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Greenhouse Effect, Carbon Cycle & Rising Temperatures


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Greenhouse Effect, Carbon Cycle & Rising Temperatures .

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Greenhouse Effect, Carbon Cycle & Rising Temperatures

  2. 2. THE QUESTION OF THE CENTURY: •Natural? OR • Human- caused? WHY THE GLOBAL TEMPERATURE RISE? This issue has been debated hotly for years
  3. 3. THE ANSWER……  In 2007, the world’s climate scientists combined to produce the single most comprehensive and authoritative research summary on climate change:  The Fourth Assessment Report of the  Intergovernmental Panel on Climate Change (IPCC)  The IPCC report summarized all scientific data on climate change, future predictions, and possible impacts and concluded:  “….global warming is very likely man- made (or anthropogenic).”
  4. 4. SUMMARY  Virtually all climate researchers agree that global climate is changing  Virtually all climate researchers agree that human fossil fuel use plays a large role in driving climate change.  In order to understand how fossil fuel is causing climate change, one must understand: 1. The Greenhouse Effect 2. Greenhouse Gasses 3. Disruption of the Carbon Cycle  Let’s take a closer look….
  5. 5. THE GREENHOUSE EFFECT, CARBON CYCLE & RISING TEMPERATURES I. The Greenhouse Effect A. Earth’s Energy Balance B. Greenhouse Gases II. Carbon Cycle A. Carbon sources & sinks B. Long-term records of carbon dioxide III. Rising Temperatures A. Recent & Long-term Temperatures Trends B. Datasets & Proxy Records IV. Modeling Climate Change A. The Earth As a System B. Forward & Negative Feedback Loops C. A closer look at the role of water vapor
  7. 7. THE GREENHOUSE EFFECT-- OVERVIEW Vocabulary in the graphic: • 1) Incoming solar energy is called solar radiation • 2) Solar radiation warms the earth • 3) The warmed earth radiates heat. However, this is not called ‘heat’, but rather in scientific terms it is energy. The correct term is infrared radiation • 4) The atmospheric ‘blanket’ is gas molecules in the atmosphere. Definition Radiation: energy that is propagated in the form of electromagnetic waves.
  8. 8. incoming radiation Solar energy reaches the Earth’s surface The earth surface absorbs the energy and warms up EARTH’S ENERGY BALANCE
  9. 9. Incoming solar radiation infrared radiation (IR) greenhouse gases The warm earth surface radiates infrared radiation (IR) Greenhouse gases absorb IR leaving the surface EARTH’S ENERGY BALANCE
  10. 10. Incoming solar radiation infrared radiation greenhouse gases Gases are energized, then emit more radiation (IR) EARTH’S ENERGY BALANCE
  11. 11. Incoming solar radiation infrared radiation greenhouse gases Some of this IR returns to the earth surface, warming it further EARTH’S ENERGY BALANCE
  12. 12. Incoming solar radiation infrared radiation greenhouse gases This process is what we call the GREENHOUSE EFFECT! EARTH’S ENERGY BALANCE
  13. 13. GREENHOUSE GASES  Obviously, those ‘greenhouse gases’ play an important role in trapping the infrared radiation. What are they? In order of abundance: 1.Water vapor (H2O) 2.Carbon Dioxide (CO2) 3.Methane (CH4) 4.Nitrous Oxide (N2O ) 5.Ozone (O3)
  14. 14. GREENHOUSE GASES  1. The atmosphere is a layer of gaseous materials, some of which interact with infrared radiation and absorb and re-radiate that energy  2. The greenhouse gases have been in the atmosphere a long time (billions of years). They maintain the planet’s global temperature in a range that allowed our life forms to evolve  3. If they have always been there, and the ‘greenhouse effect’ is natural, then why do we now hear about it causing the earth’s temperature to rise?  4. Answer? The amount of greenhouse gases in the atmosphere is increasing
  15. 15. GREENHOUSE GASES Greenhouse Gas Increases in the last 100 years Greenhouse Gas Concentration 1800s Concentration 1990s Percent Increase Anthropogenic Sources CO2 280 ppm 360 ppm 29% burning fossil fuels; deforestation CH4 0.95 ppm 1.7 ppm 79% agriculture; fuel leakage CFCs 0 0.7 ppb ---- refrigerants N2O 250 ppb 310 ppb 24% agriculture; combustion O3 15 ppb 20-30 ppb 33-100% urban pollution
  16. 16. GREENHOUSE GASES  The biggest problem is increasing CO2, carbon dioxide.  CH4, Methane, is also increasing and interacts with IR and has more “global warming potential” than CO2  Water in the atmosphere is in the gas or vapor form. (In fact if it becomes liquid form then it falls out of the atmosphere.. as..?)  Water vapor also traps heat and is a GG  But - It’s a complicated story because vapor as clouds may cool the earth Things to Know Water vapor
  17. 17. NOTICE!: 1) THE CO2-TEMP CORRELATION. IS IT CAUSE-EFFECT? 2) THE RATE AND DEGREE OF CHANGE OF C02 IN THE PAST 200 YEARS. HOW DOES IT COMPARE TO THE PAST 150,000 YEARS? Long-term Records of C02 Long-term proxy records show that the earth’s temperature varied considerably over the past 150,000 years
  20. 20. INTRODUCTION TO CARBON CYCLING  This module will introduce you to the global carbon cycle.  An important idea in this section is that the atmosphere, oceans and land are all connected through the cycling of elements such as carbon.  The earth is one system and everything that happens on our planet becomes part of the interactions between air, water, land and life.  The global carbon cycle has been disrupted and is causing climate change.
