Insights into climate change and reliability of GloSAT from integrating climate proxy, model and instrumental sources

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Climate proxies are not just for extending the record before the instrumental period but also have value in assessing the instrumental record itself (e.g. global trends: Anderson et al. 2013; Indian Ocean SST: Pfeiffer et al. 2017). This PhD will apply such comparisons to periods and regions where the insight from proxies will be most valuable. One focus will be Europe in the early instrumental period (pre-1900 and especially GloSAT's new extension before 1850) where different thermometer exposures contribute to summer temperature biases and there is a wealth of summer-sensitive well-replicated tree-ring data supplemented by documentary evidence. Another focus will be tropical temperature trends in comparison with information from coral records (PAGES 2k Consortium 2017). Novel approaches will strengthen the project, including utilising information from the Last Millennium Reanalysis (Tardif et al. 2018) and applying improved approaches to tree-ring analysis (signal-free Regional Curve Standardisation) to yield more reliable multi-centennial trends. There are undoubtedly significant uncertainties is the proxy-based multi-centennial trends which the PhD project will explore. Even where these are too large to constrain the GloSAT instrumental uncertainties from, say, 1800-present, the proxies will also provide independent information on decadal-multidecadal temperature variability and the PhD project will utilise this to evaluate the instrumental variations over comparable time-spans. For example, there are differences in temperature changes over 1800-1850 and 1850-1900 between different datasets and the climate proxies might contribute to resolving these issues.The overall outcome will be an independent evaluation of GloSAT temperature and optimised climate change information in the case study regions.ReferencesAnderson et al. (2013) Global warming in an independent record of the past 130 years. Geophys. Res. Lett., 40, 189-193, doi: 10.1029/2012GL054271.PAGES2k Consortium (2017) A global multiproxy database for temperature reconstructions of the Common Era. Sci. Data, 4,170088, doi: 10.1038/sdata.2017.88Pfeiffer et al. (2017) Indian Ocean corals reveal crucial role of World War II bias for twentieth century warming estimates. Scientific Reports 7, 14434, https://doi.org/10.1038/s41598-017-14352-6Tardif et al. (2018) Last Millennium Reanalysis with an expanded proxy database and seasonal proxy modeling, Clim. Past Discuss., https://doi.org/10.5194/cp-2018-120