Palaeoclimatology Questions and Answers

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.

Answer: A

Correct answer: regionally variable episodes

Both were real, but neither was globally synchronous or globally uniform: the warmth and cold occurred at different times in different regions, and some regions show the opposite sign. Averaged globally the anomalies are modest compared with the regional extremes, which is why they are now discussed as regional episodes rather than as global periods.

Answer: B

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

Both are true and the reason gives the motive for the change in terminology. “Medieval Warm Period” implies a global warm interval, which the evidence does not support, so “Medieval Climate Anomaly” is preferred as it describes a period of unusual climate without asserting its sign or its extent. The renaming is a correction of an implied claim rather than a change of view about the data.

Answer: C

The sequence spans some twenty thousand years and each interval is known from a different combination of proxies. The instrumental record covers only the last century and a half. Each interval rests on its own proxies.