Earth’s Atmosphere & Climate Change

1. Earth’s Atmosphere & Climate Change

3. Fig. 2, p. 312

4. Chapter Objectives • Weather, climate & climate basics • Climate change through geologic time • Ice ages • Present day climate change

5. Table 9.1

6. I. Weather & Climate Is there a difference? Absolutely! • Weather Fluctuations in temperature, precipitation, atmospheric pressure, and winds on time scales of less than a year.

7. I. Weather & Climate B. Climate “long term” changes or patterns in temperature, precipitation, wind, atmospheric pressure, etc… • generally accepted intervals of 30 years or more

8. I. Weather & Climate “Climate is what you expect, weather is what you get!”

9. II. Climate Basics A. Earth’s heat budget • Balance between incoming solar heat & heat loss to space • What controls the budget? • Atmospheric gasses vs. solar radiation

10. II. Climate Basics B. Today’s Atmosphere • gaseous envelope around solid Earth • 3 main elements  99% of atmosphere • N-O-Ar

13. II. Climate Basics C.Temperature &Greenhouse Effect • Trapping of solar heat by atmosphere • H2O, CO2, CH4, N2O, CFC’s • role of O3  filters UV radiation *natural & absolutely critical process!

14. Greenhouse Effect • The greenhouse effect is a naturally occurring process that aids in heating the Earth's surface and atmosphere. It results from the fact that certain atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the energy balance of the planet by absorbing longwave radiation emitted from the Earth's surface. • Without the greenhouse effect life on this planet would probably not exist as the average temperature of the Earth would be a chilly -18° Celsius, rather than the present 15° Celsius. (taken from The Greenhouse Effect, Chapter 7, Physical Geography.net)

17. II. Climate Basics D. Other contributing factors 1.Solar fluctuations • long term; change in solar output • short-term; solar flare (sunspots) cycles 2. Earth’s rotational changes 3. Volcanic eruptions

18. III. Climate Through Earth History Take Home Message based on geologic record Although there have been relatively long intervals of “stable” climate, overall….. Climate has been in constant long-term change throughout Earth’s history • numerous episodes of warmer & colder periods

19. III. Climate Through Earth History • Reading Earth’s Climate History • how do scientists study and interpret ancient climate? • many tools or “proxies” for interpreting past conditions

20. Studying Earth’s Climate History • Tree Rings • Thicker-thinner, lighter-darker rings  • Seasonal to annual variations in • Moisture, temperature, fires

21. Studying Earth’s Climate History 2. Sediment layers - lake beds & ocean floor • Layer thickness  seasonal variations • Wetter vs. drier years • Sediment chemistry  atmospheric conditions

22. Studying Earth’s Climate History 3. Specific rock types  sedimentary rocks • Limestones = warm water • Salts = warm (desert salt flats) • Coal = warm (swamp deposits) • Tillites = cold (glacial deposits)

23. Studying Earth’s Climate History 4. Fossils in rocks • Tropical fossils  corals and marine fauna = warm vs. cold conditions • Land animals  dinosaurs, etc. = warm • Plant fossils  deciduous vs. coniferous vs. grassland/tundra

24. Studying Earth’s Climate History 5. Ice layers • Annual layers of ice in glaciers • Trapped gasses and dust  CO2, etc. • Atmospheric conditions, volcanic activity • Dated layers tell about specific conditions

25. Ancient ice layers; summer (lighter) vs. winter (darker)

26. Studying Earth’s Climate History 6. Chemical Isotopes • abundances of oxygen isotopes give ages and atmospheric compositions • recorded in rocks, fossils, sea floor sediment, glacial ice

27. Studying Earth’s Climate History Take Home Message  Geologists and climate scientists have many tools, proxies for determining past climate conditions.

28. III. Climate Through Earth History B. Early Earth = a hot house Earth • much higher CO2, CH4, etc., very low oxygen • “intense” greenhouse effect • more “modern Earth  much less CO2, O-rich • where did the CO2 go & why did Earth become more oxygen rich over time?

30. III. Climate Through Earth History C. Ice Ages vs. Warm Periods • numerous “colder than normal” vs. “warmer than normal” episodes Ice Age  extended period of geologic time when Earth’s temperature is below the average • at least 5 ice ages throughout time

31. Earth’s Global Ice Ages (orange) Numerous “ice ages” (at least 5) recorded in the geologic record, when Earth’s temperatures where cooler than today. Also, numerous episodes when Earth’s temp. was warmer than today.

33. III. Climate Through Earth History D. Cenozoic Climate Change • warming peak at ~55 MY ago • last 55 MY, slow, gradual cooling • Continental sized glaciers in N. America  ~2.0 MY • Pleistocene ice age

34. Plot of southern ocean temperatures (based on oxygen isotopes in sediments), showing max. ocean temps. ~55-50 MY ago, presumably the warmest conditions in last 100 MY.

35. III. Climate Through Earth History E. Pleistocene Ice Age • most recent ice age • ~2.0 MY – 16,000 BP • North America  northern U.S., Canada, Greenland • Northern Europe + Siberia

37. Pleistocene North America: note distribution of major continental ice sheets, also the relative sea level differences compared to today.

38. Pleistocene North America: note the distribution of climate controlled vegetative zones compared to today’s vegetative zones.

39. III. Climate Through Earth History F. Advances vs. Retreats • numerous warming – cooling trends during the Pleistocene • Glacials vs. interglacials • Glacials cold = glaciers grow & advance southward • Interglacials  warm = glaciers melt & retreat northward Take Home  even during ice age, climate fluctuated

40. Climate fluctuations (warm-cold) over the last 3 MY, based on oxygen isotope data

41. III. Climate Through Earth History G.Closer Look: most modern times • Ice core data: Greenland & Antarctica • CO2 & CH4 concentrations in ice • Dust concentrations • Ice layers dated oxygen isotopes • CO2 & CH4 correlate to temperature

42. EPICA Ice cores from Dome Concordia archive composition of atmosphere for 650,000 years(Science/November 25, 2005)

44. Antarctic Ice Core Data (Dome Concordia) Note ~100,000 cycle peaks of CO2 & CH4

45. IV. Present Day Climate Change & Global Warming

46. So, What Do We Know About The Present Climate Change Pattern?

48. Senator James Inhofe, R-OklahomaSenate Committee on the Environment and Public Works "much of the debate over global warming is predicated on fear, rather than science." I called the threat of catastrophic global warming the "greatest hoax ever perpetrated on the American people," “most media-hyped environmental issue of all time” “the American people have been served up an unprecedented parade of environmental alarmism by the media and entertainment industry”

49. “We have a very brief window of opportunity”Dr. James Hansen, Director, NASA Goddard Institute for Space Studies “We have a very brief window of opportunity to deal with climate change . . . no longer than a decade at the most.“ If the world continues with "business as usual," temperatures will rise by 2 to 3o Celsius (3.6 to 7.2o F) and"we will be producing a different planet"

50. Eleven Warmest Years Worldwide(since the 1880) #1 2005, 2010*(tied) #2 1998 #3 2003 #4 2002 #5 2009 #6 2006 #7 2007 #8 2004 #92001 #102008 13 of the 14 warmest years have occurred since 1995! 22 of 23 warmest years have occurred since 1980!! (National Climatic Data Center, 2010)