1. Global Warming and the Dominican Republic Kerry Emanuel Program in Atmospheres, Oceans, and Climate Department of Earth, Atmospheric and Planetary Sciences MIT

2. Program History of the earth’s climateHistory of the earth’s climate The science of global warmingThe science of global warming Possible effects of climate change on the Dominican RepublicPossible effects of climate change on the Dominican Republic

4. The Faint Young Sun Paradox: Why didn’t the Earth Freeze?

5. The Snowball Earth

6. A detailed record of the earth’s climate has emerged over the last few decades, from analyses of ice cores and deep sea sediments

7. Ice Cover, Last Glacial Maximum (~18,000 years ago)

9. Paleo reconstructions of temperature change over the last 2000 years Year Instrumental Record

10. Estimates of Global Mean Surface Temperature from the Instrumental Record

11. Some Characteristics of Climate Science Described by some as the most difficult scientific problem ever faced Draws on all the major scientific disciplines: –Chemistry, geology, atmospheric science, oceanography, solar physics, orbital mechanics, biology –Climate prediction also requires understanding of economics, politics, human psychology Very much a frontier science

12. John Tyndall (1820-1893) The Greenhouse Effect

13. Tyndall’s Discovery: Oxygen (O 2 ) and Nitrogen (N 2 ), which together comprise about 97% of the atmosphere, are transparent to solar and infrared radiation If that’s all there were: = Stefan-Boltzmann constant a = Planetary albedo = Solar constant

14. But certain trace gases interact strongly with radiation: H 2 0 (water vapor) CO 2 (carbon dioxide) CH 4 (methane) Clouds also interact strongly with radiation. Together, they yield:

15. Elements of the Greenhouse Effect

16. If the Only Feedback Were Temperature, Doubling Carbon Dioxide would Increase Surface Temperature by about 1.1 o C.

17. Feedbacks in Climate Models Water vaporCloudSurface albedo Lapse rateWater vapor + lapse rate

18. Climate Forcing by Orbital Variations Milutin Milanković, 1879-1958

19. Climate Forcing and Response

20. Black: Time rate of change of ice volume Red: Summer high latitude sunlight Strong Correlation between High Latitude Summer Insolation and Ice Volume P. Huybers, Science, 2006

21. Causes of Recent Climate Change

24. Variation in carbon dioxide and methane over the past 20,000 years, based on ice core and other records

25. Contributions to net radiative forcing change, 1750-2004:

27. Distribution of temperature change, 1901-2005

28. Global Climate Models: How Good Are They, and What Do They Tell Us about The Future?

29. Global Climate Modeling General philosophyGeneral philosophy: –Simulate large-scale motions of atmosphere, oceans, ice –Solve approximations to full radiative transfer equations –Parameterize processes too small to resolve –Some models also try to simulate biogeochemical processes –First GCMs developed in 1960s

30. Equations solved by discretizing to finite volumes

31. Unresolved physical processes must be handled parametrically Convection Thin and/or broken clouds Cloud microphysics Aerosols and chemistry (e.g. photochemical processes, ozone Turbulence, including surface fluxes Sea ice Land ice Land surface processes

32. Global mean temperature (black) and simulations using many different global models (colors) including all forcings Same as above, but models run with only natural forcings

33. Projected Warming:

34. Climate Risks to the Dominican Republic

35. Warming Risks Rising sea level Concentration of rainfall into fewer but more intense events...more drought, floods Increased incidence of some tropical diseases Increased production of allergens Increased mortality from heat waves Increased consumption of electricity Increase in violent hurricanes Ocean acidification, increased species extinctions

36. Sea Level, 1860-2003 Reconstructed Tide Gauge Satellite altimetry

37. Arctic Minimum Sea Ice Extent

39. Greenland surface elevation change, 1989- 2005

40. Hurricane Power is Changing in Concert with Tropical Ocean Temperature

41. Today’s global climate models are far too coarse to simulate tropical cyclones

42. Our Approach Step 1: Seed each ocean basin with a very large number of weak, randomly located cyclones Step 2: Cyclones are assumed to move with the large scale atmospheric flow in which they are embedded Step 3: Run a coupled, ocean-atmosphere computer model for each cyclone, and note how many achieve at least tropical storm strength Step 4: Using the small fraction of surviving events, determine storm statistics.

43. 200 Synthetic U.S. Landfalling tracks (color coded by Saffir-Simpson Scale)

44. Present Climate: Spatial Distribution of Genesis Points Observed Synthetic

45. Now Use Daily Output from IPCC Models to Derive Wind Statistics, Thermodynamic State Needed by Synthetic Track Technique

46. Last 20 years of 20 th century simulations 2. Years 2180-2200 of IPCC Scenario A1b (CO 2 stabilized at 720 ppm) 1. Last 20 years of 20 th century simulations 2. Years 2180-2200 of IPCC Scenario A1b (CO 2 stabilized at 720 ppm) Compare two simulations each from 7 IPCC models:

47. Change in Destructiveness of Hurricanes

48. Return Periods

49. Sample Wind Swath

50. Sample Storm Surge

51. Sample Rain Swath

52. Sample Rain Rate at Santa Domingo

53. Change in Landslide Risk

54. Summary Earth’s climate has changed radically and often abruptly through time Primary culprits: –Changing insolation, through solar evolution and orbital variations –Changing concentrations of trace greenhouse gases –Changing concentration of aerosols: Volcanic eruptions Evidence for human-induced climate change now very compelling

55. Principle risks of Global Warming to the Dominican Republic: –Increased incidence of flash floods –Ocean acidification and damage to marine ecosystems –Coastal flooding owing to sea level rise –Increased frequency and severity of hurricanes, including storm surge and fresh-water flooding

59. Possible Benefits of Warming: Fewer deaths from exposure More vigorous plant growth Increase of arable land at high latitudes Increased mining potential in current permafrost regions Arctic waterways become navigable Reduced heating costs

60. Changing Distributions of Precipitation