Teaching the Physics of Climate Change

1. Teaching the Physics of Climate Change This ppt available on www.vicphysics.org - Teachers - Teaching the Science of Climate Change Keith Burrows AIP Education Committee PHYSCON Feb 2008

2. 6.2.2 Role of scientists in the climate debate • These stark conclusions about the threat posed by global climate change and implications for fossil fuel use are not yet appreciated by essential governing bodies … In our view, there is an acute need for science to inform society about the costs of failure to address global warming, because of a fundamental difference between the threat posed by climate change and most prior global threats. J Hansen et al

3. The conclusion from: • Dangerous human-made interference with climate: a GISS modelE study J Hansen et al • In Journal of Atmospheric Chemistry and Physics, 7, 2287–2312, 2007 www.atmos-chem-phys.net/7/2287/2007/ • Authors from: • NASA Goddard Institute for Space Studies, Columbia University Earth Institute, Sigma Space Partners LLC, Department of Earth and Environmental Sciences, Columbia University, Department of Applied Physics and Applied Mathematics, Columbia University, Clean Air Task Force, Boston, Goddard Space Flight Center, Laboratoire des Sciences du Climat et de l’Environnement, Department of Geology, Yale University, Lawrence Berkeley National Laboratory, Massachusetts Institute of Technology, Argonne National Laboratory.

5. This presentation is dedicated to our precious grandchildren – and all the others who will inherit the results of our efforts in this decade – the last that has the option to act to avoid dangerous climate change.

6. Overview • Climate science • Earth’s energy balance • Interactions between EMR and the atmosphere • The effect of changes in the system • Human induced changes • The release of millions of years of stored energy • Is the climate changing? • How can we understand it? • Climate models and their predictions. • What can we do? • Fossil fuels • Reduce energy use • Lower CO2 options • Sustainable options • The human response • Sceptics, deniers, avoiders • Change the light bulbs • The need for real change • Education • That’s where we come in

7. Climate science • Earth’s energy balance • The average temperature of the Earth is determined by the balance between incoming solar radiation and outgoing ‘heat’ radiation

8. Climate science • ~ 1/3 reflected • ~ 2/3 absorbed then re-radiated as IR EMR. • 175,000 TW in • 175,000 TW out (That’s if it is in equilibrium)

9. Climate science • Earth’s energy balance • The average temperature of the Earth is determined by the balance between incoming solar radiation and outgoing ‘heat’ radiation • Not all the IR radiation from the surface escapes immediately... • or the average temperature would be a freezing –15ºC • and there would be much greater swings between night & day, cloud & no cloud

10. Climate science • Earth’s energy balance

11. Climate science • The Greenhouse effect: • Natural: • Water vapour • Carbon dioxide • Human produced: • Carbon dioxide • Methane etc. Human produced

12. Climate science • Interactions between EMR and the atmosphere: • Blackbody spectra. All objects at ANY temperature emit EMR • Hot metal emits lots of shorter IR and some visible

13. Climate science • Interactions between EMR and the atmosphere: • Blackbody spectra. All objects at ANY temperature emit EMR • Cold objects only long IR and no visible • Slightly shorter IR

14. Climate science • Interactions between EMR and the atmosphere: • Blackbody spectra • Spectra of stars • or anything else that hot UV IR The Sun is 5800 K – UV Vis IR –

15. Interactions between EMR and the atmosphere: Blackbody spectra Sun and Earth (but note that Earth is less than a millionth of the Sun) Also note that the IR absorbed from the Sun is of much shorter wavelength than that emitted by the Earth Climate science – UV Vis short IR – long IR

16. Climate science • Interactions between EMR and the atmosphere: • Types of spectra: • Blackbody continuous spectrum

17. Climate science • Interactions between EMR and the atmosphere: • Types of spectra: • Blackbody continuous spectrum • Emission line spectrum

18. Climate science • Interactions between EMR and the atmosphere: • Types of spectra: This is what we are interested in.

19. Climate science • Interactions between EMR and the atmosphere: • First we need to know something about EMR (light). • Quantum physics tells us that it comes as ‘photons’ • Here’s a red one • Here’s a violet one • Notice that the violet one has a shorter wavelength • But it has more energy • (Violet is more violent!)

