climate change in earth history

climate change in earth history

Climate has changed throughout Earth history. Much of the time Earths climate was hotter and more humid than it is today, but climate has also been colder, as when glaciers covered much more of the planet. The most recent ice ages were in the Pleistocene Epoch, between 1.8 million and 10,000 years ago (Figure 1.1). Glaciers advanced and retreated in cycles, known as glacial and interglacial periods. With so much of the worlds water bound into the ice, sea level was about 125 meters (395 feet) lower than it is today. Many scientists think that we are now in a warm, interglacial period that has lasted about 10,000 years. For the past 1500 years, climate has been relatively mild and stable when compared with much of Earths history. Why has climate stability been beneficial for human civilization? Stability has allowed the expansion of agriculture and the development of towns and cities. Fairly small temperature changes can have major effects on global climate. The average global temperature during glacial periods was only about 5.5o C (10o F) less than Earths current average temperature. Temperatures during the interglacial periods were about 1.1o C (2.0o F) higher than today (Figure 1.2). The maximum extent of Northern Hemi- sphere glaciers during the Pleistocene epoch. Since the end of the Pleistocene, the global average temperature has risen about 4o C (7o F). Glaciers are retreating and sea level is rising. While climate is getting steadily warmer, there have been a few more extreme warm and cool times in the last 10,000 years. Changes in climate have had effects on human civilization. The Medieval Warm Period from 900 to 1300 A.D. allowed Vikings to colonize Greenland and Great Britain to grow wine grapes. The Little Ice Age, from the 14th to 19th centuries, the Vikings were forced out of Greenland and humans had to plant crops further south. The graph is a compilation of 5 recon- structions (the green line is the mean of the five records) of mean temperature changes. This illustrates the high tem- peratures of the Medieval Warm Period, the lows of the Little Ice Age, and the very high (and climbing) temperature of this decade. Click image to the left or use the URL below. URL:

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questions

throughout earths history, its climate has always been colder and less humid than it is today.

a) true

-->  b) false

glaciers during the pleistocene

a) advanced and retreated in cycles.

b) there were glacial and interglacial periods.

c) bound up a lot of earths water into ice.

-->  d) all of the above.

the most recent ice age was in the __ between __ years ago.

-->  a) pleistocene epoch; 1.8 million and 10,000

b) pleiocene epoch; 1 million and 10,000

c) pleistocene epoch; 1.8 million and 1 million

d) pleiocene epoch; 2 million and 1 million

the average global temperature during glacial periods was ____ less than current average global temperature.

a) 10.5 oc (18.9of)

-->  b) 5.5 oc (10of)

c) 2.0oc (3.6of)

d) 82 oc (148of)

when glaciers retreat, sea level rises.

-->  a) true

b) false

fairly small changes in temperature can have major effects on global climate.

-->  a) true

b) false

how is climate stability beneficial to the human civilization?

a) it allows the expansion of agriculture

b) it allows the development of towns and cities

c) it has allowed development along coastlines over the centuries.

-->  d) all of the above

the vikings colonized greenland during this period _ and were forced out during this period _.

a) the little ice age; the medieval warm period

b) the late ice age; the middle warm period

-->  c) the medieval warm period; the little ice age

d) the middle warm period; the late ice age

since the end of the ice ages, temperature had been getting steadily warmer, although not uniformly warmer.

-->  a) true

b) false

the message of this concept is

a) climate has changed throughout earth history.

b) human civilization depends on a fairly stable climate.

c) climate in the past 15 centuries or so has been fairly stable.

-->  d) all of these.

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