environ 331 exam review
REVIEW FOR EXAM 1 (Feb 13, 2024 in class)
Key points from lectures: This list is long, but it is comprehensive.
1. Introduction
- By how much has the Earth warmed since ~1850?
- +1.5°C
- IPCC: what it does, who does it
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- What is the UNFCCC? Stated goal, governing body, meetings
-UN Framework Convention on Climate Change. -an international treaty to combat “dangerous human interference with the climate system” - conference of the parties in the governing body -goal approved by 192 countries
2. Climate actions; Radiation
- Actions: US – IRA; falling costs of wind and solar; new electricity is mostly renewable -
Actions – local: strong goals for carbon emissions cuts
Radiation:
- Solar activity is high now – what does this mean (high spots, high energy, etc.)
-more sunspots, more northern lights, more solar storms,
- Basic characteristics of LW and SW radiation
-LW- low frequency, near infrared to IR, the Earth's radiation, lower temp and energy
-SW- high frequency, UV and visible, the sun's radiation, higher temp and energy
- Blackbody concept
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- Energy, wavelengths, temperature for Sun vs Earth
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- Solar constant – how do you calculate this?
-energy per unit area at a given distance from the sun
-S= POWER OF THE SUN/ AREA OF IMAGINARY SPHERE OF Re,orbit (W/m^2)
- Blackbody temperature calculation – be able to set this up; what assumptions are involved? I will provide the equations for energy in and energy out.
-?? Energy flux in=energy flux out
S*piR^2 = sigma(o)T^4 * 4piR^2
- Earth temperature
- about 15C
- What makes Earth not a blackbody?
- reflectivity is 30%
- Albedo – why might it change, what are main reflective surfaces
- reflectivity-change from surface (snow, ice, grass, deserts) and atmosphere(clouds, aerosols)
3. Greenhouse effect
- Greenhouse gases – which gases are, are not GHGs
-GHG- water vapor, CO2, CH4(methane), nitrous oxide(N2O), ozone(O3), CCl2F2
-not- N,O,argon,Ne, He
- Earth geometry and radiative balance:
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- radiation-in is received over area, radiation-out occurs over sphere.
- But: radiation-in is distributed over the sphere: need to balance radiation in and radiation out over the entire planet’s area, so we correct Rad-in for spherical area (divide by 4) - Greenhouse layer model of radiative transfer – understand. How to calculate, and be able to fill in red question marks in a sketch like that on slide 35, lecture 3
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- Understand the plots of GH layers and Earth T: nonlinear, but continually rising - How is Venus different from Earth? (qualitatively; if I ask a question that requires numbers, I will provide those numbers – you do not need to memorize them)
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4. Greenhouse gases
- Why do GH gas molecules interact with radiation?
-”incoming photon interacts with a water molecule that's rotating at a certain rate. When its absorbed it speeds up molecule, raises energy and molecule re radiates energy back into space”
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- Wavelength-specific aspect of GH absorption: window region, saturation, broadening - Nonlinear relationship between CO2 concentration and radiative forcing; climate sensitivity - Residence time
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- Characteristics of different GHGs: (do not need to distinguish different halocarbons, just treat as a single entity). Include tropospheric O3 from lecture 5.
• Concentrations for CO2, CH4, N2O
• Global warming potential (define, know for CO2, CH4, N2O, Halocarbons generally) • Lifetimes
• The primary sources and sinks
5. Forcings and feedbacks; Solar and aerosol direct effects
- Forcing vs feedbacks; examples
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- Atmo structure: troposphere, tropopause, stratosphere
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- Atmo mixing time
- about 1 year because its hard to get things across the equator. Atmospheric circulation
- CO2-equivalents
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- Solar variability: timescales, strength, cycle; is it responsible for recent warming? -
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-Tropospheric ozone: how is it different from other GHGs?
- Aerosols:
• Examples, sources, residence time
• Direct effect: scattering/reflection, cooling
• How they counteract warming, and what cleaner air might mean for atmospheric temperatures
• How health risks from aerosols are co-located with socioeconomically vulnerable populations
-natural sources: desert dust, volcanoes, biogenic emissions, sea spray, meteorite impacts
-anthropogenic sources: land use-deforestation, desertification, biomass burning; pollution- industry, transportation
