Causes of Climate Change anthropogenicand natural causes Physical Fundamentals of Global Change WS 2006/2007 Ina Sahlmann

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


2. High-Latitude Land Area

albedo of ice/snow: 65-80 %

the higher the albedo, the more ice/snow can accumulate


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


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


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


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


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




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

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Causes of Climate Change anthropogenicand natural causes Physical Fundamentals of Global Change WS 2006/2007 Ina Sahlmann