  21. 21. THE CARBON CYCLE: WHAT IS CARBON?  Carbon is an element. ‘C’  It can bond with oxygen and form Carbon Dioxide or ‘CO2’. CO2 is found in the atmosphere (and the air around us).  C can dissolve in water and bond with other molecules to form liquid compounds such as carbonic acid.  C also bonds with other carbon molecules to form numerous compounds, for example sugars and carbohydrates, that are a part of all living organisms.
  22. 22. THE CARBON CYCLE: WHAT IS CARBON?  Two important points:  1) Carbon can be in the form of a gas (in the atmosphere), a liquid (in oceans) and a solid (in all living things on land, and in some rock formations).  2) Carbon forms the backbone of the biology of all life on earth. All plants and animals on land and in the water use carbon as a basic building block. To date, no life has been observed that is not carbon-based. ( Star Trek had a silica-based life form called a horta)
  23. 23. THE CARBON CYCLE: WHAT IS A CYCLE?  The carbon cycle: what does ‘cycle’ mean?  A cycle has no distinct beginning and end  Carbon is a part of the biogeochemical cycling of elements that interconnects the land, the air, and the waters  ‘Bio’ – living or biotic elements  ‘Geo’ – earth, geology, soils  ‘Chemical’ – molecules and compounds This is a cycle. It is a circular pathway and has no clear start and finish. This is a line. This is a linear process.
  24. 24. The Carbon Cycle: What is a cycle? When you think of the earth, think of it as a system. The earth is a system in which materials, suchas carbon and water, continuously cycle. Keep this image in mind. Or, do you know another image that means ’inter- connectedness’ to you?
  25. 25. THE CARBON CYCLE  Carbon molecules cycle, meaning that they move through the land, the air, and the water.  Here is one example of a ‘trip’ that a carbon molecule may take:  A tree in a forest is made of carbon (C ). When it burns, some C is converted/released as carbon dioxide (CO2). This CO2 goes into the atmosphere and travels through the air currents. A corn plant then takes up that CO2 in photosynthesis and uses it to make carbohydrates that go into a corn kernel. The corn is harvested and made into breakfast cereal that you eat - and that C is now a part of you.  Carbon illustrates the interconnection of all organisms on earth, and their connection to the atmosphere and waters of the planet.
  26. 26. CARBON CYCLING ON THE LAND: PLANTS AND SOIL  Carbon moves in and out of plants and soil as CO2  Photosynthesis in plant leaves  Takes in CO2  CO2 is ‘food’ for plants  Respiration in plant leaves, roots, and soil  Releases CO2  CO2 is produced in metabolism and the extra is released Soils have microbes that decompose plant material when it falls to the ground. Microbes are alive and they respire as part of their metabolism.
  27. 27. CARBON CYCLING IN PLANTS AND SOIL A closer look at photosynthesis..
