Overview of the various models for ice ages in the recent past (3 MYBP to present) - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 227

variations to temperature is strong, but apparently not as simple as is usually
portrayed (e.g., see Chapter 3 of this topic).
The issue regarding the global implications of fluctuations appearing in the
Greenland ice core data partly comes down to the degree to which the patterns
observed at Greenland are also observed at other sites around the world. In this
connection, Wunsch raised a theme that he has presented previously, namely ''the
major problem in tuning or wiggle-matching is that of 'false-positives'—the visual
similarity between records that are in truth unrelated.'' He presented several
examples of time series that appear to the human eye to be related but, when a
proper statistical analysis is made of the underlying data, there is no statistical
confirmation of a relationship.
As we observed in Section 4.3, there appears to be a causal relationship
between temperature patterns at Antarctica and Greenland. The data in Figure
4.16 suggest that each sudden increase in temperature at Greenland was preceded
by a rather slow moderate temperature rise in Antarctica for a few thousand
years. However, this provides no information on how these temperature changes
at Greenland influenced the global climate.
Wunsch (2006) asserted that there is little direct support for the hypothesis
that abrupt changes in Greenland also appear in other distant records. However,
he did admit that some D-O events correlate with changes in global methane
concentration:
''Glacial-period methane sources are supposedly controlled largely by
tropical wetlands, and to the extent that those regions are showing strong
correlation with D-O events in Greenland, one infers that there is at least a
hemispheric reach. There are two issues here: (1) Whether methane sources (and
sinks) are definitively tropical, and, (2) the actual correlation in Greenland of
methane and d 18 O.''
Regarding the first point, Wunsch quoted studies that claim that most modern
wetlands occur at high latitudes and most were at low latitudes during the Last
Glacial Maximum. How wetlands would have behaved during regional warm
events lasting 1,000 years is not clear, and wetlands, though dominant, are not
the only source of methane. Regarding the second point, Wunsch said:
''Some of the D-O events are indeed correlated with methane emissions, but
the evidence that it results from a strong, remote, tropical response remains
unquantified. Nonetheless, the methane d 18 O correlation is the strongest
evidence that the D-O events reach to low latitudes, albeit the inference depends
upon the scanty knowledge of the methane sources and sinks during these times.''
He concluded that the putative large scale of D-O events is ''possible but not
demonstrated''.
Wunsch (2006) provided some counterarguments to the widespread belief that
the cause of the sudden (e.g., D-O) events can be traced back to major changes