The Greenhouse Effect, Homeostasis and Climate Control Processes

1. The Greenhouse Effect, Homeostasis and Climate Control Processes Physical Fundamentals of Global Change – GCM FH Eberswalde - Dec 5th 2006 Doris Kramm

2. First of all…. Why the name “Greenhouse Effect” is wrong: http://www.uoguelph.ca/botany/images/facilities/plant_growth/greenhouse.jpg • 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

3. Contents of this Presentation • the Greenhouse Effect Mechanism • Chemistry of the Atmosphere • Radiation and Heat Trapping • Radiation Balance and the Cooling Factors • Earth History and the Greenhouse Effect - Homeostasis • the Anthropogenic Greenhouse Effect • Human Influence on the Greenhouse Effect • Climate Control Processes GEMechanism Earth History and GE Anthropogenic GE

4. Water Vapor (H2O) Carbondioxide (CO2) Dinitrogen monoxide (N20) Methane (CH4) Greenhouse Effect Mechanism - Chemistry of the Atmosphere GE Mechanism Earth History and GE Anthropogenic GE

5. Composition of dry atmosphere, by volume GE Mechanism Earth History and GE Anthropogenic GE Source: http://en.wikipedia.org/wiki/Earth%27s_atmosphere

6. Composition of dry atmosphere, by volume GE Mechanism Earth History and GE Anthropogenic GE Mean Atmospheric Water Vapor Source: http://en.wikipedia.org/wiki/Earth%27s_atmosphere

7. Greenhouse Effect Mechanism – Radiation and Heat Trapping GE Mechanism Earth History and GE Anthropogenic GE Incoming Radiation – Outgoing Radiation = Trapped Heat • So! What do the Greenhouse Gases actually do? slide Source: http://calipsooutreach.hamptonu.edu/pbl/pbl02-budget.html http://science.nasa.gov/headlines/y2002/images/ceres/ev274_Earth_in_Space_sm.jpg

8. Atmospheric Effects of Incoming Solar Radiation Radiation GE Mechanism Earth History and GE Anthropogenic GE • 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 %. • 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. slide Source: http://www.physicalgeography.net/fundamentals/7f.html

9. Greenhouse Effect Mechanism - Chemistry of the Atmosphere GE Mechanism Earth History and GE Anthropogenic GE 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 slide Source: http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm

10. Greenhouse Effect Mechanism - Chemistry of the Atmosphere 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 GE Mechanism Earth History and GE Anthropogenic GE slide Link Vibrations Source: http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm

11. Greenhouse Effect Mechanism – Radiation and Heat Trapping • 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 GE Mechanism Earth History and GE Anthropogenic GE slide Source: http://www.ucar.edu/learn/1_3_1.htm http://qbab.aber.ac.uk/roy/ftir/absorb.htm Microsoft Encarta

12. Greenhouse Effect Mechanism – Radiation and Heat Trapping Why are O2 and N2 not considered Greenhouse Gases? 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 GE Mechanism Earth History and GE Anthropogenic GE slide Source: http://www.ucar.edu/learn/1_3_1.htm http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm

13. Greenhouse Effect Mechanism – Radiation Balance GE Mechanism Earth History and GE Anthropogenic GE slide

14. Greenhouse Effect Mechanism – the Cooling Factors GE Mechanism Earth History and GE Anthropogenic GE slide

15. Greenhouse Effect Mechanism – Effects of the Effect GE Mechanism Earth History and GE Anthropogenic GE slide The Greenhouse Effect is warming the Climate tremendously!

16. Some Definitions…. Radiative Forcing: A change in the net radiative energy available to the global Earth-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. GE Mechanism Earth History and GE Anthropogenic GE slide http://www.globalchange.umich.edu/globalchange1/current/lectures/samson/global_warming_potential/

17. Greenhouse Effect Mechanism – The Main GHG’s GE Mechanism Earth History and GE Anthropogenic GE slide

18. 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) GE Mechanism Earth History and GE Anthropogenic GE slide Rahmstorf + Schellnhuber 2006. Der Klimawandel

19. 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 GE Mechanism Earth History and GE Anthropogenic GE • change of temperature = change of atmospheric CO2 • change of atmospheric CO2 = change of temperature slide Rahmstorf + Schellnhuber 2006. Der Klimawandel

20. 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 GE Mechanism Earth History and GE Anthropogenic GE slide Rahmstorf + Schellnhuber 2006. Der Klimawandel

21. Earth History and the Greenhouse Effect - Homeostasis Homeostasis is not an ever stable similar condition. It is the up and down of extremes – the mean can then be called 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) GE Mechanism Earth History and GE Anthropogenic GE slide Rahmstorf + Schellnhuber 2006. Der Klimawandel

22. the Anthropogenic Greenhouse Effect – Human Influence on the Greenhouse Effect GE Mechanism Earth History and GE Anthropogenic GE slide

23. the Anthropogenic Greenhouse Effect – Human Influence on the Greenhouse Effect GE Mechanism Earth History and GE Anthropogenic GE slide

24. GE Mechanism Earth History and GE Anthropogenic GE slide

25. 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 GE Mechanism Earth History and GE Anthropogenic GE slide

26. 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

27. Sources Internet Sites: http://www.uoguelph.ca/botany/images/facilities/plant_growth/greenhouse.jpg http://www.whfreeman.com/ruddiman/content.htm http://www.icsu-scope.org/downloadpubs/scope29/chapter06.html http://chemistry.beloit.edu/Warming/pages/infrared.html http://www.visibleearth.nasa.gov/view_rec.php?id=102 http:// www.calstatela.edu http://qbab.aber.ac.uk/roy/ftir/absorb.htm http://en.wikipedia.org/ http://www.physicalgeography.net/fundamentals/contents.html http://www.ucar.edu/learn/1_3_1.htm http://qbab.aber.ac.uk/roy/ftir/absorb.htm Microsoft Encarta http://www.ucar.edu/learn/1_3_1.htm http://www.grida.no/ http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/irspec1.htm http://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 slide

28. Thank you for your Attention Any Questions?

29. Comments for Doris Krammfrom Manfred Stock • To be finished .....