key questions

Question 1

how does ozone affect the global energy budget

Answer 1

• stratosphere = ozone absorbs harmful UV radiation from the sun = warms stratosphere whilst protecting Earth’s surface
• troposphere = ozone acts as a greenhouse gas by absorbing infrared radiation emitted from Earth’s surface, trapping hear and contributing to warming

Question 2

for anthropogenic impact on the global energy budget, is tropospheric or stratospheric ozone more important

Answer 2

troposheric ozone has a more significant impact on the global energgy budget, human activities have depleted startospheric ozone (cooling), increase in tropospheric ozone from pollution has a stronger warming effect

3rd most important GHG after CO2 and methane

Question 3

how do the lifetimes of aerosol and ozone compare against carbon dioxide

Answer 3

aerosols = days to weeks

tropospheric ozone = weeks to months

CO2 = hundreds to thousands of years

effects how quickly the climate system responds when emissions change

Question 4

what is the net radiative forcing effect on anthropogenic land-use change

Answer 4

• the net radiative forcing effect of anthropogenic land-use change is negative (cooling) = -0.2 W/m2 (IPCC AR6)
• the cooling effect primarily comes from increased surface albedo (reflectivity) when forests are converted to croplands or pastures

Question 5

Describe how anthropogenic land-use change affects albedo in mid-latitudes and semi-arid regions?

Answer 5

MID LATITUDES:
- increases albedo
- lighter coloured agricultural surface reflects more sunlight than darker forests
- more pronounced in winter when surfaces are covered in snow

SEMI ARID
- overgrazing and desertification can increase albedo by removing vegetation and exposing lighter soil surfaces

Question 6

What process is key to the local effect of land-use change on the vertical distribution of energy?

Answer 6

• Evapotranspiration is the key process affecting the local vertical distribution of energy following land-use change.
• When forests are converted to agricultural land, evapotranspiration typically decreases, reducing the transfer of latent heat to the atmosphere.
• This shifts the energy balance toward sensible heat, altering local temperature profiles and potentially affecting cloud formation and precipitation patterns.

Question 7

what are the main other anthropogenic drivers of radiative forcing

Answer 7

CO2
CH4
N2O
Halocarbons
tropospheric ozone
aerosols
black carbon on snow and ice
land-use changes
aviation-inducing cloudiness

Question 8

where does anthropgenic aerosol come from

Answer 8

• fossil fuel combustion
• biomass burning
• industrial processes
• agricultural activities
• road dust and construction
• deforestation and land-use changes

Question 9

what is an aerosol

Answer 9

Aerosols are tiny solid or liquid particles suspended in the atmosphere.

natural = volcanoes, dust storms, sea spray
anthropogenic = pollution

Question 10

What are the three mechanisms of aerosol radiative forcing?

Answer 10

1. direct effect
   - Aerosols scatter and absorb solar radiation directly, generally causing cooling
2. cloud albedo effect
   - Aerosols serve as cloud condensation nuclei, increasing cloud droplet number concentration and decreasing droplet size, which makes clouds more reflective
3. cloud lifetime effect
   - Smaller cloud droplets reduce precipitation efficiency, increasing cloud lifetime and coverage

Question 11

Which of the “other” anthropogenic impacts on climate has the greatest radiative forcings?

Answer 11

Methane (CH₄) has the greatest positive radiative forcing among the “other” anthropogenic impacts, with a forcing of approximately +0.54 W/m² according to the IPCC AR6. This makes it the second most important anthropogenic greenhouse gas after CO₂.

Question 12

define radiative forcing

Answer 12

the change in radiation balance at the tropopause between the incoming solar radiation and the outgoing earth’s radiation (net irradiance)