1. ATMOSPHERE AND CLIMATE CHANGE

2. CLIMATE AND CLIMATE CHANGE Weather is the state of the atmosphere at a particular place at a particular time. Climate is the long-term prevailing weather conditions at a particular place based upon records taken. When comparing, let’s compare Locust Grove, GA to New York City. On any given day, these two cities may have the same weather (raining, warm, and windy) but their climates are quite different. What is Locust Grove’s climate? What is New York City’s climate?

3. WHAT FACTORS DETERMINE CLIMATE? Climate is determined by a variety of factors: latitude, atmospheric circulation patterns, oceanic circulation patterns, the local geography of an area, solar activity, and volcanic activity. The most important of these factors is the distance from the equator – latitude, which is the distance from the equator measured in degrees north or south of the equator.

4. LOW LATITUDE Latitude influences climate because the amount of solar energy an area of the Earth receives depends on its latitude. More solar energy falls on areas that are near the equator than areas that are closer to the poles. The incoming solar energy is concentrated on a relatively small surface area due to vertical rays of sunlight. Regions in these areas receive about 12 hours of day and night, temperatures are high year-round, and there is no seasonal change.

5. HIGH LATITUDES In regions closer to the poles, the amount of energy arriving at the surface is reduced. In the northern and southern latitudes, sunlight hits the Earth at an oblique angle and spreads over a larger surface area than the equator. The hours of daylight also vary: At 45 degrees north and south, the days can be as long as 16 hours in the summer to as little as 8 in the winter. At the poles, the sun may set or rise for only a few hours.

6. ATMOSPHERIC CIRCULATION Three important properties of air illustrate how air circulation affects climate: 1.Cold air sinks because it is denser than warm air; so as cold air sinks, it compresses the warmer air. 2.Warm air rises; so it expands and cools as it rises. 3.Warm air can hold more water vapor than cold air; therefore, when warm air cools, the water vapor it carries must condense into liquid water (rain, snow, fog).

8. ATMOSPHERIC CIRCULATION When solar energy heats the ground, which warms the air above it, the warm air rises and cooler air moves in to replace it. This movement of air within the atmosphere is called wind. Because the Earth rotates and because different latitudes receive different amounts of solar energy, patterns of atmospheric circulation occur.

9. ATMOSPHERIC CIRCULATION This circulation pattern determines Earth’s precipitation pattern. For example, the intense solar energy striking the Earth’s surface at the equator causes the surface as well as the air above the equator to become very warm. The warm air can hold large amounts of water that evaporate from the equatorial oceans and land. As the warm air rises, it cools, which reduces the capacity of it to hold water and therefore explains why the equator receives large amounts of rain.

10. GLOBAL CIRCULATION PATTERNS Cool air normally sinks but cool air over the equator cannot sink because hot air is rising below the cool air. As a result, the cooler air is forced away from the equator toward the North and South Poles. At about 30 degrees N and S, the air sinks back down to the Earth’s surface. The air becomes warmer as it descends. This causes the warm, dry air to move across the surface of Earth and evaporation from the land creates dry conditions.

11. PREVAILING WINDS Winds that blow predominately in one direction throughout the year are called prevailing winds. Because of the Earth’s rotation, winds do not blow directly northward or southward but toward the right in the Northern Hemisphere and the left in the Southern Hemisphere. The belts of prevailing winds that blow most of the time are in both hemispheres between 30 degrees N and S of the equator. These are known as the trade winds.

12. OCEANIC CIRCULATION PATTERNS Ocean currents have a great effect on climate because water holds large amounts of heat. The movement of surface ocean currents is caused mostly by winds and the rotation of the Earth. These surface currents affect the climate in many parts of the world through El Nino and La Nina circulation patterns.

