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Environmental Science. I. Definitions A. Weather = state of the atmosphere at a particular place at a particular moment.

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Presentation on theme: "Environmental Science. I. Definitions A. Weather = state of the atmosphere at a particular place at a particular moment."— Presentation transcript:

1 Environmental Science

2 I. Definitions A. Weather = state of the atmosphere at a particular place at a particular moment

3 B. Climate = the long-term prevailing weather conditions at a particular place based upon records taken

4 II. Factors that determine climate A. Latitude – the distance from the equator measured in degrees north or south 1. the most important factor determining climate 2. the amount of solar energy an area of Earth receives depends on its latitude

5 3. Low Latitudes A. More sun falls on this area than others B. Night and day are both about 12 hours long throughout the year C. Temperatures are high throughout the year D. No distinct summer or winter


7 4. High Latitudes – regions closer to the poles A. Sun is lower in the sky B. Sunlight hits Earth at an oblique angle and spreads over a larger surface area than at the equator C. Yearly average temperatures near the poles are lower than at the equator

8 d. Hours of daylight vary degrees north and south latitude, there is 16 hours of daylight during the summer and 8 hours of sunlight during the winter 2. near the poles, sun sets for only a few hours each day in summer and rises for only a few hours during the winter 3. Creates a large yearly temperature range

9 B. Atmospheric Circulation 1. Three important properties of air illustrate how air circulation affects climate A. Cold air sinks because it is denser than warm air 1. as it sinks, it compresses and warms

10 B. Warm air rises 1. it expands and cools as it rises C. Warm air can hold more water vapor than cold air 1. when warm air cools, the water vapor it contains may condense into liquid and form rain, snow or fog

11 2. Solar energy heats the ground which warms the air above it 3. warm air rise and cooler air moves in to replace it 4. Wind = the movement of air within the atmosphere created by the above (#2 and 3)

12 5. pattern of global atmospheric circulation results because Earth rotates and because different latitudes receive different amounts of solar energy A. Circulation pattern determines Earths precipitation pattern


14 6. Global circulation patterns A. Cool normally sinks 1. over equator cool air cannot descend because hot air is rising below the cool air 2. the cool air is forced away from the equator and toward the poles

15 B. At 30 degrees N and S latitudes air begins to accumulate in the upper atmosphere 1. some of the air sinks back to the Earths surface and becomes warmer as it descends

16 2. warm, dry air moves across the surface causing water to evaporate from land below 3. Descending air either moves toward the equator or flows toward the poles A. Air moving toward the poles warms while it is near Earths surface

17 C. At 60 degrees N and S latitude, this warmed air collides with cold air traveling from the poles 1. the warm air rises 2. a small part of this rising air returns back to the circulation pattern between 60 and 30 degrees north and south latitudes

18 3. Most of the uplifted air is forced toward the poles A. Cold, dry air descends at poles (very cold desert)

19 7. Prevailing Winds Winds that blow predominately in one direction throughout the year A. Do not blow directly northward or southward

20 1. Because of the rotation of the Earth A. Winds are deflected to right in Northern Hemisphere B. Winds are deflected to left in Southern Hemisphere

21 B. Trade winds – belts of prevailing winds in both hemispheres between 30 degrees north and south 1. blow from northeast in Northern Hemisphere 2. blow from southeast in Southern Hemisphere

22 C. Westerlies – prevailing winds produced between 30 and 60 degrees north and south latitudes 1. blow southwest in the Northern Hemisphere 2. blow northwest in the Southern Hemisphere

23 D. Polar easterlies blow from the poles to 60 degrees north and south latitude

24 C. Oceanic Circulation Patterns 1. surface ocean currents have a great effect on climate because water holds large amount of heat A. Movement of surface ocean currents is caused by winds and the rotation of the Earth B. Surface currents redistribute warm and cool masses of water around the planet

25 C. Some surface currents warm or cool coastal areas year round D. Affect the climate in many parts of the world

26 2. El Nino – Southern Oscillation - the short term (6-18 month period) periodic change in the location of warm and cools water masses in the Pacific Ocean

