Climate Change: The Move to Action (AOSS 480 // NRE 501)

1. Climate Change: The Move to Action(AOSS 480 // NRE 501) Richard B. Rood 734-647-3530 2525 Space Research Building (North Campus) rbrood@umich.edu http://aoss.engin.umich.edu./people/rbrood Winter 2008 January 22, 2008

2. Class News • A ctools site for all • AOSS 480 001 W08 • This is the official repository for lectures • Email climateaction@ctools.umich.edu • Class Web Site and Wiki • Climate Change: The Move to Action • Winter 2008 Term • Thursday I’m going to ask: “Have you been thinking about projects?”

3. Class News: Get the registration right • If you signed up for AOSS 480 or NRE 501 (Climate Change: The Move to Action), and that is what you wanted to do, then that is all good. • If you signed up for AOSS 480, but want the QuikClimate course on the physical climate system (AOSS 605), then you should change over to 605. • This course has been “approved” by SNRE as permanent! Hence, there may be a 501 number change. • Stay tuned, if you need to do anything. • If you signed up for AOSS 605 or AOSS 480 and have decided that you want to take both, then my advice would be to register for both.

4. Readings on Local Servers • Assigned • IPCC Working Group I: Summary for Policy Makers • Of Interest • Lean: Living with a Variable Sun • Doney: Ocean Acidification

5. Outline of Lecture • Greenhouse effect • Radiative Balance of the Earth • Earth’s Climate System • Atmosphere • Clouds • Oceans • Land • Ice (Cryosphere)

6. The Conservation Principle • The idea that some basic quantities are conserved. • Energy obeys a conservation equation. • Carbon dioxide obeys a conservation equation • Analysis of the conservation equation is a counting problem – the calculation of a budget. • The amount that you have is equal to the amount that you started with, plus the amount that you acquired (income or production), minus the amount that you got rid of (expense or loss)

7. Basic mathematical form of the conservation principle. COOLING Proportional to how hot it is. HEATING

8. If the energy from Earth is in balance • Then T (temperature is not changing) This is the essence of the global warming problem. What is the balance of heating and cooling?

9. Look at the Earth from Space

10. Conservation principle Energy from the Sun Stable Temperature of Earth could change from how much energy (H) comes from the sun, or by changing how much we emit, related to l. Earth at a certain temperature, T Energy emitted by Earth (proportional to T)

11. But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). The Greenhouse Effect SUN Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F). This temperature, which is higher than expected from simple conservation of energy, is due to the atmosphere. The atmosphere distributes the energy vertically; making the surface warmer, and the upper atmosphere cooler, which maintains energy conservation. Earth This greenhouse effect is well known.

12. But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). The Greenhouse Effect SUN Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F). This temperature, which is higher than expected from simple conservation of energy, is due to the atmosphere. The atmosphere distributes the energy vertically; making the surface warmer, and the upper atmosphere cooler, which maintains energy conservation. We are making the atmosphere “thicker.” Earth This greenhouse effect in not controversial.

13. Changing a greenhouse gas changes this Energy conservation of Earth • If we change the heating or the cooling rate then we will change the equilibrium. Will ultimately reach a new equilibrium.

14. Energy conservation for Earth • We reach a new equilibrium Can we measure the imbalance when the Earth is not in equilibrium? Changes in orbit or solar energy changes this

15. Some aspects of the greenhouse effect • Greenhouse warming is part of the Earth’s natural climate system. • It’s like a blanket – it holds heat near the surface for a while before it returns to space. • We have been calculating greenhouse warming for a couple of centuries now. • Water is the dominant greenhouse gas. • Carbon dioxide is a natural greenhouse gas. • We are adding at the margin – adding some blankets • Or perhaps closing the window that is cracked open. • N20, CH4, CFCs, ... also important. • But in much smaller quantities.