13. EL NINO VS. LA NINA El Nino is the name given to the short-term (6-18 months), periodic change in the location of warm and cold water masses in the Pacific Ocean. During El Nino, winds in the western Pacific push warm water eastward. Rainfall follows this warm water eastward and produces increased rainfall in the southern half of the United States. Therefore, it also causes a drought in Indonesia and Australia.

14. EL NINO VS. LA NINA La Nina takes places when the water in the eastern Pacific Ocean is cooler than usual. Therefore, the opposite happens where we have significant droughts in the Southern U.S. and Indonesia and Australia receive increased rainfall.

15. SEASONAL CHANGES IN CLIMATE The seasons result from the tilt of the Earth’s axis. Due to this tilt of 23.5 degrees, the angle at which the sun’s rays strike the Earth changes as the Earth moves around the sun. During summer in the Northern Hemisphere, it is tilted toward the sun and receives direct sunlight with the greatest number of hours. At the same time, the Southern Hemisphere is tilted away from the sun and receives less direct sunlight. The opposite happens for our winters.

16. THINGS YOU NEED TO KNOW Explain the difference between weather and climate. Name four factors that determine climate. Explain why different parts of the Earth have different climates. Explain what causes the seasons.

17. THE OZONE SHIELD The ozone layer is an area in the stratosphere where ozone is highly concentrated. Ozone is a molecule made up of three oxygen atoms. The ozone layer absorbs most of the ultraviolet (UV) light from the sun. UV radiation is harmful to organisms because it can damage the genetic material in living cells.

18. CHEMICALS THAT CAUSE OZONE DEPLETION During the 1970’s, scientists began to worry that a class of human-made chemicals, chlorofluorocarbons (CFCs) might be damaging the ozone layer. Humans had once believed that CFCs were a “miracle chemical” in that it was nonpoisonous and nonflammable and it did not corrode metals.

19. CHEMICALS THAT CAUSE OZONE DEPLETION These CFCs became popular as coolants in refrigerators and air conditioners, were used as a gassy “fizz” to make plastic foam, and as a propellant in spray cans for all everyday products. At the Earth’s surface, CFCs were chemically stable, did not break down nor did they combine with other substances. Unfortunately, we didn’t know that these same CFC molecules broke apart at the stratosphere and destroyed the ozone layer.

20. CHEMICALS THAT CAUSE OZONE DEPLETION Over a period of 10-20 years, CFC molecules released at the Earth’s surface make their way into the stratosphere. Each CFC molecule contains from one to four chlorine atoms and have estimated that one chlorine atom can destroy 100,000 ozone molecules.

21. HOW DOES THAT HAPPEN? 1.UV light causes the CFC molecule to break down releasing a chlorine atom. 2.The chlorine atom reacts with an ozone molecule to create an oxygen molecule and a chlorine monoxide (ClO) molecule. 3.The chlorine monoxide molecule then reacts with another ozone molecule, creating two molecules of oxygen and one chlorine atom as decomposition takes place.

22. THE OZONE HOLE In 1985, an article in the scientific journal Nature reported the results of studies by scientists at Antarctica. The study revealed that the ozone layer above the South Pole had thinned by 50 to 98 percent. This was the first news of the ozone hole, a thinning of stratospheric ozone that occurs over the poles.

23. THE OZONE HOLE After the results were published, NASA reviewed data being sent to Earth by satellites and were able to confirm the published results. Although the levels of ozone fluctuates during the year, the data showed a growing ozone hole.

24. EFFECTS OF OZONE ON HUMANS As the amount of ozone in the stratosphere decreases, more UV light is able to pass through the atmosphere and reach the Earth’s surface. Increased incidence of skin cancer. Premature aging of the skin. Increased incidence of cataracts. Weakened immune response.

25. PROTECTING THE OZONE LAYER In 1987, a group of nations met to take action against ozone depletion in Canada. Developed countries agreed to eliminate most CFC use by 1995 and the United States pledged to ban all substances that pose a significant danger to the ozone layer by 2000. Now, all of our aerosol cans, air conditioners, and fizzy foam fillers are made with CFC free replacements.

