Climate Change

•UNIT 9•STANDARDS: NCES 2.6.1, 2.6.2, 2.6.3, 2.6.4, 2.7.2,

2.7.3•LESSON 5

Lesson Objectives

In this lesson, you will learn about:The different types of climate changeWhy climatic change occursWhat is the human activity in each climateWhat is the human impact on the climate as a whole

Climatic Change: Ice AgeGlaciers Have advanced and retreated for

over the past 2 million years.During these periods of extensive glacial coverage, called ice ages, the global temperature was decreased by 5oC.Ice ages alternate with warm periods called interglacial intervals. We are currently experiencing such an interval. The most recent Ice Age ended about 10,000 years ago.

Short-Term Climatic Change

Seasons While Ice Ages take place over thousands of years, other climatic changes occur faster.The most obvious are seasons.The variations are a result of solar radiation received.When the Earth is tilted toward the sun, temperatures increase.Winter in Northern Hemisphere happens at the same time as summer in the Southern Hemisphere.

Short Term Climatic Change

El Niňo Other short term climatic changes are caused by El Niňo, a warm ocean current that develops off the west coast of South America.When trade winds blow flat, warm water from the South Pacific head to South America.The sudden presence of warm water heats the air.Warm moist air now spreads east.This causes severe flooding across the US.

One good thing about El Niňo, is fewer hurricanes strike the US.

Normal Climatic ChangeSolar Activity

Evidence relating the Earth’s climate and solar activity was first released in 1893. Sun spots cycles occur every 11 years on average.When sunspot activity is small or nonexistent, the planet cools. This was seen during the Little Ice Age.When sunspot activity increases, the Earth’s atmosphere heats and temperatures rise.

Normal Climatic ChangeEarth’s Orbit

Climatic changes may be triggered by changes in the Earth’s axis and orbit.The orbit of the Earth’s elliptical orbit appears to change, becoming more circular and then elliptical again.When the orbit is elliptical, the Earth passes closer to the sun, temperature increase.When the orbit is more circular, the Earth passes farther from the sun, the temperature decreases.The tilt of the Earth on its axis also changes. Tilts can explain warmer winters and cooler summers.

Normal Climatic ChangeEarth’s Wobble

The Earth wobbles on its axis as it spins.During a 26,000 year cycle, the Earth will tile toward another star, Vega and not the Polaris.When this happens, warmer summers and colder winters.

Normal Climatic ChangeVolcanic Activity Climatic change

can also be caused by volcanic activity.The volcanic ash and smoke blocks out the sun, causing the planet to cool.

Normal Climatic ChangeMeteor or Comet Impact

The Earth is hit by meteors every day. Some meteors can change climate in the most dramatic ways.The extinction of dinosaurs was caused by a meteor impact, blocking out the sun for millions of years.

Humans: Greenhouse Effect The retention of

heat by the atmosphere is the greenhouse effect.Without the greenhouse effect, our planet will become cold like Mars or hot like Venus.

Carbon dioxide is believed to be a major factor in the Earth’s Greenhouse effect.

Humans: Global WarmingTheory Temperatures over the

world have risen over the past 200 years.

If the trend continues, the ice caps might melt.

Some scientists believe the change is because of carbon dioxide.

Other scientist believe it is part of the Earth’s natural cycle.

Very controversial.

Human Activity: Tropical Savanna

The cattle ranches of Brazil use the savanna grass to feed cattle. The large sugar plantations of the Caribbean and the smaller family farms of West Africa are located in the savanna areas.

Human Activity: Tropical Monsoon

Tropical monsoons climates vary with the seasons agriculture revolves around the monsoons. Seeds are planted before the rains so that they will have time to take hold in the soil; the monsoon rains water the crops. If the monsoon rains are too heavy, widespread flooding may result and damage homes and crops. If the monsoon rains are too late, the crops die from lack of water.

Human Activity: Tropical Rainforest

The clearing of the rainforest destroys valuable naturally occurring plant life, only helps the farmers in short terms. The soil of the rainforest is not rich in nutrients and can only support a crop for a few years before becoming unsuitable for farming. Hardwoods found only in the tropical rainforest are in great demand for finished wood products such as furniture and cabinetry. This adds to the rate of rainforest depletion.

Human Activity: Steppe

The steppe areas are like tropical savanna areas in that their grassy vegetation can be used for grazing. The steppe areas are unlike the tropical savanna areas because they make for poor farmland. Some crops are grown, but unless the dry soil is irrigated, it cannot support more than family farming for a short time. Many farmers in the steppe areas have to move to another area every few years because the soil quality is easily depleted.

DesertsDubai

The desert climate areas have very sparse vegetation, so any farming or grazing must be done with great care. People native to these areas have developed practices that sustain the sparse vegetation and soil nutrients that are available.With advancements of irrigation and damming techniques, many oases have been created from desert areas. Human activity in these areas can be varied, but is dependent on water sources from outside the area.

Human Activity: Humid Subtropical

Mixed forest refers to forest that contain coniferous trees, which keep their needles year –round, and deciduous trees, that shed their leaves. Pines and cedars are coniferous, while oaks and maples are deciduous. The moist growing seasons and nutrient-rich soil make the humid subtropical areas some of the most fertile in the world.Cities that are humid subtropical are: Atlanta, Georgia; Charleston, S.C.

Human Activity: Marine West Coast

Forestry: Many marine west coast areas are also logging regions because of their coniferous forest growth.Agriculture: These areas are also home to a lot of non-citrus fruit orchards of the world.

Human Activity: Mediterranean

The Mediterranean climate areas have some unique qualities that make them excellent places for growing of grapevines and olive trees. Other crops such as wheat and barley, which do not require a lot of water, can be grown in Mediterranean areas. Mediterranean climate land that has access to water, such as a river or irrigation, can grow a wide variety of crops abundantly.

Human Activity: Humid Continental

Agriculture and LoggingThe humid continental areas have abundant farmlands, but their growing seasons are shorter than temperate climates. The soil conditions and climate make them perfect for some crops like potatoes and certain grains.

Human Activity: Subarctic

Fishing is a predominant activity in subarctic areas with access to bodies of water. Lapland in Northern Finland is home to many herds of reindeer and goats. While the coniferous forest of Siberia are logging regions. The thin coniferous trees found there are called taiga vegetation; it is used primarily to make paper.

Human Activity: Tundra

Seal hunting is still an important activity of the Inuit of Canada. The tundra’s beautiful and unique vegetation has begun to draw tourists in the short summer months. As more and more mineral deposits are found in tundra areas, and as the means to mine these resources improve, mining is becoming more popular.

Human Activity: Polar

Hunting of seals and whales in these areas have all but stopped. Antarctica has no permanent settlements but has many research stations monitoring climate changes.

Section Review 9.5.1

Why do some scientists believe global warming is not the result of increased carbon dioxide in the atmosphere?What are some possible consequences of the global warming scenario?Discuss human activity in each of the 5 major climates.