16. Something of a summary • We know that CO2 in the atmosphere holds thermal energy close to the surface. Hence, more CO2 will increase surface temperature. • Upper atmosphere will cool. • How will the Earth respond? • Is there any reason for Earth to respond to maintain the same average surface temperature? • Why those big oscillations in the past? • They are linked to solar variability. • Release and capture of CO2 by ocean plausibly amplifies the solar oscillation. • Solubility pump • Biological pump • What about the relation between CO2 and T in the last 1000 years? • Look to T (temperature) variability forced by factors other than CO2 • Volcanic Activity • Solar variability • CO2 increase • Radiative forcing other than CO2? • Other greenhouse gases • Aerosols (particulates in the atmosphere)

17. Radiative Balance of The Earth • Over some suitable time period, say a year, maybe ten years, if the Earth’s temperature is stable then the amount of energy that comes into the Earth must equal the amount of energy that leaves the Earth. • Energy comes into the Earth from solar radiation. • Energy leaves the Earth by terrestrial (mostly infrared) radiation to space. • (Think about your car or house in the summer.)

18. Radiation Balance Figure

19. Let’s build up this picture • Follow the energy through the Earth’s climate. • As we go into the climate we will see that energy is transferred around. • From out in space we could reduce it to just some effective temperature, but on Earth we have to worry about transfer of energy between thermal energy and motion of wind and water.

20. But the Earth’s surface temperature is observed to be, on average, about 15 C (~59 F). The sun-earth system(What is the balance at the surface of Earth?) SUN Based on conservation of energy: If the Earth did NOT have an atmosphere, then, the temperature at the surface of the Earth would be about -18 C ( ~ 0 F). Welcome Back Radiative Balance. This is conservation of energy, which is present in electromagnetic radiation. Earth

21. Energy is coming from the sun. Two things can happen at the surface. In can be: Reflected Or Absorbed Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space

22. Reflect or Absorb Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space We also have the atmosphere. Like the surface, the atmosphere can:

23. Reflect a lot Absorb some Building the Radiative Balance What happens to the energy coming from the Sun? Top of Atmosphere / Edge of Space In the atmosphere, there are clouds which :

24. Building the Radiative Balance What happens to the energy coming from the Sun? RS Top of Atmosphere / Edge of Space For convenience “hide” the sunbeam and reflected solar over in “RS”

25. Building the Radiative Balance What happens to the energy coming from the Sun? RS Top of Atmosphere / Edge of Space Consider only the energy that has been absorbed. What happens to it?

26. Building the Radiative Balance Conversion to terrestrial thermal energy. RS Top of Atmosphere / Edge of Space 1)It is converted from solar radiative energy to terrestrial thermal energy. (Like a transfer between accounts)

27. Building the Radiative Balance Redistribution by atmosphere, ocean, etc. RS Top of Atmosphere / Edge of Space 2)It is redistributed by the atmosphere, ocean, land, ice, life. (Another transfer between accounts)

28. It takes heat to • Turn ice to water • And water to “steam;” • that is, vapor RADIATIVE ENERGY (infrared) PHASE TRANSITION OF WATER (LATENT HEAT) WARM AIR (THERMALS) Building the Radiative Balance Terrestrial energy is converted/partitioned into three sorts RS Top of Atmosphere / Edge of Space 3) Terrestrial energy ends up in three reservoirs (Yet another transfer ) CLOUD ATMOSPHERE SURFACE

29. Building the Radiative Balance Which is transmitted from surface to atmosphere RS Top of Atmosphere / Edge of Space 3) Terrestrial energy ends up in three reservoirs CLOUD CLOUD ATMOSPHERE (LATENT HEAT) (THERMALS) (infrared) SURFACE

30. 1) Some goes straight to space 4) Some is absorbed by clouds and atmosphere and re-emitted upwards 2) Some is absorbed by atmosphere and re-emitted downwards 3) Some is absorbed by clouds and re-emitted downwards Building the Radiative Balance And then the infrared radiation gets complicated RS Top of Atmosphere / Edge of Space CLOUD CLOUD ATMOSPHERE (LATENT HEAT) (THERMALS) (infrared) SURFACE

