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

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Dinitrogen monoxide (N20)

Carbondioxide (CO2)

Water Vapor (H2O)

Methane (CH4)

Greenhouse Effect Mechanism - Chemistry of the Atmosphere

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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

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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

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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

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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

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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

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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

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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

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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

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Greenhouse Effect Mechanism – the Cooling Factors

Greenhouse Effect Mechanism – Effects of the Effect

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slideThe Greenhouse Effect is warming the Climate tremendously!

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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

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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

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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

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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

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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

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the Anthropogenic Greenhouse Effect – Human Influence on the Greenhouse Effect

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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?

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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

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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!

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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

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