IB Biology 4.4 Climate change


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Outline the greenhouse effect.
- Short wave radiation from the sun reaches the Earth and some is reflected by the Earth's atmosphere.
- Most of it gets through the Earth's atmosphere and is absorbed by the Earth's surface.
- The Earth's surface warms up and emits longer wave infrared radiation (heat).
- Some longer wave radiation escapes into space.
- Most of the longer wave radiation is absorbed by greenhouse gases in the atmosphere.
- The greenhouse gases scatter the longer wave radiation and this traps the heat in the atmosphere.
List the greenhouse gases and outline their impact on the greenhouse effect.
- Greenhouse gases include: carbon dioxide, water vapour, methane and nitrogen oxides.
- All greenhouse gases can absorb longer wave radiation but not with the same ability.
- The impact of a greenhouse gas depends on how able it is to absorb longer wave radiation and on its concentration.
- Although methane absorbs longer wave radiation better than carbon dioxide, it is present at much lower concentrations.
- Highest impact greenhouse gases are carbon dioxide and water vapour.
- Lowest impact greenhouse gases are methane and nitrogen oxides.
Outline the influence of greenhouse gases on global temperatures and climate patterns.
- It is expected that any further increase in the concentration of greenhouse gases will increase the average temperature of the Earth.
- Increasing global temperature will also impact climate patterns, causing extreme weather.
Outline the threat to coral reefs from increasing concentrations of dissolved carbon dioxide.
- Increased atmospheric carbon dioxide concentration in the atmosphere has led to an increase in the amount of carbon dioxide dissolved in the ocean.
- This has caused the ocean to become less alkali since carbon dioxide reacts with water to form carbonic acid (which dissociates).
- Hydrogen ions react with carbonate ions and reduce carbonate ion concentrations.
- Carbonate ions are required by coral to synthesise calcium carbonate for their skeletons so coral will grow more slowly.
- Hydrogen ions can also react with the calcium carbonate skeletons of the corals and cause it to break down.
- Any future increases in carbon dioxide concentration will increase the threat to coral reefs.