31. Put it all together and this what you have got.The radiative balance

32. Thinking about the greenhouse A thought experiment of a simple system. Top of Atmosphere / Edge of Space • Let’s think JUST about the infrared radiation • Forget about clouds for a while • 3) Less energy is up here because it is being held near the surface. • It is “cooler” ATMOSPHERE • 2) More energy is held down here because of the atmosphere • It is “warmer” (infrared) SURFACE

33. Remember we had this old idea of a temperature the Earth would have with no atmosphere. • This was ~0 F. Call it the effective temperature. • Let’s imagine this at some atmospheric height. 3) Up here it is cooler than Teffective T < T effective T > T effective 2) Down here it is warmer than Teffective Thinking about the greenhouse A thought experiment of a simple system. Top of Atmosphere / Edge of Space ATMOSPHERE T effective (infrared) SURFACE

34. 3) The part going to space gets a little smaller • It gets cooler still. • 2) The part coming down gets a little larger. • It gets warmer still. Thinking about the greenhouse Why does it get cooler up high? Top of Atmosphere / Edge of Space 1) If we add more atmosphere, make it thicker, then ATMOSPHERE (infrared) SURFACE The real problem is complicated by clouds, ozone, ….

35. Changes in the sun THIS IS WHAT WE ARE DOING Things that change reflection Things that change absorption If something can transport energy DOWN from the surface. So what matters?

36. CLOUD-WORLD The Earth System SUN ATMOSPHERE OCEAN ICE (cryosphere) LAND

37. CLOUD-WORLD The Earth System SUN Where absorption is important ATMOSPHERE OCEAN ICE (cryosphere) LAND

38. CLOUD-WORLD The Earth System SUN Where reflection is important ATMOSPHERE OCEAN ICE (cryosphere) LAND

39. CLOUD-WORLD The Earth System SUN Solar Variability ATMOSPHERE OCEAN ICE (cryosphere) LAND

40. CLOUD-WORLD The Earth System SUN ATMOSPHERE OCEAN ICE (cryosphere) LAND Possibility of transport of energy down from the surface

41. From Warren Washington

42. Transport of heat poleward by atmosphere and oceans • This is an important part of the climate system • One could stand back far enough in space, average over time, and perhaps average this away. • This is, however, weather ... and weather is how we feel the climate day to day • It is likely to change because we are changing the distribution of average heating

43. While Building the Radiative Balance Figure Redistribution by atmosphere, ocean, etc. RS Top of Atmosphere / Edge of Space 1)The absorbed solar energy is converted to terrestrial thermal energy. 2)Then it is redistributed by the atmosphere, ocean, land, ice, life. CLOUD ATMOSPHERE SURFACE

44. After the redistribution of energy, the emission of infrared radiation from the Earth is ~ equal from all latitudes. Because of tilt of Earth, Solar Radiation is absorbed preferentially at the Equator (low latitudes). Another important consideration. Latitudinal dependence of heating and cooling Top of Atmosphere / Edge of Space CLOUD ATMOSPHERE SURFACE South Pole (Cooling) Equator (On average heating) North Pole (Cooling)

45. Transfer of heat north and south is an important element of the climate at the Earth’s surface. Redistribution by atmosphere, ocean, etc. Top of Atmosphere / Edge of Space This predisposition for parts of the globe to be warm and parts of the globe to be cold means that measuring global warming is difficult. Some parts of the world could, in fact, get cooler because this warm and cool pattern could be changed. CLOUD ATMOSPHERE heat is moved to poles cool is moved towards equator cool is moved towards equator SURFACE This is a transfer. Both ocean and atmosphere are important!

46. Hurricanes and heat: Sea Surface Temperature

47. Weather Moves Heat from Tropics to the Poles HURRICANES

48. Mid-latitude cyclones & Heat

49. CLOUD-WORLD The Earth System SUN ATMOSPHERE OCEAN ICE (cryosphere) LAND

50. CLOUD-WORLD SUN Earth System: Sun • SUN: • Source of energy • Generally viewed as stable • Variability does have discernable signal on Earth • Impact slow and small relative to other changes Lean, J., Physics Today, 2005 Lean: Living with a Variable Sun ATMOSPHERE OCEAN LAND ICE (cryosphere)