The astronomical theory and data compared - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 299

through ocean currents. This is an unproven theory. Yet Toggweiler and Lea
(2010) treat it as if it were proven fact.
Toggweiler and Lea (2010) claimed: ''The two hemispheres therefore do not
warm and cool together.'' They said:

''Antarctica is warmest on the terminations when the ice sheets in the north
are melting back but are still fairly large and are still keeping the north relatively
cool. During glacial onsets, Antarctica has cooled to its glacial minimum level by
the ends of stages 5, 7, and 9 when the northern ice sheets are just starting to
grow. Thus, terminations are times with the smallest temperature difference
between the hemispheres. Glacial onsets, delineated by the isotope stage bound-
aries 5/4, 7/6, and 9/8, are the times with the largest temperature difference. This
would appear to be no accident: the biggest climate transitions seem to occur
when the temperature differences between the hemispheres are most extreme.''

The implication is that Antarctic climate changes precede NH climate changes.
This is in contrast to the widely held belief that events in the NH produce ice ages.
As before, there is no experimental basis for these claims. It is true, however, that
solar inputs to the NH and the SH are out of phase by 11,500 years corresponding
to precession of the Earth's orbit about the Sun. However, as discussed in Section
10.2.1, oscillations in the phase of solar input seem to be unimportant compared
with the variability of eccentricity and obliquity.
Wolff et al. (2009) emphasized that '' the detailed sequence of events that

leads to a glacial termination remains controversial. It is particularly unclear
whether the northern or southern hemisphere leads the termination.'' They also
said: ''the reason for the spacing and timing of interglacials, and the sequence of
events at major warmings, remains obscure.'' They presented a hypothesis that
''glacial terminations, in common with other warmings that do not lead to termi-
nation, are led from the southern hemisphere, but only specific conditions in the
northern hemisphere enable the climate state to complete its shift to interglacial
conditions.'' Their hypothesis seems rather speculative.
Huybers and Langmuir (2009) found that volcanic activity increased by a
factor of 2 to 6 during the second half of the last termination. They conjectured
that magma production increases with mantle decompression as the ice sheets
melt. Volcanoes located in polar areas would then emit significant amounts of
CO 2 , adding to the already rising CO 2 concentration during termination.
Volcanoes also produce aerosols, but the cooling effects of aerosols from
volcanoes are relatively short lived, whereas CO 2 accumulates in the atmosphere
adding to ongoing warming. This would imply that reduction of the CO 2 concen-
tration as glacial ice sheets build up might be augmented by a decrease in volcanic
activity.
Stott and Timmerman (2011) wrote a very interesting paper on the close
relationship between the rise and fall of the CO 2 concentration and glacial-
interglacial cycles. They noted that there is ample data showing that over the past
20,000 years, as the Earth moved from the LGM to the present interglacial state,

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