The Atmosphere Atmosphere- A thin layer of gases that surrounds the Earth –78% nitrogen –21% oxygen –1% water vapor, argon, carbon dioxide, neon, helium and other gases

The Atmosphere Life on Earth would not exist without the atmosphere –Blocks UV rays –Provides Oxygen and Carbon Dioxide for living things –Allows light to reach the surface –Keeps the Earth warm

The Atmosphere Early Earth –Contained no oxygen –Bacteria started to photosynthesize about 4 billion years ago Added oxygen to the atmosphere and conditions for other living things improved

The Atmosphere Layers of the atmosphere –Troposphere- Surface to 10 km above the surface Contains 90% of the gases of the atmosphere Most weather occurs here

The Atmosphere –Stratosphere- 10 km to 50 km above the Earth Air is less dense Contains the ozone layer Planes fly in the stratosphere

The Atmosphere –Mesosphere- 50 km to 80 km –Thermosphere- 80 km- 500km –Exosphere- 500 km to space Air is very thin in these three layers

Assignment P Keep this and add the next assignment to it

Climate Weather- The local conditions in an area at a given time Climate- The long term average conditions in an area

Climate Consists of: –Precipitation –Temperature –Humidity –Winds

Climate What determines climate? –Latitude –Air circulation –Proximity to oceans –Air circulation –Geography

Latitude How far from the equator a location lies –Sun angle decreases as you move from the equator

Atmospheric Circulation Patterns Air is heated at the equator, rises and then cold air replaces it from the poles –This causes winds and precipitation to form in the tropics

Atmospheric Circulation Patterns Cool air from the tropics moves away toward the poles and sinks at 30 0 latitude. –This causes the air to become dry and deserts form

Atmospheric Circulation Patterns Air that sinks at 30 0 rises again at –This causes precipitation in the temperate regions of the Earth

Atmospheric Circulation Patterns The air that rises at 60 0 sinks at the poles –This causes the air there to be very dry and cold

Ocean Circulation Patterns Ocean currents have a great effect on climate –Warm currents warm areas that would normally be and cold currents cool areas that would normally be warm Ex. London is relatively warm due to the Gulf Stream

Ocean Circulation Patterns Oceans moderate temperatures in areas causing them to have cool summers and warm winters –Ex. Los Angeles

Local Geography Elevation has a large impact on climate –High elevations are cooler that low elevations Ex. It snows regularly in Hawaii on top of a 20,000 ft volcano –Every 1000m the temperature drops 11 0 F

Local Geography Mountains also influence precipitation patterns –As moist air is forced up a mountain it loses the ability to hold moisture. –This squeezes most of the moisture from the air

Local Geography –This is called the orographic effect –Rainforests occur on one side of a range and rain shadow deserts form on the other side of a mountain range

Local Geography

Seasonal Changes in Climate Seasons are caused by the orbit of the Earth around the sun –The Earth is tilted on its axis and this causes the sun angle to change throughout the year

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Greenhouse Earth The Earths atmosphere acts as the glass of a greenhouse –As sunlight enters the Earths atmosphere some of its energy is trapped by the gases This keeps the Earth warm and hospitable for life

Greenhouse Gases Water Vapor Carbon Dioxide Chlorofluorocarbons Methane Nitrous Oxide

Greenhouse Effect It is suspected that increases in greenhouse gases are causing the Earth to heat up above its normal temperature –Burning of fossil fuels has caused levels of greenhouse gases to rise

Greenhouse Effect Some scientists believe that the Earth is heating up due to increased greenhouse gas production while others do not agree.

Global Warming The average temperature of the Earth has risen very slightly over the past 100 years –Is this due to greenhouse gases or is it due to natural events?

Global Warming We only have records back to 150 years ago –We do know that the climate has changed drastically in the past (ice age etc.) –We don’t know if the current change is due to man or if it is a result of changes that occur naturally

Global Warming Many people want to reduce emissions of carbon dioxide in order to combat climate change –Smaller cars –Energy efficient homes –Recycling –Conservation

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Ozone Layer Three oxygen atoms that are chemically combined –Absorbs UV radiation from the sun Harmful to living things

Ozone Layer CFC’s have been accused of destroying the ozone layer –An ozone hole developed over Antarctica –It has since become smaller since CFC’s were banned

Ozone Hole Effects of ozone depletion –It damages DNA in organisms –UV radiation causes skin cancer –Kills phytoplankton in the oceans which are the base of the food chain

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