climate change

global warming and shortterm climate change

Some scientists think that global warming is affecting the cycle of El Nio and La Nia. These short-term changes seem to be cycling faster now than in the past. They are also more extreme.

shortterm climate change

Youve probably heard of El Nio and La Nia. These terms refer to certain short-term changes in climate. The changes are natural and occur in cycles. To understand the changes, you first need to know what happens in normal years. This is shown in Figure 17.24.

how will climate change in the future

Earths temperature will keep rising unless greenhouse gases are curbed. The temperature in 2100 may be as much as 5 C (9 F) higher than it was in 2000. Since the glacial periods of the Pleistocene, average temperature has risen about 4 C. Thats just 4 C from abundant ice to the moderate climate we have today. How might a 5 C increase in temperature affect Earth in the future? Warming will affect the entire globe by the end of this century. The map in Figure 17.22 shows the average temperature in the 2050s. This is compared with the average temperature in 1971 to 2000. In what place is the temperature increase the greatest? Where in the United States is the temperature increase the highest? As temperature rises, more sea ice will melt. Figure 17.23 shows how much less sea ice there may be in 2050 if temperatures keep going up. This would cause sea level to rise even higher. Some coastal cities could be under water. Millions of people would have to move inland. How might other living things be affected?

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effects of global warming

As Earth has gotten warmer, sea ice has melted. This has raised the level of water in the oceans. Figure 17.21 shows how much sea level has risen since 1880.

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el nio

During an El Nio, the western Pacific Ocean is warmer than usual. This causes the trade winds to change direction. The winds blow from west to east instead of east to west. This is shown in Figure 17.25. The warm water travels east across the equator, too. Warm water piles up along the western coast of South America. This prevents upwelling. Why do you think this is true? These changes in water temperature, winds, and currents affect climates worldwide. The changes usually last a year or two. Some places get more rain than normal. Other places get less. In many locations, the weather is more severe.

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explaining longterm climate change

Natural processes caused earlier climate changes. Human beings are the main cause of recent global warming.

earths recent temperature

Since the Pleistocene, Earths temperature has risen. Figure 17.18 shows how it changed over just the last 1500 years. There were minor ups and downs. But each time, the anomaly (the difference from average temperature) was less than 1 C (1.8 F). Since the mid 1800s, Earth has warmed up quickly. Look at Figure 17.19. The 14 hottest years on record have all occurred since 1900. Eight of them have occurred since 1998! This is what is usually meant by global warming.

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causes of global warming

Recent global warming is due mainly to human actions. Burning fossil fuels adds carbon dioxide to the atmosphere. Carbon dioxide is a greenhouse gas. Its one of several that human activities add to the atmosphere. An increase in greenhouse gases leads to greater greenhouse effect. The result is increased global warming. Figure 17.20 shows the increase in carbon dioxide since 1960.

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causes of climate change in earth history

Several natural processes may affect Earths temperature. They range from sunspots to Earths wobble. Sunspots are storms on the Sun. When the number of sunspots is high, the Sun gives off more energy than usual. Still, there is little evidence for climate changing along with the sunspot cycle. Plate movements cause continents to drift closer to the poles or the equator. Ocean currents also shift when continents drift. All these changes can affect Earths temperature. Plate movements trigger volcanoes. A huge eruption could spew so much gas and ash into the air that little sunlight would reach the surface for months or years. This could lower Earths temperature. A large asteroid hitting Earth would throw a lot of dust into the air. This could block sunlight and cool the planet. Earth goes through regular changes in its position relative to the Sun. Its orbit changes slightly. Earth also wobbles on its axis of rotation. The planet also changes the tilt on its axis. These changes can affect Earths temperature.

how earths climate has changed

Earths climate has changed many times through Earths history. Its been both hotter and colder than it is today.

la nia

La Nia generally follows El Nio. It occurs when the Pacific Ocean is cooler than normal. Figure 17.26 shows what happens. The trade winds are like they are in a normal year. They blow from east to west. But in a La Nia the winds are stronger than usual. More cool water builds up in the western Pacific. These changes can also affect climates worldwide.

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pleistocene ice age

The last major ice age took place in the Pleistocene. This epoch lasted from 2 million to 14,000 years ago. Earths temperature was only 5 C (9 F) cooler than it is today. But glaciers covered much of the Northern Hemisphere. In Figure 17.17, you can see how far south they went. Clearly, a small change in temperature can have a big impact on the planet. Humans lived during this ice age.

