lecture recording on 27 February 2025 at 11.44.35 AM

Climate Change and Carbon Dioxide

• Trace Gas in Atmosphere

  • Carbon dioxide (CO2) is a trace gas, present in minute amounts in the atmosphere.

  • Despite rising levels, it remains a trace gas, which can be viewed as advantageous.

• Historical Context

  • Past higher carbon levels led to significant changes in climate and larger organisms.

  • Example: Ancient insects and arachnids grew to enormous sizes, indicating that higher oxygen levels allowed for larger body sizes due to more efficient oxygen diffusion.

Oxygen and Organism Size

• Passive Breathing Systems

  • Certain organisms, like insects, rely on spiracles for air intake, which limits their size based on atmospheric oxygen levels.

  • Larger past organisms thrived when oxygen levels were greater.

• Carbon Cycle Breakdown

  • Carbon Sources

    • Most carbon found underground in fossil fuels and decomposing organic matter.

    • Secondary source in plants and animals; smallest amounts are in the atmosphere.

  • Plant Component of Carbon Cycle

    • Soil carbon moves to the atmosphere via decomposition.

    • Plants absorb CO2 from the atmosphere during photosynthesis.

    • Plants respire CO2 back into the atmosphere, completing the plant part of the cycle.

  • Animal Component of Carbon Cycle

    • Animals obtain carbon from consuming plants or other animals.

    • Excrete carbon back into the soil through waste or decomposition.

Human Impact on Carbon Cycle

• Fossil Fuel Use

  • We extract carbon from underground stores and release it into the atmosphere by burning fossil fuels.

  • This process leads to an increase in atmospheric CO2 levels, contributing to global warming.

  • Government Policy Influence

    • Political administrations shift focus on energy sources (renewables vs. fossil fuels).

    • Inconsistent policies lead to cycles of opening and closing coal power plants, affecting carbon emissions.

The Greenhouse Effect

• Absorption of Solar Radiation

  • Various surfaces (ocean, soil, roads) absorb sunlight, which they reradiate as infrared radiation (heat).

  • Greenhouse gases trap infrared radiation, preventing it from escaping, which increases atmospheric energy and alters climate patterns.

• Analogy with Cars

  • Just as a parked car traps heat due to its closed windows, the Earth’s atmosphere traps heat due to greenhouse gas accumulation, leading to temperature increases.

Solutions and Renewable Energy

• Renewable Energy Potential

  • Transition to renewable energy sources like solar, wind, and geothermal could significantly reduce reliance on fossil fuels.

  • Modern technology can effectively process renewables to meet energy needs consistently.

• Carbon Sequestration

  • Capturing carbon and storing it underground as a temporary solution.

  • Seen as a Band-Aid approach; does not fundamentally change carbon output behavior or reduce greenhouse gas contributions.

Phosphorus Cycle

• Importance of Phosphorus

  • Essential for DNA and cellular function; known as a limiting factor in ecosystems.

  • Occurs primarily in rocks and becomes available through geological activities like erosion and weathering.

• Plant and Animal Interaction

  • Plants acquire phosphorus from the soil, and through consumption, animals obtain phosphorus, which is cycled back into the soil upon decomposition.

Nitrogen Cycle

• Role of Bacteria

  • Nitrogen makes up 78% of the atmosphere, but plants cannot utilize it directly.

  • Symbiotic bacteria in legume roots convert atmospheric nitrogen into usable forms (like ammonia and nitrates) that plants can absorb.

• Balance of Nitrogen Levels

  • Optimal nitrogen levels result in healthy plant growth.

  • Excessive nitrogen leads to poor plant health and unbalanced ecosystems.