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However, this Chapter 5 in question [MAS 13] does not make the
slightest mention of the famous publication from M. Mann
et al
. [MAN 99]
neither in the text nor among the some 1,000 specific bibliographical
references in this chapter. Given the extensive use that the IPCC made of it
in the past (cited six times in the Third Assessment Report), and the
controversy it still causes, this absence is peculiar
7
.
Moreover, there is a recurrent debate on the local or global nature of large
climatic events. Figure 2.2 shows that proxies which detect a MWP or a
LIA, are distributed across the Earth's surface, including the oceans and are
not limited to central England or to Greenland (green-land) mythologized by
Eric the Red. The IPCC admits that in the last SPM (section 5.5):
“Continental-scale temperature reconstructions show, with high
confidence, multi-decadal periods during the Medieval Climate Anomaly
(year 950 to 1250) that were in some regions as warm as in the late 20
th
Century. These regional warm periods did not occur as coherently across
regions as the warming in the late 20
th
Century (high confidence).”
This lack of synchronization is apparent in Figure 3.2. It is insufficiently
emphasized at the whim of some governmental delegations
8
, but on the other
hand, it shows that the warm medieval period stretches over several
centuries, while the sudden current warming only spans several decades.
This lack of coherence in the reconstructions based on proxies is just as
present for the modern-day (see Figure 2.4) as it is for the past.
The use of the expression “Medieval Climate Anomaly” can be seen
above. In AR4,
Medieval Warm Period
was still also often used (although
always in inverted commas). In the AR5, it has quite simply been removed
from climate-specific language, to be replaced by the milder MCA:
Medieval Climate Anomaly. This is the mortal blow that Overpeck was
looking to deal regarding the use of this term.
7 According to
Google Scholar,
Mann (1999) is quoted 1681 times in scientific literature,
Moberg 1008 times, Ljungqvist 103 times and Loehle 56 times (for their respective
reconstructions).
8 Concerning text on the Medieval Climate Anomaly, Belgium and Ireland underscored that
this phenomenon was regional in nature, unlike global warming in late 20th Century.
(Kosolapova, E, 2013)
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