27 A. Winds in the western Pacific which are usually weak, strengthen and push warm water eastward

28 B. Rainfall follows and produces increased rainfall in southern US and in equatorial South America C. Causes drought in Indonesia and Australia

29 d. La Nina – the water in the eastern Pacific is cooler than usual E. El Nino and La Nina are opposite phases of the El Nino-Southern Oscillation (ENSO) cycle 1. El Nino is the warm phase 2. La Nina is the cool phase

30 3. Pacific Decadal Oscillation - a long-term (20-30 years) change in the location of warm and cold water masses in the Pacific

31 A. PDO influences the climate in the northern Pacific Ocean and North America B. Affects ocean surface temperatures, air temperatures, and precipitation patterns

32 D. Topography 1. Elevation – height above sea level A. Temperatures fall about 11 degrees for every 1,000 m increase in elevation

33 2. Mountains and ranges also influence the distribution of precipitation A. Rain shadow – one side of the mountain gets rain from the ocean air while the opposite side receives dry air

34 E. Other Influences 1. Solar maximum – the sun emits an increased amount of UV radiation

35 A. UV radiation produces more ozone B. The increase in ozone warms the atmosphere C. Increased solar radiation can also warm the lower atmosphere and surface of the Earth

36 2. Volcanic eruptions – cause sulfur dioxide gas to reach the upper atmosphere A. The sulfur dioxide can remain in the atmosphere for up the 3 years B. Reacts with smaller amounts of water vapor and dust in the atmosphere

37 C. This reaction forms a bright layer of haze that reflects enough sunlight to cause the global temperature to decrease

38 III. The Ozone Shield A. Ozone layer – an area in the stratosphere where ozone is highly concentrated 1. ozone – molecule made of three oxygen molecules 2. ozone layer absorbs most of the ultraviolet (UV) light from the sun A. UV light can damage genetic material in living organisms

39 B. Ozone Depletion 1. chloroflourocarbons (CFCs) – class of human-made chemicals; can damage ozone A. Non-poisonous, nonflammable, and non- corrosive to metals B. Used as coolants in refrigerators and air conditioners, in making plastic foams, and as propellants in spray cans

40 C. Are chemically stable at Earths surface D. Break apart in stratosphere and absorb UV radiation which destroys ozone 1. each CF molecule contains one – four chlorine atoms 2. a single chlorine atom can destroy 1,000,000 ozone molecules

41 2. ozone hole – a thinning of stratospheric ozone that occurs over the poles during the spring A. First reported in 1985 above the South Pole 1. ozone had thinned 50-98%

42 B. NASA went back and looked at data from 1979 and discovered the first signs of zone thinning C. Ozone thinning is also occurring over the Artic D. in 1997, ozone levels over part of Canada were 45% below normal

43 3. How ozone holes form A. Polar vortex – strong circulating winds over Antarctica during winter 1. isolates cold air from surrounding warmer air 2. air inside vortex grows extremely cold and fall below -80 degrees C

44 3. form polar stratospheric clouds – high altitude clouds made of water and nitric acid B. On surface of polar stratospheric clouds, the products of CFCs are changed to chlorine

45 1. when sunlight returns in spring, chlorine is split into two chlorine atoms by UV rays 2. chlorine atoms rapidly destroy ozone

46 3. destruction of ozone causes a thin spot or ozone hole that lasts several months A. Some estimate that 70% of ozone layer can be destroyed during this time

47 C. Ozone produced as air pollution does not repair the ozone hole 1. ozone produced by pollution breaks down or combines with other substances in troposphere before it can reach the stratosphere

48 4. Effects of ozone thinning on humans A. More UV light reaches Earths surface which damages DNA B. Makes body more susceptible to skin cancer C. May cause other damaging effects to human body

49 5. Effects of ozone thinning on plants and animals A. Higher UV light can kill phytoplankton 1. disrupts ocean food chains 2. increases amount of CO 2 in atmosphere

