Causes of global climate change
● The atmospheric system, including the natural greenhouse effect and energy balance (incoming
shortwave radiation and outgoing longwave radiation)
○ 4 layers of atmosphere
Ozone layer: protects the earth from harmful ultraviolet radiation, ozone is a greenhouse
gas but the effect it has is negligible
○ Natural greenhouse effect: good phenomenon and vital for life
■ Natural causes of the change in heat budget
● Changes in the level of solar activity
● Volcanic activity - extra dust in the atmosphere leads to cooling
● Variations in Earth’s orbit (distance from sun differs)
● Changes in humidity and cloud cover (more humidity will more heat)
○ Climate change
■ Caused by the change in balance between insolation and energy radiated back to
space: radiative forcing
● Positive forcing: warms atmosphere, insolation>radiation back to space
● Negative forcing: cools atmosphere, insolation>radiation back to space
, ○ Energy balance
● Changes in the global energy balance, and the role of feedback loops, resulting from:
○ Solar radiation variations: changes in energy produced by the sun
■ Global dimming: decreased absorption due to tiny particles suspended in the
atmosphere from volcanoes, cools the atmosphere
■ Change in earth’s orbit: when earth is closer, more absorption of heat
■ Sunspots: certain areas of the sun with low temperature
○ Terrestrial albedo changes and feedback loops
■ Albedo: proportion of insolation that is reflected by the surface of the earth
■ Positive feedback loop
● The atmospheric system, including the natural greenhouse effect and energy balance (incoming
shortwave radiation and outgoing longwave radiation)
○ 4 layers of atmosphere
Ozone layer: protects the earth from harmful ultraviolet radiation, ozone is a greenhouse
gas but the effect it has is negligible
○ Natural greenhouse effect: good phenomenon and vital for life
■ Natural causes of the change in heat budget
● Changes in the level of solar activity
● Volcanic activity - extra dust in the atmosphere leads to cooling
● Variations in Earth’s orbit (distance from sun differs)
● Changes in humidity and cloud cover (more humidity will more heat)
○ Climate change
■ Caused by the change in balance between insolation and energy radiated back to
space: radiative forcing
● Positive forcing: warms atmosphere, insolation>radiation back to space
● Negative forcing: cools atmosphere, insolation>radiation back to space
, ○ Energy balance
● Changes in the global energy balance, and the role of feedback loops, resulting from:
○ Solar radiation variations: changes in energy produced by the sun
■ Global dimming: decreased absorption due to tiny particles suspended in the
atmosphere from volcanoes, cools the atmosphere
■ Change in earth’s orbit: when earth is closer, more absorption of heat
■ Sunspots: certain areas of the sun with low temperature
○ Terrestrial albedo changes and feedback loops
■ Albedo: proportion of insolation that is reflected by the surface of the earth
■ Positive feedback loop
