ATMOSPHERE Lesley Monk Balfron High School Session 20056
ATMOSPHERE Lesley Monk Balfron High School Session 2005/6 1
ATMOSPHERE GLOBAL WARMING – ARE WE TO BLAME ? This is one of the most frequently asked environmental questions in recent times. We really don’t know ! That the planet’s climate is changing, there is no doubt. But who or what is the reason for this is a hotly debated point. We shall put the evidence in front of you and let you decide! So what is the answer ? 2
ATMOSPHERE Graph 1 shows the temperature of the Earth over 1 million years. Note the line showing today’s average temperatures, and the arrow to the last Ice Age. Graph 2 is a close-up from the last few years of the Ice Age till today. Graph 3 shows the time since the Vikings began raiding Britain. 3
ATMOSPHERE 1. ICE CORE ANALYSISAir trapped in ancient snow - now ice- can show what the atmosphere was like millions of years ago. 2. TREE RING ANALYSISTree rings record good and bad years for tree growth and can go back to prehistoric times. WHAT EVIDENCE IS THERE OF GLOBAL WARMING ? Copy text 3. OCEAN FLOOR SEDIMENTS-The mud in the ocean deep has been there for millennia and can be analysed for oxygen isotopes. 4. POLLEN ANALYSISThis will show the types of plants that were growing in an area millions of years ago, and we can work out the likely conditions from comparison with today’s plant needs. 4
ATMOSPHERE So you can see that our planet hasn’t exactly had a stable climate ! But are we responsible for the changes, or is it natural forces at work? Read pages 25 and 26 of the booklet. You will need to be able to discuss each of these factors in a way that shows you appreciate their potential importance. 5
ATMOSPHERE There are different possible causes of these raised temperatures. They fall into two categories- Physical and Human. Physical Factors n n Human Factors Solar variation Volcanic activity Ocean currents Milankovitch cycles n n n Burning fossil fuels Increased output of methane etc. Deforestation Let’s look at each in turn. 6
ATMOSPHERE PHYSICAL 1 - SOLAR VARIATION Sunspots: an increase in sunspot activity may lead to a very slight increase in the sun’s output and a temporary warming of the earth. Sunspot activity follows 11 and 22 year cycles. The Little Ice Age of 14501700 may have been linked to periods of very low sunspot activity. 7
ATMOSPHERE PHYSICAL 2 - VOLCANIC ERUPTIONS n n n Eruptions of volcanoes can throw millions of tonnes of ash, dust and sulphur dioxide into the atmosphere. This produces aerosols that can reduce the amount of sunlight reaching the earth. This can lead to a temporary cooling of the earth. 8
ATMOSPHERE VOLCANIC ERUPTIONS 2 n n n Major eruptions in the past which have been linked to short periods of global cooling include; Tambora (1815), Krakatoa (1883), Mt. St Helens (1980) Pinatubo (1991) 9
ATMOSPHERE PHYSICAL 3 – OCEAN CURRENTS Changes in the pattern and strength of ocean currents may lead to changes in the distribution of heat around the planet. A longer term example A short term example would be El Niño, which would be the North appears every few years. Atlantic Drift, which may change position every few thousand years. 10
ATMOSPHERE ENSO - the El Niño Southern Oscillation The “normal” conditions, with cool surface water off the coast of Peru. A La Niña year Every 2 -7 years the western Pacific becomes much warmer, disrupting weather patterns possibly on a global scale. An El Niño year 11
ATMOSPHERE One theory suggests that global warming will increase the number of icebergs in the Atlantic, cooling the sea and switching off the North Atlantic Drift / Atlantic Conveyor system. This would be bad news for us! 12
ATMOSPHERE PHYSICAL 4 - MILANKOVITCH CYCLES • Milankovitch cycles are three variations in the earth’s orbit. Although they may be linked to very long term changes in the climate, their effect would not be noticed on a scale of a few hundred years. 13
ATMOSPHERE HUMAN FACTORS THE ENHANCED GREENHOUSE EFFECT. 14
ATMOSPHERE These are the main greenhouse gases See how they have increased over the years of industrial activity. HOW ? 15
ATMOSPHERE HUMAN 1 - BURNING FOSSIL FUELS The fossil fuels are: q COAL q OIL q NATURAL GAS They are called fossil fuels because they are formed from the remains of ancient plants (coal) and marine animals (oil). 16
ATMOSPHERE When we burn these fuels, we release millions of tonnes of Carbon Dioxide (CO 2) into the atmosphere. There has been an enormous increase in these greenhouse gases since the Industrial Revolution began about 200 years ago. 17
ATMOSPHERE Power stations are one of the main producers of greenhouse gases such as Carbon Dioxide. 18
ATMOSPHERE Environmental campaigners all over the world are demanding cuts in CO 2 emissions. Here Greenpeace uses a light display to get its message across. 19
ATMOSPHERE Vehicle exhausts are the main source of Nitrous Oxides. 20
ATMOSPHERE HUMAN 2 - INCREASED METHANE n n A cow can burp / fart about a quarter of a kg. of methane a day. The number of cattle has doubled in the past 40 years. Sheep, goats and camels are also ruminants. There are now 1. 3 billion cattle, each burping / farting methane several times a minute! The New Zealand government is proposing to bring in a “flatulence” tax on cattle farms. I am a ruminant when I digest grass, I produce methane lots of it! 21
ATMOSPHERE The huge increase in world population and in the area of land given over to crops in general and to rice production in particular, has led to a rapid rise in global methane production. Farmland for rice has doubled in 45 years. 22
ATMOSPHERE HUMAN 3 - DEFORESTATION Forests absorb CO 2 and release oxygen: . . . if they are cut down, atmospheric levels of CO 2 must rise as a consequence. 23
ATMOSPHERE This is known as a double- whammy ! n n Clearing forest by burning releases huge amounts of stored CO 2 back into the atmosphere. The smoke from the fires also adds to global air pollution. 24
ATMOSPHERE KEY TERMS TO REMEMBER n n n n n Solar variation / Sunspots Volcanic eruptions /Sulphur dioxide /Aerosols Milankovitch cycles El Niño Enhanced Greenhouse effect Carbon Dioxide / Methane / Nitrous Oxides The Industrial Revolution / burning fossil fuels Padi fields / cattle / methane production Deforestation 25
CONGRATULATIONS !! You have now finished the Higher Geography Course! All that remains is to learn it all! 26
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