50 B. Higher UV light is damaging to amphibians 1. kills eggs which do not have shells 2. amphibians are indicator species –species used to indicate environmental changes

51 C. Higher UV light can damage plants by interfering with photosynthesis 1. results in lower yield crops

52 6. Protecting the Ozone Layer A. Montreal Protocol of meeting of nations in Canada which agreed to take action against ozone depletion 2. agreed to limit the production of CFCs

53 B. A second Conference was held in Copenhagen, Denmark in 1992\ 1. Developed countries agreed to eliminate most CFCs by US pledge to ban all substances that endanger the ozone layer by 2000

54 C. Chemical companies have developed CFC replacements 1. spray cans no longer use CFCs as propellants 2. air conditioners are becoming CFC free

55 D. There has been a decline in CFC production since Montreal Protocol E. CFC molecules remain active in stratosphere for years 1. CFC released 30 years ago are still destroying ozone today 2. it will be many years before the ozone layer recovers

56 IV. Global Warming A. Greenhouse Effect - the process of heat absorption in which sunlight streams through the atmosphere and heats the Earth 1. some of the heat escapes into space 2. some of the heat is absorbed by gases in the troposphere and warms the air


58 3. Greenhouse Gases – gases that absorb and radiate heat A. Water vapor B. Carbon dioxide C. Chlorofourocarbons D. Methane E. Nitrous oxide F. Water vapor and carbon dioxide account for most of the absorption of heat that occurs in the atmosphere

59 B. Measuring carbon Dioxide in the Atmosphere 1. First measured in 1958 by Charles David Keeling in Mauna Loa in Hawaii A. 1 st measurement was 314 parts per million of carbon dioxide in air or.0314% 1. levels fell and rose seasonally

60 B. By 2000 the average level of carbon dioxide was about 368 parts per million 1. in 42 years, carbon dioxide increased 54 parts per million 2. 17% increase 3. Largely due to burning of fossil fuels

61 C. Greenhouse gases and Earths temperature 1. scientists believe that greenhouse gases trap heat near the Earths surface and increase the temperature

62 2. Comparisons of carbon dioxide and average global temperatures for past 400,000 years support this view

63 3. Today, we are releasing more carbon dioxide than another other greenhouse gas A. Results of power plants and vehicles B. We are also releasing CFCs, methane and nitrous oxide

64 D. Global Warming – predicted increase in global temperatures

65 1. Earths average global temperature increased in the 20 th century 2. Most agree it will continue during 21 st century

66 3. not all scientists agree that it is caused by greenhouse gases A. Some believe that the warming is due to part of natural climatic variability B. This type of fluctuations in temperature have occurred throughout time

67 E. Modeling Global Warming 1. scientist cannot make accurate predictions about the rate of global warming

68 A. Climatic patterns are too complex B. Too many variables

69 V. Consequences of a Warmer Earth A. Melting ice and rising sea levels

70 1. would cause sea levels around world to rise 2. coastal areas may flood 3. people who live near coastline would lose homes and sources of incomes

71 4. beaches are eroded 5. salinity of bays and estuaries may increase and thus affect marine fisheries 6. coastal freshwater aquifers may become salty

72 B. Global Weather Patterns 1. oceans may absorb more heat, making hurricanes more common 2. may alter ocean currents 3. could affect weather patterns

73 C. Human Health Problems 1. Heat related deaths may increase 2. Increase in ground level ozone may cause more respiratory problems 3. warmer temperatures may enable insects, such as mosquitoes, to increase causing more disease

74 D. Agriculture 1. Extreme weather patterns may become more common affecting crops

75 E. Effects on Plants and Animals 1. could alter range of plant species and change composition of plant communities 2. may cause shift in geographical range of some animals 3. warming tropical waters may affect coral reefs

76 VI. Reducing the Risk A. 1997, 160 countries met and set time tables to reduce emissions of greenhouse gases B. Kyoto Protocol – requires developed countries to decrease emissions of carbon dioxide and other greenhouse gases by an average of 5 % below their 1990 levels by 2012 C. US did not ratify treaty


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