Post on 11-Jan-2016
The Greenhouse Effect, Homeostasis and Climate
Control Processes
Physical Fundamentals of Global Change – GCM FH Eberswalde - Dec 5th 2006Doris Kramm
First of all….
Why the name “Greenhouse Effect” is wrong:
In a greenhouse,
• air is warmed by radiation• warm air cannot escape•convection and air-mixing is suppressed
In the atmosphere,
• radiation, not hot air is trapped• the loss of radiation is reduced by greenhouse gases
http://www.uoguelph.ca/botany/images/facilities/plant_growth/greenhouse.jpg
Contents of this Presentation
1) the Greenhouse Effect Mechanism Chemistry of the Atmosphere
Radiation and Heat Trapping
Radiation Balance and the Cooling Factors
2) Earth History and the Greenhouse Effect
- Homeostasis
3) the Anthropogenic Greenhouse Effect Human Influence on the Greenhouse Effect
Climate Control Processes
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
Dinitrogen monoxide (N20)
Carbondioxide (CO2)
Water Vapor (H2O)
Methane (CH4)
Greenhouse Effect Mechanism - Chemistry of the Atmosphere
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
Composition of dry atmosphere, by volume
ppmv: parts per million by volume
Gas Volume
Nitrogen (N2) 780,840 ppmv (78.084%)
Oxygen (O2) 209,460 ppmv (20.946%)
Argon (Ar) 9,340 ppmv (0.9340%)
Carbon dioxide (CO2) 381 ppmv
Neon (Ne) 18.18 ppmv
Helium (He) 5.24 ppmv
Methane (CH4) 1.745 ppmv
Krypton (Kr) 1.14 ppmv
Hydrogen (H2) 0.55 ppmv
Not included in above dry atmosphere:
Water vapor (H2O) typically 1% to 4%(highly variable)
Source: http://en.wikipedia.org/wiki/Earth%27s_atmosphere
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
Composition of dry atmosphere, by volume
Mean Atmospheric Water Vapor
Source: http://en.wikipedia.org/wiki/Earth%27s_atmosphere
Greenhouse Effect Mechanism – Radiation and Heat Trapping
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slideSource: http://calipsooutreach.hamptonu.edu/pbl/pbl02-budget.html
¿So! What do the Greenhouse Gases actually do?
http://science.nasa.gov/headlines/y2002/images/ceres/ev274_Earth_in_Space_sm.jpg
Incoming Radiation – Outgoing Radiation= Trapped Heat
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Atmospheric Effects of Incoming Solar Radiation
Scattering no alteration to the wavelength of the
electromagnetic energy reduction of amount of incoming radiation
reaching the Earth's surface Redirection of large proportion of scattered
shortwave solar radiation to space The amount of scattering depends on
wavelength of the incoming radiation size of the scattering particle or gas
molecule.
Reflection 180° light redirection, striking
an atmospheric particle 100 % loss of the insolation. Most of the reflection in our
atmosphere by clouds: light interception with
particles of liquid and frozen water
Reflectivity of a cloud can range from 40 to 90 %.
Radiation
Source: http://www.physicalgeography.net/fundamentals/7f.html
Greenhouse Effect Mechanism - Chemistry of the Atmosphere
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Source: http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm
The positions of atoms in a molecules are not fixed; they are subject to a number of different vibrations. Vibrations fall into the two main catagories of stretching and bending.
Atomic Structure
Greenhouse Effect Mechanism - Chemistry of the Atmosphere
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Source: http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm
Stretching: Change in inter-atomic distance along bond axis
Bending: Change in angle between two bonds. There are four types of bend:
•Rocking •Scissoring •Wagging •Twisting
Link Vibrations
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slideSource: http://www.ucar.edu/learn/1_3_1.htmhttp://qbab.aber.ac.uk/roy/ftir/absorb.htmMicrosoft Encarta
Example: Carbondioxide
Photons from IR hit GHG Molecule
Energy is used to move electrons to a higher energy level
Vibration of Molecule is changed
Molecule will emit the energy in form of radiation
>90% of emitted longwave energy is directed back
to earths surface
Energy will be absorbed by another molecule
Absorption-emission-absorption cycle
=> Energy is trapped near the earth‘s surface in a repeating cycle
Greenhouse Effect Mechanism – Radiation and Heat Trapping
Greenhouse Effect Mechanism – Radiation and Heat Trapping
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slideSource: http://www.ucar.edu/learn/1_3_1.htmhttp://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm
GHGs are all molecules composed of more than 2 atoms
molecular vibration causes fluctuations in the dipole moment
molecular vibration matches frequency of radiation
IR is absorbed
amplitude of vibration is changed
N2 and O2 are symmetrical
cannot absorb frequencies of visible or IR waves
absorb of UV light instead
they do not contribute to the GH Effect
Why are O2 and N2 not considered Greenhouse Gases?
Greenhouse Effect Mechanism – Radiation BalanceG
E M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Greenhouse Effect Mechanism – the Cooling Factors
Greenhouse Effect Mechanism – Effects of the Effect
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slideThe Greenhouse Effect is warming the Climate tremendously!
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Some Definitions….
Radiative Forcing:A change in the net radiative energy available to the globalEarth-atmosphere system is termed a radiative forcing. Positive radiative forcings tend to warm the Earth’s surface and lower atmosphere. Negative radiative forcings tend to cool them.
