Global Warming

Question 1

What is the enhanced greenhouse effect?

Answer 1

• an inc. in greenhouse gases: allows shortwave radiation to penetrate through them, but prevents longwave
• so traps more radiation inside atmo., causing global avg. T°C to rise

Question 2

How has certain greenhouse gases inc. as a result of human activity (causing enhanced greenhouse effect)?

Answer 2

• CO2:
  
  • 315ppm = 1950, >400ppm = 2020
  • due to burning fossil fuels + deforestation (inc. emissions + reduce trees dec. emissions)
• methane:
  
  • inc. at 0.5-2%/yr
  • cattle produces 75M tonnes + wetlands 150M tonnes/yr
  • released as perma-frost melts
• CFCs:
  
  • inc. at 6%/yr
  • 10,000x more efficient at preventing longwave radiation from penetrating than CO2
  • destroys ozone

Question 3

What is the evidence for the enhanced greenhouse effect + global warming?

Answer 3

• rising sea lvls (3.1mm/yr) from thermal expansion + melting glaciers
• ocean acidity inc. by 26% since 1750
• melting ice + glaciers are showing signs of dec., exposing more land + adding to sea lvl rise
  • Arctic ice sheet shrunk by 65% since 1975

Question 4

What are the possible causes of the enhanced greenhouse effect + global warming?

Answer 4

• albedo change: deforestation + urbanisation has resulted in more darker surfaces
  
  • so ground absorbs more radiation that’s released back to atmo., heating it
• Natural causes:
  
  • variations in Earth’s orbital, axial tilt + solar output
  • changes in axial precession + ocean currents
  • inc. atmospheric dust from volcanoes
• during El Niño: warm water stays closer to surface + pools in Eastern Pacific + radiates heat into air

Question 5

What are the atmospheric impacts of the enhanced greenhouse effect + global warming?

Answer 5

• rising sea levels:
  
  • 200M ppl could be displaced
  • 200M at risk from flood/drought
  • 4M km2 of land threatened by floods from melting glaciers
• warming oceans: 1°C fluctuate causes plankton + coral to stress, bleach + die
• inc. storm activity so more frequent + intense hurricanes
• changes in agri. patterns: e.g. USA’s grain belt will dec., Canada’s growing season will inc.
• widespread drought as dec. rainfall over Europe + USA
• inc disease: 60M more ppl exposed to malaria, as mosquitoes breed faster in heat
• dec. wildlife: 40% of species will become extinct if T°Cs rise by 2°C