (not GHGs)

Answer 4

Nitrogen, Oxygen and water vapour

Question 5

GHG molecules, natural gases

Trace atmospheric gases

Answer 5

Co2, methane

Nitrous oxide, ozone

Question 6

Unnatural gases

Answer 6

Halocarbons
Sulfa Hexafluoride Sf6
= human made and most potent and long lasting of the GHGs

Question 7

Absorption capacity of atmosphere depends on

Answer 7

amount of each type of molecule present

absorption spectrum of each type of molecule

Question 8

In order for the greenhouse effect to work what must be present in the atmosphere?

Answer 8

Greenhouse gases

Question 9

Changing the atmospheric composition of greenhouse gases such as Co2 does what to the atmosphere?

Answer 9

Alters the atmosphere’s capacity to absorb and re-radiate energy

Question 10

To balance the input and output of energy what is required?

Answer 10

heating of atmosphere and
Earth surface – a planet with atmosphere is
warmer than it would otherwise be

Question 11

What affects energy pathways?

Answer 11

Albedo

Question 12

Why is energy exchange usually measured at the top of the troposphere?

Answer 12

GHGs are active below tropopause and therefore lose energy at the top of the troposphere

Question 13

What is the lapse rate of the troposphere?

Answer 13

warms and becomes denser towards the surface

Question 14

The more molecules of GHG added, the more what?

Answer 14

interception and re-radiation

Question 15

What is currently resultant of the ongoing process of adding GHGs and what does this mean?

Answer 15

Disequilibrium - heat loss from the upper troposphere is not keeping up with heat gain via increased GHGs

Question 16

What is a net radiation?

Answer 16

the
balance between the incoming and outgoing radiation for the
planet—measured at the tropopause
Net positive at the equator and negative at the poles

Question 17

What can drive a change in net radiation, temporarily disturbing the balance? and what results from this?

Answer 17

A perturbation (change in GHG concentration
Causes temperature change

Question 18

What is radiative forcing?

Answer 18

Change in net radiation driving a temperature change - not a always change in radiation e.g incoming solar, but a change that affects net radiation

Question 19

What is a perturbation? And examples

Answer 19

Change in net radiation leads to a temporary energy imbalance
1. Less solar energy in (e.g
change in solar constant )
2. Overall reduction of energy
in system
3. temperature
decreases
4. emissions
decrease to reach new balance
= negative radiative forcing

Question 20

What are the preindustrial, 2x and current levels of Co2

Answer 20

280ppm, 400ppm, 560ppm

Question 21

For a temporary decrease in radiation out ( more absorbing in troposphere) what type of radiative forcing?

Answer 21

Positive:

temperature increases overtime as a result

Question 22

Examples of positive radiative forcing? (in order)

Answer 22

Co2 increase, methane halocarbons increase, ozone increase, water vapour

Question 23

Examples of negative radiative forcing

Answer 23

Cloud albedo effect, land use

Question 24

If warming happened instantaneously, using the average value

of Earth’s emissivity, what forcing value causes a temperature rise?

Answer 24

a positive forcing of 3.75 W m-2 (that of

2xCO2) should result in a 1°K* rise in temperature

Question 25

Oceans have what heat capacity?

Answer 25

High heat capacity

Question 26

Temperature increase since GHGs began to rise?

Answer 26

0.5oC

Question 27

Emergy imbalance due to GHG increasing to 400 ppm is..?

Answer 27

1.0 wm-2

Question 28

Planet’s sensitivity =

Answer 28

How much the earth finally warms for 2xCo2

Question 29

Positive feedbacks raise the estimates of 2xCo2 temperature increase to

Answer 29

2.1 - 4.4 oC

Question 30

Climate models attempt to do what?

Answer 30

Deal with all the critical forcings and feedbacks and take into account earth’s varied surface and interactions between land, ocean and atmosphere

Question 31

Climate sensitivity

Answer 31

The net response of the climate to a 2xCo2 forcing is 2.1-4.4 oC Response of the earth system to the overall radiative forcing

Question 32

What temperature rise is aimed to limiting

Answer 32

2oC