Climate and Climate Change

Weather vs. Climate Weather – state of the atmosphere at a given time and place Climate – long term prevailing weather conditions based on historical data

Factors that Determine Climate Latitude Distance North or South of the equator (0o) North Pole (90oN) Low latitudes (near equator) Solar energy concentrated on small area Night/Day = ~12 hours High latitudes (near poles) Sun hits at an oblique angle – distributes solar energy over large area

Factors that Determine Climate Atmospheric circulation Cold, dense air sinks  compresses and warms Warm, less dense air rises Holds more water vapor than cold air Clouds form when it cools (after rising) Sun heats earth  warms air  it rises  replaced by cooler air Wind

Factors that Determine Climate Prevailing winds Direction of wind throughout the year Don’t move directly N or S Deflected due to Earth’s rotation To the right in northern hemisphere Left in southern

Factors that Determine Climate Oceanic Circulation Patterns Ocean holds large amount of heat Affected by wind and rotation of earth Distribute warm/cold masses of water Special circumstances El Nino La Nina http://oceanservice.noaa.gov/facts/ninonina.html https://www.youtube.com/watch?v=5qPibjwo21g http://www.cnbc.com/2016/01/08/severe-el-nino-puts-world-in-uncharted-territory-un.html

Southern Oscillation Winds normally travel E  W in the tropical Pacific (trade winds) From high pressure area in Eastern Pacific To low pressure area in Western Pacific 3 to 8 years these pressure areas change Reasons unknown Winds travel in opposite direction (WE) Southern Oscillation

Factors that Determine Climate Topography Mountains influence precipitation Rain shadow Warm air forced to rise  cool  precipitation  dry air

Factors that Determine Climate Seasonal changes Tilt of Earth’s axis (23.5o) Angle of sun’s energy changes Summer – northern hemisphere tilted towards the sun Receives direct sunlight

The Ozone Layer Ozone = O3 Ozone layer Absorbs most UV light from sun Harmful to plants and animals Natural sunscreen

Harmful Chemicals Chlorofluorocarbons (CFCs) Harmless, very stable Coolant, spray cans Break apart in upper atmosphere Cl atoms destroy O3 1 Cl can destroy 100,000 O3

Ozone Hole Thinning of stratosphere over Antarctica during the spring Reported a few years after CFCs became widely used Some areas are over 50% lost

Effects on Life Loss of ozone layer  more UV light reaches earth  more mutations Humans Cancer Weakened immune response Marine life Kills primary producers (less photosynthesis) Land plats Interferes with photosynthesis Reduced crop yield

Can We Change It? Montreal Protocol (1987) International agreement to protect ozone layer US agreed to ban all substances that pose a significant danger by 2000 CFC production has decreased worldwide CFCs remain active for 60-120 years Will take a long time to repair