Description: Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data–model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model’s ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices.

Description: There is an urgent requirement to understand how large fluctuations in tropical heat distribution associated with the El Niño-Southern Oscillation (ENSO) will respond to anthropogenic emissions of greenhouse gases. Intervals of global warmth in Earth history provide a unique natural laboratory to explore the behaviour of the ENSO in a warmer world. To investigate interannual climatic variability, specifically ENSO, in the mid-Piacenzian Warm Period (mPWP: 3.26 - 3.03 Ma), we integrate observations from the stable isotopes of multiple individual planktonic foraminifera from three different species from the eastern equatorial Pacific (EEP) with ENSO simulations from HadCM3, a fully coupled ocean-atmosphere climate model. Our proxy data and model outputs show persistent inter-annual variability during the mPWP caused by a fluctuating thermocline, despite a deeper thermocline and reduced upwelling. We show that the likely cause of the deeper thermocline is due to warmer equatorial undercurrents rather than reduced physical upwelling. We conclude that the mPWP was characterized by ENSO related variability around a mean state akin to a modern El Niño event. Furthermore, HadCM3 predicts that the warmer Pliocene world is characterized by a more periodic, regular amplitude ENSO fluctuation, suggestive that the larger and deeper west Pacific warm pool is more easily destabilized eastwards. These conclusions are comparable to the observed trend over the last forty years to more regular and intense ENSO events. Future research must resolve whether global warming alone, or in concert with tectonic factors, was sufficient to alter ENSO variability during warm intervals of the Pliocene.

Description: Important data from the African Centre of Meteorological Applications for Development (ACMAD) collection have been recently rescued from unstable fiche media and scanned to digital images by the EU funded Copernicus Climate Change Service and the Royal Meteorological Institute (RMI) of Belgium. The team at the C3S2-311 Lot 1 Collection and Processing of In Situ Observations service led by the Irish Climate Analysis and Research UnitS (ICARUS) at Maynooth University, Ireland enrolled the help of 2nd year university undergraduate students to transcribe quickly and effectively some of these important ACMAD meteorological surface observations. New and unique datasets for Macenta, Guinea (1947-1953) and Andapa, Madagascar (1949-1957) were digitised with each station consisting of sub-daily observations for: cloud, temperature, humidity, evaporation, pressure and wind as well as daily observations for: evaporation, precipitation and temperature. The newly digitised Sub-Saharan African data will increase the temporal and spatial coverage of data in this important data-sparse region where climate change impact studies are crucial., Students gained new skills and a deep appreciation of historical climatology while helping the global scientific community unearth new insights into past sub-Saharan African climate. The Climate Data Rescue Africa project (CliDaR-Africa project) model has the potential for a broader roll-out to other educational contexts and there is certainly no shortage of data to be rescued with millions of images remaining untouched. Therefore, this paper provides details of the project, and all supporting information such as project guidelines and templates to enable other organisations to instigate similar programs in future.