  28. 28. CARBON CYCLING ON THE LAND: PLANTS AND SOIL  Just to be sure you understand this…..  Plants run the carbon cycle on land. CO2 + Water + Sunlight Photosynthesis Make C-rich sugars and carbohydrate s to feed themselves and grow Respiration Grow and store C in the plant Some CO2 is lost from the plant in the process of metabolism CO2 + O2 Die, decay and store C in soil
  29. 29. CAN YOU DRAW THE PLANT AND SOIL C CYCLE ?  For practice - draw a simple diagram of the carbon cycle in a forest.  Where is CO2 moving into and out of the atmosphere? Draw arrows showing how CO2 cycles between the atmosphere, plants, and soil.  Leaves take in CO2 from the air and use it for photosynthesis  All plant parts – leaves, wood, even roots – respire CO2 back out to the air  Also, as plants decay, soil microbes respire CO2 into the air  Where is carbon stored? Label where Carbon is stored as plant material or in soils.  Carbon is in wood, leaves, flowers, all plant parts  Carbon is belowground in the roots  Carbon is in the soil as organic matter – the decaying plant parts
  30. 30. CARBON CYCLING IN THE OCEAN  The oceans play a vital role in the global carbon cycle  CO2 mixes in the ocean and cycles between the ocean surface and the atmosphere  CO2 is stored in the ocean waters and in sediments of the deep ocean floor Carbon is stored in the ocean as it dissolves in sea water, and it is stored when it forms sedimentary rock in the deep ocean floor CO2 mixing Dissolved carbon in ocean water Calcium carbonate in ocean floor
  31. 31. CAN YOU DRAW THE GLOBAL C CYCLE FOR LAND AND OCEANS ?  Go back to the simple drawing you did of the carbon cycle on land in a forest. Now add carbon cycling of the ocean to the drawing.  Where is CO2 moving into and out of the atmosphere? ? Draw arrows showing how CO2 cycles between the atmosphere, plants, and soil. Draw arrows showing how CO2 cycles between the atmosphere and ocean.  Where is carbon stored? Label where carbon is stored as plant material or in soils. Also label the carbon stored in seawater and in the ocean floor.  IMPORTANT: The movement of C in and out of the atmosphere as CO2 is called a ‘flux’. Fluxes are shown by arrows in a diagram. When C is stored it is just labeled as carbon or else it is shown in a box in a diagram.  Student Handout #2 – graphic of the carbon cycle. Compare your drawing and check to see if your drawing has the correct ideas.
  32. 32. THE GLOBAL CARBON CYCLE Which exchanges of CO2 with the atmosphere have always been a part of the global carbon cycling system and are in your drawing? Which are not in your drawing? These are due to human activities! Terrestrial Oceans (Student Handout #2 here – “Intro to C cycling” for use in class with next 3 slides)
  33. 33. DISRUPTION OF THE NATURAL GLOBAL CARBON CYCLE  The two human activities that add the most CO2 to the atmosphere are: Extracting the very old, buried C that is oil, coal and natural gas. Burning it for energy releases CO2. Land clearing and deforestation of tropical forests. The slash piles are burned and release CO2
  34. 34. THE GLOBAL CARBON CYCLE  Ok – one more time: Where is carbon?  1)Atmosphere  2) Ocean  3) Land  And…  buried deep in the earth as decayed plant material from long ago.... Fossil Fuels such as coal, oil and gas
  35. 35. DO YOU GET THE CONCEPT?  Take a minute and answer these questions:  What is a possible connection between a car driving down the road and the amount of CO2 in the atmosphere. Between a tree growing in a forest and the amount of CO2 in the atmosphere? CO 2 CO 2CO2 CO2
  36. 36. CARBON CYCLING: IMPORTANT!!! THE AMOUNT OF CO2 IN THE ATMOSPHERE IS INCREASING  Since the 1970s scientists have been measuring the concentration of CO2 in the atmosphere at a tower in Mauna Loa, Hawaii. Concentration is measured in ppm (parts per million).  CO2 has increased from an average of about 325 ppm in 1970 to an average of about 385 ppm in 2008 (Student Handout #3 here – “Increasing atmospheric CO2” - for use in class with next 2 slides)
  37. 37. CO2 IN THE ATMOSPHERE IS INCREASING  How can scientists know what the atmospheric concentration of CO2 was before they had the Mauna Loa tower?. They can estimate CO2 using ice cores pulled from ice sheets in Antarctica and Greenland.  This is called a ‘proxy record’  Measurements from Antarctic ice cores show that atmospheric CO2 concentrations stayed between about 200 and 290 ppm during the preceding 400,000 years.
