CLIMATE CHANGE AND ENERGY Juan Carlos de Obeso October 12 2013

1. CLIMATE CHANGE AND ENERGY Juan Carlos de Obeso October 12 2013

2. Climate System

3. What is Climate? • Climate is the characteristicsof the environment, defined over a finite time interval, at a given location.- This includes the mean values or the range of values or even frequency of events for weather variables, such as wind, temperature, precipitation, humidity, cloudiness, pressure, visibility, and air quality. • A complete description of the climate system and the understanding of its characteristics and change require the study of the physical properties of the high atmosphere, deep ocean, and the land surface, and sometimes the measurement of their chemical properties. • Climate is a quantitative science, involving the understanding and modeling of the transfer of energy from the sun to the earth, from earth to space, and between atmosphere, ocean, and land, all under fundamental physical laws such as conservation of mass, heat, and momentum.

5. What is evident from this graphs? 1958-2012? 1700-2012? Latest CO2 Reading 393.28 ppm October 09, 2013 Source:http://keelingcurve.ucsd.edu/

7. Modeling the Climate

8. Models • Conceptual Illustrate principal relationships or balances • Empirical/statistical Describe relationship between observed parameters (e.g. sea surface temperature and rainfall) • Numerical/dynamical Based on set of mathematical equations describing physical processes, that allow the system to evolve in time

9. How do we model climate?[physically] • Physical/dynamical equations - 3-D equations of motion (conservation of momentum) - Continuity equation (conservation of mass) - Thermodynamic equation (conservation of energy) - Equation of state for air - Balance equation for water vapor • Parameterizations Small-scale processes that are treated statistically and their effects related to average conditions over much longer periods of time and larger space scales e.g. clouds, radiative transfer, turbulence

10. ClimateChange Decadal Initial & ProjectedAtmospheric Composition Weather & Climate Prediction Initial & ProjectedState of Ocean Initial & ProjectedState of Atmosphere CurrentObservedState Uncertainty Time Scale, Spatial Scale

11. Global Climate Change Projections Source: IPCC 4th Assessment Report, Working Group 1: The Physical Science Basis for Climate Change http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html EESC W4400x

12. http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-3.htmlhttp://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-3.html

13. - - - - Radiation - - - - Conduction/Convection Sensible Heat Flux Latent Heat Flux Radiative Heat Flux Surface Energy Budget How is energy/temperature transferred from surface to atmosphere? GH Effect(LW) Net Solar Radiation(SW) Atmos. Ground

14. Blackbody: Definition A blackbody is a hypothetical body made up of molecules that absorb and emit electromagnetic radiation in all parts of the spectrum • All incident radiation is absorbed (hence the term black), and • The maximum possible emission is realized in all wavelength bands and in all directions In other words… A blackbody is a perfect absorber and perfect emitter of radiation with 100% efficiency at all wavelengths

15. Planck Function & Blackbody Radiation • The radiation emitted by a blackbody can be described mathematically by the Planck Function. • Relates the the intesity of radiation from a bb to it’s wavelength or frequency. • Mathematically complicated (we will skip). • But will help us derive a simple model of Earth’s energy balance. • Wein’s Law (flux of radiation emitted by a bb reachest its peak value at wavelength (picture b) • Sun is at ~ 5780 K. What is max wavelength? (Think about this).

16. Note logarithmic scales Blackbody emission curves for the Sun and Earth. The Sun emits more energy at all wavelengths.

17. Electromagnetic Spectrum Sensitivity of human eyes to EM radiation Definition of visible spectrum

18. 1st Law of Thermodynamics ΔEint = Q – W Earth’s atmosphere: (1) Constant volume: W=0 (in equilibrium) (2) Sun is approx. constant ΔQin = 0 (although Qin > 0) (3) dEint = 0, over long time periods, at least before the anthropocene If Earth’s [effective] temperature is constant (dE = 0) then how does surface temperature increase?Hint: What about Qout?

19. Blackbody Equilibrium(Energy Conservation) Energy In EESC W4400x

20. Effect of latitude on solar flux 2 1 The solar flux of beam 1 is equal to that of beam 2. However, when beam 2 reaches the Earth it spreads over an area larger than that of beam 1. The ratio between the areas (see figure above) varies like the inverse cosine of latitude, reducing the energy per unit area from equator to pole. What happens at the pole? The effect of the tilting earth surface is equivalent to the tilting of the light source

21. Blackbody Equilibrium(Energy Conservation) Energy In = Energy Out Emitted“Earthlight” 4πR2Earth x SEarth

22. Blackbody Equilibrium(Energy Conservation) Energy In = Energy Out Consider albedo  Emitted“Earthlight” 4πR2Earth x SEarth EESC W4400x

23. Reflection of Solar Radiation: The Earth’s Albedo • The ratio between incoming and reflected radiation at the top of the atmosphere (TOA) is referred to as the planetary albedo. • The albedo varies between 0 and 1. Components of the Earth’s albedo and their value in % and the processes that affect incoming solar radiation in the Earth’s atmosphere

24. Emission Temperature of a Planet Solar radiation absorbed = planetary radiation emitted Ein = Eout = S (1-A) p R2 = sT4 4p R2 using: A = 0.3; S = 1370 W/m2; s = 5.67 10-8 W/m2/K4 T ~ 255 °K ~ -18 °C [ T0] Is that an reasonable answer? => T4 = S (1-A) / (4s)

25. Incomingsolar radiation Reflection Atmos. Emission Atmos. Emission Transmission Surface Emission Greenhouse Effect Energy in = πr2 S, which is spread over the earth having area 4πr2 so we have πr2 S/4πr2 = S/4 for the incoming radiation (W/m2) The simple model has one layer of greenhouse gases that are transparent to short wave radiation but absorb all long wave radiation. The temperature of the absorbing layer is Te The temperature at the surface is Ts Te is the “effective” or “emitting” temperature of the planet.

