Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries

Analyses of historical patterns of rainfall variability are essential for understanding long-term changes in precipitation timing and distribution. Focussing on former Natal and Zululand (now KwaZulu-Natal, South Africa), this study presents the first combined annual and seasonal reconstruction of rainfall variability over southeast Africa for the 19th century. Analyses of documentary sources, including newspapers and colonial and missionary materials, indicate that the region was affected by severe or multi-year drought on eight occasions between 1836 and 1900 (the rainy seasons of 1836-38, 1861-63, 1865-66, 1868-70, 1876-79, 1883-85, 1886-90 and 1895-1900). Six severe or multi-year wet periods are also identified (1847-49, 1854-57, 1863-65, 1879-81, 1890-91 and 1892-94). The timing of these events agrees well with independent reconstructions of 19th century rainfall for other parts of the southern African summer rainfall zone (SRZ), suggesting subcontinental scale variability. Our results indicate that the relationship between El Niño and rainfall in southeast Africa was relatively stable, at least for the latter half of the 19th century. El Niño conditions appear to have had a more consistent modulating effect upon rainfall during the 19th century than La Niña. The rainfall chronology from this study is combined with other annually-resolved palaeoclimate records from mainland southern Africa and surrounding oceans as part of a multi-proxy rainfall reconstruction for the SRZ. This reconstruction confirms (i) the long-term importance of ENSO and Indian Ocean SSTs for modulating regional rainfall; and (ii) that summer precipitation has been declining progressively over the last 200 years

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“…The proxy matrix was infilled over the 1921-1995 period using the composite plus scale method (Neukom et al, 2011;Neukom et al, 2014).…”

Section: S33 Multi-proxy Reconstruction Detailsmentioning

confidence: 99%

“…The reconstruction was performed using nested principal component regression (Cook et al, 1994;Neukom et al, 2011). We used an ensemble approach to quantify reconstruction uncertainty (Neukom et al, 2010;Wahl and Smerdon, 2012;Neukom et al, 2014).…”

Section: S33 Multi-proxy Reconstruction Detailsmentioning

confidence: 99%

Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources

Nash

Pribyl

Klein³

et al. 2015

Climatic Change

119

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“…Mann et al 2008;Ljungqvist 2010). On the other hand, despite recent efforts (e.g., Conroy et al 2009;Tierney et al 2010;Neukom et al 2011) fewer records are available from the tropics, and the Southern Hemisphere, particularly at interannual to decadal resolution prior to about A.D. 1200 (e.g., Neukom and Gergis 2011). Furthermore, most records provide estimates for a particular season, making annual estimates and comparisons with other (seasonally different) records problematic (Bradley et al 2003b).…”

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confidence: 99%

Spatial and Temporal Characteristics of Climate in Medieval Times Revisited

Díaz

Trigo

Hughes

et al. 2011

Bull. Amer. Meteor. Soc.

141

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The increase in high-resolution proxy records over expanding areas of the globe helps deepen understanding of the unusual climate patterns-and the forcing mechanisms responsible for them-during the years 950 to 1400. C limate in medieval times, a period usually understood to extend from A.D. ~950 to ~1400, is of considerable interest to students of modern and future climate. This is because the period differs from recent centuries mainly by predating the Industrial Revolution with its associated changes in the composition of the atmosphere and oceans and the nature of the land surface (Hughes and Diaz 1994; Crowley and Lowery 2000; Bradley et al. 2003a,b). In this sense it represents an appealing, but imperfect "control case" for the unintended global climate experiment that has resulted from industrial and agricultural development and population growth.In order to stimulate a synthesis of recent work on these topics, we convened a meeting of international experts to consider the following issues: 1) What were some of the key regional patterns of climatic anomalies during medieval times derived from the proxy climate records and from model simulations, and how do they compare with the twentieth-century patterns? 2) Recognizing that multiple proxy climate records are needed to constrain as much as possible the spatial and temporal variability of climate, what do recent studies using powerful statistical methods tell us about the timing and geographic coverage of the major features of climate in medieval times? 3) A number of numerical simulations using climate models of varying complexity and external forcing histories have been completed in the past few years. What do the latest model results tell us about geographic patterns and temporal characteristics of the simulated climate of this period?

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“…The RegEM algorithm is a sophisticated method used in paleoclimate reconstructions (Guiot et al 2010;Mann et al 2008;Wang et al 2014;Neukom et al 2011) to build a transfer function. We used the PPR to locate predictor proxies, which is important for the Asian region, due to its complex topography and heterogeneous climate.…”

Section: Reconstruction Methodsmentioning

confidence: 99%

A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium

Shi

Yang

et al. 2015

Climatic Change

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To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June-July-August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the Institute of Geography, Russian Academy of Sciences, Moscow, Russia warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial timescales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.

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Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries

Cited by 154 publications

References 82 publications

Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources

Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources

Spatial and Temporal Characteristics of Climate in Medieval Times Revisited

A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium

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