Chapter 12 Notes UPDATED

Chapter 12 Climate Change and Humans

Global Warming

  • The average temperature on Earth may increase due to global warming, but the concept of impact on the environment remains uncertain.

  • Potential effects could be both positive and negative for Canadians.

Positive Effects of a Warmer Climate in Alberta

  • Reduced Heating Needs: Warmer winters could lead to less fossil fuel consumption for heating.

  • Extended Growing Season: A longer growing season may benefit agriculture.

  • Shift in Climate Zones: Northern Alberta may become more suitable for agriculture as the taiga diminishes, making way for grasslands and deciduous forests.

Greenhouse Effect

  • Key Greenhouse Gases:

    • Water vapor

    • Carbon dioxide (CO2)

    • Methane (CH4)

    • Dinitrogen monoxide (N2O)

    • Halocarbons

    • Tropospheric ozone (O3)

Role of Water Vapor in the Greenhouse Effect

  • Water vapor accounts for about 65% of infrared radiation absorbed by Earth's surface.

  • Increased human activity raises greenhouse gases, leading to:

    • More water evaporation.

    • Potential enhancement of the greenhouse effect due to warmer atmospheres possibly holding more water vapor.

  • Enhanced Greenhouse Effect: Describes the cycle where warming leads to more water vapor, which in turn causes further warming.

The Greenhouse Mechanism

  • Sunlight enters a greenhouse, where it is absorbed and re-emitted as long-wave infrared radiation.

  • The greenhouse glass reflects infrared energy, further warming objects inside.

  • Similarly, Earth's heated surface radiates infrared energy which may be trapped by greenhouse gases.

    • The more greenhouse gases present, the more energy is retained, increasing Earth's temperature.

Essential Nature of the Greenhouse Effect

  • Without this effect, Earth's average temperature would be too low to support life.

  • Excessive greenhouse gases could lead to dangerously high temperatures, threatening life sustainability.

Feedback Mechanisms

Positive Water Vapor Feedback

  • Increased warming leads to more water vapor, perpetuating the initial warming effect.

Negative Water Vapor Feedback

  • More water vapor may cause cloud formation that reflects sunlight, inducing a cooling effect.

  • Research supports that positive feedback appears to dominate.

Deforestation

  • The clearing of trees has significant repercussions on:

    • Biodiversity

    • Climate stability

    • Atmospheric composition (trees consume CO2 for oxygen during photosynthesis)

  • Deforestation is often done for:

    • Lumber and firewood

    • Agricultural land

Deforestation Challenges

  • Cleared areas in rainforests yield poor agricultural conditions due to nutrient-poor soil.

  • Tree removal releases CO2 into the atmosphere, accounting for about 25% of global CO2 emissions from human activities.

The Carbon Cycle Contributions

  • Various components of the carbon cycle include:

    • Atmosphere, vegetation, oceans, and fossil fuels, with their respective carbon reservoirs.

Precautionary Principle

  • The 1992 Rio Declaration advocates for a precautionary approach to environmental threats, promoting cost-effective measures to prevent degradation even amid scientific uncertainty.

Gaia Hypothesis

  • Proposed by Dr. James Lovelock in the 1960s, it suggests:

    • Earth functions as a single, interconnected living organism.

    • All forms of life contribute to maintaining the environment suitable for life.

Complexity of the Biosphere

  • The biosphere interacts through complex systems to provide an optimal environment for living organisms.

Skepticism on Global Warming

  • Some scientists, such as Richard Lindzen, argue that:

    • The threat of global warming may be overstated.

    • Human contributions to global warming may not be as significant as perceived.

Assignments

  • Reference Assignment BLM 12-6 on page 27 for further studies.