Palaeoclimatology Questions and Answers

Answer: C

The periods appear clearly in the isotope records, which is the strongest evidence for the orbital theory. The dominance of the hundred thousand year period is nonetheless still debated. The periods appear in the records.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason states the mechanism. Eccentricity, obliquity and precession change the shape of the orbit and the tilt and orientation of the axis, so they redistribute sunlight between latitudes and seasons while leaving the total solar output essentially unchanged. High-latitude summer insolation is the quantity that matters, because it determines whether the previous winter’s snow survives.

Answer: A

The first two are correct. The third is not accepted, since feedbacks involving ice albedo and carbon dioxide are needed to amplify the modest orbital signal. Insolation alone is too small a lever. Feedbacks do most of the amplification.

Answer: B

Correct answer: False

The insolation changes are small, and the eccentricity cycle in particular is very weak while the 100,000-year glacial rhythm is strong - the long-standing problem of the hundred thousand year cycle. Orbital forcing sets the timing, and feedbacks amplify it into the observed magnitude: ice albedo, greenhouse gas changes released from the ocean, dust and vegetation. The pacemaker is astronomical and the amplifier is terrestrial.

Answer: C

They demonstrate that the climate system can change very quickly indeed, which was a considerable surprise when first found. Changes in the Atlantic overturning are the leading explanation. Decades rather than millennia were involved.

Answer: D

Both are true and the reason gives the significance, and the possibility of such a transition in future is one reason abrupt change receives so much attention. Gradualism was the prior expectation. The events recur through the last glacial period.

Answer: A

Correct answer: about 20 thousand years

The last glacial maximum was around 20,000 years ago, when ice sheets reached their greatest extent and sea level stood about 120 metres below the present. It is the best documented cold state available, which is why it is used so heavily as a test case for climate models - the forcings are reasonably well known and the response is large.

Answer: B

The water was locked up in the great northern ice sheets, and the exposed continental shelves are what allowed the human migrations of the period. Recovery took several thousand years. Exposed shelves changed the geography entirely.

Answer: C

Correct answer: deep ocean sediment cores

Deep ocean sediment accumulates at centimetres per thousand years and is stirred by burrowing organisms, so it cannot resolve individual years. Varved lake sediments, coral bands and tree rings all lay down a visible annual increment, which is what allows them to be counted and dated directly rather than by radiometric means.

Answer: D

The first two are correct. The third overstates the stability, since the Holocene contains events such as the eight point two thousand year cooling and substantial shifts in monsoon strength. Stability is relative rather than absolute.