ESS Topic 6: Atmospheric Systems Notes

Introduction to the Atmosphere (Topic 6.1)

  • The atmosphere is a dynamic, constantly changing system essential for life on Earth.
  • Incoming solar radiation transfers and transforms energy within the atmosphere.
  • Review Topics 1.2 and 1.3 for systems and models.

Greenhouse Effect vs. Global Warming

  • The greenhouse effect is essential for life, making Earth habitable.
  • Without the greenhouse effect, Earth would be a cold, dead planet.
  • Climate change is a human-induced positive feedback of the greenhouse effect, leading to rising temperatures and a new equilibrium.

Atmosphere and Terrestrial Biomes

  • The atmosphere is responsible for the development of terrestrial biomes.
  • The Whittaker biome diagram (Topic 2.4) shows how precipitation and temperature influence biome types.

Structure of the Atmosphere

  • Layers: troposphere, tropopause, stratosphere, stratopause, mesosphere, mesopause, thermosphere.
  • Focus on the troposphere (where we live) and the stratosphere (where the ozone layer is located).

Dynamic Atmosphere

  • Carbon dioxide, temperature, and sea levels fluctuate over time.
  • Changes in carbon dioxide correlate with changes in temperature and sea level.
  • Temperature and sea level influence moisture in the atmosphere (precipitation).
  • Atmosphere influences global climate and creates terrestrial biomes.
  • CO2 levels: ~385 ppm (years ago) to 416-418 ppm (September 2023).

Composition of the Atmosphere

  • 78% nitrogen gas (N2).
  • 21% diatomic oxygen gas (O2).
  • 1% trace gases (water vapor, carbon dioxide, other greenhouse gases).

Human Impact on the Atmosphere

  • Combustion releases large stores of carbon into the atmosphere.
  • Rate of carbon transfer from geological reservoirs to the atmosphere has radically changed in the last 200 years.

Troposphere and Stratosphere

  • Troposphere: where life processes, weather, human activities, and transportation occur.
  • Stratosphere: contains the ozone layer, which protects us from the sun's ultraviolet radiation.

Clouds and Albedo Effect

  • Clouds regulate Earth's temperature through the albedo effect.
  • Albedo: measure of surface reflectivity.
    • High albedo (light colors): high reflectivity, low absorption (keeps things cool).
    • Low albedo (dark colors): low reflectivity, high absorption (warms things up).

Albedo Data

  • Dry snow, wet snow, bare ice: high reflectivity.
  • Exposed water: low reflectivity, high absorption.

Greenhouse Effect Mechanism

  • Incoming solar radiation passes through the atmosphere.
  • It may be reflected (albedo effect) or absorbed by water/land.
  • Absorption warms the planet; molecules vibrate and expel infrared radiation.
  • Some infrared radiation passes into space, but some is trapped by greenhouse gases like carbon dioxide, water vapor, and methane.

Albedo Effect Feedback

  • Incoming solar radiation strikes snow/ice, reflecting most of it and keeping it cool.
  • As temperatures warm, water absorbs light, melts ice, exposing more water to absorb radiation (positive feedback).

Role of Clouds

  • Clouds reflect sunlight, creating albedo, which cools things off.
  • Cooler temperatures lead to less evaporation, fewer clouds, more sunlight striking the surface, and warming the planet.
  • Clouds act as a negative feedback mechanism to regulate climate.

Greenhouse Effect and Earth's Temperature

  • Without the atmosphere, Earth would be much colder.
  • Don't confuse the greenhouse effect with global warming or climate change.

Pollution and International-Mindedness

  • Ozone-depleting substances, photochemical smog, and acid deposition are examples of non-point source pollution.
  • These pollutants cross political boundaries and may not affect the places where they're released.
  • Relate back to Topic 1.5: Humans and Pollution, and pollution management strategies.

Stratospheric Ozone (Topic 6.2)

  • Ozone in the stratosphere protects living organisms from ultraviolet radiation.
  • Stratospheric ozone filters out ultraviolet B and ultraviolet C.

Stratospheric vs. Tropospheric Ozone

  • Stratospheric ozone (good): found in the stratosphere, protects from UV radiation.
  • Tropospheric ozone (bad): surface-level ozone, contributes to smog and urban air pollution.

Ozone Formation

  • Ozone (O3) is made of three oxygen atoms.
  • Diatomic oxygen molecules (O2) are split by hard UV rays into individual oxygen atoms.
  • Individual oxygen atoms combine with O2 to form ozone (O3) through photolysis.

