Percentages of Gases in the Atmosphere

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1 Chapter 7 - Atmosphere and Climate 7.1 The atmosphere atmosphere - thin layer of gases that surrounds the earth - extends from the surface of the Earth to hundreds of kilometers above the surface - without it life would not be possible Percentages of Gases in the Atmosphere Nitrogen 78% Oxygen 21% Other 1% * Other gases are Argon, water vapor, carbon dioxide, neon, helium and various other gases air - mixture of all the gases above, the most important being oxygen and carbon dioxide Role of the atmosphere: 1. contain the earth's air so that it doesn't escape into space 2. protect the inhabitants of earth from ultra violet radiation 3. also allows visible light to reach the surface - which allows photosynthesis to occur 4. also radiates heat back to the surface helping to warm the planet *The atmosphere acts much like a window in a car - it allows light in and helps trap the energy Photosynthesis and the Atmosphere Though it is not known for sure, from scientific study it is believed that the earth's atmosphere contained very little oxygen. Scientists believe that about 4 billion years ago certain bacteria evolved to the point at which they could perform photosynthesis and thus put oxygen in the air up to the point today that oxygen makes up about 21% of the air in our atmosphere Today the O 2 - CO 2 balance is kept in "balance" by the photosynthesis/respiration process. For comparison sake CO 2 makes up about 0.035% of our air. This small amount is what keeps Earth in its temperature range. Of course we know that an increase in CO 2 is causing an increase in our global temperature.

2 The Five Layers of the Atmosphere 1. Troposphere 2. Stratosphere 3. Mesosphere 4. Thermosphere 4.1. Ionosphere 5 Exosphere Troposphere - extends to about 10km above the surface - contains nearly 90% of the atmospheric gases - most weather occurs here, as air current flow, swirl and mix here - air currents here bring air from different parts of the globe - temperature decreases as altitude increases Stratosphere - extends from 10km to 50km above the Earth - air is less dense - there is wind but it doesn't have the same effect here - most commercial planes fly in the lower part of this layer due to reduced air resistance - ozone layer is in this section of the atmosphere - temperature increases with altitude Mesosphere - middle layer of the atmosphere - temperatures may reach -100 o C - temperature decreases as altitude increases - meteors burn up in this layer and can be seen by humans as shooting stars Thermosphere - extends from 80km upward to over 500km - comprised of both the ionsphere and the exosphere - temperature rises with altitude Ionosphere - not considered one of the five layers - extends from 80km upward to over 600km - layer of ionized air in the atmosphere that is created when the Sun's energy is so strong that is breaks apart the atoms of air. This causes the molecules to lose electrons which are free floating and the molecules themselves become ions - not technically a layer of the atmosphere (part of the thermosphere) Exosphere - highest layer of the atmosphere - extends to 10, 000km above the earth's surface - extremely thin air - the atmosphere merges with space here - hydrogen and helium are the prime components - level at which many satellites orbit the Earth

3 7.2 Climate weather - simply the conditions (rain, wind, storm, etc) that are occurring in the atmosphere at a given place at a given time climate - is the average weather that occurs over a long period of time - important parts of climate are the temperature, humidity, wind, and precipitation - one of the largest factors that determine the type of organisms that live in a particular region Factors that Affect Climate 1. Latitude - most important factor - the sun's energy is more direct at the equator - the further from the equator the less intense the sun's energy is - because of the shape of the globe the sun's rays are spread over a greater area making it less in intense at higher latitudes 2. Atmospheric Circulation Patterns Three important facts about air: - cold air sinks and warms as it sinks - warm air rises and cools as it rises - warm air can hold more water vapor than cold air, as warm air cools it causes the water vapor to condense Process - Sun heats the earth's surface causing the air to rise and cool air moves in to replace it which causes the movement of air. The same thing happens throughout the atmosphere. - Different latitudes receive different amounts of the sun's energy causing patterns of air on a global scale. - This whole process explains why it rains heavily at the equator. The sun's energy is intense and warms the air holding a great deal of water vapor that causes precipitation as it cools. Trade Winds Cold air can not sink at the equator because warm air is always rising. As such the air moves towards the poles away from the equator. It eventually falls at around 30 0 latitude and warms as it falls. This air will eventually move either toward or away from the equator and causes what are called the trade winds which are shown on the diagram

4 In addition this air will be warm and pick up moisture as it moves across this area, this is the reason that most deserts exist at around 30 0 latitude. A similar process occurs at around 60 0 latitude where the tundra is. Tundra is basically a desert, the ice that is there has been unable to thaw. 3. Ocean Circulation Patterns - ocean currents are caused mostly by winds and the earth's rotation - they hold large amounts of heat - as a result large amounts of heat are transferred from around the equator to areas away from the equator. - large amounts of cool water can also be transferred from polar areas toward areas of lower latitude - the Gulf Stream helps to warm our region and also Eastern Europe - these ocean currents help to moderate temperatures of coastal areas and also provide more moisture and precipitation than is recieved by inland areas 4. Local Geography - Height above sea level affects the temperature - temps fall about 6 0 C for every 1000m increase in elevation (hence the reason for snow on mountains around the equator - mountains also effect the amount of precipitation that falls - as the air goes up the side of a mountain it cools and the water vapor condenses causing precipitation - the air continues down the other side of the mountain range and warms and draws up moisture. The areas on the inland side are where you are most likely to find deserts or grasslands 5. Seasonal Changes in Climate - due to the tilt of the earth - earth is tilted at 23 0 relative to its orbit - during spring and summer in the Northern Hemisphere the tilt of the earth causes the Northern hemisphere to receive more intense sunlight - at the same time the sunlight is less intense in the Southern Hemisphere - the opposite occurs in the fall and winter - the areas around the equator do not experience seasons because the sun concentration is constant throughout the year

