4.4- climate change

Question 1

what are the two most significant greenhouse gases and how are they released and removed from the atmosphere?

Answer 1

carbon dioxide:
- cell respiration in living organisms, combustion of biomass and fossil fuels.
- removed by photosynthesis and dissolving in oceans

water vapour:
- evaporation from the oceans and transpiration in plants
- removed by rainfall and snow

Question 2

why does temperature drop so much more quickly at night in areas with clear skies than in areas with cloud cover?

Answer 2

water continues to retain heat after it condenses to form droplets of liquid water in the clouds - the water absorbs heat energy, radiates it back to the earth’s surface, and reflects the heat energy back

Question 3

give 2 other greenhouse gases that have less of an impact

Answer 3

methane:
- emitted from marshes/waterlogged habitats and landfill sites where organic wastes have been dumped
- released during extraction of fossil fuels and from melting ice in polar regions

nitrous oxide:
- released naturally by bacteria in some habitats and also by agriculture and vehicle exhausts

Question 4

what two things does the impact of a gas depend on?

Answer 4

its ability to absorb long-wave radiation
its concentration in the atmosphere (determined by the rate at which it is released into the atmosphere and how long on average it remains there)

Question 5

give the steps of climate change

Answer 5

1. surface of the earth absorbs short-wave energy from the sun
2. the warmed earth emits longer-wave (mostly infrared) radiation
3. this is reabsorbed by greenhouse gases which retains the heat in the atmosphere, causing global warming

Question 6

what does data collected from the Vostok ice core demonstrate?

Answer 6

There is a strong positive correlation between carbon dioxide concentrations and temperature (↑ CO2 levels ∝ ↑ temperature)

Question 7

how can past global temperatures and carbon dioxide concentrations be deduced?

Answer 7

with Ice cores taken from the Vostok station in Antarctica:
- temperatures can be deduced from ratios of hydrogen isotopes in the water molecules
- bubbles of air trapped in the ice can be extracted and analysed to find the carbon dioxide concentration

Question 8

what are global temperatures and climate patterns influenced by?

Answer 8

concentrations of greenhouse gases; these will affect how much heat is retained

Question 9

give examples of how global temperatures influence other aspects of climate

Answer 9

Enhanced greenhouse effect:
- higher temp = more evaporation of water from oceans and more frequent/protracted periods of rain
- more frequent extreme weather conditions (e.g. heat waves, cyclones, more powerful tropical storms, etc.)
- some areas to become more drought affected, while other areas become more prone to periods of heavy rainfall
- changes to circulating ocean currents – which may cause longer warming and cooling events

Question 10

state the relationship between industrialisation and climate change

Answer 10

there is a correlation between rising atmospheric concentrations of carbon dioxide since the start of the industrial revolution two hundred years ago and average global temperatures

here, combustion of coal, oil, and natural gas increased rapidly

Question 11

give factors (aside from greenhouse gas emissions) that may influence global average temperatures

Answer 11

• Milankovitch cycles in the earth’s orbit
• variation in sunspot activity
• volcanic activity
• cycles in ocean currents

Question 12

what are recent increases in atmospheric CO2 largely due to?

Answer 12

increases in the combustion of fossilised organic matter
- deforestation
- increased farming and agriculture

Question 13

state the relationship between CO2 Emissions and Ocean Acidification

Answer 13

Rising levels of atmospheric carbon dioxide are causing a decrease in the pH of ocean water (ocean acidification)

CO2 solubility is temperature dependent (more soluble when cooler), so less CO2 will be absorbed as temperatures rise

• some CO2 will remain dissolved in a gaseous state but most will combine with water to form carbonic acid, which dissociates into hydrogen ions and hydrogen carbonate
• H+ ions will lower the ocean pH (acidification) and will also combine with free carbonate ions to form more hydrogen carbonate

Question 14

describe the effects of ocean acidification on marine biodiversity

Answer 14

• with less free carbonate ions in the water, marine organisms are less able to produce calcium carbonate (via calcification)
• shells and coral exoskeletons are also likely to begin to dissolve when ocean conditions are more acidic
• this threatens the viability of coral reefs and certain molluscs