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Causes of Climate ChangeCauses of Climate Change
anthropogenicanthropogenicand and
natural causesnatural causes
Physical Fundamentals of Global ChangeWS 2006/2007
Ina Sahlmann
Table of ContentsTable of Contents
Introduction
Natural Causes
Anthropogenic Causes
Conclusion
Introduction
processes, altering the globe continously:
● Natural Geology● Hydrology
● Atmosphere● Biotic Factors
Introduction
processes devided into two types:
internal processes external processes- motion of plate tectonics - solar energy
Introduction
Def. Climate: sub-system of the earthlong term changes of climatologic patterns
subsystems of climate:
atmospherehydrospherelithospherebiosphere
Climate change occurred throughout earth's history. Changes may affect the basic environment necessary for our existence.
Natural Causes
Table of Contents:
Plate TectonicsConfiguration of the Continents
Surface AlbedoHigh-Latitude Land AreaTransfer of Latent HeatRestrictions to Ocean CurrentsThermal Inertia
Elevation of ContinentsChanging ElevationGeneral CirculationRegional Climate
Atmospheric Concentration of Carbon Dioxide
Natural Causes
Table of Contents:Milankovitch Cycles
EccentricityObliquityPrecession
VolcanoesSolar Activity
Natural Causes – Plate Tectonics
= motion in earth's astenosphere which causes global scale dynamics of the rigid lithosperic plates
affects climate through 3 major mechanisms:● altering the distribution of land masses
● changing continental elevation● variability in atmospheric concentration of carbon
dioxide
Natural Causes – Plate TectonicsConfiguration of the Continents
1. Surface Albedo
= amount of energy reflected by surfaceaverage albedo – tropical forest: 7 %average albedo – desert: 25 %
lower latitudes receive greater amount of solar radiation
poleward latitudes – less
amount of ocean versus land surface at low latitudes:
great affect of absorbed solar energy or reflection
Natural Causes – Plate TectonicsConfiguration of the Continents
2. High-Latitude Land Area
albedo of ice/snow: 65-80 %
the higher the albedo, the more ice/snow can accumulate
Natural Causes – Plate TectonicsConfiguration of the Continents
3. Transfer of Latent Heat
= the energy needed for a substance to change states
e.g. water evaporation from ocean and the following precipitation
heat loss over oceanic regions higher than over land
Natural Causes – Plate TectonicsConfiguration of the Continents
4. Restrictions to Ocean Currents
oceanic circulation is primary mechanism by which heat is redistributed from equatorial to polar latitudes
transport is blocked by continental barriers
distribution of moisture is affected
Natural Causes – Plate TectonicsConfiguration of the Continents
5. Thermal Inertia
oceans have a higher thermal heat capacity than land
summer: solar energy stored
winter: solar energy released
Natural Causes – Plate TectonicsElevation of Continents
1. Changing Elevation
atmospheric temperatures decrease with hight (6,5°C per km)
cold temperatures lead to snow coverage and high albedo
Natural Causes – Plate TectonicsElevation of Continents
2. General Circulation
oceanic circulation driven by excess heat energy at the equator and a deficit at the poles
wind belts of the earth are influenced by pressure differences across mountain chains
a change in topography may alter the distribution of cold air masses
glaciationwarming of high-latitude regions
Natural Causes – Plate TectonicsElevation of Continents
3. Regional Climate
different climates on different mountain sides:luf: wetlee: rain-shadow effect
Natural Causes – Plate TectonicsAtmospheric Concentration of Carbon Dioxide
atmospheric carbon dioxide is fixed in the process of weathering of silicates and transported to inner parts of the earth
carbon dioxide is released through:
drifting of the continents (formation of mountains)
volcanic activity
weathering of silicates is accelerated by:
higher temperatures
collision of continents
Natural Causes – Milankovitch Cycles
earth's orbital cycle alters:
amount and distribution of heat
periodic glacial & interglacial cycles
3 components:
Eccentricity
Obliquity
Precession
Natural Causes – Milankovitch CyclesEccentricity
orbit of earth changes shape from circular to elliptical
yearly maximum & mini- mum distance between earth & sun varies
enhanced seasonality
Natural Causes – Milankovitch CyclesObliquity
decreased tilt: less sunlight on polar regions
increased tilt: enhanced seasonality
Natural Causes – Milankovitch CyclesPrecession
slight wobble in the earth's spin
equinoxes: length of night & day are equal
solistice: max. distance from sun to equator
local distribution and timing of insolation affected
Natural Causes – Volcanoes
Anthropogenic CausesGreen-House Effect
Anthropogenic CausesGreen-House Effect
Anthropogenic CausesGreen-House Effect
Anthropogenic CausesGreen-House Effect
Conclusion
● climate system is very complex, changes occur over a wide range of temporal and spatial scales
● climate parameters change simultaneously
● the system is continuously responding to each push and pull
● climate change and their forcing factors are not easily linked
Conclusion
the main factors influencing the climate are:● Variations in the Earth's orbital characteristics
Computer models and historical evidence suggest that the Milankovitch cycles exert their greatest cooling and warming influence when the troughs and peaks of all three cycles coincide with each other
● Atmospheric carbon dioxide variations● Volcanic eruptions
● Variations in solar output
● Human activities
Literature
Introduction to the atmosphere. Causes of climate change.http://www.physicalgeography.net/fundamentals/7y.html
What causes global climate change? http://ccir.ciesin.columbia.edu/nyc/ccir-ny_q1a.html
Rahmstorf, S. Schellnhuber, H.J.(2006): Der Klimawandel. München. S. 15ff.
Impacts on the climate system. http://www.geo.umn.edu/courses/1001/climate.html
Comments for Ina Sahlmann from Manfred Stock
1. To be finished .....