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 CARBONATE SEDIMENTARY rocks
How was the majority of methane and ammonia gas from the Earth’s early atmosphere removed (word equations) ?
- 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
- 0.9% argon
- 0.06% water vapour + other noble gases
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
What are the main atmospheric (greenhouse gas) pollutants and their sources ?
- sulfur dioxide from burning fossil fuels with sulfur impurities
- carbon dioxide from complete combustion of fossil fuels or hydrocarbon fuels
- water vapour from complete combustion of hydrocarbon fuels
- nitrogen oxides from nitrogen + oxygen in air reacting in high temperature engines
- carbon monoxide from hydrocarbon fuels burnt in non-plentiful air
- carbon particulates (soot) and unburnt hydrocarbons from incomplete combustion of hydrocarbons like diesel
