Climate Climate• The general condition of temperature and precipitation for an area for an extended period of time.• The climate of any region of the world is determined by 2 factors: 1) temperature and 2) precipitation.
Factors that Affect Temperature1) Latitude• Areas close to the equator receive direct rays (warmer).• In Polar Regions, sun’s rays are not as direct. (cooler temperatures).
2 ) Elevation• As elevation increases, the temperature decreases.• Air is less dense.
3. Ocean Currents• Some currents are warm.• Surface temperature of water affects the temperature of the air above it.• Land near warm currents has warmer temperatures. Ex: IrelandLand near cold currents has cooler temperatures. Ex: California coast.
Major Ocean Currents: Warm Current Cold Current
California surfer during the summer…wearing a wetsuit!!!
Factors that Affect Precipitation (2 factors)1) Prevailing winds• They tend to blow from one direction• Influences climate• Moisture content may vary:a) Warm air holds more moisture than cold air.b) Winds from rising warm air tend to bring precipitationc) Winds from rising cold air tend to bring little precipitation.• Direction form which wind blowsa) land breeze – dry Ex. Sahara desert in Africab) sea breeze – moisture Ex. England, Scotland, Ireland.
2. Mountain Ranges • Act as a barrier to winds and precipitationa) Windward side – side facing wind receives moreprecipitation (wet).b) Leeward side – side facing awy from wind receives lessprecipitation (dryer).Process:1) Moist Air moves up windward side – cools, droppingprecipitation.Moves over mountaintop to leeward side bringing dryer air.There is little precipitation.Example: Sierra Nevada mountain range: western side is moist, east side isdry.
Changes in ClimateWhat causes the climate to change?3 natural factors:1) slow drifting of continents2) changes in the sun’s energy output3) variations in the position of the Earth relative to the sun,collectively known as the “Milankovitch Cycles.”
1. Ice Ages•Periodically, the Earth’s surface have been covered enormoussheets of ice.•4 major ice ages (major glaciations) during the past 2 millionyears.•Average temperature was about 6° C below today’s avg. temp.•Lasts about 100,000 or more. The most recent began about 1.75mya and ended 10,000 ago.•Time period between major glaciations are called interglacials.(warm period - today)What kind of life existed?
2. Drifting Continents• Approximately 200 mya, Pangaea started to drift.• Plate tectonics.• Temp and precip dropped.• Moves only a few cm/yr. So, climate changes willhappen over millions of years.Where did our present continents originate from?
3. Extinction of Dinosaurs Possible reasons:1) Dinosaurs could not adapt to the slow change in climate. 2) Many plants became extinct.3) Asteroid struck the Earth 65 mya. This resulted in enormous clouds and dust worldwide blocking the sun’s rays. Temperatures dropped.Actually, the real reason why dinosaurs became extinct isbecause of…
4. Variations in Radiant Energy Some scientists believe the sun’s energy output changes over time, affecting the Earth’s temperature. But there is no evidence. 5. Global Warming• Human activity may have influenced the climate.• Fossil fuels – coal, oil, and natural gas. These release a greenhouse gas - CO2 (Carbon Dioxide) which traps heat in the atmosphere.• In the past 25 years, CO2 levels have increased by 8%. If this continues, an increase of 2° C can be drastic.
6. El Nino• Normally, tradewinds off the coast of South America flow east-to-west and pile up warm water in the western Pacific.• Every few years, the tradewinds change direction, allowing the pool of warm water to move east where it blocks the rising cold water. • These changes help trigger the global weather changes associated with El Niño. EX. Increased rainfall in the southern half of the U.S. & droughts in Indonesia.
Every 100,000 years, the Earth’s eccentricity changes from a moreelliptical (oval-shaped) to a less elliptical shape (circular).
TILT - Every 41,000 years, the angle or the Earth’s axis shifts from 21.4 degrees to 24.5 degrees.
Every 23,000 years, the Earth’s axis“wobbles” from one end to the other.