Unit 6 - Climate Modeling Flashcards
What is the difference between weather and climate?
Answer: Weather refers to specific atmospheric conditions at a particular place and time, while climate is defined as average weather over a 30-year period.
Name the four main components of the climate system.
- Atmosphere
- Hydrosphere (e.g., ocean)
- Cryosphere (e.g., ice, ice sheets, glaciers)
- Biosphere (e.g., land)
Explain how the water vapor feedback mechanism works.
Answer: The water vapor feedback creates an amplifying feedback loop where:
- Increased CO2 leads to increased temperatures
- This causes more water vapor in the atmosphere
- Which further increases temperature
This creates a continuous amplifying cycle.
What is (Equilibrium) Climate Sensitivity?
Answer: It is defined as the equilibrium change in global mean surface temperature following a doubling of the atmospheric CO2 concentration relative to pre-industrial state. The range of sensitivity values are:
- Lower estimate: 1.5°C
- Medium estimate: 2.5°C
- Upper estimate: 4.5°C
What are the three main types of climate models, from most to least complex?
Answer: The model hierarchy is:
1. Process-based models (General Circulation Models - GCMs)
2. Simple models of IPCC (Reduced Form Models)
3. Conceptual models
Explain Process-based Models (General Circulation Models - GCMs)
- Most complex and detailed climate models
- Can be used to model ocean-atmosphere interactions, ocean circulation, cryosphere, land atmosphere interactions
- Results can show temperature, precipitation change, etc. and help determine future scenarios
- Circulation models
- Three dimensional GCMs express the governing equations for fluid motion in discrete form (e.g. finite difference) and integrate these forward in time
- Essentially, they use math to simulate how fluids (like air and water in atmosphere-ocean models) move in the Earth’s climate system. They break down these complex movements into smaller, manageable calculations and compute how these movements change over time.
- Three dimensional GCMs express the governing equations for fluid motion in discrete form (e.g. finite difference) and integrate these forward in time
What are four main limitations or sources of uncertainty in climate models?
Answer:
1. Model resolution limitations
2. Incomplete understanding of some processes
3. Computational constraints
4. Parameterization of sub-grid processes
Explain how the ice-albedo feedback mechanism contributes to global warming.
Answer: The ice-albedo feedback creates a positive feedback loop where:
- Reduction in ice cover decreases surface reflectivity
- This leads to more absorption of solar radiation
- Temperatures rise
- More ice melts, further reducing ice cover
Each step strengthens and reinforces global warming.
What are the four governing equations/principles used in process-based climate models?
Answer:
1. Energy conservation
2. Momentum conservation (Navier-Stokes equations)
3. Mass conservation (continuity equations for water in air and salt in ocean)
4. Property relations (e.g., ideal gas law)
How do cloud-radiation feedbacks differ from other climate feedbacks?
Answer: Cloud-radiation feedback represents the greatest uncertainty in climate projections because it can have both warming and cooling effects:
- Warming: Clouds can absorb terrestrial radiation
- Cooling: Clouds can increase albedo/surface reflectivity
This dual nature makes it particularly complex to model and predict.
Explain Simplified (“Reduced Form”) Models
- Upwelling-diffusion models
- Used by IPCC for simplified calculations
- Include:
- Single atmospheric box
- Surface layer (land and ocean mixed-layer)
- Deep ocean representation
- Heat exchange processes
- Results of these models can help show CO2 emissions, CO2 concentrations, SO2 emissions, temperature change, sea level rise, etc.
Explain conceptual models
- Based on global energy balance equations
- Include parameters for:
- Global mean temperature
- Ocean heat capacity
- Radiation energy balance
- Temperature response parameters