  38. 38. NOTICE: 1) THE CO2-TEMP CORRELATION. IS IT CAUSE-EFFECT? 2) THE RATE AND DEGREE OF CHANGE OF C02 IN THE PAST 200 YEARS. HOW DOES IT COMPARE TO THE PAST 150,000 YEARS? Long-term records of temperature & C02 Long-term proxy records show that the earth’s temperature varied considerably over the past 150,000 years
  39. 39. atmospheric CO2 ocean land fossil fuel emissions deforestation 7.6 1.5 4.1 2.2 2.8 2000-2006 CO2flux(PgCy-1 ) SinkSource Time (y) Perturbation of Global Carbon Budget (1850-2006) Le Quéré, unpublished; Canadell et al. 2007, PNAS
  40. 40. Houghton, unpublished Carbon Emissions from Tropical Deforestation PgCyr-1 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Africa Latin America S. & SE Asia Source: Anthropogenic C Emissions: Land Use Change SUM 2000-2006 1.5 Pg C y-1 (16% total emissions)
  41. 41. Source: Anthropogenic C Emissions: Fossil Fuel Raupach et al. 2007, PNAS; Canadell et al 2007, PNAS 1990 - 1999: 1.3% y-1 2000 - 2006: 3.3% y-1 0 1 2 3 4 5 6 7 8 9 1850 1870 1890 1910 1930 1950 1970 1990 2010 FossilFuelEmission(GtC/y) Emissions 280 300 320 340 360 380 400 Atmoapheric[CO2](ppmv) [CO2] 2 ppm/year 1850 1870 1890 1910 1930 1950 1970 1990 2010 2006 Fossil Fuel: 8.4 Pg C [2006-Total Anthrop. Emissions:8.4+1.5 = 9.9 Pg]
  42. 42. Partition of Anthropogenic Carbon Emissions into Sinks Canadell et al. 2007, PNAS Ocean removes _ 24% Land removes _ 30% 55% were removed by natural sinks 45% of all CO2 emissions accumulated in the atmosphere The Airborne Fraction The fraction of the annual anthropogenic emissions that remains in the atmosphere Atmosphere [2000-2006]
  43. 43. Carbon Intensity and the Global Economy Canadell et al. 2007, PNAS Carbonintensity (KgC/US$) Kg Carbon Emitted to Produce 1 $ of Wealth 1960 1970 1980 1990 2000 20 Photo:CSIRO
  44. 44. Raupach et al 2007, PNAS 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1980 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1980 World 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1980 1985 1990 1995 2000 2005 F (emissions) P (population) g = G/P h = F/G Factor(relativeto1990) Emissions Population Wealth = per capita GDP Carbon intensity of GDP Drivers of Anthropogenic Emissions Population growth & Carbon Intensity
  45. 45. The Efficiency of Natural Sinks: Land and Ocean Fractions Land Ocean Canadell et al. 2007, PNAS
  46. 46.  Part of the decline is attributed to up to a 30% decrease in the efficiency of the Southern Ocean sink over the last 20 years.  This sink removes annually 0.7 Pg of anthropogenic carbon.  The decline is attributed to the strengthening of the winds around Antarctica which enhances ventilation of natural carbon-rich deep waters.  The strengthening of the winds is attributed to global warming and the ozone hole. Causes of the Declined in the Efficiency of the Ocean Sink Le Quéré et al. 2007, Science Credit:N.Metzl,August2000,oceanographiccruiseOISO-5
  47. 47. PART III: RISING TEMPERATURES Recent & Long-term Temperature Trends Datasets & Proxy Records
  48. 48. RISING TEMPERATURE  The earth’s temperature has increased in the last 200 years - this is a scientific fact.  The temperature increase of the last 200 years has been measured.  Temperature change is not the same all over the world. In fact, some places are the same or cooler, although most places are warmer. It’s the global average that’s increased. Here is the important point: The globally averaged earth surface temperature has increased, it has increased in the last 200 years, and the increase was measured by weather instruments.
  49. 49. WHAT IS KNOWN—THE EARTH IS WARMING “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.” IPCC report 2007, synthesis, p. 30
  50. 50. IPCC 2007 REPORT  Eleven of the last twelve years (1995–2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850).  The linear warming trend over the last 50 years (0.13°C [0.10°C to 0.16°C] per decade) is nearly twice that for the last 100 years.  The total temperature increase from 1850–1899 to 2001–2005 is 0.76°C [0.57°C to 0.95°C].  Urban heat island effects are real but local, and have a negligible influence (less than 0.006°C per decade over land and zero over the oceans) on these values.
  51. 51. RISING TEMPERATURE Student Handout #4: go over handout of this data
  52. 52. RISING TEMPERATURE  200 years  Measured  Scientific Fact  What about the last 2000 years? Or 200,000 years?  How do we determine this?  Scientists use “proxy methods” to estimate temperature and carbon dioxide concentrations Temperature Increase What about longer than 200 years?
  53. 53. PROXY RECORDS: ICE CORES  Ice caps and glaciers accumulated over thousands or millions of years.  They contain bubbles of gas preserved from the time when each layer formed.  Scientists drill cores and analyze the gas bubbles in each layer to see what the atmosphere was like at that time. Figure 12.5
  54. 54. PROXY RECORDS: POLLEN ANALYSIS  Scientists also drill cores into the sediments of ancient lake beds.  By identifying types of pollen grains in each layer, they can tell what types of plants were growing there at the time.
