Week 5 - Air Pollution Flashcards
What is solar radiation at Earth’s distance for the Sun?
~1370 W m-2 (solar constant ,So)
% of Solar,short wave radiation (SW) absorbed by the Earth?
~70%
% of Solar,short wave radiation (SW) reflected by the Earth
~30%
Global mean mole fraction of CH4?
~1800 ppbv
Atmospheric lifetime of methane?
~10 years
How does atmospheric mixing time compare to a species’ lifetime in determining its distribution?
If 𝜏𝑥 ≪ 𝜏mixing , the species is removed much faster than it can be mixed throughout the atmosphere, the species is removed much faster than it can be mixed throughout the atmosphere.
Therefore, mixing has little influence on its spatial distribution, and the species remains concentrated near its source.
What are the main sources of methane (CH₄)?
Natural: Wetlands, termites, ocean sediments
Human-made: Agriculture (livestock, rice), landfills, fossil fuels, biomass burning
What are some examples of non-CO2 greenhouse gases and their characteristics?
Long-lived: N₂O (Nitrous Oxide), CFCs (Chlorofluorocarbons), CH₄ (Methane)
Short-lived: O₃ (Ozone)
Interact with outgoing long-wave (LW) terrestrial radiation
How do aerosols (PM) impact climate?
Aerosols scatter and absorb incoming short (SW) solar radiation
E.g. sulphate, nitrate, organic aerosols , black carbon
What factors influence radiative forcing, which impacts climate?
Change in atmospheric concentration from pre-industrial to present-day.
Efficiency in impacting radiation (e.g., spectroscopy, aerosol size/composition).
How are future impacts of emissions of different species compared?
Using Global Warming Potentials (GWP) based on:
(Radiative Forcing of GHG × Atmospheric Lifetime) / (Radiative Forcing of CO₂ × Atmospheric Lifetime of CO₂)
What is the basic concept of the simple climate model involving blackbody radiation?
Incoming energy: Solar (short-wave) radiation of ~1370 W m².
Earth’s albedo: Earth reflects ~30% and absorbs ~70% of incoming solar radiation.
Outgoing energy: Earth emits long-wave radiation back into space (Stefan-Boltzmann Law).
Why does the effective temperature of Earth differ from its average surface temperature?
- Effective temperature: ~255 K (-18°C), ~33 K colder than Earth’s surface temperature.
- This is due to greenhouse gases in the atmosphere, which absorb and emit long-wave radiation, keeping Earth’s surface warmer.
Effective temperature vs surface temp of Earth?
Effective temp (Te)= 255k (-18C)
Surface temp (T0) = 288K (15C)
Where does the effective temperature originate?
~5.5 km altitude where temps are at 255K
What can we use to look at past changes in CO2, CH4, N2O, Halocarbons?
Data from ice cores
Why can’t we look at data from ice cores for most pollutants?
But most air pollutants are too reactive/short-lived: ozone & aerosols are not well sampled/preserved by ice cores
- to estimate pre-industrial levels, need to construct models that can simulate the past atmospheric composition
What is radiative forcing
The net change in Earth’s energy balance caused by a climate driver e.g. GHGs, aerosols
What gases are long-lived greenhouse gases?
CO2,CH4,N2O,CFCs
What are aerosols and how do they affect climate?
Tiny particles that scatter/absorb shortwave solar radiation,causing cooling (e.g. sulphates) or warming (e.g. black carbon)
What is blackbody radiation?
Radiation emitted by an ideal object that absorbs all incoming radiation. The Sun and Earth approximate blackbodies
What does Wien’s Displacement Law describe?
It gives the wavelength at which a blackbody emits most energy:
𝜆=2897/𝑇 (μm)
What is the Earth’s incoming solar energy (solar constant )
~1370 W/m2 averaged to ~342W/m2 across the Earth’s surface
How much solar energy does Earth reflect and absorb?
Reflects ~30% (albedo = 0.3), absorbs ~70%.
