Summary of Key Concepts in Climate Change Theory
Theory of Climate Change
Global Climate Change
Influential factors: atmospheric CO₂, seasonal solar irradiance
Goal: Understand quantitative reasons for climate change, focusing on Earth's energy budget.
Budget Equation
Conservation laws: Energy, water, carbon conserved but can change forms.
General structure: \frac{dX}{dt} = I - O (with I = input, O = output).
Rate of change \Delta X = X2 - X1; Predict future values using inputs/outputs, e.g., X2 = X1 + (I - O) \times \Delta t.
Electromagnetic Radiation
Definition: Waves of electric and magnetic fields, transfer energy (speed of light).
Spectrum: Visible light: 400nm - 700nm.
Energy of photons: E = h\nu = \frac{hc}{\lambda}, where h = Planck's constant, higher energies for shorter wavelengths.
Blackbody Radiation
An ideal object absorbing/emitting all radiation stated by Planck's law.
Total energy flux: F = \sigma T^4, with \sigma = 5.67 \times 10^{-8} \text{Wm}^{-2}\text{K}^{-4}.
Emissivity (ε): Material-specific (0<ε<1), e.g., water: ε = 0.96, snow: 0.8 - 0.9.
Earth’s Energy Balance
Input: Absorbed solar radiation (ASR); Output: Emitted terrestrial radiation (ETR).
ASR = (1 - a)S, where average albedo a ≈ 0.3; ETR: \sigma T^4.
Greenhouse Effect
Atmosphere absorbs 25-30% of solar radiation; 70-85% terrestrial radiation.
Key absorbers: Water vapor, CO₂, others (ozone, methane).
Gases lacking dipole moment cannot absorb IR; only those with dipole moments can.
Climate Forcings and Feedbacks
Radiative Forcing: Change in radiative balance; positive/negative forcing leads to warming/cooling.
Feedback Processes: Amplification (positive feedback) or dampening (negative feedback) of temperature response.
Example feedbacks: Water vapor (positive), Planck (negative), ice-albedo (positive).
Climate Sensitivity
Defined as surface temperature change for doubled CO₂; ranges from approximately 1.5 to 4.5 K.
Total feedbacks calculated as \gamma = \gamma{pl} + \gamma{wv} + \gamma{lr} + \gamma{ia} + \gamma_{cl}.