C13 Flashcards
Describe the composition of the Earth’s early atmosphere.
- mainly carbon dioxide gas
- nitrogen gas
- ammonia gas
- traces of methane
- a small amount of water vapour that condensed when the earth cooled down and fell as rain to form the first oceans
How was the Earth’s early atmosphere formed ?
- volcanic activity released these gases (nitrogen, ammonia, carbon dioxide, methane, water vapour)
- alternative theories speculate that alien asteroids/rocks crashed into the Earth and vaporised, leaving these gases
How were the first oceans formed ?
- water vapour from atmosphere condensed + fell as rain when Earth cooled down over time
- icy comets from space fell and melted into water
How was oxygen introduced into the atmosphere ?
- photosynthetic bacteria + algae evolved ~2.7 bn years ago
- took light energy from the sun and carbon dioxide from the atmosphere to photosynthesise
- oxygen as waste product
- plants and other photosynthetic life evolved and successfully populated the earth both in water and on land
- atmosphere became oxygen rich
- most anaerobic organisms died out
Describe how the majority of carbon dioxide was removed from the early atmosphere of the Earth.
- used up by plants and in new animals/organisms
- used to form sedimentary rocks
- crude oil, fossils
- dissolved in oceans
- reacting with metal oxides to form carbonate compounds to form more rocks
How was the majority of methane and ammonia gas from the Earth’s early atmosphere removed ?
- reactions with oxygen
- methane + oxygen –> carbon dioxide + water
- ammonia + oxygen –> nitrogen + water
Why is nitrogen so heavily present in today’s atmosphere ?
unreactive, so can build up
Describe the composition of the atmosphere today.
- 0.04% carbon dioxide
- 78% nitrogen gas
- 21% oxygen
- all noble gases (1% in total)
- water vapour
Why have carbon dioxide levels in the atmosphere risen recently ?
- more frequent use of fossil fuels (combustion)
- destruction of carbon sinks (peat bogs, forests)
- as temp rises, CO2 is less soluble in water, making oceans less effective as carbon sinks
Why have methane levels in the atmosphere risen recently ?
- emissions from cattle and their decomposing waste
- human waste decomposing in landfill sites
- swamps
- rice fields
What is one piece of hard evidence that the levels of greenhouse gases in the atmosphere are directly linked to climate change ?
- gases trapped in ice cores from the Greenland ice sheet
- analysing these gases shows that levels of greenhouse gases are higher today than anywhere in the last 440 000 years
- if also compared with the upwards trend of temperature, proves the link
Give 4 consequences of the changing weather patterns due to global warming.
- changes to distribution of wildlife and extinction of some species
- increased frequency of extreme weather events
- rising sea levels that may flood many low-lying areas and drown islands, increased erosion of coasts
- increase in temperature in some areas, possibly making them less suitable as food-growing areas etc.
Define the term ‘carbon footprint’.
The carbon footprint of a product, service or event is the total amount of carbon dioxide and other greenhouse gases emitted over its entire life cycle.
Describe 7 ways in which greenhouse gas emissions can be reduced (on a large scale).
- carbon capture and storage (CCS)
- use of land to cultivate plants for a largely plant based diet instead of beef
- “carbon taxes” on buying vehicles that use fossil fuels
- government funding for research into renewable energies
- policies to offset carbon emissions by planting trees
- widening the use of biofuels instead of fossil fuels
- limits to be set internationally on greenhouse gas emissions
Why is it hard to begin to reduce the global carbon footprint ?
- there are still scientific disagreements on the cause of climate change
- any restrictions may impact developing nations’ main trades etc.
- not enough people are implementing emission-cutting ways of life (although this is very minor in comparison to big businesses)
- restrictions on emissions imply major costs for businesses and industries
