I came accross this paper in the latest edition of the Journal of Quaternary Science entitled: ‘A pre-deforestation pollen-climate calibration model for New Zealand and quantitative temperature reconstructions for the
past 18 000 years BP.’ JQS (2007) 22(5) 535–547
JANET M. WILMSHURST,1* MATT S. McGLONE,1 JOHN R. LEATHWICK2 and REWI M. NEWNHAM3
1 Landcare Research, Lincoln, Canterbury, New Zealand
2 National Institute of Water and Atmospheric Research, Hamilton, New Zealand
3 University of Plymouth, School of Geography, Plymouth, Devon, UK
In case any readers don’t know, the current 12,000 year old interglacial period that we are fortunate to live in is known as the ‘Holocene,’ SST refers to ‘Sea Surface Temperature, ‘ MAT is ‘Mean Annual Temperature,’ and BP is ‘Before Present.’
The Abstract says:
Quantification of modern pollen rain–vegetation–climate relationships in New Zealand has been complicated by human destruction of at least 75% of the original forest cover since ca. 750 years BP, causing contemporary pollen rain over large areas to bear little resemblance to the pre-human vegetation. We use a pre-deforestation pollen database to circumvent this complication. The relationships between the pre-deforestation pollen assemblages and six climatic variables were explored using principal components analysis and constrained regressions (redundancy analyses). Quantitative estimates of the most significant climate variable (mean annual temperature) were made at seven lowland to montane fossil pollen sites from throughout New Zealand using the modern analogue technique and a transfer function. These showed an initial increase in mean annual temperature after 18 000 cal. yr BP, a cooling at the time of the Antarctic Cold Reversal (centred on 13 500 cal. yr BP) and continuation of warming from ca. 12 000 cal. yr BP across the Younger Dryas chronozone, reaching a Holocene thermal optimum that may have been between 1.5 and 3.08C warmer than present and lasted from 9000 to 7000 cal. yr BP depending on the site. Cooling to present-day temperatures was well advanced by 4000–3000 cal. yr BP.
The paper concludes:
It is clear that the early Holocene was an unusually warm period with the pollen results, marine core assemblage, and isotopic SST estimates and other proxy biological evidence pointing to several millennia of MATs between 1.5 and 3.08C above those of the early 20th century. Given that there is considerable alarm about similar increases in MAT by the end of the current century, these results suggest that the early Holocene could profitably be used as an analogue to explore the consequences for biological change.