Section 11.4 Long-term climate drivers
Subsection 11.4.1 Geologic and Orbital Effects
Large-Scale Causes of Climate Changecontinental drift & plate tectonics
movement toward poles may result in glaciation
cannot explain glacial cycles within an ice age
insolation changes from Earthโs orbital mechanics
exaggerate normal seasonal effects
examination of glacial activity at 65ยฐN; approx 100,000 year cycle
variations in solar insolation are principle controlling factor
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orbital effects
variation in eccentricity of Earthโs orbit
100,000 and 400,000 year cycles
axial tilt
variation in angle of Earthโs rotation axis,
relative to orbital plane
currently 23.5ยฐ; 41,000 year cycle
precession
wobble in Earthโs rotation axis
26,000 year cycle; current pole star is Polaris
ocean currents: in Atlantic, currents transport heat from tropics to higher latitudes
solar energy: variations in output; can be tracked by sunspot cycles
cause of ice ages remains an area of active research
Subsection 11.4.2 Climate Feedback Loops
positive feedback (increase glaciation)increased ice cover lowers solar absorption (albedo effect)
increase in freshwater flow to oceans
Milankovitch cycles
greenhouse gas concentrations
weathering (which removes CO2) decreases during glaciation
anthropogenic effects
ice/albedo
methane release
water-vapor feedback
water/cloud
blackbody/height
CO2 sequestration