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This analysis highlights the potential value in reanalysing early national meteorological records from around the world. These were oftentimes measured via techniques that preceded standardisation of instrumentation and methods of observation and thus could be subject to considerable biases and uncertainties. This analysis uses the techniques pioneered by WMO record assessment teams. The highest currently recognised air temperature (33.3 ∘C) ever recorded in the Republic of Ireland was logged at Kilkenny Castle in 1887. The original observational record however no longer exists. Given that Ireland is now the only country in Europe to have a national heat record that was set in the 19th century, a reassessment of the verity of this record is both timely and valuable. The present analysis undertakes a fundamental reassessment of the plausibility of the 1887 temperature record using methods similar to those used to assess various weather extremes under WMO auspices over recent years. Specifically, we undertake an inter-station reassessment using sparse available records and make recourse to the new and improved 20CRv3 sparse-input reanalysis product. Neither surrounding available stations nor the reanalysis offer substantive support for the Kilkenny record of 33.3 ∘C being correct. Moreover, recent data rescue efforts have uncovered several earlier extreme values, one of which exceeds the Kilkenny value (33.5 ∘C on 16 July 1876 recorded at the Phoenix Park). However, the sparsity of early observational networks, a distinct lack of synoptic support from 20CRv3 for many of the extreme heat values, and the fact that these measurements were obtained using non-standard exposures lead us to conclude that there is grossly insufficient evidence to support any of these 19th century extremes as robust national heat record candidates. Data from the early 20th century onwards benefit from a denser network of stations undertaking measurements in a more standardised manner, many und

This paper outlines progress of the Copernicus Climate Change Service's (C3S) Global Land and Marine Observations Database service in securing data sources and introduces the data upload component. We present details of land and marine data holdings inventoried, highlighting priority needs in terms of periods, regions and Essential Climate Variables (ECVs) where additional data could bring most benefit. These holdings are being iteratively merged and integrated to best meet user needs and are served to the user via the Copernicus Climate Data Store (CDS). The secure Data Upload Server enables any data provider to share additional data and metadata with the service. We outline the process for registering as a data provider and how data sets are prioritized for integration. We encourage all data owners to share their data with the C3S service via our Data Upload Server. All unique and relevant data acquired or submitted will be also archived at the NOAA National Centers for Environmental Information World Data Center for Meteorology, Asheville, North Carolina, USA and used in their database curation efforts which are being jointly developed.

Historical precipitation records are fundamental for the management of water resources, yet rainfall observations typically span 100–150 years at most, with considerable uncertainties surrounding earlier records. Here, we analyse some of the longest available precipitation records globally, for England and Wales, Scotland and Ireland. To assess the credibility of these records and extend them further back in time, we statistically reconstruct (using independent predictors) monthly precipitation series representing these regions for the period 1748–2000. By applying the Standardized Precipitation Index at 12‐month accumulations (SPI‐12) to the observed and our reconstructed series we re‐evaluate historical meteorological droughts. We find strong agreement between observed and reconstructed drought chronologies in post‐1870 records, but divergence in earlier series due to biases in early precipitation observations. Hence, the 1800s decade was less drought prone in our reconstructions relative to observations. Overall, the drought of 1834–1836 was the most intense SPI‐12 event in our reconstruction for England and Wales. Newspaper accounts and documentary sources confirm the extent of impacts across England in particular. We also identify a major, “forgotten” drought in 1765–1768 that affected the British‐Irish Isles. This was the most intense event in our reconstructions for Ireland and Scotland, and ranks first for accumulated deficits across all three regional series. Moreover, the 1765–1768 event was also the most extreme multi‐year drought across all regional series when considering 36‐month accumulations (SPI‐36). Newspaper and other sources confirm the occurrence and major socio‐economic impact of this drought, such as major rivers like the Shannon being fordable by foot. Our results provide new insights into historical droughts across the British Irish Isles. Given the importance of historical droughts for stress‐testing the resilience of water resources, droug

This paper outlines progress of the Copernicus Climate Change Service's (C3S) Global Land and Marine Observations Database service in securing data sources and introduces the data upload component. We present details of land and marine data holdings inventoried, highlighting priority needs in terms of periods, regions and Essential Climate Variables (ECVs) where additional data could bring most benefit. These holdings are being iteratively merged and integrated to best meet user needs and are served to the user via the Copernicus Climate Data Store (CDS). The secure Data Upload Server enables any data provider to share additional data and metadata with the service. We outline the process for registering as a data provider and how data sets are prioritized for integration. We encourage all data owners to share their data with the C3S service via our Data Upload Server. All unique and relevant data acquired or submitted will be also archived at the NOAA National Centers for Environmental Information World Data Center for Meteorology, Asheville, North Carolina, USA and used in their database curation efforts which are being jointly developed.

