PSY320H1 Lecture Notes - Lecture 10: Ocean Current, Sea Level Rise, Global Temperature Record
Causes of Recent Climate Change
• The largest contribution to total radiative forcing is caused by the increase in the atmospheric
conc. Of CO2
• Radiative forcing: the amount of change in energy that a given factor causes
o measure of the influence that a factor has in altering the balance of incoming and outgoing
energy in the earth-atmosphere system
• Positive forcing warms the surface; negative forcing cools it
• Earth experienced net positive radiative forcing of 2.3 (enough to alter climate)
Greenhouse Gases
• Increase in CO2from fossil fuel burning and land use changes
• Increase in CH4 from agriculture
• Increase in O3, CFCs, Nos
• All of these factors contribute to the enhanced Greenhouse effect (GHE)
• CO2 is not the most potent GHG but it is the most abundant
o CFCs and Nos are much more potent
Negative Effects (cooling)
• Human increases in aerosols (e.g. sulfate, dust)
o Direct cooling = reflection/scattering of solar radiation
o Indirect cooling = increase cloud coverage
• Changes in surface albedo due to changed in land cover
• All GHG show exponential graphs
Atmospheric Increase in CO2
• Atmospheric increases = sources of CO2 - sinks of CO2
o [Emissions from fossil fuels + emissions from changes in land use] - [oceanic uptake]
• ∼ 50% of what we have emitted still in atmosphere
• ∼ 25% taken up by ocean
• ∼ 25% taken up by terrestrial vegetation
• Ocean can absorb most CO2 we have emitted and will emit; however, rate at which CO2 is being
deposited into atmosphere is faster than uptake by oceans
• CO2 has a long residence time of 100s of years in atmosphere
Models of Climate Change
• Climate models are representations of the interactions between the atmosphere, oceans, land
surfaces, ice and the sun
o Include; atmospheric circulations, ocean circulation, interactions, and feedback mechanisms
• Models are tested against the past where we know what happened and all models are unable to
predict recent warming without taking CO2 levels into account
• Generally climate models are conservative these days
Concentration Pathway
• Report of CO2 and avg temp by 2100
o Lo Caro eissios peak i the et deade: . → .C
o Mediu Stailizatio searios: . → .C
o High Caro eissios otiue throughout this etur: . → .C
Global Climate Change Prediction
• Increased temperatures
• Decrease in sea ice and glaciers
• Permafrost loss
o Melting permafrost causes more carbon release and methane release which contributes to
further global warming
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Document Summary
Causes of recent climate change: the largest contribution to total radiative forcing is caused by the increase in the atmospheric conc. Increase in co2from fossil fuel burning and land use changes. Increase in o3, cfcs, nos: all of these factors contribute to the enhanced greenhouse effect (ghe, co2 is not the most potent ghg but it is the most abundant, cfcs and nos are much more potent. Negative effects (cooling: human increases in aerosols (e. g. sulfate, dust, direct cooling = reflection/scattering of solar radiation. Indirect cooling = increase cloud coverage: changes in surface albedo due to changed in land cover, all ghg show exponential graphs. Models of climate change: climate models are representations of the interactions between the atmosphere, oceans, land surfaces, ice and the sun. Increased temperatures: decrease in sea ice and glaciers, permafrost loss, melting permafrost causes more carbon release and methane release which contributes to further global warming.
