The Atmosphere B7: Global Changes in the Atmosphere

Short-Term Climate Changes El Niño and La Niña are short-term climate changes caused by changes in ocean surface currents – El Niño – Begins when an unusual pattern of winds form over the western pacific – Causes a vast sheet of warm water to move eastward towards the South American Coast – Disrupts the cold ocean currents and changes the weather patterns there – El Niño also effects weather patterns around the world bringing severe condition such as heavy rain or drought

Short-Term Climate Changes – Occur every two to seven years and can last for one or two years – La Niña – Also begins when an unusual pattern of winds form over the western pacific – In this case, the surface waters in the eastern pacific are colder than normal – It is the opposite of an El Niño event – Typically brings colder than normal winters and greater precipitation to the Pacific Northwest and North Central U.S. – It also results in greater hurricane activity in the Western Atlantic

– Impact – In addition to the impact on weather, they also impact the environment and economy – Changes the water temperature – warm water cannot hold as much oxygen as cold water – Created a drop in nutrients and oxygen in the water, causing fish to die – Reduced supply of fish increased costs for industries that depend on fish meal such as poultry farm and pet food manufacturers – Caused the fish industry in some areas to collapse – Prices everywhere went up for chicken, eggs, bread, etc

Global Warming Global Warming – Gradual increase in the temperature of the Earth’s troposphere – Certain gases trap heat and hold it within the Earth’s atmosphere – Many scientists believe that the increase in the greenhouse gas carbon dioxide is a major factor in global warming Greenhouse Hypothesis – That human activities that add greenhouses gases to the air may be warming the Earth’s atmosphere

Global Warming – Scientist are able to determine the level of carbon dioxide by taking ice core samples in Antarctica – The ice contains air that was trapped in the water at the time that it froze – Since the late 1800’s the levels of CO 2 has increased drastically – This increase has been blamed on the industrial revolution, an increase in populations, and deforestation

Global Warming Climate Variation Hypothesis – Some scientist believe that the increase in global temperature is part of a natural process – There is evidence to show that ice ages occur in cycles over tens of thousands of years. – Scientists have determined that there have been at least 5 major ice ages in recent history – The most recent ice age ended between 10,000 and 12,000 years ago

Global Warming – This cycle of extended periods of cold followed by long periods of increasing warmth cause glaciers to grow and then shrink – As glaciers shrink, they melt leaving behind large amounts of fresh water – The 5 Great Lakes in the U.S. were created by a glacier

Global Warming Possible Effects – Global warming could have some positive and negative effects – Positive Effects – A global climate change could have positive effects in areas that are currently considered hostile – Areas currently too cold for farming could warm up enough to produce good crops – Amounts of rain could increase in desert areas enough to create forests – Extremely hot areas could become cooler with more moderate temperatures

Global Warming – Negative Effects – A global climate change could have the exact opposite on currently temperate areas – Warmer ocean water with less nutrients and oxygen would be less able to support sea life – Warmer ocean water could also increase the strength and frequency of hurricanes – As temperatures rise, farmland could receive less water, crops would fail, and dust bowls could form – Some scientist believe that global warming could lead to another ice age

Ozone Depletion Ozone Depletion – Chemicals produced by humans are damaging the ozone layer – The ozone layer protects the Earth from the sun’s ultra-violet radiation – By the year 2000, the area was over 28.5 million km 2 (almost the size of Africa) – In the 1970’s scientists notices a thinning area in the ozone over Antarctica

Ozone Depletion Chlorofluorocarbons – Chemical used in air conditioners, refrigerators, aerosol sprays, and deodorants – Major cause of ozone depletion – Takes decades to break down and can rise all the way to the stratosphere – Breaks down into atoms of chlorine, which then breaks down the ozone layer further

Ozone Depletion Effects – Effect of ozone depletion is an increase in the amount of UV radiation that reaches Earth’s surface – UV radiation can damage eyes and cause skin cancer – It can also increase Earth’s average temperature – With more heat coming in and less heat able to escape because of the increase in greenhouse gases, ozone depletion could be catastrophic

In Closing – How does an increase in carbon dioxide levels and decrease in the ozone layer work together to become even more dangerous?