Unit 6: Atmosphere Notes Part 3: Chapter 17: Climate

17.1: Climate and Its Cause Lesson Objective Vocabulary Describe the effect of latitude on climate. Diagram the Hadley, Ferrell, and Polar atmospheric circulation cells and show how they influence the climate of various locations. Discuss the other important location factors that influence a locations’ climate: position in the global wind belts, proximity to a larger water body, position relative to a mountain range, and others. Continental Climate Intertropical Convergent Zone (ITCZ) Maritime Climate

Introduction Although almost anything can happen with the weather, climate is more predictable. Climate then is the long-term average of weather. Good climate is why we choose to vacation in Hawaii in February, even though the weather is not guaranteed to be good.

What is Climate? The average of weather in that location over a period of time, usually for at least 30 years. A location’s climate can be described by its: Air temperature, humidity, wind speed and direction The type, quantity, and frequency of precipitation Climate can change, but only over long periods of time. The climate of a region depends on its position relative to many things.

Latitude The main factor influencing the climate of a region - because different latitudes receive different amounts of solar radiation. The equator receives the most solar radiation The polar regions receive the least solar radiation

Atmospheric Circulation Cells The position of a region relative to the circulation cells and wind belts has a great effect on climate.

The ITCZ (Intertropical Convergence Zone) The low pressure area near the equator in the boundary between the two Hadley Cells

Cell Boundary Hadley Cell and Ferrell Cell Boundary At this location the air is descending, and shrinking air warms and causes evaporation. Ferrell Cell and Polar Cell Boundary The meeting of the two different air masses causes the polar jet stream, which is known for its stormy weather.

Prevailing Winds The bases of the Hadley, Ferrell, and Polar Cells. Bring weather from the locations they come from.

Continental Position When a particular location is near an ocean or large lake, the body of water plays an extremely important role in affecting the regions’ climate. Maritime climate is strongly influenced by the nearby sea Temperatures vary a relatively small amount seasonally and daily Continental Climate – more extreme With greater temperature differences between day and night and between summer and winter

Ocean Currents The temperature of the water offshore influences the temperature of a coastal location, particularly if the winds come off the sea. Coastal upwelling also brings cold, deep water up to the ocean surface off of California, which contributes to the cool coastal temperatures.

Altitude and Mountain Ranges Air pressure and air temperature decrease with altitude. The closer molecules are packed together, the more likely they are to collide. Collisions between molecules give off heat, which warms the air. Mountain ranges have two effects on the climate of the surrounding region: Rainshadow Effect – which brings warm dry climate to the leeward side of a mountain range Separation of the coastal region from the rest of the continent.

17.3: Climate Change Lesson Objective Vocabulary Describe some ways that climate change has been an important part of Earth’s history. Discuss what factors can cause climate to change and which of these can be exacerbated by human activities. Discuss the consequences of rising greenhouse gas levels in the atmosphere, the impacts that are already being measured, and the impacts that are likely to occur in the future. El Nino Global Warming La Nina Milankovitch Cycles Slash-and-burn Agriculture Sunspots

Introduction For the past two centuries, climate has been relatively stable. People placed their farms and cities in location that were in a favorable climate without thinking that the climate could change. But climate has changed throughout Earth’s history, and a stable climate is not the norm. Stability has allowed the expansion of agriculture and the development of towns and cities.

Short – Term Climate Change Are common – the largest and most important of these is the oscillation between El Nino and La Nina conditions The cycle is called the ENSO (El Nino Southern Oscillation) The ENSO drives changes in climate that are felt around the world about every two to seven years

In a normal year, the trade winds blow across the Pacific Ocean near the equator from east to west (towards Asia) In an El Nino year, when water temperatures reaches about 820F, the trade winds weaken or reverse direction and blow east (towards South America) Upwelling stops

