Climate indices in historical climate reconstructions: A global state-of-the-art

Abstract

Abstract. Evidence contained within historical documents and inscriptions provides an important record of climate variability for periods prior to the onset of systematic meteorological data collection. A common approach used by historical climatologists to convert such qualitative documentary evidence into continuous quantitative proxy data is through the generation of ordinal-scale climate indices. There is, however, considerable variability in the types of phenomena reconstructed using an index approach and the practice of index development in different parts of the world. This review, written by members of the PAGES CRIAS Working Group – a collective of climate historians and historical climatologists researching Climate Reconstructions and Impacts from the Archives of Societies – provides the first global synthesis of the use of the index approach in climate reconstruction. We begin by summarising the range of studies that have used indices for climate reconstruction across six continents (Europe, Asia, Africa, the Americas, Australia) plus the world's oceans. We then outline the different methods by which indices are developed in each of these regions, including a discussion of the processes adopted to verify and calibrate index series, and the measures used to express confidence and uncertainty. We conclude with a series of recommendations to guide the development of future index-based climate reconstructions to maximise their effectiveness for use by climate modellers and in multiproxy climate reconstructions.

Climate indices in historical climate reconstructions: a global state of the art

“…. Regional studies from southern Africa have recently been combined with instrumental data and other annually resolved proxies (including sea surface temperature data derived from analyses of fossil coral) to produce two multi-proxy reconstruc-tions of rainfall variability (Neukom et al, 2014a;Nash et al, 2016).…”

“…Owing to the relatively paucity of documentary data for Africa compared with Europe, conditions for specific rainy seasons are categorised at a quarterly (e.g. Nash et al, 2016) or, more commonly, annual level. Again, key descriptors are used to distinguish the various index classes.…”

A global inventory of historical documentary evidence related to climate since the 15th century

“…Besides discussing 5 available source types and methods of documentary-based drought reconstructions, they provide an extensive compilation of available documentary drought proxies from all continents. Similarly valuable is the global overview on climate indices in climate reconstructions from archives of societies (Nash et al 2021) that summarizes studies using climate indices to reconstruct climate. They present a concise review of the many different derivation and verification practices for climate indices based on qualitative documentary evidence and thus creating quantitative proxy data.…”

Impact of Gaussian Transformation on Cloud Cover Data Assimilation for Historical Weather Reconstruction

“…In Japan, the Historical Weather Database (HWDB) stores historical weather diaries, where more than 18 daily observation records are available from the 1750s to 1870s (Yoshimura, 2007). These diaries can be used to reconstruct past climate at high temporal resolution (e.g., Nash et al, 2020).…”