New developments in CLAMP: Calibration using global gridded meteorological data

Abstract

Climate Leaf Analysis Multivariate Program (CLAMP) is a versatile techniquefor obtaining quantitative estimates for multiple terrestrial palaeoclimate variables from woody dicot leaf assemblages. To date it has been most widely applied to the Late Cretaceous and Tertiary of the mid-to high latitudes because of concerns over the relative dearth of calibration sites in modern low-latitude warm climates, and the loss of information associated with the lack of marginal teeth on leaves in paratropical to tropical vegetation. This limits CLAMP's ability to quantify reliably climates at low latitudes in greenhouse worlds of the past.One of the reasons for the lack of CLAMP calibration samples from warm environments is the paucity of climate stations close to potential calibration vegetation sites at low latitudes. Agriculture and urban development have destroyed most lowland A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTsites and natural vegetation is now largely confined to mountainous areas where climate stations are few and climatic spatial variation is high due to topographic complexity. To attempt to overcome this we have utilised a 0.5° x 0.5° grid of global interpolated climate data based on the data set of New et al. (1999) supplemented by the ERA40 re-analysis data for atmospheric temperature at upper levels. For each location, the 3-D climatology of temperature from the ECMWF re-analysis project was used to calculate the mean lower tropospheric lapse rate for each month of the year. The gridded data were then corrected to the altitude of the plant site using the monthly lapse rates. Corrections for humidity were also made. From this the commonly returned CLAMP climate variables were calculated. A bi-linear interpolation scheme was then used to calculate the climate parameters at the exact lat/long of the site.When CLAMP analyses using the PHYSG3BR physiognomic data calibrated with the climate station based MET3BR were compared to analyses using the gridded data at the same locations (GRIDMET3BR), the results were indistinguishable in that they fell within the range of statistical uncertainty determined for each analysis. This opens the way to including natural vegetation anywhere in the world irrespective of the proximity of a meteorological station.

Palaeoenvironmental evaluation of Cainozoic plant assemblages from the Bohemian Massif (Czech Republic) and adjacent Germany

“…Climate Leaf Analysis Multivariate Program (CLAMP) is based on the multivariate statistical technique for quantitative determining for a range of palaeoclimate parameters based on leaf physiognomy of woody dicotyledonous flowering plants. CLAMP has first been introduced by Wolfe (1993) and subsequently this technique has been refined (Wolfe & Spicer 1999;Spicer et al 2004;Spicer 2000Spicer , 2007, metodologicaly modificated (e.g., Yang et al 2011;Teodoridis et al 2011cTeodoridis et al , 2012Yang et al in press) and updated using gridded meteorological data (Spicer et al 2009) and new CLAMP calibration data (e.g., Jacques et al 2011, Srivastava et al 2012. Mathematically, this method is based on Canonical Correspondence Analysis (CCA) -see Ter Braak (1986).…”

Tracing the Eocene–Oligocene transition: a case study from North Bohemia

“…To verify the obtained estimates, the value of sampling errors (SE1) and (SE2) were calculated following Wilf (1997) Miller et al (2006) -SE 2 MAT = √([1 + ϕ (n-1) P(1-P)] × (P(1-P))/n), where the following symbols are used: c (slope of the MAT vs. leaf margin regression, equals 30.6 here), n (total species number), P (proportion of n species with entire margin, 0 < P < 1) and ϕ = 0.052 (dispersion factor). An updated version (see Teodoridis et al 2012) of the special tool developed by Teodoridis et al (2011c) was used to select relevant physiognomical datasets for using CLAMP, as characterized by e.g., Wolfe & Spicer (1999), Spicer et al (2009), andYang et al (2011). Physiognomic characteristics of the studied floras are presented in Appendix 1.…”

Refining CLAMP — Investigations towards improving the Climate Leaf Analysis Multivariate Program

“…Variants on this are possible (Spicer et al, 2009) but this requires recalibration of the results spreadsheet.…”

“…Although much work has been devoted to this kind of research, it has to be kept in mind that so far all methods and approaches have their own limitations and shortcomings and that perhaps there will never be an optimal, universally applicable and absolutely reliable technique for the quantitative estimation of palaeoclimatic parameters from fossil plants (e.g., Mosbrugger and Utescher, 1997;Wilf, 1997;Wilf et al, 1998;Wiemann et al, 1998;Uhl et al, 2007aUhl et al, , 2007bTraiser et al, 2005Traiser et al, , 2007Spicer et al, 2004;Spicer, 2000Spicer, , 2007Yang et al, 2007). This is largely due to complex spatial and temporal variations in the natural environment and plant adaptations that require finite time to equilibrate, and ultimately are compromise solutions to often conflicting environmental constraints (Spicer, 2007;Spicer et al, 2009). Nevertheless the development of a wide variety of different approaches and techniques is desirable, and as well as developing new techniques attempts should be made to improve existing methodologies.…”

“…A. Wolfe (1990Wolfe ( , 1993Wolfe ( , 1995 and subsequently refined by various authors (e.g., Kovach and Spicer, 1995;Stranks and England, 1997;Wolfe and Spicer, 1999;Spicer et al, 2004;Spicer 2000Spicer , 2007Spicer et al, 2009). Methodologically, CLAMP is a development of Leaf Margin Analysis (LMA).…”