The abstract is included in the text.

The Global Land and Marine Observations Database aims to produce a comprehensive land-based meteorological data archive and inventory. This requires the compilation of available information on data from land-based meteorological stations from all known available in situ meteorological data repositories/sources at multiple timescales (e.g. sub-daily, daily, and monthly). During this process the service team members have identified that many of the data sources contain stations with incorrect location coordinates. These stations cannot be included in the processing to be served via the Copernicus Climate Change Service until the issues are satisfactorily resolved. Many of these stations are in regions of the world where a sparsity of climate data currently exists, such as Southeast Asia and South America. As such, resolving these issues would provide important additional climate data, but this is a very labour-intensive task. Therefore, we have developed the Geo-locate project – that enrols the help of undergraduate geography students at Maynooth University, Ireland – to resolve some of the landbased station geolocation issues. To date, we have run two Geo-locate projects: the first in the 2017/2018 academic year and the second in the 2018/2019 academic year. Both iterations have been very successful with 1926 of the 2168 total candidate stations ostensibly resolved, which equates to an 88 % success rate. At the same time, students have gained critical skills that helped to meet the expected pedagogical outcomes of the second-year curriculum, while producing a lasting scientific legacy. We asked the class of 2018/2019 to reflect critically upon the outcomes, and we present the results herein; these results provide important feedback on what students felt that they gained from their participation and how we may improve the experience and learning outcomes in future. We will be continuing to run Geo-locate projects over the next few years. We encourage other organizatio

Globally, few precipitation records extend to the 18th century. The England Wales Precipitation (EWP) series is a notable exception with continuous monthly records from 1766. EWP has found widespread use across diverse fields of research including trend detection, evaluation of climate model simulations, as a proxy for mid-latitude atmospheric circulation, a predictor in long-term European gridded precipitation data sets, the assessment of drought and extremes, tree-ring reconstructions and as a benchmark for other regional series. A key finding from EWP has been the multi-centennial trends towards wetter winters and drier summers. We statistically reconstruct seasonal EWP using independent, quality-assured temperature, pressure and circulation indices. Using a sleet and snow series for the UK derived by Profs. Gordon Manley and Elizabeth Shaw to examine winter reconstructions, we show that precipitation totals for pre-1870 winters are likely biased low due to gauge under-catch of snowfall and a higher incidence of snowfall during this period. When these factors are accounted for in our reconstructions, the observed trend to wetter winters in EWP is no longer evident. For summer, we find that pre-1820 precipitation totals are too high, likely due to decreasing network density and less certain data at key stations. A significant trend to drier summers is not robustly present in our reconstructions of the EWP series. While our findings are more certain for winter than summer, we highlight (a) that extreme caution should be exercised when using EWP to make inferences about multi-centennial trends, and; (b) that assessments of 18th and 19th Century winter precipitation should be aware of potential snow biases in early records. Our findings underline the importance of continual re-appraisal of established long-term climate data sets as new evidence becomes available. It is also likely that the identified biases in winter EWP have distorted many other long-term European p

A continuous 305-year (1711–2016) monthly rainfall series (IoI_1711) is created for the Island of Ireland. The post 1850 series draws on an existing quality assured rainfall network for Ireland, while pre-1850 values come from instrumental and documentary series compiled, but not published by the UK Met Office. The series is evaluated by comparison with independent long-term observations and reconstructions of precipitation, temperature and circulation indices from across the British–Irish Isles. Strong decadal consistency of IoI_1711 with other long-term observations is evident throughout the annual, boreal spring and autumn series. Annually, the most recent decade (2006–2015) is found to be the wettest in over 300 years. The winter series is probably too dry between the 1740s and 1780s, but strong consistency with other long-term observations strengthens confidence from 1790 onwards. The IoI_1711 series has remarkably wet winters during the 1730s, concurrent with a period of strong westerly airflow, glacial advance throughout Scandinavia and near unprecedented warmth in the Central England Temperature record – all consistent with a strongly positive phase of the North Atlantic Oscillation. Unusually wet summers occurred in the 1750s, consistent with proxy (tree-ring) reconstructions of summer precipitation in the region. Our analysis shows that inter-decadal variability of precipitation is much larger than previously thought, while relationships with key modes of climate variability are time-variant. The IoI_1711 series reveals statistically significant multi-centennial trends in winter (increasing) and summer (decreasing) seasonal precipitation. However, given uncertainties in the early winter record, the former finding should be regarded as tentative. The derived record, one of the longest continuous series in Europe, offers valuable insights for understanding multi-decadal and centennial rainfall variability in Ireland, and provides a firm basis for benchmarkin

