Chapter s 23

1. Chapters 23 The Atmosphere, Climateand Global Warming

3. Climate Change Central Questions & Key Concepts • What is the atmosphere • What is the difference between weather & climate • How does the Earth’s climate fluctuate • What factors affect climate • What are the possible effects of global warming • What can humans do about potential climate change • Ozone depletion and global warming are two very different things

4. The Atmosphere • The thin layer of gases that envelops the Earth • Chemical reactions – smog, acid rain, ocean/atmosphere interactions and ozone • Atmospheric circulation produces weather and climates

7. Processes That Remove Materials from the Atmosphere • Sedimentation: • Particles that are heavier than air settle out as a result of gravity. • Ex: Coal /volcanic particles will settle out over time • Rain out: • Precipitation will physically and chemically flush materials from the atmosphere. • Ex: CO2 + H2O  H2CO3 carbon dioxide is removed • Oxidation: • Where oxygen is chemically combined with other subtances. • Ex: atmospheric sulfur dioxide oxidizes to form sulfur trioxide which produces sulfuric acid • Photodissociation: • Solar radiation can break down bonds in this chemical process. For example ozone may break down due to this process from O3 to O2.

8. Vocabulary Used to Characterize Air • Pressure: force per unit area • Atmospheric pressure: is the weight of overlying atmosphere per unit area Question: Does the atmospheric pressure increase as altitude increases or does it decrease? • Temperature: a measure of thermal energy, ie the kinetic energy of the motion of atoms in a substance. Question: as temperature increases does kinetic energy increase or decrease? • Water vapor: The amount of water vapor present in a particular place depends on several things including air temperature, air pressure and available water vapor (from various processes – remember the water cycle?)

9. Weather vs. ClimateNOT THE SAME THING!! • Weather: • Weather is what conditions of the atmosphere are over a short period of time, (hours, days, weeks) • Climate: • climate is how the atmosphere "behaves" over relatively long periods of time (seasons, decades) • that “behavior” includes the representative or characteristic atmospheric conditions for a region on Earth • Microclimate • The climate of a very small local area

10. Short Term Climate Variation • In addition to long-term climate change, there are shorter term climate variations. This so-called climate variability can be represented by periodic or intermittent changes related to El Niño, La Niña, volcanic eruptions, or other changes in the Earth system.

11. Normal El Niño El Niño/Southern Oscillation (ENSO) • Natural. Occurs every 5-10 years. Last 12-18 months • A disruption in the natural weather circulation • The trade winds that usually blow warm surface water towards the western edge of Australia and Indonesia, and nutrient rich cold water (good for fish) towards the west coast of South America weaken or change direction totally. • Causes small changes in ocean temperature that in turn cause very large changes in global weather patterns. • Events believed to have been caused by El Nino: • drought conditions in Indonensia, Africa and Australia. Flooding in South America as well as 1993 Mississippi and 1995 California floods, • So what is La Niña (see page 511)

15. Researchers continue to investigate possible interactions between hurricane frequency and El Niño. El Niño is a phenomenon where ocean surface temperatures become warmer than normal in the equatorial Pacific. (The chart below shows the anomaly associated with the most recent El Niño in 1997-1998.) In general, warm El Niño events are characterized by more tropical storms and hurricanes in the eastern Pacific and a decrease in the Atlantic, Gulf of Mexico and the Caribbean Sea.

17. El Nino vs La Nina • El Nino FAQs • La Nina FAQs

23. Major Climatic Change • Major climatic changes have occurred during the past 2 million years • Appearances and retreats of glaciers • During the past 100 years, the mean global annual temperature has increased by .5 degrees Celsius

26. The Greenhouse Effect • Greenhouse Effect • The process of trapping heat in the atmosphere • NATURAL! • Without it the world would be too cold to support life! • Water vapor (85% of greenhouse warming), wate particles (12%) and several other gases warm the Earth’s atmosphere because they absorb and emit radiation • Greenhouse Gasses • Gasses that have a greenhouse effect • Water vapor • Anthropogenic sources: carbon dioxide,methane, nitrous oxide, CFCs (page 507)

27. The Natural Greenhouse Effect Albedo: known as surface reflectivity of sun’s radiation

28. Changes in the Earth’s Temperature During the Past Million Years • The mean average temperature of the Earth has swung up and down by several degrees Celsius over the past million years due to variations in the Earth’s orbit around the sun. • Interglacial periods – Times of relatively ice free periods, whereas times of low temperature reflect glacial events. • Global climate can also change in shorter times – ex: continental glaciation ended 12,500 years ago with rapid warming – only lasting a few decades.

