Environmental & Atmospheric Chemistry

The atmosphere and ocean as reactors, and how we know what they are doing

About this course

Atmospheric and environmental chemistry from budgets, residence times and photochemistry through stratospheric and tropospheric ozone, radiative forcing and the carbon cycle, aerosols and clouds, acid deposition, natural waters and ocean acidification, persistent pollutants, and how a change is measured and attributed.

What you will be able to do

  • Build budgets and residence times for atmospheric species, and explain the hydroxyl radical's role as oxidant
  • Explain the Chapman cycle, the heterogeneous chemistry of the ozone hole, and tropospheric ozone formation
  • Compare greenhouse gases by radiative forcing, lifetime and global warming potential, and trace the airborne fraction of carbon
  • Assess how aerosols, clouds and acid deposition alter climate and ecosystems, and why their uncertainty is large
  • Use alkalinity and partitioning to reason about ocean acidification and bioaccumulation, and weigh measurement against attribution

What this course covers

  • Solar flux, effective temperature, and brightness temperature
  • Chapman layer: altitude from optics alone
  • Third-body constraint and why ozone is stratospheric
  • Odd-oxygen steady state and the square-root relationship
  • Chapman's factor of 2.63 and the missing sink
  • Residual as measurement: a general method
  • The greenhouse effect as a measured quantity
  • Dipole-moment selection rule for infrared absorption
  • CO₂ vibrational modes and spectral placement
  • Logarithmic forcing and the no-feedback temperature response
  • Climate feedbacks and the uncertainty decomposition
  • Reconciling the 33 K total effect with the ~1 K marginal increment
  • Policy implications of the logarithm and marginal GWP
  • Charge balance exactness and alkalinity definition
  • Alkalinity conservation under fast reactions
  • Buffer intensity proportional to alkalinity
  • Column alkalinity: depth dominates ocean–lake contrast
  • Critical load, geological map of damage, and recovery asymmetry
  • Choosing conserved variables to simplify fast-process systems
  • Mie scattering and code validation
  • Mass scattering efficiency and the optimal particle size
  • Direct aerosol forcing calculation
  • Quadrature compounding of seven uncertain factors
  • Short aerosol lifetime and the absence of a global aerosol
  • Aerosol uncertainty and the climate sensitivity denominator
  • IMO 2020 shipping regulation as a natural experiment
  • Weighing the atmosphere from first principles
  • From mixing ratio to atmospheric burden
  • The budget equation τ = B/F and its three directions
  • Lifetime vs. mixing time: the Junge relationship and its limits
  • Köhler curve and activation threshold
  • Twomey effect: droplet number, optical depth, and cloud albedo
  • Three-fold saturation and logarithmic non-linearity
  • Cloud adjustment and the unknown sign
  • Turnover time vs. removal time for CO₂
  • CO₂ impulse response: the constant term
  • Global warming potential: definition and the horizon problem
  • Four categories of scientific quantities
  • Flow vs. stock pollutants: the non-constant ratio
  • Collapsing distributions to scalars: a general diagnostic
  • Stratospheric frost point and polar cloud formation
  • Catalytic chlorine cycles and chain length
  • Heterogeneous activation on polar stratospheric clouds
  • Quantitative ozone loss and the three-condition geography
  • Calcite vs. aragonite: two polymorphs, different solubility
  • Saturation state Omega: definition and threshold
  • What a tenth of a pH unit actually costs
  • Buffering and harm as the same reaction
  • Omega − 1 as the true calcification drive and polar amplification
  • The aragonite saturation horizon and its shoaling
  • Which number to quote: reporting the governing variable
  • Hatchery worked case: diagnosis, dose, and decision
  • Photon energy and bond-dissociation thresholds
  • Limits of the energy gate: absorption cross-section and quantum yield
  • Beer-Lambert filtering by O₂ and O₃ and UV amplification
  • Photolysis rate J as a residence time; the three-gate diagnostic procedure
  • Effective Henry's constant and clean rain pH
  • Aqueous vs. gas-phase oxidation rates
  • Two oxidants, pH dependence, and self-limitation
  • Oxidant budget and sublinear policy response
  • Costs, co-benefits, and unmasked aerosol forcing
  • Five tractability conditions and the CO₂ comparison
  • Octanol-water and air-water partition coefficients
  • Bioaccumulation and food-chain magnification
  • Bioaccumulation window: a peak, not a slope
  • Global distillation and long-range polar transport
  • The two-window rectangle and the Stockholm Convention
  • Named blind spots of the partitioning screen
  • Applying the screen: a regulatory worked case
  • Thermodynamic origin of nitric oxide from combustion
  • The NO₂–O₃ photochemical cycle and the Leighton relation
  • Peroxy radicals as the loop-opening mechanism
  • Non-monotonic ozone response and the NOₓ crossover
  • Tropospheric ozone as a regional pollutant
  • Altitude as a proxy for density: unifying the three lectures
  • Why the ocean buffer exists: carbonate chemistry
  • Carbonate equilibrium solve and the Revelle factor
  • Equilibrium airborne fraction derived from first principles
  • Two reservoirs, two clocks, and the shape of the burn curve
  • Buffer weakening, ocean acidification, and the airborne fraction
  • Ocean alkalinity enhancement as a worked case
  • Collision rate ceiling for bimolecular reactions
  • Hydroxyl radical: source, steady state, and concentration
  • Global mean hydroxyl as a weighted effective rate
  • Hydroxyl sink coupling and methane's self-feedback
  • Activation barriers, molecular structure, and lifetime regimes
  • Ratio-building as an uncertainty-management habit
  • Anthropogenic forcing ledger: term-by-term accounting
  • No-feedback temperature response and the Planck parameter
  • Water-vapor feedback bounded by Clausius–Clapeyron
  • Fingerprint attribution and falsifiability
  • Independent-route methodology: the course as its own case study

Syllabus

  1. The Atmosphere as a Reactor

    1. L1 · The Atmosphere as a Reactor: Budgets and Residence Times
    2. L2 · Photochemistry: What a Photon Can and Cannot Do
    3. L3 · The Hydroxyl Radical: the Atmosphere's Detergent

  2. Ozone, Above and Below

    1. L4 · Stratospheric Ozone: the Chapman Cycle, and Why It Fails
    2. L5 · The Ozone Hole: Chemistry That Needs a Surface
    3. L6 · Tropospheric Ozone: the Same Molecule, the Opposite Problem

  3. Climate Forcing and the Carbon Cycle

    1. L7 · Radiative Forcing: Why Carbon Dioxide and Not Oxygen
    2. L8 · Lifetimes and GWP: Comparing Gases That Do Not Compare
    3. L9 · The Carbon Cycle, and the Fraction That Stays

  4. Aerosols, Clouds and Deposition

    1. L10 · Aerosols: the Largest Uncertainty in the Whole Subject
    2. L11 · Clouds and Nucleation: the Indirect Effect
    3. L12 · Acid Deposition: a Problem That Was Actually Solved

  5. Waters, Pollutants and Attribution

    1. L13 · Natural Waters: Alkalinity, and Why the Ocean Resists
    2. L14 · Ocean Acidification: the Number Behind the Headline
    3. L15 · Persistent Pollutants: Partitioning and Bioaccumulation
    4. L16 · Measurement and Attribution, and the Course as One Argument