26. Incomingsolar radiation Reflection Atmos. Emission Atmos. Emission Transmission Surface Emission Greenhouse EffectIR-Opaque Atmosphere Top of the atmosphere balance: (S/4) (1-A) = σTe4 Te4 = S (1-A) / (4σ) IR Absorbing Layer: 2 σTe4= σTs4 Earth’s surface budget: S (1-A)/4 + σTe4 = σTs4 Ts= 2(1/4) Te Te is the “effective” or “emitting” temperature of the planet.

27. Incomingsolar radiation Reflection Atmos. Emission Atmos. Emission Transmission Surface Emission Greenhouse Effect IR-Opaque Atmosphere End Result (assuming atmos. absorbs all IR): Ts= 2(1/4) Te =1.19 Te Substituting previous results Te4 = S (1-A) / (4s) using: A = 0.3; S = 1370 W/m2 Te ~ 255 K ~ -18 C  T0 Ts =1.19*Te ~ 303 K ~ 30 C  T1 very warm Earth !

28. Greenhouse EffectIR-Opaque Atmosphere Tobserved 288K = 15 C so T0 (-18C) < Tobs < T1 (+30C) What are we missing? OK, we are missing almost everything, but what is important?

29. Absorption of Infrared (Longwave) Radiation in Earth’s Atmosphere Absorption of 100% means that no radiation penetrates the atmosphere. The nearly complete absorption of radiation longer than 13 micrometers is caused by absorption by CO2 and H2O. Both of these gases also absorb solar radiation in the near infrared (wavelengths between about 0.7 μm and 5 μm). The absorption feature at 9.6 micrometers is caused by ozone. EESC W4400x

30. Absorption of Infrared (Longwave) Radiation in Earth’s Atmosphere

31. Emissivity From http://m-w.com(similar info from wikipedia) So, if atmosphere behaved like a blackbody, it would absorb all incoming radiation at all wavelengths, and emit at all wavelengths (appropriate to its temperature)

32. with an atmosphere that is not 100% opaque 4 4 4 (1-)σTs4 σTa4 σTs4 σTs4 σTa4 Greenhouse EffectIR-Semi-Opaque Atmosphere Ts(obs) = 288K, ε=0.77 ε is the atmospheric emissivity

33. Earth’s Globally Averaged Atmospheric Energy Budget All fluxes are normalized relative to 100 arbitrary units of incident radiation. Values are approximate. Figure 3-19 (Kump et al)

34. Greenhouse Effect The difference between the longwave radiation from the Earth’s surface and OLR is the greenhouse effect. Note the strong GH effect in areas which are dominated by deep tropical clouds that precipitate a lot (above). These clouds reach high into the atmosphere (more than 10 Km) where the temperature is low, thus the radiative longwave flux from their tops is relatively small. At the same time the surface underneath is warm and the surface emitted longwave radiation is almost entirely trapped in the cloudy atmosphere.

35. Climate change occurs when either side of energy balance is perturbed. Example 1: • Increase planetary albedo -- • Decrease absorbed solar-- • Emitted thermal exceeds absorbed solar -- • Temperature must decrease to restore balance.

36. Climate change occurs when either side of energy balance is perturbed. Example 2: • Increase greenhouse gases  • Decrease IR radiation to space  • Absorbed solar exceeds emitted thermal  • Temperature must increase to restore balance.

37. Climate Feedbacks: The Ice Albedo Feedback

41. Precipitation Changes

42. Climate Trends: Sea Level Rise

43. I present multiple lines of evidence indicating that the Earth’s climate is nearing, but has not passed, a tipping point, beyond which it will be impossible to avoid climate change with far ranging undesirable consequences. The changes include not only loss of the Arctic as we know it, with all that implies for wildlife and indigenous peoples, but losses on a much vaster scale due to worldwide rising seas. Sea level will increase slowly at first, as losses at the fringes of Greenland and Antarctica due to accelerating ice streams are nearly balanced by increased snowfall and ice sheet thickening in the ice sheet interiors. But then the balance will tip toward ice loss, thus bringing multiple positive feedbacks into play and causing rapid ice sheet disintegration. The Earth’s history suggests that with warming of 2-3°C the new equilibrium sea level will ……. raising sea level of the order of 25 meters (80 feet). Contrary to lethargic ice sheet models, real world data suggest substantial ice sheet and sea level change in centuries, not millennia. The century time scale offers little consolation to coastal dwellers, because they will be faced with irregular incursions associated with storms and with continually rebuilding above a transient water level. The grim “business-as usual” climate change is avoided in an alternative scenario in which growth of greenhouse gas emissions is slowed in the first quarter of this century, primarily via concerted improvements in energy efficiency and a parallel reduction of non-CO2 climate forcings, and then reduced via advanced energy technologies that yield a cleaner atmosphere as well as a stable climate.

46. The Ocean induces a lag in response – as it slowly warms up and then releases the heat to the atmosphere

48. Approaching the warmest period in almost a million years