Global Warming Potential:GWPs are a measure of the relative radiative effect of a given substance compared to CO2, integrated over a chosen time horizon.
http://www.globalchange.umich.edu/globalchange1/current/lectures/samson/global_warming_potential/
Greenhouse Effect Mechanism – The Main GHG’sG
E M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Earth History and the Greenhouse Effect - Homeostasis
Regular changes of climate: Iceages – warm periods Balance between incoming and outgoing solar radiation
– changes in this energy balance lead to climate changes
Three regulating factors: Amount of incoming solar radiation Reflection factor (Albedo currently 30%) Change in IR relevant gases – atmospheric content
Earths history of the GHE Age of the solar system: 4,5 billion years Solar radiation then: 25-30% less than todays => 20°C colder
Faint Young Sun Paradox Colder climate = higher Albedo and less water vapor in the
atmosphere, yet evidence of running water Solution: higher GHE (CO2 and CH4)
Rahmstorf + Schellnhuber 2006. Der Klimawandel
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Earth History and the Greenhouse Effect - Homeostasis
Earths Regulatory cycles
Sequestration of CO2 in eroding rocky material, sedimentation in new layers Release into atmosphere by volcanism and geological activity Very slow process – no regulation of fast processes
Ice-Albedo-Cycle
“Snowball Earth” 600 mio years ago Earth covered in ice – positive feedback by albedo Upper cycle is stopped because carbon sink through erosion stops But: volcanism continues – GHG content is increased (up to 10%) Temperature increases slowly inspite of high albedo Ice melts, high concentrations lead to extreme temperatures Ice ages followed by heat periods
Rahmstorf + Schellnhuber 2006. Der Klimawandel
change of temperature = change of atmospheric CO2
change of atmospheric CO2 = change of temperature
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Earth History and the Greenhouse Effect - Homeostasis
Historic Data
2 phases of low CO2 concentrations of the atmosphere
- last millions of years
- 300 mio years ago
Other times: concentrations > 1000 ppm (CO2)
Large masses of ice coincide with low CO2 concentrations
55 mio years ago: palocene-eocene-temperature-maximum:
Sudden increase in GHG concentrations:
temperature increase of 5-6 °C in <1000 years
Relaese of methane? Volcanic activity? Meteorite impact?
Milankovitch Cycles
Regular changes of the earths elipse around the sun=> changed solar radiation
Periods of cycles: 23,000; 41,000; 100,000; 400,000 years
Rahmstorf + Schellnhuber 2006. Der Klimawandel
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
Earth History and the Greenhouse Effect - Homeostasis
Homeostasis
Natural regulatory cycles cause temperature extremes – the
median creates longterm homeostatic conditions on earth
Driven by….
Change of incoming solar radiation (Milankovitsch Cycles)
regulation of GHG content by sequestration and release (volcanic
activity)
Albedo effects (deserts, ice)
Rahmstorf + Schellnhuber 2006. Der Klimawandel
Homeostasis is not an ever stable similar condition. It is the up and down of extremes – the mean can then be called homeostasis
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
the Anthropogenic Greenhouse Effect – Human Influence on the Greenhouse Effect
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
the Anthropogenic Greenhouse Effect – Human Influence on the Greenhouse Effect
Natural Greenhouse Effect Anthropogenic Greenhouse Effect
• Change of incoming solar radiation (Milankovitsch Cycles)
• regulation of GHG content by sequestration and release (volcanic activity)
• Albedo effects (deserts, ice)
• humans do have influence
• fossil fuel emissions, fertilizers, metal production etc.
• increase of gas concentrations
• decrease of GHE by Albedo changes
• Is steered regulation possible?
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
GE M
ech
anism
Earth
Histo
ry a
nd G
E A
nth
ropogenic G
E
slide
the Anthropogenic Greenhouse Effect – Human Influence on the Greenhouse Effect
humans have been taking great influence on the natural
regulatory processes causing a stronger greenhouse effect
earth history shows, that the climate feedback cycles have large
temperature amplitudes – and lead to extremes
the consequences of a strong GHE have been shown
eventually, earths regulatory cycles will even-out the gas increase
(longterm sequestration of CO2)
unfortunately it will be too late for human life as we know it
In order to continue civilisation as it has been:
=> necessary to buffer the changes in atmospheric content caused
by man
=> politics, lifestyle, technology
slide
Takehome Messages….
There is a chemical / physical explanation for the
Greenhouse Effect
Natural Climate Control Processes result in a
homeostatic condition as earth history shows
Homeostatic does not mean STATIC but equalizing
the Anthropogenic Greenhouse Effect has no natural
regulation – it is up to humanity to create one!
slide
Sources
Internet Sites:
http://www.uoguelph.ca/botany/images/facilities/plant_growth/greenhouse.jpghttp://www.whfreeman.com/ruddiman/content.htmhttp://www.icsu-scope.org/downloadpubs/scope29/chapter06.htmlhttp://chemistry.beloit.edu/Warming/pages/infrared.htmlhttp://www.visibleearth.nasa.gov/view_rec.php?id=102http:// www.calstatela.eduhttp://qbab.aber.ac.uk/roy/ftir/absorb.htmhttp://en.wikipedia.org/http://www.physicalgeography.net/fundamentals/contents.htmlhttp://www.ucar.edu/learn/1_3_1.htmhttp://qbab.aber.ac.uk/roy/ftir/absorb.htmMicrosoft Encartahttp://www.ucar.edu/learn/1_3_1.htmhttp://www.grida.no/http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htmhttp://www.globalchange.umich.edu/globalchange1/current/lectures/samson/global_warming_potential/http://www.answers.com/topic/global-warming-potential
Published Works:Rahmstorf, S. and H.-J. Schellnhuber 2006. Der Klimawandel. Beckverlag. 144 Seiten
Thank you for your Attention
Any Questions?
Comments for Doris Kramm from Manfred Stock
1. To be finished .....