Question

1. The average global temperature during the last decade was

(a) higher than during any decade since 1900

(b) higher than at any time since the first century C.E.

(c) higher than at any time since the dawn of civilization (around 6000 B.C.E.)

(d) higher than at any time since the last ice age

(e) none of the above

2. During the last 100 years, global average sea level

(a) rose at first and is now falling again

(b) has fluctuated around a roughly constant value

(c) has risen more than 10 cm

(d) has fallen between 5 and 10 cm

(e) none of the above

3. During the last half million years,

(a) there has been only one ice age, and it lasted about 100,000 years

(b) there has been only one ice age which lasted about 10,000 years

(c) the earth has been in interglacials for about the same amount of time that it has been in ice ages

(d) most of the time the earth has been in ice ages

(e) none of the above

4. The term “greenhouse effect” refers to

(a) decrease in Earth’s infrared emissivity due to gases in the atmosphere

(b) storage of heat in clouds

(c) cooling via emission of visible light from the earth’s surface

(d) heating due to absorption of ultraviolet light by gases in the atmosphere

(e) none of the above

Answer 1

1 a) higher than during any decade since 1900. The temperature in the last decade was the hottest on record, the period of which extend to about 200 years.There may have been warmer periods before this (in fact there was a warm period around 3000 years ago, but its magnitude is not accurately knwon).

2 c) has risen more than 10 cm. The range of sea level rise in the past 100 years based on tide gauge data is in the range 10 to 20 cm.

3 c) the earth has been in interglacials for about the same amount of time that it has been in ice ages. The Pleistocene epoch was known largelt for its glaciation, but there were many interglacial periods as well, so that both glacials and interglacials lasted for about the same amount of time.

4 a) decrease in Earth’s infrared emissivity due to gases in the atmosphere. The greenhouse gases reduce the transparency of the Earth's atmosphere, which reduces the amount of infrared radiation reflected back into space.