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4000-Year δ18O Histories of New Zealand's North and South Islands
Lorrey, A., Williams, P., Salinger, J., Martin, T., Palmer, J., Fowler, A., Zhao, J.-X. and Neil, H. 2008. Speleothem stable isotope records interpreted within a multi-proxy framework and implications for New Zealand palaeoclimate reconstruction. Quaternary International 187: 52-75.

What was done
Two master speleothem (stalactite, stalagmite or flowstone cave deposit) δ18O records were developed for New Zealand's eastern North Island (ENI) and western South Island (WSI) for the period 2000 BC to about AD 1660 and 1825, respectively. The WSI record is a composite chronology composed of data derived from four speleothems from Aurora, Calcite, Doubtful Xanadu and Waiau caves, while the ENI record is a composite history derived from three speleothems from Disbelief and Te Reinga caves.

What was learned
For both the ENI and WSI δ18O records master speleothem histories, their warmest periods fall within the AD 900-1100 time interval, which is also where the peak warmth of a large portion of the temperature records found in our Medieval Warm Period Project fall (see our Interactive Map and Time Domain Plot).

What it means
Not wanting to acknowledge that the earth was likely as warm as, or even warmer than, it is currently a thousand or so years ago (when the atmosphere's CO2 concentration was much lower than it is today), the world's climate alarmists have been loath to admit there was an MWP or Medieval Warm Period anywhere other than in countries surrounding the North Atlantic Ocean. Consequently, the seven independent speleothem records that produced the results reported by Lorrey et al. are of great importance to the ongoing global warming debate, as they greatly advance the thesis that the MWP was indeed a global phenomenon, and that there is thus nothing unusual, unnatural or unprecedented about earth's current warmth, and that it therefore need not be attributed to the historical increase in the air's CO2 content.

Reviewed 31 December 2008