KH

University of Houston: Climate Science Exam 1 Review Notes

Weather Versus Climate

  • Weather: Atmosphere's state at a time/place.

  • Climate: Statistical weather description over decades.

  • Analogy: "Climate is what you expect; Weather is what you get." (Mark Twain)

Defining Climate and Environmental Systems

  • Environment: Five interacting components: Atmosphere, Hydrosphere, Cryosphere, Lithosphere, Biosphere.

  • Climate Change: Systematic shift in long-term climate statistics.

  • Climate Normal: Standard 30-year average.

Systems: Open vs. Closed

  • System: Bounded universe portion with matter/energy.

  • Open System: Exchanges energy and mass.

  • Closed System: Exchanges energy, not mass (Earth is largely closed for matter, open for energy).

Earth's Coordinate System and Regions

  • Equator: Imaginary line equidistant from poles.

  • Latitudes: Lines parallel to equator.

  • Longitudes: Vertical lines pole to pole.

  • Major Climatic Regions: Tropics (\approx 1/2), Mid-latitudes (\approx 1/3), Polar regions (\approx 1/6).

How Science Works: The Scientific Method

  • Systematic process: observation, experiment, hypothesis, conclusions.

  • Peer Review: Experts critically assess work.

Climate Change Versus Climate Variability

  • Climate Variability: Short-term deviations from long-term averages.

  • Climate Change: Long-term, systematic shift in climate elements over decades.

Temperature Records and Anomalies

  • Focus: Global Average Temperature due to GHG impact & reliability.

  • Absolute Temperature: Measured temp at a location.

  • Temperature Anomaly: Absolute Temp minus Climate Normal.

Recent Climate Change Observations

  • Global Warming: Earth warmed \approx 1.29^{\circ} \text{C} (2014-2023 vs 1850-1900), rapid rate.

  • Spatial Distribution: NH warms faster than SH (land vs. ocean).

  • Satellite vs. Surface: Agree (+1.3^{\circ} \text{C}/\text{century}).

  • Cherry Picking: Misrepresenting trends with short data.

Ice Dynamics: Glaciers and Ice Sheets

  • Glaciers/Ice Sheets: Snow \to firn \to ice (trapped air).

  • Major Ice Sheets: Greenland, Antarctic (>$200$ ft sea level rise if melt completely).

  • Sea Ice: Arctic melts faster; no significant global sea level impact (already floating).

Ocean Systems and Sea Level

  • Ocean Temps: >90% Earth's excess heat absorbed.

  • Sea Level Rise: From land ice melt & thermal expansion.

  • Melting sea ice doesn't significantly contribute.

Evidence for Climate Change

  • Earth's warming is "unequivocal."

  • NOT climate change: Single storm, hot/cold day/year (these are weather/variability).

Proxy Climate Records: Reconstructing Past Climates

  • Proxy Records: Climate info from natural sources before instruments.

  • Paleoclimatology: Study of past climates via proxies (e.g., ice cores, tree rings, sediments).

  • Uncertainty: Increases with age of record.

Tree Rings (Dendroclimatology)

  • Dendroclimatology: Study of tree rings for climate.

  • Rings: Wider = wet/warm years.

  • Limitations: Subpolar terrestrial trees; \approx 1,000 years back.

Glaciers and Landscapes

  • Glacial Impact: Erosive, transport sediments (glacial erratics).

  • Climate and environment are interdependent.

Ice Cores

  • Location: Cold regions.

  • Dating: Up to 2 million years of continuous climate data.

  • Info: Isotopes (^{18}\text{O} for temperature), air bubbles (\text{CO}_2), dust (winds, droughts, volcanoes).

Isotopes in Climate Analysis

  • Isotopes: Atoms with same protons, different neutrons.

  • Oxygen Isotopes: $^{16}\text{O}$ evaporates preferentially, $^{18}\text{O}$ condenses preferentially.

  • Glacial/Interglacial: Warmer periods = more $^{16}\text{O}$ in oceans. Colder periods = more $^{18}\text{O}$ in oceans (as $^{16}\text{O}$ locked in ice).

