DP IB Physics: SL
B: The particulate nature of matter
B. 2 Greenhouse effect
DP IB Physics: SLB: The particulate nature of matterB. 2 Greenhouse effect
Guiding questions: |
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| a) | How does the greenhouse effect help to maintain life on Earth and how does human activity enhance this effect? |
| b) | How is the atmosphere as a system modelled to quantify the Earth–atmosphere energy balance? |
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a) How does the greenhouse effect help to maintain life on Earth and how does human activity enhance this effect?
- Solution:
- The greenhouse effect is a natural mechanism where certain gases in the atmosphere trap heat, keeping Earth warm enough to support life.
- However, by releasing additional greenhouse gases into the atmosphere, human activity is intensifying this impact, resulting in climate change and global warming.
- By retaining heat from the Sun, the greenhouse effect is a natural phenomenon that keeps the Earth’s surface warm enough to sustain life.
- How the greenhouse effect helps maintain life:
- Like the glass walls of a greenhouse, the gases that make up the Earth’s atmosphere—such as carbon dioxide, methane, and water vapor—trap part of the heat from the sun.
- The earth is kept from becoming too cold to support liquid water and life as we know it thanks to the natural greenhouse effect, which heats the globe to a temperature that is conducive to life.
- The average temperature on Earth would be much below freezing without this natural greenhouse effect, rendering the planet uninhabitable.
- How human activities enhance the greenhouse effect:
- Carbon dioxide emissions from burning fossil fuels (coal, oil, and natural gas) for energy are significant.
- The quantity of carbon dioxide-absorbing trees decreases as a result of deforestation.
- Numerous greenhouse gases are also released during industrial operations.
- A greater greenhouse effect results from these human activities, which dramatically raise the atmospheric concentration of greenhouse gases.
- Climate change results from increased heat trapping caused by the amplified greenhouse effect.
- Figure 1 Natural and human enhanced greenhouse effect
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b) How is the atmosphere as a system modelled to quantify the Earth–atmosphere energy balance?
- Solution:
- Quantifying the incoming solar radiation, the exiting infrared radiation, and the energy exchanges within the atmosphere itself allows one to simulate the energy balance of the Earth-atmosphere system.
- This entails comprehending how solar radiation is collected, reflected, and emitted back into space, as well as how the atmosphere contributes to the greenhouse effect by retaining part of this outgoing radiation.
- Figure 2 Earth energy balance
- ⇒ Incoming solar radiation:
- A part of the electromagnetic energy emitted by the sun enters the Earth’s atmosphere.
- Shortwave radiation is the common term used to describe this incoming solar energy.
- The incoming solar energy at the top of the atmosphere is around 340 watts per square metre (W/m2) on average throughout the course of a year and the whole planet.
- The Earth’s cross-sectional area and the solar constant, or the quantity of solar energy received per unit area, are used to calculate this number.
- ⇒ Energy absorption and reflection:
- Clouds and aerosols, as well as the Earth’s surface (albedo), reflect some of the incoming solar energy back into space.
- The atmosphere and the Earth’s surface absorb the remaining solar energy.
- The surface and atmosphere are heated by the absorbed solar radiation, which causes energy exchanges.
- ⇒ Outgoing infrared radiation:
- Longwave radiation, another name for infrared radiation, is sent into space by the Earth’s atmosphere and surface.
- The main method that the Earth loses energy and balances the incoming solar energy is through this outgoing infrared radiation.
- A part of this emitted infrared radiation is absorbed by the atmosphere, which traps some of the heat and causes global warming (greenhouse effect).