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the big picture

Over much of Earths past, the climate was warmer than it is today. Picture in your mind dinosaurs roaming the land. Theyre probably doing it in a pretty warm climate! But ice ages also occurred many times in the past. An ice age is a period when temperatures are cooler than normal. This causes glaciers to spread to lower latitudes. Scientists think that ice ages occurred at least six times over the last billion years alone. How do scientists learn about Earths past climates?

instructional diagrams

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questions

Which of the following statements about climate change is false?

a. Earths climate has changed many times in the past.

b. Earths climate has been hotter than it is today.

c. Earths climate has been colder than it is today.

-->  d. Earths climate has never changed before now.

How much have temperatures risen since the end of the Pleistocene ice ages?

a. -4 C

b. 0 C

-->  c. 4 C

d. 40 C

The 14 hottest years on record have all occurred since

-->  a. 1900.

b. 1990.

c. 1995.

d. 1998.

Atmospheric greenhouse gas levels

a. are currently falling

b. are currently stable

c. are not being measured

-->  d. are currently rising

Natural processes that may have affected Earths temperature in the past include a ##change in the tilt of Earths axis.

a. large asteroid striking Earth.

b. huge volcanic eruption.

c. all of the above

Sunspots

a. are storms on the Suns surface

b. change in number over time

c. have not been found to be the cause of global warming

-->  d. all of these

Burning fossil fuels,

a. increases the ozone content of the atmosphere

-->  b. releases carbon dioxide into the atmosphere

c. create an ozone hole that destroy the ozone layer

d. none of these

Recent global warming is due mainly to

a. plate tectonics.

b. sunspot activity.

-->  c. human actions.

d. none of the above

Effects of global warming include all of the following except

a. sea ice melting.

b. coral reefs dying out.

c. more extreme weather.

-->  d. fewer short-term climate changes.

An El Nio event

a. shuts down upwelling off of South America

b. changes water temperature

c. affects worldwide weather for as long as two years

-->  d. all of these

What happens during El Nio?

-->  a. The trade winds change direction.

b. The Pacific Ocean cools off more than usual.

c. Upwelling occurs off the west coast of South America.

d. Warm water travels from northeast to southwest across the Pacific Ocean.

La Nia occurs

a. when the Pacific Ocean is warmer than normal.

b. because the trade winds change direction.

c. only in the Atlantic Ocean.

-->  d. following El Nio.

Small changes in temperature can make big changes in climate.

-->  a. true

b. false

From O C.E. to 2010 C.E. average global temperature has gone straight up.

a. true

-->  b. false

Climate can change as continents shift position.

-->  a. true

b. false

Global warming will cause weather to be more extreme.

-->  a. true

b. false

All global warming projections show temperature rising during this century.

-->  a. true

b. false

It takes large changes in Earths climate to affect living things.

a. true

-->  b. false

Only one ice age occurred over the past billion years.

a. true

-->  b. false

In the Pleistocene ice age, Earths temperature was 5 C cooler than it is today.

-->  a. true

b. false

During the last ice age, glaciers covered much of North America.

-->  a. true

b. false

Temperatures were higher during the Medieval warm period than they have been over the past decade.

a. true

-->  b. false

Plate tectonics may cause ocean currents to shift.

-->  a. true

b. false

An enormous volcanic eruption would increase Earths temperature.

a. true

-->  b. false

Solar storms are the main cause of recent global warming.

a. true

-->  b. false

Greenhouse gases block sunlight and cool the planet.

a. true

-->  b. false

The amount of carbon dioxide in the air has been increasing for many decades.

-->  a. true

b. false

dramatic increase in Earths temperature since the middle of the 1800s

a. medieval warm period

b. La Nia

c. ice age

-->  d. global warming

e. El Nio

f. upwelling

g. temperature anomaly

short-term climate change in which the Pacific Ocean is warmer than usual

a. medieval warm period

b. La Nia

c. ice age

d. global warming

-->  e. El Nio

f. upwelling

g. temperature anomaly

slight increase in Earths temperature that occurred about 1000 years ago

-->  a. medieval warm period

b. La Nia

c. ice age

d. global warming

e. El Nio

f. upwelling

g. temperature anomaly

period in Earths history when temperatures were cooler than normal

a. medieval warm period

b. La Nia

-->  c. ice age

d. global warming

e. El Nio

f. upwelling

g. temperature anomaly

movement of cold water from the bottom to the surface of the ocean

a. medieval warm period

b. La Nia

c. ice age

d. global warming

e. El Nio

-->  f. upwelling

g. temperature anomaly

difference from average temperature

a. medieval warm period

b. La Nia

c. ice age

d. global warming

e. El Nio

f. upwelling

-->  g. temperature anomaly

short-term climate change in which the Pacific Ocean is cooler than usual

a. medieval warm period

-->  b. La Nia

c. ice age

d. global warming

e. El Nio

f. upwelling

g. temperature anomaly

diagram questions

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