BIO3082 Lecture Notes - Lecture 2: Radiative Forcing, Carbon Cycle, Kyoto Protocol
Lecture 2 – Global Climate Change
Critique evidence that Human Activity is Causing Climate Change
• *If given graph – interpret what it means
• Since 1950, earth’s atmosphere and oceans have warmed, snow and sea ice
have decreased and sea levels have risen
• Human influence is main cause of warming since mid-20th century
Greenhouse Effects and how it is Enhanced by Humans
• Natural greenhouse effect – supports
life on earth
o Gases in earth’s atmosphere
captures solar radiation
reflected from the earth’s
surface
o Resultant heat retention is
critical for keeping the
biosphere at a temperature
suitable for life
• Enhanced by humans
o Less heat escapes into space
o Greater layer of greenhouse
gases
Major Sources and Sinks of Atmospheric CO2
• Greenhouse gases have increased since industrialisation
o Increases of CO2, N2O (nitrooxide), CH4 (methane)
• Current atmospheric CO2 levels are unprecedented
o Ice cores enable accurate dating of past gas concentrations and
temperatures
o CO2 levels correlate with temperature
• Greenhouse gases contribute to Radiative Forcing
o Radiative forcing – the measure used to describe climate change
o The differences between the sunlight absorbed by earth and the energy
radiated back to space
▪ Measured in Watts per m2
o Carbon dioxide, methane, nitrous oxide and fluorocarbons all increase
radiation forcing
▪ Methane escapes quickly
o Magnitude of the effect depends on their concentration, residence time
and radiative properties
• Where are CO2 emissions coming from?
o Global carbon cycle result in exchange of carbon between four
reservoirs: atmosphere, terrestrial biosphere, oceans and subsurface
o Sources and sinks of CO2 were once balanced
o Atmospheric CO2 levels remained in a steady state
▪ Balance has been disrupted by human activity → increased
atmospheric CO2 loading
▪ Increased sources through fossil fuel burning, while also
decreasing the terrestrial sink through deforestation
o Plants take up CO2
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