Transcript 07_CC_Causes_I_Sahlmann - Potsdam Institute for Climate

Causes of Climate Change
anthropogenic
and
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 processes
- motion of plate tectonics
external processes
- 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: 65-80 %
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 & minimum 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
Anthropogenic Causes
Green-House Effect
Anthropogenic Causes
Green-House Effect
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.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 .....