Sound water policy and management rests on sound hydrometeorological and ecological data. Conversely, unrepresentative, poorly collected, or erroneously archived data introduce uncertainty regarding the magnitude, rate, and direction of environmental change, in addition to undermining confidence in decision-making processes. Unfortunately, data biases and errors can enter the information flow at various stages, starting with site selection, instrumentation, sampling/measurement procedures, postprocessing and ending with archiving systems. Techniques such as visual inspection of raw data, graphical representation, and comparison between sites, outlier, and trend detection, and referral to metadata can all help uncover spurious data. Tell-tale signs of ambiguous and/or anomalous data are highlighted using 12 carefully chosen cases drawn mainly from hydrology (‘the dirty dozen’). These include evidence of changes in site or local conditions (due to land management, river regulation, or urbanization); modifications to instrumentation or inconsistent observer behavior; mismatched or misrepresentative sampling in space and time; treatment of missing values, postprocessing and data storage errors. Also for raising awareness of pitfalls, recommendations are provided for uncovering lapses in data quality after the information has been gathered. It is noted that error detection and attribution are more problematic for very large data sets, where observation networks are automated, or when various information sources have been combined. In these cases, more holistic indicators of data integrity are needed that reflect the overall information life-cycle and application(s) of the hydrological data.

This work created a 250‐year historic drought catalogue by applying the Standardized Precipitation Index (SPI) to the Island of Ireland precipitation network (1850–2015) and a reconstructed precipitation series from 1765. Documentary sources from newspaper archives spanning the last 250 years, together with other historical sources are used to (1) add confidence to the quantitative detection of drought episodes and (2) gain insight to the socio‐economic impacts of historic droughts. The results show that Ireland is drought prone but recent decades are unrepresentative of the longer‐term drought climatology. A large decline in 30‐year accumulated SPI‐12 values is evident from around the 1990s onwards. During the years 1850–2015 seven major drought rich periods were identified with an island‐wide fingerprint in 1854–1860, 1884–1896, 1904–1912, 1921–1923, 1932–1935, 1952–1954 and 1969–1977. These events exhibit substantial diversity in terms of drought development, severity and spatial occurrence. Two exceptionally long events are found in the record: the continuous drought of 1854–1860 and the drought of 1800–1809 (in fact a series of three droughts with brief interludes). Over the last 250 years, droughts have resulted in agricultural hardship, water resource crises and failures and preceded some of the major famines of the eighteenth and nineteenth centuries. This work shows that newspaper archives can be used to trace the progression of drought events and impacts and we thus advocate their wider use in corroborating quantitative assessments. The resulting catalogue challenges prevailing perceptions about drought in Ireland while strengthening the evidence base for future drought and water resource planning across the island.

‘Irish drought’ might appear to be an oxymoron. However, the island of Ireland has been surprisingly drought prone over the last couple of centuries, but perhaps less so in living memory. We recently established a 160-year drought catalogue for the island covering the period 1850–2015 (Noone et al., 2015; Wilby et al., 2015). This was subsequently extended by Noone et al. (2017) to create a 250-year drought catalogue for Ireland (1765–2015) based on the Standardised Precipitation Index (SPI). In constructing this extended drought catalogue we used documentary sources from newspaper archives spanning the last 250 years. Together with other historical sources, these add confidence to the quantitative detection of drought episodes from rainfall records and provide glimpses into the socioeconomic impacts of historic droughts.

This paper investigates the spatial and temporal properties of persistent meteorological droughts using the homogeneous Island of Ireland Precipitation (IIP) network. Relative to a 1961–1990 baseline period it is shown that the longest observed run of below average precipitation since the 1850s lasted up to 5 years (10 half-year seasons) at sites in southeast and east Ireland, or 3 years across the network as a whole. Dry spell and wet spell length distributions were represented by a first-order Markov model which yields realistic runs of below average rainfall for individual sites and IIP series. This model shows that there is relatively high likelihood (p=0.125) of a 5-year dry spell at Dublin, and that near unbroken dry runs of 10 years or more are conceivable. We suggest that the IIP network and attendant rainfall deficit modelling provide credible data for stress testing water supply and drought plans under extreme conditions.