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

Table 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 processesexternal processes - motion of plate tectonics- solar energy

Introduction Def. Climate: sub-system of the earth long term changes of climatologic patterns subsystems of climate: atmosphere hydrosphere lithosphere biosphere Climate change occurred throughout earth's history. Changes may affect the basic environment necessary for our existence.

Natural Causes Table of Contents: Plate Tectonics Configuration of the Continents Surface Albedo High-Latitude Land Area Transfer of Latent Heat Restrictions to Ocean Currents Thermal Inertia Elevation of Continents Changing Elevation General Circulation Regional Climate Atmospheric Concentration of Carbon Dioxide

Natural Causes Table of Contents: Milankovitch Cycles Eccentricity Obliquity Precession Volcanoes Solar 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 Tectonics Configuration of the Continents 1. Surface Albedo = amount of energy reflected by surface average 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 Tectonics Configuration of the Continents 2. High-Latitude Land Area albedo of ice/snow: % the higher the albedo, the more ice/snow can accumulate

Natural Causes – Plate Tectonics Configuration 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 Tectonics Configuration 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 Tectonics Configuration 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 Tectonics Elevation 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 Tectonics Elevation 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 glaciation warming of high-latitude regions

Natural Causes – Plate Tectonics Elevation of Continents 3. Regional Climate different climates on different mountain sides: luf: wet lee: rain-shadow effect

Natural Causes – Plate Tectonics Atmospheric 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 Cycles Eccentricity orbit of earth changes shape from circular to elliptical yearly maximum & mini- mum distance between earth & sun varies enhanced seasonality

Natural Causes – Milankovitch Cycles Obliquity decreased tilt: less sunlight on polar regions increased tilt: enhanced seasonality

Natural Causes – Milankovitch Cycles Precession 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 Causes Green-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. What causes global climate change? Rahmstorf, S. Schellnhuber, H.J.(2006): Der Klimawandel. München. S. 15ff. Impacts on the climate system.

Comments for Ina Sahlmann from Manfred Stock 1.To be finished.....