What is being taught lesson by lesson:
- The proportions of gases in the atmosphere.
- Earth’s atmosphere in the past, how it has changed and what caused it.
- Linking our atmosphere to the atmosphere of Mars through contextualised learning.
- The greenhouse effect and how humans are increasing it – Global Warming.
- Carbon footprint. What is our carbon footprint and how can it be changed?
- Atmospheric pollutants.
Key Terms for this topic (Tier 3 vocabulary)
Atmospheric – evolution – terraforming – carbon sink – greenhouse effect – global warming – climate change – carbon footprint – pollution.
What everyone needs to know:
The Earth’s atmosphere over the past 200 million years has been 78% Nitrogen, 21% Oxygen and 1% Argon. There are others in tiny proportions like water vapour and other noble gases. Most important of these less common ones is carbon dioxide. This is about 0.04% of our atmosphere and rising.
Our atmosphere has evolved over the planet’s 4.6 billion year life. We can predict what the early atmosphere was like based on the atmosphere’s of Mars and Venus as well as analysing the gases that come out of volcanoes.
To begin with, the gases mainly came from volcanoes – Nitrogen and carbon dioxide with small amounts of methane and ammonia. CO2 dissolved into the oceans (formed from cooling water vapour and ice from many comets) which produced minerals such as calcium carbonate CaCO3 which produced rocks/sediments.
The first algae and early plants began the process of changing the atmosphere through photosynthesis. The huge amounts of CO2 were slowly converted (along with water needed for the process) to O2 and glucose in the presence of uv light. Since this began, approximately 2.7 billion years ago, animals have been able to live. You need to be able to describe the changes over time to get from our early atmosphere to the present day one.
The greenhouse effect is not a bad thing. Without it, Earth would be too cold. Greenhouse gases such as CO2, methane and water vapour trap in infrared radiation that is normally reflected out into space. Shortwave radiation from the sun gets through but lots of the longwave reflections are absorbed.
We have increased the greenhouse effect be releasing more CO2 and methane into the atmosphere. Mainly CO2 is a concern as it is released when we burn fossil fuels. This began to accelerate at the start of the industrial revolution and then again with population growth and cars. Climate change is real, however, it is difficult to convince many people, especially those who have a financial incentive to deny that it is happening. The average surface temperature increases as the percentage of CO2 increases. You may be expected to interpret graphs. You should also be aware of the predicted effects of climate change from rising sea levels, food shortages and extreme weather.
The carbon footprint of an item is the amount of CO2 and other greenhouse gases released in the full life of that product. You need to describe ways of reducing a carbon footprint.
Combustion of fuel produced atmospheric pollutants, there is sulfur in fossil fuels, these produce oxides of sulfur. Along with oxides of atmospheric nitrogen they can cause asthma and acid rain. Unburned hydrocarbons can cause global dimming. Carbon monoxide is a toxic gas that is not easily detected but is present in car exhaust gases. These all cause health problems for humans.
Extra topics needed for the Higher papers:
In this topic, there is nothing extra for the higher papers, the questions will just be more challenging.