Copy of Unit 9_ Global Change

9.1 Stratospheric Ozone Depletion

• Importance of Stratospheric Ozone

  • Critical for the evolution and survival of life.

  • Depletion caused by both anthropogenic factors (CFCs) and natural factors (melting ice crystals in Antarctic spring).

  • Decrease in ozone leads to higher UV rays reaching Earth, heightening risks like skin cancer and cataracts.

• Anthropogenic Ozone Depletion

  • Primary cause: CFCs used in refrigeration and aerosols.

  • Mechanism: UV radiation releases chlorine from CFCs, which depletes ozone (1 Cl can destroy 100,000 O3).

• Natural Ozone Depletion

  • Polar Stratospheric Clouds (PSCs) form in Antarctic spring, leading to reactions that release chlorine.

9.2 Reducing Ozone Depletion

• Chemicals Substituting CFCs

  • Aim to replace ozone-depleting chemicals with non-depleting substitutes (e.g., HFCs).

  • HFCs are greenhouse gases but do not deplete ozone.

• Solution

  • Phase out CFCs via the Montreal Protocol (1987) and replace CFCs with HCFCs, later HFCs.

  • Long-term goal: Replace HFCs with HFOs, which have shorter atmospheric lifetimes.

9.3 The Greenhouse Effect

• Definition of Greenhouse Gases

  • Major greenhouse gases include CO2, methane, nitrous oxide, and CFCs.

  • Greenhouse gases trap heat and are crucial for maintaining Earth's surface temperature.

• Mechanism of the Greenhouse Effect

  • Traps heat necessary for life; solar radiation heats Earth’s surface, which then emits infrared radiation.

9.4 Increase in Greenhouse Effect

• Key Greenhouse Gas Sources

  • CO2: Fossil fuel burning and deforestation.

  • Methane: Agricultural emissions.

  • N2O: Agricultural soil management.

  • CFCs: Used in various products.

• Global Warming Potential (GWP)

  • Measures the contribution of gases to warming relative to CO2.

  • Key GWP Values: CO2 (1), Methane (28-36), N2O (298), CFCs (up to 13,000).

9.5 Global Climate Change

• Effects of Greenhouse Gas Increases

  • Global climate change results in environmental issues like sea level rise and shifting disease vectors.

• Historical Climate Change

  • Earth has undergone temperature fluctuations driven by natural cycles (Milankovitch Cycles) impacting ecosystems and species patterns.

9.6 Ocean Warming

• Impact of Global Warming

  • Increased greenhouse gases lead to ocean warming, influencing marine ecosystems and weather patterns.

9.7 Ocean Acidification

• Cause of Ocean Acidification

  • Result of increased CO2 levels; oceans absorb CO2, leading to chemical changes that harm marine life and ecosystems.