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Describe and Explain earth’s early atmosphere
One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans.
At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.
Why did levels of nitrogen in the atmosphere increase
Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia
Why did levels of water vapour and carbon dioxide decrease
As the earth cooled, water vapour in the atmosphere condensed to form oceans
When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere
Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.
Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
Why did levels of oxygen increase
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis, which can be represented by the equation:
Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere.
Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
Why can scientists not be sure about the abundance of gases in earth’s early atmosphere
It was 4.6 billion years ago
Little/no evidence
What are greenhouse gases
Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life
What are the three main greenhouse gases
Water vapour (H2O)
Methane (CH4)
Carbon dioxide (CO2)
Describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter
Short wavelength electromagnetic radiation (UV) passes through the Earth's atmosphere.
The Earth absorbs most of the radiation and warms up.
The Earth radiates energy as longer wavelength radiation (IR).
Some of the infrared radiation goes into space.
Some of the infrared radiation is absorbed by greenhouse gases in the atmosphere, and emitted in all directions, including back to earth and into space
The lower atmosphere warms up.
Describe 2 human activities which increase the levels of carbon dioxide in the atmosphere
Increased population leads to increased cars (vehicles) on the road, and increased energy demand (from power stations). Combustion of fuels in car engines and power stations releases carbon dioxide
Increased food demand from an increasing population leads to increasing need for space, in order to farm crops and cattle- in order to do this, deforestation has increased, which releases carbon dioxide, and reduces the amount of trees, which reduces the amount of carbon dioxide taken out of the atmosphere in photosynthesis
Describe 2 human activities which increase the levels of methane in the atmosphere
Increasing population leads to increasing waste- as waste decomposes and is composted, microorganisms release methane
Farming cattle and rice releases methane, increased from an increasing demand for food from our increasing population
Why do we believe climate change is happening
Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change
Why might climate change not be happening how we think
It is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.
What should be taken into account when evaluating evidence on global warming
who did the research and whether they are trustworthy, skilled and experienced
who funded the research, because that might cause some bias
what methods were used to collect and analyse the data, because that might cause uncertainties in the evidence base
which organisation is reporting or publishing the evidence
What are 4 potential effects of climate change
Sea levels rising, because of melting glaciers, leading to flooding
Increasing temperatures causing crops to die, and causing famines
Increasing temperatures drying up water sources, and leading to droughts
Extreme weather conditions like hurricanes, heatwaves, forest fires, etc
What is a carbon footprint
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
How can emissions of carbon dioxide be reduced
Use cars and combustion engine vehicles less, and instead use transport like bikes which don’t emit carbon dioxide, or public transport which emits less carbon dioxide per person
Reduce our energy usage by turning off lights, and using less technology, to reduce the demand for energy from power stations, which combust fuels and release carbon dioxide
How can emissions of methane be reduced
Eat less beef and waste less beef so that there is less demand for cows to be farmed, which releases methane
Produce less waste, as the decomposition of waste by microorganisms releases methane
Why can actions to reduce emissions of carbon dioxide and methane be limited
Reducing carbon footprint can be expensive, as alternative more sustainably sourced products are more expensive
Some people may not be able to use public transport, and are forced to use cars as there isn’t availability
What is the equation for incomplete combustion
Hydrocarbon + Oxygen → Carbon + Carbon monoxide + Water
How is carbon monoxide produced
Produced in incomplete combustion when there is insufficient oxygen for complete combustion
It is toxic, colourless and odourless so hard to detect
How is carbon particulate produced
Produced in incomplete combustion when there is insufficient oxygen for complete combustion
Particulates cause global dimming and health problems for humans.
How is sulfur dioxide produced
When coal is burned in combustion with sulfur impurities, the high temperatures allow the sulfur to react with the oxygen in the atmosphere
Sulfur dioxide causes health problems for humans, and dissolves in water in the atmosphere to form acid rain
How are nitrogen oxides produced
Because combustion causes high temperatures, other than allows nitrogen and oxygen in the air to react to form nitrogen oxides
Nitrogen oxides also produce acid rain and cause health problems for humans