Dynamic Equilibrium of Ozone

  • O3 is less stable than O2, so it breaks down and reforms O2 molecules.
  • Formation and destruction happen constantly in a dynamic equilibrium.
  • The overall concentration of ozone in the stratosphere remains constant, even though individual molecules are constantly being formed, broken, and reformed.
  • Rate of ozone formation equals the rate of ozone destruction.

Photochemical Smog (Topic 6.3)

  • Fossil fuels produce primary pollutants that create secondary pollutants, which cause smog.

Primary Pollutants

  • Sulfur dioxide (SO2) and oxides of nitrogen (NOx).
  • Sulfur dioxide mainly from electricity production through burning coal.
  • Oxides of nitrogen predominantly from vehicular traffic.

Smog Formation

  • Primary pollutants (SO2 and NOx) undergo chemical reactions in the atmosphere.
  • Reactions produce ozone in the troposphere (ground-level ozone), which is the main component of photochemical smog.
  • Primary pollutants interact with hydroxides to release individual oxygen atoms which bond with diatomic oxygen to create ozone.

Impacts of Smog

  • Significant health and environmental impacts.
  • Economic impacts: healthcare costs (e.g., California estimated $0.5 billion annually).
  • Human health effects: eye irritation, lung damage, shortness of breath, cardiovascular stress.
  • Direct impacts on producers: ozone damage to leaves reduces photosynthesis, weakens plants, and allows disease pathogens to enter.

Key Points

  • Smog irritates eyes and causes respiratory illnesses.
  • It is a complex mixture of pollutants.
  • Distinguish tropospheric (ground-level) ozone from stratospheric ozone.

Thermal Inversion

  • Mountains or valleys can cause thermal inversions.
  • Warm air rises, but cold air (denser) sinks and presses down on the warm air, trapping smog underneath.

Smog Sources

  • Smog can come from outside cities (e.g., farmers burning land).
  • Significant economic costs (percentage of GDP loss due to urban air pollution).

Economic Losses

  • Crop losses due to ground-level ozone (e.g., wheat, rice, maize in China, Japan, and South Korea).
  • Approximately $$63 billion lost every year.

Pollution Management Strategies (Three Tiers)

Tier 1: Altering Human Activity
  • Consume fewer fossil fuels.
  • Use public transport, walk, or cycle.
Tier 2: Regulating and Reducing Pollutants
  • Carbon pricing, cap-and-trade mechanisms.
  • Catalytic converters in vehicles trap primary pollutants.
  • Regulate fuel quality (carbon content).
Tier 3: Cleaning Up
  • Carbon sequestration (e.g., plant trees).

Tiered Strategies Recap

Tier 1
  • Change human behaviors.
Tier 2
  • Capture or regulate emissions: cap and trade, tax polluters, install catalytic converters, scrubbers on industrial smokestacks, regulate fuel quality.
Tier 3
  • Clean up environment: reforestation, carbon sequestration.

Acid Deposition (Topic 6.4)

  • Acid deposition is a form of air pollution that affects soil, water, and living organisms.
  • Impacts living systems and the built environment.

Causes

  • Combustion of fossil fuels (coal, oil, gas) releases sulfur dioxide and oxides of nitrogen (primary pollutants).
  • Gases react with water vapor to form sulfuric acid and nitric acid (secondary pollutants).
  • Acids fall as dry deposition (ash, particles) or wet deposition (rain, snow).

Effects

Direct
  • Damages aquatic organisms and coniferous forests by lowering pH.
Indirect Toxic
  • Increases the solubility of metals (e.g., aluminum ions), which are toxic to fish and plants especially in low pH conditions.
Indirect Nutrient
  • Leaches essential nutrients from the soil (calcium, magnesium), affecting plant growth.
  • Regional and global problem
  • Impacts downwind areas, even across state or country lines. (e.g., China's emissions affecting North America.)

Pollution Management Strategies:

Tier 1: Altering Human Activity:
  • Reduce fossil fuel use.
  • Use alternative energy sources (natural gas, solar power, wind power).
  • Improve energy efficiency and conservation
Tier 2: Regulating and Monitoring Pollutants:
  • International agreements and national governments reduce pollutant production.
  • Emission standards, taxes, incentives.
  • Install scrubbers to remove sulfur dioxide and catalytic converters for oxides of nitrogen.
Tier 3: Cleaning Up and Restoring Ecosystems:
  • Counteract the effects of acid deposition in soils, water, and living organisms.
  • Spread ground limestone in acidified lakes.
  • Recolonize damaged systems with acid-tolerant species.

Evaluation:

  • Cost-benefit analyses, stakeholder involvement, technology, political will, public awareness, environmental ethics.
  • Monitor changes in acid deposition levels over time using indicators (pH measurements, precipitation chemistry analysis, soil nutrient status assessments, biological diversity surveys).