26. THINGS YOU NEED TO KNOW Describe the process by which CFCs destroy ozone molecules in the stratosphere. Describe the process by which the ozone hole forms over Antarctica in spring. List four harmful effects that UV radiation could have on humans as a result of ozone thinning.

27. THE GREENHOUSE EFFECT The Earth is similar to a greenhouse and the atmosphere is like the glass. 1. Solar radiation passes through the atmosphere and warms the Earth’s surface. 2. Energy from the sun is absorbed by Earth’s surface and then radiated into the atmosphere as heat, some of which escapes into space. 3. Greenhouse gases also absorb some of the sun’s energy and radiates it back toward the lower atmosphere and the Earth’s surface

28. MEASURING CARBON DIOXIDE Charles Keeling installed CO 2 detectors at distances away from cities to get accurate worldwide readings. He installed his at the Mauna Loa volcano in Hawaii. He reasoned that the average CO 2 level in the air could be measured for the entire Earth.

29. MEASURING CARBON DIOXIDE Most of the CO 2 that is released into the air, dissolves in the ocean or is used by plants for photosynthesis. As a result, the levels of CO 2 in the air vary with the seasons. During the summer months, more CO 2 is used by plants than the winter months.

30. RISING CARBON DIOXIDE LEVELS After a few years, Keeling found that CO 2 levels were obviously changing other than seasonal fluctuations. CO 2 levels increased by over 20 percent in less than 50 years. This increase is due largely to the CO 2 released into the air when fossil fuels are burned.

31. ICE CORES Levels of CO 2 in the atmosphere from thousands of years ago can be analyzed through ice cores. These measurements show that CO 2 levels in the atmosphere today are higher than they have been for the last 420,000 years.

32. GREENHOUSE GASES AND EARTH’S TEMPERATURE Many scientists believe that because greenhouse gases trap heat near the Earth’s surface that an increase of them will result in increased global temperatures. Today, we are releasing more CO 2 than any other greenhouse gas. Millions of tons of it are released each year from power plants that burn coal or oil and from cars. Also, from the millions of trees that are burned at the tropical rainforest to clear land for farming.

33. GLOBAL WARMING The increase of average temperature at Earth’s surface increased during the 20 th century. This increase is known as global warming. Because temperatures are rising at a similar rate to the increase in greenhouse gases, many scientists have hypothesized that the increase in greenhouse gases has caused the increase in temperature.

34. THE CONSEQUENCES OF GLOBAL WARMING Animals are nesting earlier, plants are flowering earlier due to the increase in temperatures. Melting ice at the poles are increasing the amount of water in the oceans and could cause low-lying areas to flood. Increase in the amount of hurricanes and typhoons because of the change in ocean current patterns.

35. HUMAN CONSEQUENCES OF GLOBAL WARMING Greater numbers of heat related deaths could occur. An increase in the number and longevity of allergies for those that suffer from plants. More instances of mosquitoes due to warmer temperatures may increase disease such as malaria, dengue fever, and encephalitis to areas that were once too cold for them.

36. HUMAN CONSEQUENCES OF GLOBAL WARMING Agriculture would be most severely impacted by global warming as droughts would be more frequent. Higher temperatures could reduce crop yields. The demand for irrigation could increase which could further deplete the water supplies for humans.

37. REDUCING THE RISK In 1997, representatives from 160 countries met and developed a treaty known as the Kyoto Protocol. It requires developed countries to decrease emissions of CO 2 and other greenhouse gases by 5% by 2012. The need to slow global warming has been recognized… but are we doing enough?

38. THINGS YOU NEED TO KNOW Explain why Earth’s atmosphere is like the glass in a greenhouse. Explain why carbon dioxide in the atmosphere is increasing. Explain one theory for why Earth’s climate is becoming warmer. Name some of the possible consequences of a warmer Earth.