C11 Flashcards
How much of nitrogen has been in our atmosphere over the last 200 million years
About 80% nitrogen
How much of oxygen has been in our atmosphere over the last 200 million years
About 20% oxygen
Which gases in the atmosphere are there small proportions of?
Carbon dioxide
Water vapour
Noble fases
Why are we not certain what the Earth’s early atmosphere was like?
The Earth is 4.6 billion years old, and there’s a lack of evidence throughout this long timescale.
What five changes occurred at the early atmosphere
Oxygen increased
Carbon dioxide decreased
Methane decreased
Ammonia decreased
Nitrogen increased
How oxygen increased in the atmosphere
Algae first produced oxygen about 2.7 million years ago by photosynthesis, and this appeared in the atmosphere.
Over the next billion years,plants evolved and the percentage of oxygen increased gradually to a level for animals to evolve
How carbon dioxide decreased in the atmosphere
CO2 was used up in processes like photosynthesis and the formation of sedimentary rocks/fossil fuels
Examples of sedimentary rocks(which use up CO2)
Limestone and coal
Formation of limestone
CO2 dissolved in oceans to form carbonate ions.
Carbonate ions used by marine organisms to build shells/skeletons out of calcium carbonate.
Upon death, the shells sank.
Shells/skeletons buried/compressed over millions of years to form sedimentary rock
Formation of coal
1) Plants and trees used CO2 during photosynthesis to build their tissues.
2)Plants and trees died in swamps and decayed in the absence of oxygen.
3)They were compressed over millions of years to form coal.
How crude oil and natural gas formed
1) Crude oil and natural gas both formed from an ancient biomass(plankton) buried in mud.
2) The remains of the plankton were covered by more sediment.
3) They were compressed over millions of years to form crude oil and natural gas.
4) Temperature during burial determines whether oil/gas are produced.
How has the carbon cycle affected CO2 levels?
The amount of CO2 in the atmosphere has stayed the same for the last 200 million years because of the carbon cycle.
How methane decreased in the atmosphere
Methane reacted with the oxygen that was being produced by photosynthesis
How ammonia decreased in the atmosphere
Ammonia reacted with the oxygen that was being produced by photosynthesis
How nitrogen increased in the atmosphere
Nitrogen gas is very unreactive so was able to build up in the atmosphere
What are the main greenhouse gases in the atmosphere
Water
Carbon dioxide
Methane
How do greenhouses work?
1) Greenhouses allow short-wavelength radiation from the
Sun through
2) The glass absorbs the long-wavelength radiation emitted from inside the greenhouse.
3) This keeps the plants inside the greenhouse warm
Fossil fuels using up CO2
Crude oil and natural gas
The Greenhouse effect
1) The Sun emits short-wavelength radiation which warms the Earth, but the Earth loses this heat by emitting long-wavelength radiation.
2)Greenhouse gases absorb some of this long-wavelength radiation.
3) They re-radiate this thermal radiation in all directions, including back to the Earth. This warms the atmosphere.
How’s methane produced?
Cattle is reared for humans producing methanes.
The decay of waste in landfill by microrganisms produces methane
What do most scientists believe human activities will cause?
The temperature of the Earth’s atmosphere to increase at the surface and this will cause global climate change
Evidence that global warming will cause climate to change
Other scientists(peers) check evidence before it’s published.
Scientists collecting and analysing data(evidence).
How does modelling climate change work?
1) Scientist has hypothesis
2)Scientist collects data and writes computer program = model
3) Model predicts future
Challenges with modelling climate change
Scientists have a duty to report any uncertainties in their models.
Non-scientists with a vested interest
(individual’s own stake in an investment or project) may present a biased opinion based on only part of the evidence in the media.