By altering atmospheric and oceanic circulation, El Nino events change global climate patterns. Some regions receive more than average rainfall, including the west coast of North and South American, the southern US and Western Europe Drought occurs in other parts of S. America, the western Pacific, southern and northern Africa, and southern Europe. An El Nino cycle last one to two years – sometimes circulation patterns bounce back quickly and extremely – this is called a La Nina In a La Nina year, as in a normal year, trade winds moves from east to west and warm water piles up in the western Pacific Ocean. Ocean temperatures along coastal S. America are colder than normal (instead of warmer like in El Nino) Cold waters reach farther into the western Pacific than normal

Causes of Long-term Climate Change Many processes can cause climate to change. These include changes: In the amount of energy the Sun produces over years In the positions of the continents over millions of years In the tilt of Earth’s axis and orbit over thousands of years. That are sudden and dramatic because of random catastrophic events, such as a large asteroid impact In greenhouse gases in the atmosphere, caused naturally or by human activites.

Causes of Long-term Climate Change Solar Radiation The amount of energy the Sun radiates is variable Plate Tectonics Can alter climates Over millions of years as seas open and close, ocean currents may distribute heat differently When the continents separate, heat is more evenly distributed. Triggers volcanic eruptions, which release dust and CO2 into the atmosphere.

Milankovitch Cycle Scientist attribute a series of ice ages to variation in the Earth’s position relative to the Sun 1.) The shape of the Earth’s orbit changes slightly as it goes around the Sun. 2.) The planet wobbles on its axis of rotation. The planet’s tilt on its axis varies between 22.10 and 24.50 Seasons are caused by the tilt of Earth’s axis of rotation

Changes in Atmospheric Greenhouse Gas Levels A decrease in greenhouse gas levels decrease global temperatures and an increase raises air temperature. Natural processes add and remove CO2 from the atmosphere: Add CO2 Volcanic eruptions and decay or burning of organic matter Remove CO2 Absorption by plant and animal tissue

So CO2 is removed from the atmosphere When plants are turned into fossil fuels the CO2 in their tissue is stored with them. So CO2 is removed from the atmosphere Fossil fuels use has skyrocketed in the past few decades – this has released CO2 into the atmosphere Burning tropical rainforests, to clear land for agriculture, also increases atmospheric CO2 CO2 is the most important greenhouse gas that human activities affect because it is so abundant. Methane Chlorofluorocarbons (CFCs) – human-made chemicals Tropospheric Ozone – from vehicle exhaust

Global Warming With more greenhouse gases trapping heat, average global temperatures are rising (aka GLOBAL WARMING)

Temperatures are Rising The rate of increase has been more rapid in the past century, and has risen even faster since 1990. The nine warmest years on record have all occurred sine 1998, and 10 of the 11 warmest years have occurred since 2001 Annual variations aside, the average global temperature has increased The US has long been the largest emitter of greenhouse gases China’s rapid economic growth, its emissions surpassed those of the US in 2008 The average US citizen produces far more greenhouse gases than the average Chinese person

Future Warming In the developed nations it will depend on technological advances or lifestyles changes that decrease emissions. In the developing nations, it will depend on how much their lifestyles improve and how these improvements are made. Computer models are used to predict the effects of greenhouse gas increase on climate for the planet as a whole and also for specific regions. If nothing is done to control greenhouse gas emissions and they continue to increase at current rates, the surface temperature of the Earth can be expected to increase

Whatever the temperature increase, it will not be uniform around the globe The North Pole has been affected more than the South Pole BUT the temperatures are still increasing in Antartica

The timing of events for species is changing Glaciers are melting and vegetation zones are moving uphill As greenhouse gases increase, changes will be more extreme. Oceans will become slightly more acidic (making it hard for coral reefs to grow) Decreased snowpacks, shrinking glaciers, and the earlier arrival of spring will lessen the amount of water available in some regions of the world Weather will become more extreme with heat waves and droughts.

Although scientists do not all agree, hurricanes are likely to become more severe and possibly more frequent. Sea level is expected to rise

Food For Thought? Are the increase in global temperatures natural? In other words, can natural variations in temperature account for the increase in temperature that we see? NO! Changes in the Sun’s irradiance, El Nino and La Nina cycles, natural changes in greenhouse gas, and other atmospheric gases cannot account for the increase in temperature that has already happened in the past decade!