Chapter 3: causes of climate change P2

Question 1

The resulting positive or negative changes in energy balance due to climate forcing are expressed as

Answer 1

radiative forcing

Question 2

The resulting positive or negative changes in energy balance due to climate forcing are expressed as radiative forcing, which is used to

Answer 2

compare the relative importance of the various forcings of climate change

Question 3

The radiative forcing is defined as

Answer 3

the (instantaneous) imbalance between the incoming and outgoing radiation at the top of the troposphere.

Question 4

Radiative forcing, /_\ F which is the

Answer 4

difference between net incoming and outgoing energy

Question 5

Radiative forcing, ΔF which is the difference between net incoming and outgoing energy, can be expressed as:

Answer 5

Question 6

if /_\ F = 0

Answer 6

under equilibrium

Question 7

For ΔF > 0

Answer 7

a positive radiative forcing, the incoming energy is higher than the outgoing. To counterbalance this forcing, the surface temperature has to increase by ΔT to produce a planetary radiative flux that is larger than the incoming flux.

Question 8

For ΔF > 0, the required counterbalance

Answer 8

The required counterbalance (increase in temperature), assuming no changes in other factors affecting the climate, is represented by this equation. :

Question 9

Climate Sensitivity

Answer 9

How sensitive is Earth ’s climate to change?

Question 10

One way to measure sensitivity of Earth’s climate is to

Answer 10

measure the change in average surface temperature of the Earth due to radiative forcing.

Question 11

Thus, climate sensitivity refers to

Answer 11

the change (increase/decrease) in the average surface temperature of the Earth for a given radiative forcing (positive/negative) .

Question 12

the increase in surface temperature, ΔT can be obtained as:

Answer 12

Question 13

If we know the radiative forcing due to various factors (forcings), we can calculate

Answer 13

the resultant change in the average surface temperature due to those factors

Question 14

Fig‐a (equilibrium) radiative forcing

Answer 14

the globally averaged solar radiation intercepted by the Earth (the 100 units, equivalent to 342 W m−2)

Question 15

positive radiative forcing

Answer 15

Assuming that the planetary albedo is unchanged (at 31%), an increase in the solar constant (Fig‐b) produces a positive radiative forcing: the rate at which the Earth‐atmosphere system absorbs solar radiation (69.69 units) is now greater than the rate at which it emits longwave radiation to space (69 units).

warming effect

Question 16

negative radiative forcing

Answer 16

Conversely, a reduction in the solar constant (Fig‐c) produces a negative radiative forcing, which has a cooling effect.

Question 17

According to the Figure above, what is the radiative forcing, in W m−2, associated with a ±1% change in the solar constant?

Answer 17

The radiative forcing is the difference between the rate at which the Earth–atmosphere system absorbs solar radiation and the rate at which it emits longwave radiation to space.

From parts (b) and (c) of Figure, the magnitude of the radiative forcing is:

(69.69 − 69) units or (69 − 68.31) units = 0.69 units, which is equivalent to:

(342 W m−2/100) × 0.69 = 2.4 W m−2 (to 2 significant figures).

The forcing is positive for a 1% increase in the solar constant (Fig‐b) and negative for a 1% decrease (Fig‐c).

Question 18

The power of a process to change the climate by altering the earth’s energy balance is estimated by its

Answer 18

radiative forcing

Question 19

Primary climate forcings graph

Answer 19

some climate forcings are positive, causing globally averaged warming, and some are negative, causing cooling.

Question 20

Natural forcings include

Answer 20

changes in the amount of energy emitted by the Sun, very slow variations in Earth’s orbit, and volcanic eruptions

Question 21

Since the start of the industrial revolution, the only natural forcing with any longterm significance has been a

Answer 21

small increase in solar energy reaching Earth.

However, this change is not nearly enough to account for the current warming.

Question 22

Climate forcing can also be caused by human activities. These activities include

Answer 22

• greenhouse gas and aerosol emissions from burning fossil fuels and
• modifications of the land surface, such as deforestation.

Question 23

Greenhouse gases are a …………….. climate forcing; that is, they

Answer 23

positive

have a warming effect. Carbon dioxide emitted from the burning of fossil fuel is presently the largest single climate forcing agent, accounting for more than half of the total positive forcing since 1750.

Question 24

Burning fossil fuels adds

Answer 24

aerosols to the atmosphere

Question 25

Burning fossil fuels adds aerosols to the atmosphere. Aerosols are

Answer 25

tiny particles in the atmosphere composed of many things, including water, ice, ash, mineral dust, or acidic droplets.

Question 26

Aerosols can

Answer 26

deflect the Sun’s energy and impact the formation and lifetime of clouds. Aerosols are a negative forcing; that is, they have a cooling effect.

Question 27

the emission from the atmosphere is ……………. to …………………

Answer 27

inversely proportional (i.e., if CO2 concentration increases emission decreases) to the logarithm of the concentration of CO2 in ppm, when other variables are held constant.

Question 28

The baselines for comparison of the increases are usually taken as the

Answer 28

concentrations in 1750, at the beginning of the Industrial Revolution. For CO2, the baseline value, C0, is 278 ppm.

Question 29

The slope of the line in the figure then gives the radiative forcing for C (another CO2 concentration):

Answer 29