Notes on Global Change and Environmental Science

Unit 9: Global Change

Stratosphere & Ozone Layer

  • Stratosphere: The second layer of Earth’s atmosphere, where the ozone layer is located.
  • Ozone Layer: Contains ozone (O₃) which absorbs the majority of the sun's harmful ultraviolet (UV) radiation.

UV Radiation Types

  • Types of UV Radiation:
    • UV-A: Longest wavelength, less harmful but can contribute to skin aging.
    • UV-B: Medium wavelength; responsible for sunburn and skin cancer.
    • UV-C: Most harmful, mostly absorbed by the atmosphere.

Effects of UV Radiation

  • Health Effects:
    • Cataracts and retinal diseases.
    • Skin cancer due to increased UV exposure.
  • Protection Measures:
    • Sunscreen with different SPF levels protects against UV radiation:
    • SPF 15: 93% protection.
    • SPF 30: 97% protection.

Chlorofluorocarbons (CFCs)

  • Chemical Composition: CCl₃F (contains chlorine, fluorine, and carbon).
  • Uses of CFCs:
    • Employed in fire extinguishers, air conditioning, and Teflon cookware.
  • Environmental Impact:
    • Long lifespan in atmosphere, contributes to ozone layer depletion in Antarctica due to sunlight exposure.

Chemical Reactions Involving Ozone

  • Reaction in Stratosphere:
    • Winter: O₂ + O₂ → O₃ (ozone formation).
    • Summer: O₃ → O₂ + O₂ (ozone decomposition due to sunlight).
  • Role of CFCs:
    • CFCs release chlorine which bonds with ozone, reducing ozone levels significantly.

Ozone Hole in Antarctica

  • Formation Causes:
    • Cold, windy conditions combined with sunlight create conditions for ozone depletion.
    • Polar vortex winds trap CFCs, leading to ozone loss when sunlight returns.

Good vs. Bad Ozone

  • Good Ozone (Stratospheric):
    • Protects against UV radiation, essential for life.
  • Bad Ozone (Tropospheric):
    • Secondary pollutant from vehicle emissions, harms respiratory health and is a greenhouse gas.
    • Formed through reactions involving nitrogen dioxide (NO₂), which can create smog.

Global Warming

  • Greenhouse Effect:
    • Gases like CO₂, CH₄, N₂O, O₃, and CFCs trap heat in the troposphere, essential for regulation of Earth's temperature.
  • Negative Effects of Global Warming:
    • Extreme weather events, biodiversity loss, glacier melting, and increased disease.
  • Key greenhouse gases:
    • Water vapor (most abundant), CO₂, CH₄ (methane), and N₂O (nitrous oxide).

Climate Change Indicators

  • Greenhouse Gas Emissions:
    • Major sources include electricity, transportation, industry, and agriculture.
  • Measuring Climate Change:
    • Ice core samples show historical CO₂ levels, rapid increases in recent years.

Impacts of Global Warming

  • Temperature Increases:
    • Average global temperature rise of 4°C predicted, severe impacts on climate systems.
  • Sea Level Rises:
    • Coastal areas at risk due to rising sea levels from melting glaciers.
  • Food and Water Shortages:
    • Threats to global food supply and access to clean water, especially in vulnerable regions.

Climate Action Agreements

  • Montreal Protocol (1987):
    • Aimed to phase out the use of CFCs.
  • Paris Agreement (2015):
    • Focused on limiting global temperature increase to well below 2°C.

Acid Rain and Ocean Acidification

  • Acid Rain Formation:
    • Result of fossil fuel emissions (SO₂, NO₂) reacting with water to form sulfuric and nitric acid.
  • Impact of Ocean Acidification:
    • Excess CO₂ absorbed by oceans, lowering pH and harming marine ecosystems and species dependent on calcium carbonate.

Biodiversity & Climate Change

  • Threats to Species:
    • Increased disease cases, invasive species, and habitat destruction.
  • Conservation Laws:
    • CITES and the Endangered Species Act which protect threatened species from extinction.

Summary of Climate Changes Affecting Humans

  • Increased diseases, flooding, extreme weather, and food/water shortages lead to climate refugees.