20. Climate science • Interactions between EMR and the atmosphere: • First we need to know something about EMR (light). • Quantum physics tells us that it comes as ‘photons’ • Here’s an ultraviolet (UV) one – even shorter wavelength • Here’s an infrared (IR) one • Notice that the IR one has a longer wavelength again • It also has much less energy – • but it’s IR that is of interest to us

21. Climate science • Interactions between EMR and the atmosphere: • The gases in the atmosphere absorb, and then re-radiate some parts of the spectrum but not others. • The structure of the molecule determines what sort of energy is absorbed. • Oxygen and Nitrogen molecules are ‘tight’ and it takes a lot of energy to ‘shake’ them. • IR and visible EMR goes right past • Only high energy UV can give its energy to oxygen • (but there’s very little of that even in sunlight)

22. Climate science • Interactions between EMR and the atmosphere: • H2O and CO2 molecules (and other GHGs) are more ‘floppy’ • and so take on energy more easily • IR gives them energy • which they re-radiate – in random directions. • So some goes back down to Earth • keeping us warmer • The Greenhouse effect!

23. Climate science • The effect of changes • Remember we wouldn’t be here without it! • Water vapour is the main GHG • But what if we add more CO2?

24. Climate science • The effect of changes – Feedback and Forcing • More CO2→ more warmth → more H2O (evaporation) → more warmth → more H2O → more warmth → ??? • Water vapour goes in and out of the atmosphere very quickly • Carbon dioxide is there for ~ 100 years • That makes a very big difference in the way they act

25. The effect of changes – Feedback and Forcing Human added H2O is not a problem – it soon rains out again. But CO2 is another story! Climate science

26. Climatepseudo science “the combined effect of these greenhouse gases is to warm Earth's atmosphere by about 33 ºC, from a chilly -18 ºC in their absence to a pleasant +15 ºC in their presence. 95% (31.35 ºC) of this warming is produced by water vapour, which is far and away the most important greenhouse gas. The other trace gases contribute 5% (1.65 ºC) of the greenhouse warming, amongst which carbon dioxide corresponds to 3.65% (1.19 ºC). The human-caused contribution corresponds to about 3% of the total carbon dioxide in the present atmosphere, the great majority of which is derived from natural sources. Therefore, the probable effect of human-injected carbon dioxide is a miniscule 0.12% of the greenhouse warming, that is a temperature rise of 0.036 ºC. Put another way, 99.88% of the greenhouse effect has nothing to do with carbon dioxide emissions from human activity.” Prof. Bob Carter, Research Professor at James Cook University, palaeontologist, stratigrapher, marine geologist and environmental scientist. [Web link to source of this quote as well as the RealClimate discussion are given on the notes page below] • The effect of changes – Feedback and Forcing

27. Climatepseudo science • The effect of changes – Feedback and Forcing • His argument in short: • GHE → 33°C (–18ºC to 15ºC) • H2O → 95% of this (ie.31ºC) • OGHG → 5% of which CO2 → 3.6% • Human CO2 is 3% of CO2 so only 0.1% of GHE • ie. 0.04°C No worries ☺

28. ClimateReal science • The effect of changes – Feedback and Forcing • Sounds impressive – if only! – but  • www.realclimate.org A group of real climate scientists who try to help people like Carter – and us. RealClimate.org Gavin A. Schmidt: climate modeller at the NASA Goddard Institute for Space Studies Dr. Michael E. Mann: Penn State University Departments of Meteorology and Geosciences and the Earth and Environmental Systems Institute, IPCC lead author Dr. Caspar Ammann: National Center for Atmospheric Research (NCAR). Dr. Rasmus E. Benestad: Norwegian project called RegClim, Norwegian Meteorological Institute Prof. Raymond S. Bradley: Director of the Climate System Research Center University of Massachusetts, Ray Bradley: Advisor to U.S., Swiss, Swedish, and U.K. National Science Foundations, NOAA, IPCC, IGBP, Stockholm. William M. Connolley: Climate modeller with the British Antarctic Survey. Prof. Stefan Rahmstorf: New Zealand Oceanographic Institute, Institute of Marine Science in Kiel, Potsdam Institute for Climate Impact Research in Germany, IPCC. Dr. Eric Steig: Isotope geochemist, University of Washington Dr. Thibault de Garidel: Institute of Marine and Coastal Sciences at Rutgers University. Dr. David Archer: Computational ocean chemist at the University of Chicago.

