scholarly journals New insights into the reconstructed temperature in Portugal over the last 400 years

2015 ◽  
Vol 11 (6) ◽  
pp. 825-834 ◽  
Author(s):  
J. A. Santos ◽  
M. F. Carneiro ◽  
A. Correia ◽  
M. J. Alcoforado ◽  
E. Zorita ◽  
...  
Keyword(s):  
Low Frequency ◽  
Volcanic Eruptions ◽  
Maunder Minimum ◽  
Depth Profiles ◽  
Low Frequency Variability ◽  
Reconstructed Temperature ◽  
Late Maunder Minimum ◽  
Temperature Indices ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. The consistency of an existing reconstructed annual (December–November) temperature series for the Lisbon region (Portugal) from 1600 onwards, based on a European-wide reconstruction, with (1) five local borehole temperature–depth profiles; (2) synthetic temperature–depth profiles, generated from both reconstructed temperatures and two regional paleoclimate simulations in Portugal; (3) instrumental data sources over the twentieth century; and (4) temperature indices from documentary sources during the late Maunder Minimum (1675–1715) is assessed. The low-frequency variability in the reconstructed temperature in Portugal is not entirely consistent with local borehole temperature–depth profiles and with the simulated response of temperature in two regional paleoclimate simulations driven by reconstructions of various climate forcings. Therefore, the existing reconstructed series is calibrated by adjusting its low-frequency variability to the simulations (first-stage adjustment). The annual reconstructed series is then calibrated in its location and scale parameters, using the instrumental series and a linear regression between them (second-stage adjustment). This calibrated series shows clear footprints of the Maunder and Dalton minima, commonly related to changes in solar activity and explosive volcanic eruptions, and a strong recent-past warming, commonly related to human-driven forcing. Lastly, it is also in overall agreement with annual temperature indices over the late Maunder Minimum in Portugal. The series resulting from this post-reconstruction adjustment can be of foremost relevance to improve the current understanding of the driving mechanisms of climate variability in Portugal.

scholarly journals New insights into the reconstructed temperature in Portugal over the last 400 years

2015 ◽  
Vol 11 (1) ◽  
pp. 1-25 ◽  
Author(s):  
J. A. Santos ◽  
M. F. Carneiro ◽  
A. Correia ◽  
M. J. Alcoforado ◽  
E. Zorita ◽  
...  
Keyword(s):  
Linear Trend ◽  
Volcanic Eruptions ◽  
Maunder Minimum ◽  
Temperature Series ◽  
Depth Profiles ◽  
Reconstructed Temperature ◽  
Late Maunder Minimum ◽  
Temperature Indices ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. The reliability of an existing reconstructed annual (December–November) temperature series for the Lisbon region (Portugal) from 1600 onwards is assessed in the present study. The consistency of this series with: (1) five local borehole temperature-depth profiles; (2) synthetic temperature-depth profiles generated from both reconstructed temperatures and paleoclimate simulations in Portugal; (3) instrumental data sources over the twentieth century; and (4) temperature indices from documentary sources during the late Maunder Minimum (1675–1715) is assessed. It is found that reconstructed annual mean temperature series in Portugal, after European-wide reconstructions, is not consistent with both borehole profiles and paleoclimate simulations in their long-term variability and trends. Hence, the non-linear trend in the paleoclimate simulations is estimated and added to the reconstructed series (first-stage calibration). The annual reconstructed series is then calibrated in its location and scale parameters, using the instrumental series and a linear regression between them (second-stage calibration). The resulting calibrated series is then in clear accordance with the low-frequency variability of both borehole temperature-depth profiles and paleoclimate simulations. This calibrated series shows clear footprints of the Maunder and Dalton minima, mainly attributed to changes in solar activity and explosive volcanic eruptions, and a strong recent-past warming, attributed to human-driven forcing. Lastly, it is also in overall agreement with independently-derived annual temperature indices for the late Maunder Minimum. Thus, the series resulting of this re-calibration process for Lisbon can be of foremost relevance to improve the current understanding of the driving mechanisms of climate variability in Portugal.

scholarly journals Late Holocene temperature variability in Tasmania inferred from borehole temperature data