5 Assignment - Due Wednesday, Jan 16 th - Optional. For the following locations -State the average climate (high and low temp, rain fall) include a climograph -State their latitude - State the elevation -State how you think each of the four climate factors affect the region (make predictions if it isn't stated) - State which of the four climate factors has the greatest affect and support your answer 1. Punta Arenas, Chile 2. Glasgow, Scotland 3. Mexico City, Mexico 4. Cordova, United States (Alaska) 5. Thule, Greenland 6. One city of your choice State your references (copy and paste) 7.4 The Ozone Shield (*most of these notes are from The Weather Makers) ozone - form of oxygen molecule made up of 3 oxygen atoms - at ground level it is considered a toxic pollutant - located in the layer of the atmosphere - up in the atmosphere it absorbs most of the ultraviolet light from the sun's rays History - in 1920's scientist Gordon Dobson and his partner FA Lindeman realized that ozone played an important role in the stratosphere and we use 'Dobson units' as the measurement today - problems with the ozone layer were first noticed in the 1970's - results from measurements showed a decrease in ozone between 1955 and 1995 over the Antarctic (320 Dobson units in 1955, 280 Dobson units (1975) and only 90 Dobson units in 95) - a hole in the ozone layer is defined as an area with less than 220 Dobson units - by 2000 there was a hole over the Antarctic and it was thinning over most of the Earth that is below 40 o S How Does it Form? - up in the stratosphere, UV radiation forces 2atom oxygen molecules to join together with single Oxygen atoms to form ozone. Although ozone often loses its extra atom due to its instabiliy it always gaining extra atoms to reform more ozone - if you brought all the ozone in the stratosphere to ground level it would make a layer that is just 3mm thick, think about that! Earth's sunscreen - ozone can block UV radiation that has a wavelength between 0.28 and 0.32 microns - normal oxygen (O 2 ) can block UV rays less than 0.28 microns - ozone shields us from 95% of the UV radiation (that which is less than 0.4 microns) that reaches Earth

6 - without it UV radiation would destroy your DNA and break other chemical bonds in your cells CFC - chlorofluorocarbons - invented in 1928 and found to be extremely useful for refrigeration, making styrofoam and propellants for spray cans as well as for use in air conditioning units - they were very stable and did not react with other chemicals or cause corrosion - their stability also meant that they did not break down in the atmosphere - by 1985 there were 1.8 million tonnes of CFCs in the atmosphere - they easily evaporate but take about 5 years to rise to stratospheric levels CFCs and the hole in the Ozone layer - it is in the stratosphere where problems occur - UV slowly causes the chlorine molecule to break free from the CFC - 1 Cl molecule will combine with O 3 molecule to create ClO and O 2 the ClO molecule then reacts with another O 3 to form 2 O 2 molecules and another free Cl molecule. The process then repeats - 1 Cl molecule can destroy ozone molecules!! - this process is maximized at temperatures below -43 o C, hence the reason that the hole first formed over the South Pole (statospheric temp here is -62 o C) - because the temp over the North Pole is a warm -42 o C it took much longer for the 'hole' to appear there Public and Industry Response - once scientists started to discover the hole and began to prove the problem existed the public wanted to see changes - industry fought to disprove the claims (initially scientists could not provide a link) - the public pushed for changes and the eventual result was the Montreal protocol Montreal Protocol Results - industrialized nations agreed to eliminate most CFCs by industrialized nations to set up a fund to help developing countries - banning of other substances that cause ozone depletion Results of the Ozone hole - there has been an incredible increase in skin cancer rates in people living below 40 o S - in Punta Arenas in Chile, which is the southernmost town in the world (53 0 S) skin cancer rates have increased by 66% since cases of cataracts has also increased - ozone layer depletion has made it easier for UV to cause damage to human immune systems (the Inuit are already feeling the impact) - single celled plants that provide the basis for the food chain in the ocean, as well as many fish larvae are particularly affected - agriculture is also affected, research has shown that crops like peas and beans have a 1% decrease in yield for every 1% increase in UV radiation

