23. November 2011

Was hat sich getan?

Seitdem ich das letzte Mal zur Sache gebloggt habe, ist einige Zeit vergangen. Viele neue Studien sind eruierbar, einige in Druck.

Viau et al. weisen in ihrer Pollenrekonstruktion der letzten zwei Millennia für Nord-Amerika eine MWP und LIA nach:
The temperature of the warmest month was reconstructed for the past 2000 years using 748 pollen sites from the North American Pollen Database. The Modern Analog Technique was used to quantify paleoclimate conditions using a modern pollen database with calibration sites from across North America. Across North America, both the Medieval Warm Period (MWP) and Little Ice Age (LIA) were cooler than the present (AD 1961–1990).
Polovodova et al. finden in The benthic foraminiferal record of the Medieval Warm Period and the recent warming in the Gullmar Fjord, Swedish west coast Nachweise für eine MWP:
A high-resolution study of benthic foraminiferal assemblages was performed on a ca. eight metre long sediment core from Gullmar Fjord on the west coast of Sweden. The results of 210Pb- and AMS 14C-datings show that the record includes the two warmest climatic episodes of the last 1500 years: the Medieval Warm Period (MWP) and the recent warming of the 20th century. 
Toker et al. finden Evidence for centennial scale sea level variability during the Medieval Climate Optimum (Crusader Period) in Israel, eastern Mediterranean. Sie setzen eine MWP voraus, wenn sie schreiben:
The Crusader low levels overlap the period known as the ‘Medieval Warm Period’ (MWP) or the ‘Medieval Climate Anomaly’ (MCA).

Interessant auch, dass sie einen Anstieg des Meeresspiegels um rund 1,25 mm +/-0,5mm im Jahr für die Periode zwischen 900 und 1300 A.D. für die "eastern coasts of the Mediterranean basin" feststellen. Zur Erinnerung, das IPCC spricht 2007 von einem durchschnittlichen Anstieg des Meeresspiegels bis 2100 in einer Größenordnung von 18 bis 59 cm. Das wären dann, in niedrigster Schätzung, rund 1,8 mm Anstieg im Jahr.

Larsen et al. finden in ihrer Arbeit A 3000-year varved record of glacier activity and climate change from the proglacial lake Hvítárvatn, Iceland die größte "perturbation", beginnend im Jahre 1250 A.D., was sie zur Aussage führt:
The largest perturbation began ca 1250 AD, signaling the onset of the Little Ice Age and the termination of three centuries of relative warmth during Medieval times.
D'Arrigo et al. fanden in Regional climatic and North Atlantic Oscillation signatures in West Virginia red cedar over the past millennium Belege für eine warme MWP im Untersuchungsgebiet:
Using ensemble methods of tree-ring standardization, above average ring widths are indicated for the period between ~ 1000 and 1300 CE, the approximate time of the Medieval Climate Anomaly (MCA), the most recent major warm episode prior to the modern era.
Kaniewski et al. belegen in ihrer Pollenanalyse The medieval climate anomaly and the little Ice Age in coastal Syria inferred from pollen-derived palaeoclimatic patterns eine MWP für (north-western coastal) Syrien:
The pollen-derived climatic proxy inferred from a 315 cm deep core of alluvial deposits suggests that a shift towards wetter climatic conditions occurred from circa (ca.) 1000 to 1250 calibrated (cal) yr AD. This period is situated within the time frame of the Medieval Climate Anomaly. The reconstructed temperature trends show that the warming during this medieval episode was not as high as the modern scores, except for short intervals during the early 12th century AD.
Woodbridge und Roberts halten in ihrer Studie Late Holocene climate of the Eastern Mediterranean inferred from diatom analysis of annually-laminated lake sediments fest:
After a drier phase in the Nar record from AD 800–950, the period of the Medieval Climate Anomaly (AD 950–1400) was generally well watered.