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 CO2 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 km2 (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?