29. ClimateReal science • The effect of changes – Feedback and Forcing • H2O 95% should actually be 90-95% and is for clouds also. • Can’t simply subtract leaving 5-10% for GHGs. • H2O and CO2 absorb different parts of the IR radiation spectrum. H2O CO2 CH4

30. ClimateReal science • The effect of changes – Feedback and Forcing • So it doesn’t matter how much water vapour is in the atmosphere, adding CO2 and CH4 will absorb more IR because they absorb different parts of the IR radiation spectrum.

31. ClimateReal science • The effect of changes – Feedback and Forcing The Real Science: • Take away all H2O: OGHGs absorb ~34% • Take away OGHGs: H2O absorb ~85% • So effect of H2O ~ 66% – 85% [100 – 34 = 66] • Not a linear problem! • So Carter’s 5% for OGHGs should be ~ 15% – 34% [100 – 85 = 15] • So CO2 on its own is 9% – 26% of the GHE • [As CO2 is about 60% of GHGs] • Assuming Carter’s linearity → ΔT ~ 3 to 9°C • (But it isn’t a linear problem)

32. Climatepseudo science • The effect of changes – Feedback and Forcing • Carter also said that human CO2 is 3% of CO2 so 0.1% of GHE • ie. 0.04°C No worries ☺ • But where did he get that figure from? ?

33. ClimateReal science • The effect of changes – Feedback and Forcing • Anthropogenic CO2 is NOT 3%!

34. ClimateReal science • The effect of changes – Feedback and Forcing • Anthropogenic CO2: < 300 ppm → 380 ppm • Rise of > 30% • linear extrapolation: AGHG → 1 to 2.6°C (AGHG = Anthropogenic GHGs) • so we can all look forward to more time on the beach!

35. Climate science • The effect of changes – Feedback and Forcing • Carter ignores complex mechanisms of the GHE. Assumes effects are linear – Just plain wrong. • Overlaps: gases absorb overlapping wavelengths. • Saturation: more gas makes no difference. • Feedback: Particularly important. Positive and negative. • Positive feedback:

36. Climate science • The effect of changes – Feedback and Forcing • Examples of feedback: • Increased water vapour → more clouds • reflect sunlight (negative feedback) • trap IR radiation (positive feedback)

37. Climate science • The effect of changes – Feedback and Forcing • Water vapour is a ‘feedback’ GHG • CO2, CH4, O3 etc are ‘forcing’ agents • They stay in the atmosphere whatever and ‘force’ more heat into the climate system. • Effect measured by ‘Radiative forcing constant’ • or: the extra heat flowing into (or out of) the climate system as a result of a change in some part of the system (in W/m²) "The radiative forcing of the surface-troposphere system due to the perturbation in or the introduction of an agent (say, a change in greenhouse gas concentrations) is the change in net (down minus up) irradiance (solar plus long-wave; in Wm-2) at the tropopause AFTER allowing for stratospheric temperatures to readjust to radiative equilibrium, but with surface and tropospheric temperatures and state held fixed at the unperturbed values". (IPCC)

38. Climate science • The effect of changes – Feedback and Forcing • Computer models are the only way of taking all this into account – a little later.

39. Overview • Climate science • Earth’s energy balance • Interactions between EMR and the atmosphere • The effect of changes in the system • Human induced changes • The release of millions of years of stored energy • Is the climate changing? • How can we understand it? • Climate models and their predictions. • What can we do? • Fossil fuels • Reduce energy use • Lower CO2 options • Sustainable options • The human response • Sceptics, deniers, avoiders • Change the light bulbs • The need for real change • Education • That’s where we come in

40. Human induced changes • The release of solar energy and carbon stored over 100 million years ...

41. The release of solar energy and carbon stored over 100 million years in only 100’s of years That is, a MILLION times faster. We have to ask whether it might have an effect! Human induced changes

42. Human induced changes • Is the climate changing?

43. IPCC SynRep

44. Human induced changes • Is the climate changing?

45. Human induced changes • We now know it has:

46. Human induced changes • We now know it has:

47. Human induced changes • Franz Josef glacier NZ

48. Human induced changes • The Arctic Sea Ice is melting at a much faster rate than predicted.

49. Human induced changes • The Arctic Ice is melting at a much faster rate than predicted

50. Human induced changes • The Arctic Ice is melting at a much faster rate than predicted. • This is a real problem because water absorbs far more solar energy than snow: • Average of Earth 0.3 • Albedo of snow & ice 0.8 – 0.9 • Albedo of water 0.07 • A positive feedback effect