7 How are we doing today? - in 2004 measurements indicate that the hole over the South Pole is 20% smaller - since CFCs last in the atmosphere for over 30 years the problem still exists but is hopefully going away - China is still producing CFCs and isn't required to stop until 2010 What Might Have Happened - bromine and chlorine can be used in place of each other but bromine is more expensive and harder to work with - bromine on the other hand only lasts one year in the stratosphere compared to chlorine - However, bromine is 45 times more destructive to ozone than chlorine, if bromine had have been used instead of chlorine it is possible that the ozone layer may have been destroyed before scientists discovered what was happening - the results would have been huge increases in skin cancer, blindness and our food supply may have collapsed The success of the Montreal protocol is what gives environmentalists hope that the Kyoto accord, which we will discuss later, will eventually have a positive affect climate change Global Warming/Climate Change From the movie list 8 things that Mr. Gore points at to prove that Global Climate change is happening

8 Where does Canada fit into this Climate change picture? - is climate change all bad? It is predicted that as the Earth warms the best growing areas will move away from the equator to areas with more rainfall and less intense heat - scientists believe that if this happens Canada will actually see an increase it its growing seasons and increased crop yield - scientists have also been using computer models based on temperature and climate data and the models have made predictions that could affect Canada in the following ways 1. sea level will rise which could flood major cities around the world including ones in Canada 2. the models also predict that if the arctic continues to melt, the large flow of cold water may affect the Gulf Stream and actually cool Atlantic Canada and Europe (*both of these scenarios are shown in "Inconvenient Truth" - how are we on a global scale as far as CO 2 emissions are concerned? Canada combined with Greenland emit approximately 2.5% of the world's CO 2 emissions whereas the United States emits over 30% as does Europe. China is only around 10% and Australia is only around 1%. - a large portion of our emissions are due to our long and cold winters that half of the US doesn't have - on the other hand we should look at the per capita emissions as Australia is considered the worst polluters in the world, and we only have 10% of the population of the US What does the Future Hold - in his movie Al Gore made many statements about rising temperatures, water levels and future catastophic events - scientists point to Hurricane Katrina that devasted New Orleans. It started as a category 1 storm when it hit and passed through Florida but when it was in the Gulf of Mexico it picked up extra energy from the warm Gulf waters and became a category 5 hurricane - scientists claim that the warming trend of the earth has made the oceans warmer - the warmer bodies of water add energy to these tropical storms that have been occurring more frequently over the last few years - not everyone is in agreement over many of the statements made by Mr.Gore. They say he lacks scientific support in his claims and that the earth is going through a natural cycle which they claim is supported by science - one scenario that is quite possible is a carbon trading system where each country gets a per person carbon credit - in this system countries who produce less CO 2 emissions than they are required may sell their credits to other countries that are over polluting. - the goal is the overall emissions of the world will decrease and poorer countries will have more money available for development - when and how this will take place is unknown but it is very likely to happen Kyoto and its successor as mentioned in the movie and is publicly known, only two countries refused to sign the Kyoto agreement - world wide plan to reduce CO 2 emissions over the next several years - they argued that it would not be economically feasible and it gave an unfair advantage to developing countries such as China - just recently these two countries have agreed to come on board at UN meeting of the world's nations

9 Your place in this - although you may doubt some of the things that have been discussed or you are scared for the future you should do your best to do the 3 R's - reuse, recycle and reduce. It will make the world a cleaner place, leave some non-renewable energy for future generations and quite possibly put extra money in your pocket. - if everyone were to reduce their reliance on fossil fuels we will reduce the amount of CO 2 entering the atmosphere but we will also make the supplies of fossil fuels last longer Global Warming/Climate Change There are 2 different camps that scientists researching Climate Change fall into 1. Humans are causing an increase in global temperature by their continued use/overuse of fossil fuels which are putting large amounts of CO 2 into the atmosphere 2. The earth is going through a climatic cycle that has existed for thousands of years Both camps agree that the current temperature of the earth is increasing. The side that believes humans are responsible list many pieces of data to support their side 1. 7 of the 10 hottest years have occurred in the last 20 years 2. The amount of CO 2 in the atmosphere has increased at a rate similar to the increase of temperature which means increased carbon dioxide is the main cause of climate change 3. Permafrost is thawing 4. Glaciers are melting, and snow on mountain tops is disappearing 5. Invasive species are moving up mountains 6. The arctic and the Antarctic are melting The other side of debate says that the earth is indeed warming but it is a regular pattern that the earth experiences every 1500 years. Some of their arguments are 1. Many of the hottest years are not in the last 2 decades but many of the modern era's hottest years are in the 1930's before industrialization could have pumped enough CO 2 into the atmosphere to cause change. NASA has admitted that many of their land temp readings may have actually been wrong and were affected by the surroundings. 2. Climate change causes and increase in CO 2. Not the other way around. Oceans are the biggest holder of carbon dioxide and when the oceans warm they can't hold any more CO The edge of Antarctica is melting but the main landmass is actually cooling. 4. They have taken temperatures from ice and core samples that show warming and cooling periods that correspond to the 1500 year cycle that they are presenting 5. Old records from Medieval times show periods of warming based on crop yield and location of crops. For example they looked at records that show the location of vineyards. The location of the vineyards are dependent on temperature. Both sides present valid arguments and it is your choice to decide which argument you agree with.