2017 ◽  
Vol 13 (6) ◽  
pp. 559-572 ◽  
Author(s):  
Asadusjjaman Suman ◽  
Fiona Dyer ◽  
Duanne White
Keyword(s):  
East Coast ◽  
Past Century ◽  
Borehole Data ◽  
Depth Profiles ◽  
The Past ◽  
North East ◽  
The North ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. Thirty-six borehole temperature–depth profiles were analysed to reconstruct the ground surface temperature history (GSTH) of eastern Tasmania for the past 5 centuries. We used the singular value decomposition method to invert borehole temperatures to produce temperature histories. The quality of borehole data was classified as high or low based on model misfit. The quality of the borehole data was not dependent on topography or land use. Analysis reveals that three to five high-quality borehole temperature–depth profiles were adequate to reconstruct robust paleotemperature records from any area. Average GSTH reconstructed from Tasmanian boreholes shows temperature increases about 1.2 ± 0.2 °C during the past 5 centuries. Reconstructed temperatures were consistent with meteorological records and other proxy records from Tasmania during their period of overlap. Temperature changes were greatest around the north-east coast and decreased towards the centre of Tasmania. The extension of the East Australian Current (EAC) further south and its strengthening around the north-east coast of Tasmania over the past century was considered a prime driver of warmer temperatures observed in north-east Tasmania.

scholarly journals Selection of borehole temperature depth profiles for regional climate reconstructions

2007 ◽  
Vol 3 (1) ◽  
pp. 121-163 ◽  
Author(s):  
C. Chouinard ◽  
J.-C. Mareschal
Keyword(s):  
Surface Temperature ◽  
Joint Inversion ◽  
Regional Climate ◽  
Ground Surface ◽  
Temperature History ◽  
Data Set ◽  
Ground Surface Temperature ◽  
Depth Profiles ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. Borehole temperature depth profiles are commonly used to infer time variations in the ground surface temperature on centennial time scales. We compare different procedures to obtain a regional ground surface temperature history (GSTH) from an ensemble of borehole temperature depth profiles. We address in particular the question of selecting profiles that are not contaminated by non climatic surface perturbations and we compare the joint inversion of all the profiles with the average of individual inversions. We show that the resolution and the stability of the inversion of selected profiles are much improved over those for a complete data set. When profiles have been selected, the average GSTH of individual inversions and the GSTH of the joint inversion are almost identical. This is not observed when the entire data set is inverted: the average of individual inversions is different from the joint inversion. We also show that the joint inversion of very noisy data sets does not improve the resolution but, on the contrary, causes strong instabilities in the inversion. When the profiles that are affected by noise can not be eliminated, averaging of the individual inversions yields the most stable result, but with very poor resolution.

scholarly journals Temperature variability of the Iberian Range since 1602 inferred from tree-ring records

2016 ◽  
Author(s):  
E. Tejedor ◽  
M. A. Saz ◽  
J. M. Cuadrat ◽  
J. Esper ◽  
M. de Luis
Keyword(s):  
Tree Ring ◽  
Full Range ◽  
Ring Width ◽  
Low Frequency ◽  
Basal Area ◽  
Volcanic Eruptions ◽  
Temperature Variability ◽  
Iberian Range ◽  
Cambial Age ◽  
Low Frequency Variability

Abstract. Tree-rings are an important proxy to understand the natural drivers of climate variability in the Mediterranean basin and hence to improve future climate scenarios in a vulnerable region. Here, we compile 316 tree-ring width series from 11 conifer sites in the western Iberian Range. We apply a new standardization method based on the trunk basal area instead of the tree cambial age to develop a regional chronology which preserves high to low frequency variability. A new reconstruction for the 1602–2012 period correlates at −0.78 with observational September temperatures with a cumulative mean of the 21 previous months over the 1945–2012 calibration period. The new IR2Tmax reconstruction is spatially representative for the Iberian Peninsula and captures the full range of past Iberian Range temperature variability. Reconstructed long-term temperature variations match reasonably well with solar irradiance changes since warm and cold phases correspond with high and low solar activity, respectively. In addition, some annual temperatures downturns coincide with volcanic eruptions with a three year lag.

scholarly journals Selection of borehole temperature depth profiles for regional climate reconstructions

