L6- other anthropogenic impacts on climate Flashcards
Describe the main components of the Earth’s energy budget
Incoming shortwave radiation from the sun (mostly visible and UV light)
Reflected shortwave radiation from clouds, aerosols, and Earth’s surface (albedo effect)
Absorbed shortwave radiation by the atmosphere and surface
Outgoing longwave radiation (infrared) emitted by Earth’s surface and atmosphere
Absorbed longwave radiation by greenhouse gases
Re-emitted longwave radiation back toward the surface, contributing to the greenhouse effect
What are the internal forcings influencing the main components of Earth’s energy budget?
Internal forcings are within the Earth system and include:
Cloud cover (affects both albedo and greenhouse effect)
Atmospheric water vapor and aerosols
Surface albedo (e.g., snow, ice, forests, deserts)
Carbon cycle feedbacks, including vegetation response and oceanic absorption
What are the external forcings influencing the main components of Earth’s energy budget?
External forcings come from outside the climate system:
Solar variability (solar output)
Orbital changes (Milankovitch cycles)
Volcanic eruptions (inject aerosols into the stratosphere, increasing albedo)
Anthropogenic emissions (GHGs, aerosols, land-use change)
What factors would you consider when assessing how these forcings influence the main components of Earth’s energy budget?
Radiative properties (reflectivity, absorptivity)
Geographical distribution (latitude, surface type)
Atmospheric lifetime (how long they persist)
Magnitude of radiative forcing (W/m²)
Feedback mechanisms (e.g., water vapor, ice-albedo)
Rapid adjustments (e.g., cloud formation or evaporation)
How does aerosol influence the energy budget?
Directly (Aerosol–Radiation Interaction):
Non-absorbing aerosols (sulfate, nitrate) scatter sunlight → cooling effect
Absorbing aerosols (black/brown carbon) absorb sunlight → warming, especially over clouds
Indirectly (Aerosol–Cloud Interaction):
Act as cloud condensation nuclei (CCN) → more, smaller cloud droplets
Increase cloud albedo (more reflection = cooling)
May prolong cloud lifetime
Semi-direct effects: absorption can warm air and evaporate clouds, reducing cooling
Net ERF from aerosols: ~–1.3 W/m² (cooling)
How does ozone influence the energy budget?
Tropospheric ozone: absorbs infrared radiation, contributes to warming (positive radiative forcing)
Stratospheric ozone: absorbs UV radiation, protects life and has a smaller warming effect
Radiative forcing:
Tropospheric ozone = major anthropogenic influence
ERF is positive, about half the size of aerosols, and double that of land-use change
How does land-use change influence the energy budget?
Alters surface albedo
Forest → farmland in snow-covered areas = higher albedo → cooling
In tropical zones = less evapotranspiration → warming
Impacts vertical distribution of energy
Less water = more sensible heat (warming effect)
More water = more latent heat (cooling via evapotranspiration)
Mixed effect on cloud formation
Irrigation may increase clouds; deforestation may decrease clouds
Rapid adjustments ≈ zero, ERF ≈ half of ozone and ¼ of aerosols