29. 20th Century Rise • The first 5 years of the 20th century were some of the warmest in the 142 years since temperatures have been recorded and in the last 1,000 years according to geologic data (see pages 499-501 for how this data is collected). • Warming since the mid 70s has been approximately 3X as fast as the previous 100 years • The 10 warmest years have all occurred since 1990 and the five warmest since 1997 • The warmest year on record was 2005, with 1998 second, and 2002 and 2003 tied for second. (2005 data) • In the US 2003 was cooler and wetter than average in the eastern US, warmer and drier in the western part. New Mexico had its warmest year on record. • In Europe in 2003 summer heat waves occurred with the warmest seasonal temperatures ever recorded in several countries. 15,000 people died in Paris. • Warm conditions with drought contributed to severe wildfires in Australia, the United States and Canda. A year or two of high temperatures is NOT by itself and indication of global warming, however, the persistant trend of increasing temperatures over three decades is compelling evidence that global warming is real.

32. So what is “Global Warming” • A natural or human induced increase in the average global temperature of the atmosphere near the earth’s surface • 4 factors • Amount of sunlight Earth receives • Amount of sunlight Earth reflects • Retention of heat by atmosphere • Evaporation and condensation of water vapor • Negative and Positive feedback cycles affect the atmosphere • Increase in emission of greenhouse gasses • Solar Forcing, Natural Cycles, Aerosols (global dimming), Volcanic Eruptions, El Nino

33. Projecting Future Changes in Earth’s Climate • Climate models • Apparent influence of human activities • Could be natural changes

34. http://www.climatescience.gov

35. Negative Feedback Cycles Associated with the Greenhouse Effect • Warming stimulates algae growth. • Algae absorbs CO2. • Warming stimulates plant growth. • Plants absorb CO2. • Polar regions receive more precipitation from warmer air carrying more moisture • Increased snow and ice could cause the solar energy to be reflected causing cooling • Increases in water evaporation from the ocean and the land could increase clouds. • The clouds reflect the sunlight and cool the surface.

36. Positive Feedback Cycles Associated with the Greenhouse Effect • Increased evaporation • Added water vapor in the air that does not condense will cause additional warming. • Melting permafrost at high latitudes • Releases methane, as a by product of decomposition of organic materials in the melted permafrost layer, which would cause additional warming. Releasing old carbon locked in the soil.. • Reduction in the amount of snow pack • Replaced by darker vegetation/soil could increase absorption of solar energy further warming the Earth’s surface. • Increased use of air conditioning in warmer climates • Increased use of fossil fuels could increase release of CO2.

37. Old Carbon vs. New Carbon • Old carbon can be defined as carbon that is trapped and not currently part of our current carbon cycle. • In fossil fuels – released through burning. • In Arctic Soils – being released as temperatures increase. • New carbon is carbon that is part of the current carbon cycle. It has recently entered the soil through vegetation. • Biofuels release CO2 but it is NEW carbon

38. Factors Affecting Changes in Earth’s Average Temperature • Changes in solar output • Changes in Earth’s albedo • Moderating effect of oceans • Clouds and water vapor • Air pollution

39. Climate Change and Human Activities • Increased use/burning of fossil fuels • Adds ~ 5.5 gigatons per year to the atomosphere. The carbon combines with oxygen to produce CO2 • Deforestation • Adds ~ 1.6 gigatons per year to the atomosphere. Burning of the trees releases carbon stored in the wood that combines with oxygen to produce CO2 • Not to mention the fact that the trees are no longer taking IN CO2!

40. Effects of Global Warming • Changes in climatic patterns • Melting icecaps & glaciers • Rise in sea level • Coral reef bleaching • Changes in biosphere

41. Some Possible Effects of a Warmer World

42. Solutions: Dealing with the Threat of Climate Change • Options • Do nothing • Do more research • Act now to reduce risks • Precautionary Principle

43. Coal power plant Tanker delivers CO2 from plant to rig Tree plantation Oil rig CO2 is pumped down from rig for Deep ocean disposal Abandoned oil field CO2 is pumped down to reservoir through abandoned oil field Crop field Switchgrass field Spent oil reservoir is used for CO2 deposit = CO2 deposit = CO2 pumping Removing CO2 From the Atmosphere

44. Reducing Greenhouse Gas Emissions • European Climate Exchange: Carbon Trading • A nation will agree to cap its emissions • Corporations are issued emission permits that allow X amount of emissions. These can be traded. • Rio Earth Summit (1992) • Rio de Jeneiro, Brazil: Blueprint for reduction of CO2 emissions. USA disagreed said it was too costly. • Kyoto Treaty (1997) • Legally binding emission limits discussed. • 166 nations signed. USA refused to sign, though eventually agreed to cut emissions 7% below 1990 levels. Recommended levels were 60-80%.

45. Reducing Greenhouse Gas Emissions Continued… • G-8 meeting (2008) • New U.N. treaty to be discussed in Copenhagen in 2009. Leaders including USA agreed to consider and adopt reductions of greenhouse gas emission of at least 50%. • Facts: • United States has 5% of the world’s population, yet emits 25% of the atmospheric CO2. • California by ITSELF is 12th in the world for CO2 emissions. CA, however, passed legislation in 2006 to reduce emissions by 25% by 2020.

46. The ozone hole is a completely different phenomenon to global warming! There are links between them. For next time: What are those links?