  55. 55. PROXY RECORDS: PACKRAT MIDDENS  For information on other tools used to reconstruct past climate, see White-throated woodrat A giant 28,000+ year-old packrat midden under an overhang at Capitol Reef National Park, Utah. Orange notebook is 7" X 4". Photo by Ken Cole Note: Photos & text on this slide are from: Fossil packrat (or woodrat) middens provide information on past environments because they are a rich source of debris collected by packrats in the past. The packrat often urinates on its garbage pile, marking its territory. When this urine crystallizes, it acts as a glue holding the entire garbage pile together. Fossil debris held within the midden becomes mummified, preserving it indefinitely.
  56. 56. CLIMATE CHANGE AND THE IPCC REPORT  Proxy indicators of temperature (from pollen, ice cores, etc.) were reviewed to establish ancient temperatures.  These data (BLUE) overlapped with the direct temperature measurements (RED). (Gray shows statistical uncertainty.)
  57. 57. PART IV: MODELING CLIMATE CHANGE Earth as a System Forward and Negative Feedback Loops
  58. 58. STUDYING CLIMATE CHANGE: MODELING  To predict what will happen to climate in the future, scientists use climate models:  Computer simulations that use known behavior of past climate to analyze how climate should behave as variables are changed.  Coupled general circulation models (CGCMs) are models that combine, or couple, the effects of both atmosphere and ocean.
  59. 59. EARTH’S ENVIRONMENTAL SYSTEMS Our planet consists of many complex, large-scale, interacting systems. System = a network of relationships among a group of parts, elements, or components that interact with and influence one another through the exchange of energy, matter, and/or information Feedback loop = a circular process whereby a system’s output serves as input to that same system.
  60. 60. FEEDBACK LOOPS: NEGATIVE FEEDBACK In a negative feedback loop, output acts as input that moves the system in the opposite direction. This compensation stabilizes the system
  61. 61. NEGATIVE FEEDBACK LOOPS 1. Increase oceanic algae = more absorption 2. Increase plant growth = more absorption 3. More polar snow = more reflectance 4. More clouds = more reflectance
  62. 62. FEEDBACK LOOPS: POSITIVE FEEDBACK In a positive feedback loop, output acts as input that moves the system further in the same direction. This magnification of effects destabilizes the system.
  63. 63. POSITIVE FEEDBACK LOOPS 5. More clouds = more greenhouse effect 6. Melting permafrost = more methane 7. Less snow/ice = less reflectance 8. More warmth = more air conditioning
  64. 64. Surface temperature Atmospheric H2O Greenhouse effect (+) ⇒Positive feedback loop ⇒As the earth warms, there is an increase in water vapor, increase in warming, increase in water vapor, increase in warming … GREENHOUSE GASES WATER VAPOR FEEDBACK
  65. 65. GREENHOUSE GASES WHAT ABOUT CLOUDS? Most scientists predict that cloudiness will increase as the climate warms. But, what do more clouds do to the earth’s temperature? 1. Increase temperature because water vapor traps heat? A positive feedback 2. Decrease temperature by shielding the earth from incoming solar radiation. A negative feedback. 3. Hard to know. Plus – depends on the
  66. 66. WHAT ABOUT CLOUDS? Altitude 10 km Cumulus/stratus clouds Cirrus clouds (Thin) (Thicker) Less reflection More reflection Fat, low clouds could cool the earths temperature by blocking incoming radiation Thin, High clouds could warm the earth’s temperature by trapping IR IR
  67. 67.  Canadell JG, Corinne Le Quéré, Michael R. Raupach, Christopher B. Field, Erik T. Buitehuis, Philippe Ciais, Thomas J. Conway, NP Gillett, RA Houghton, Gregg Marland (2007) PNAS.  Canadell JG, Pataki D, Gifford R, Houghton RA, Lou Y, Raupach MR, Smith P, Steffen W (2007) in Terrestrial Ecosystems in a Changing World, eds Canadell JG, Pataki D, Pitelka L (IGBP Series. Springer-Verlag, Berlin Heidelberg), pp 59-78.  Raupach MR, Marland G, Ciais P, Le Quéré C, Canadell JG, Klepper G, Field CB, PNAS (2007) 104: 10288-10293.  Le Quéré C, Rödenbeck C, Buitenhuis ET, Thomas J, Conway TJ, Langenfelds R, Gomez A, Labuschagne C, Ramonet M, Nakazawa T, Metzl N, et al. (2007) Science 316:1735-1738. References