2007 ◽  
Vol 3 (2) ◽  
pp. 297-313 ◽  
Author(s):  
C. Chouinard ◽  
J.-C. Mareschal
Keyword(s):  
Surface Temperature ◽  
Joint Inversion ◽  
Regional Climate ◽  
Ground Surface ◽  
Temperature History ◽  
Data Set ◽  
Ground Surface Temperature ◽  
Depth Profiles ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. Borehole temperature depth profiles are commonly used to infer time variations in the ground surface temperature on centennial time scales. We compare different procedures to obtain a regional ground surface temperature history (GSTH) from an ensemble of borehole temperature depth profiles. We address in particular the question of selecting profiles that are not contaminated by non climatic surface perturbations and we compare the joint inversion of all the profiles with the average of individual inversions. Very few profiles of the Canadian data set meet the selection criteria (e.g. only 13 out of 73 profiles in Manitoba and Saskatchewan were retained). We show that the resolution and the stability of the inversion of selected profiles are much improved over those for a complete data set. When profiles have been selected, the average GSTH of individual inversions and the GSTH of the joint inversion are almost identical. This is not observed when the entire data set is inverted: the average of individual inversions is different from the joint inversion. We also show that the joint inversion of very noisy data sets does not improve the resolution but, on the contrary, causes strong instabilities in the inversion. When the profiles that are affected by noise can not be eliminated, averaging of the individual inversions yields the most stable result, but with very poor resolution.

scholarly journals Late Holocene temperature variability in Tasmania inferred from borehole temperature data

2016 ◽  
Author(s):  
Asadusjjaman Suman ◽  
Fiona Dyer ◽  
Duanne White
Keyword(s):  
East Coast ◽  
Temperature History ◽  
Borehole Data ◽  
Depth Profiles ◽  
The Past ◽  
North East ◽  
The North ◽  
Borehole Temperature ◽  
Temperature Depth

Abstract. Thirty six borehole temperature depth profiles were analysed to reconstruct the Ground Surface Temperature History (GSTH) from eastern Tasmania for the past five centuries. We used the Singular Value Decomposition method to invert borehole temperatures to produce temperature histories. The quality of borehole data was classified as high or low based on model misfit. The quality of the borehole data was not dependent on topography, or land use. Analysis reveals that 3–5 high quality borehole temperature depth profiles were adequate to reconstruct robust paleotemperature records from any area. Temperature changes were greatest around the north east coast and decreases towards midland of Tasmania. Warm East Australian Current (EAC) flow towards north east coast of Tasmania during summer was considered a prime driver of warmer temperatures observed for the north east coast. Average, GSTH reconstructed from Tasmanian boreholes shows temperature increases about 1.2 ± 0.2 °C during the past five centuries. Some boreholes show temperature cooling in the beginning of 20th Century that may be an indication of late LIA response in Tasmania. Reconstructed temperatures were consistent with meteorological records and other proxy records from Tasmania during their period of overlap.

scholarly journals Temperature variability in the Iberian Range since 1602 inferred from tree-ring records

2017 ◽  
Vol 13 (2) ◽  
pp. 93-105 ◽  
Author(s):  
Ernesto Tejedor ◽  
Miguel Ángel Saz ◽  
José María Cuadrat ◽  
Jan Esper ◽  
Martín de Luis
Keyword(s):  
Tree Ring ◽  
Full Range ◽  
Ring Width ◽  
Low Frequency ◽  
Basal Area ◽  
Volcanic Eruptions ◽  
Temperature Variability ◽  
Iberian Range ◽  
Cambial Age ◽  
Low Frequency Variability

Abstract. Tree rings are an important proxy to understand the natural drivers of climate variability in the Mediterranean Basin and hence to improve future climate scenarios in a vulnerable region. Here, we compile 316 tree-ring width series from 11 conifer sites in the western Iberian Range. We apply a new standardization method based on the trunk basal area instead of the tree cambial age to develop a regional chronology which preserves high- to low-frequency variability. A new reconstruction for the 1602–2012 period correlates at −0.78 with observational September temperatures with a cumulative mean of the 21 previous months over the 1945–2012 calibration period. The new IR2Tmax reconstruction is spatially representative for the Iberian Peninsula and captures the full range of past Iberian Range temperature variability. Reconstructed long-term temperature variations match reasonably well with solar irradiance changes since warm and cold phases correspond with high and low solar activity, respectively. In addition, some annual temperature downturns coincide with volcanic eruptions with a 3-year lag.

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