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 225

convection, and deep-water formation was instead driven by brine-release during
sea-ice freezing. These shifting magnitudes and modes nested within the overall
continuity of deep-water formation were probably important for the structuring
and rapidity of the prevailing climate changes.
We conclude that common to all stadial-interstadial cycles (D-O and
Heinrich-events) is a shift in the mode of overturning in the Nordic Seas, with
normal deep-water formation (similar to the modern form, although less vigor-
ous) in the warmer phases of the glacial, interrupted by a shift to deep-water
formation dominated by brine-release during the cold phases with meltwater
injection.''
These dramatic climate changes observed in the North Atlantic are heavily
muted or absent in Antarctica. For example, Figure 4.15 shows no evidence of the
Younger Dryas in the Antarctic ice core.
CO 2 variability does not appear to be involved as a cause of rapid climate
change because changes in CO 2 concentration occur too slowly.
Adams et al. (1999) pointed out that another potential factor in rapid regional
or global climate change may be shifts in the albedo of the land surface that result
from changes in vegetation or algal cover on desert and polar desert surfaces.
Increased dust levels occur during cold periods, but it is unclear whether this is a
cause or an effect.
8.6.3 Wunsch's objections
The field of climatology seems to be permeated by studies that draw a dollar's
worth of conclusions from a penny's worth of data. While there is nothing funda-
mentally wrong with conjecturing what might be, there is an unfortunate tendency
for such contemplations to become hardened in the annals of climatology as fact.
This can (and does) happen in other fields as well. 5 Carl Wunsch of MIT has
pointed out the frailty of some of these conjectural arguments in several instances.
For example, in Sections 3.2.10, 4.3, 5.2, and 6.1.4 we referred to his criticism
of the way in which curves are compared visually, in which he concluded:
''Sometimes there is no alternative to uncertainty except to await the arrival of more
and better data'' (emphasis added). This writer strongly endorses this viewpoint.
5 I am reminded of an event that occurred in the 1970s. At that time, there was some
controversy regarding the altitude at which the Earth's ionosphere transitioned from mainly
O þ to H þ . This was dependent on the rate of the reaction O þ þ H ) O þ H þ . On the first day
of a national meeting, a leading expert, Alec Dalgarno, made a presentation on this topic. At
the end of his talk, someone asked him what the rate of the charge exchange reaction was. He
said he didn't know. They pressed him to make a guess. So, he guessed. Three days later at the
meeting wrap-up, Dalgarno was asked to present a summary. In doing this, he used the
aforesaid reaction rate. Someone asked him where he obtained that figure. He replied: ''I don't
know. Someone provided it on the first day of the meeting!''