Ice Core \text{CO}_2 Record

  • Strong link between past \text{CO}_2 and global temperatures.

  • Current Levels: \approx 425 ppm (significantly higher than natural range).

Ocean Sediments as Climate Proxies

  • Records: Millions of years.

  • Info: Organism remains (isotopes for past temps), dust (aridity, wind).

Past Climates: Ice Cover Fluctuations and Thermal Maximums

  • Earth cycles: Icehouse (present) and Greenhouse (no permanent ice).

  • PETM (55 MYA): Abrupt global warming (5-9^{\circ} \text{C}) from massive GHG release.

  • Holocene Anomalies: "Little Ice Age" (regional cooling).

Fundamentals of Energy and Temperature

  • Temperature: Internal energy measure of atoms/molecules. Objects > 0\text{ K} radiate.

  • Scales: Fahrenheit (32^{\circ}\text{F} freeze), Celsius (0^{\circ}\text{C} freeze), Kelvin (0\text{ K} = -273.15^{\circ}\text{C}).

Mechanisms of Energy Transfer

  • Photon: Energy packet.

  • Conduction: Direct kinetic energy transfer.

  • Convection: Heat by fluid movement.

  • Electromagnetic Radiation: Energy via photons through vacuum.

Radiation Properties and Characterization

  • Wavelength (\lambda): Distance between wave crests; shorter = higher energy.

  • Frequency (f): Waves per unit time.

  • Relationship: c = f \lambda.

  • Spectrum: Visible (0.4-0.7 \text{ µm}); Infrared (IR - longer \lambda, heats atmosphere).

Blackbody Radiation

  • Blackbody: Ideal absorber/emitter based on temperature.

  • Wien's Law: \lambda_{\text{max}} = \frac{2897}{T} (peak \lambda inversely to temp). Earth peaks at \approx 10.1 \text{ µm} (IR).

  • Emission: Hot objects (Sun) emit short-wave; cold (Earth) emit long-wave.

Stefan-Boltzmann Law

  • Total energy from blackbody: E = \sigma T^4.

  • Implication: Small temp increase \to large energy increase.

Earth's Energy Balance

  • Radiative Equilibrium: Absorbed energy = emitted energy.

  • Global Radiative Equilibrium: Outgoing IR balances incoming solar.

Incoming Solar Energy

  • Solar Constant (S): \approx 1,360 \text{ W/m}^2 at atmosphere top.

  • Total In: S \times \pi R^2.

  • Intensity: Tropics most (direct), Poles least (oblique).

Albedo

  • Definition: Fraction of solar radiation reflected (\alpha).

  • Earth's Avg: \approx 0.3.

  • Surface Albedos: Vary (snow high, ocean low).

Calculating Average Incoming Energy Per Square Meter

  • E_{\text{in}} = \frac{S (1 - \alpha)}{4} \approx 238 \text{ W/m}^2.

Earth's Expected Temperature Without Atmosphere (Bare Rock Model)

  • Model result: T \approx 255 \text{ K} (-18^{\circ}\text{C}).

  • Discrepancy: Actual avg 15^{\circ}\text{C} vs. -18^{\circ}\text{C} highlights greenhouse effect.

The Greenhouse Effect

  • Mechanism: Atmosphere absorbs surface-emitted IR, transmits solar.

  • GHGs: \text{CO}_2, methane, water vapor (efficient IR absorbers).

  • Importance: Natural effect keeps Earth habitable.

Simple Models of the Greenhouse Effect

  • Models: One-Layer, N-Layer to understand energy balance.

  • Key: Changes in GHG concentration (n), solar constant (S), or albedo (\alpha) adjust Earth's temperature.

Planetary Insights

  • Takeaway: Surface temp set by energy equilibrium.

  • Examples: Mercury (no atmosphere, no greenhouse), Venus (dense \text{CO}_2 atmosphere, massive greenhouse effect) show atmospheric impact.