Overall Warming with Reduced Seasonality: Temperature Change in New England, USA, 1900–2020

The ecology, economy, and cultural heritage of New England is grounded in its seasonal climate, and this seasonality is now changing as the world warms due to human activity. This research uses temperature data from the U.S. Historical Climatology Network (USHCN) to analyze annual and seasonal temperature changes in the New England region of the United States from 1900 to 2020 at the regional and state levels. Results show four broad trends: (1) New England and each of the states (annually and seasonally) have warmed considerably between 1900 and 2020; (2) all of the states and the region as a whole show three general periods of change (warming, cooling, and then warming again); (3) the winter season is experiencing the greatest warming; and (4) the minimum temperatures are generally warming more than the average and maximum temperatures, especially since the 1980s. The average annual temperature (analyzed at the 10-year and the five-year average levels) for every state, and New England as a whole, has increased greater than 1.5 °C from 1900 to 2020. This warming is diminishing the distinctive four-season climate of New England, resulting in changes to the region’s ecology and threatening the rural economies throughout the region.

Classification of the flood severity of the Guadalquivir River in the Southwest of the Iberian Peninsula during the 13th to 19th centuries

This study estimates the pluviometric evolution between the 13th and 19th centuries on the southwestern Iberian Peninsula based on the historic records of the impacts of the Guadalquivir River flooding on the city of Seville (Spain). The main documentary source was “Critical history of the floods of the Guadalquivir in Seville”, published in 1878, which compiles news from different observers, who were contemporaries of each event. Regarding the methodology, it was necessary to transfer the information from different documentary sources to ordinal indices, which required developing allocation criteria per flood impact. From the annual assigned flood index, an interannual series was generated. Moreover, for the last decades of the 21st century, quantifying the flooding levels in the records allowed us to relate them directly to instrumental records of rainfall and establish a relationship between these two phenomena. Through interannual weighing of the flooding indices, it was possible to deduce the durations and intensities of sequences of rainy periods between 1250 and 1850. This allowed us to reconstruct the pluviometric evolution. Of the ten floods classified as most destructive during the five centuries analysed, i.e., from 1280 to 1880, five occurred during little more than a century (1598-1701). The obtained results contribute to knowledge on regional rainfall, as well as to historical climatology and hydrology, over multiple centuries.

Similarity assessment and adjustment of integrated temperature databases. Cuyo region, Argentina

Given the frequent spatial-temporal limitations and deficiencies of instrumental meteorological records, the use of alternative information sources, such as integrated databases, are important for analyses and studies of diverse nature. The research aim was to evaluate the accuracy of integrated databases of monthly temperature, belonging to Climate Research Unit, University of Delaware and Global Historical Climatology Network, gridded with a pixel size of 3,098.01 km2 (0.5º x 0.5º), surface area of 151,802.5 km2 and temporary length of 22 years (1993-2014), through the modified structural similarity index (mSSIM). The study area is located in central-western Argentina (between 30º and 35º S, and 71º and 66º W). The University of Delaware grid showed the best fit of the data series from 10 weather stations located in the study area. Therefore, a proposal was presented to increase similarity indices, especially for those cells without instrumental reference information. The study determined that by applying this modification, the gridded datasets increases the similarity of the measured data, especially in mountainous areas, where originally there were differences of more than 7.5 ºC between the gridded data and observed one. The proposal decreases these differences to average values below 1 ºC. The use and subsequent adjustment of these integrated databases, allows access to information in areas without meteorological records.

SC-Earth: A Station-based Serially Complete Earth Dataset from 1950 to 2019

Meteorological data from ground stations suffer from temporal discontinuities caused by missing values and short measurement periods. Gap filling and reconstruction techniques have proven to be effective in producing serially complete station datasets (SCDs) that are used for a myriad of meteorological applications (e.g., developing gridded meteorological datasets and validating models). To our knowledge, all SCDs are developed at regional scales. In this study, we developed the serially complete Earth (SC-Earth) dataset, which provides daily precipitation, mean temperature, temperature range, dew-point temperature, and wind speed data from 1950 to 2019. SC-Earth utilizes raw station data from the Global Historical Climatology Network-Daily (GHCN-D) and the Global Surface Summary of the Day (GSOD). A unified station repository is generated based on GHCN-D and GSOD after station merging and strict quality control. ERA5 is optimally matched with station data considering the time shift issue and then used to assist the global gap filling. SC-Earth is generated by merging estimates from 15 strategies based on quantile mapping, spatial interpolation, machine learning, and multi-strategy merging. The final estimates are bias corrected using a combination of quantile mapping and quantile delta mapping. Comprehensive validation demonstrates that SC-Earth has high accuracy around the globe, with degraded quality in the tropics and oceanic islands due to sparse station networks, strong spatial precipitation gradients, and degraded ERA5 estimates. Meanwhile, SC-Earth inherits potential limitations such as inhomogeneity and precipitation undercatch from raw station data, which may affect its application in some cases. Overall, the high-quality and high-density SC-Earth dataset will benefit research in fields of hydrology, ecology, meteorology, and climate.

The risk is in the detail: historical cartography and a hermeneutic analysis of historical floods in the city of Murcia

The study of historical floods is a growing research trend that has generated numerous methodologies that aim to convert the qualitative historical documentation into quantitative information. This codification process aims to make comparable in time and space the manner in which past societies adapted to floods, and so extract the positive or negative points that can help reduce vulnerability and increase the resilience of current societies. However, the diversity of cultural and historical contexts, as well as the spatial-temporal heterogeneity of documentary sources, makes it difficult to extrapolate quantitative methods in historical climatology. This situation means that interpretative analyses of texts are still necessary as a complement to quantitative studies. In this paper, we make a hermeneutic analysis of the three most catastrophic floods that have occurred in the city of Murcia (south-eastern Spain) in the last 400 years. We complete this analysis with a historical cartographic reconstruction of a quantitative nature. Among the main conclusions, we highlight the fact that the society of Murcia had strategies to overcome catastrophes that included the whole of society and an integrated emergency management. However, the state of poverty of privation prior to a flood is a determining factor in explaining the resilience of a social system. A large increase in exposure of flood-prone areas over the past two centuries is noteworthy but unsurprising. However, it is surprising that the percentage of urban area exposed to flooding is now smaller than in the past. Therefore, if we consider hazard avoidance as a form of management, we can say that pre-industrial Murcian society was less efficient in using the mechanisms available to adapt to flooding.

Does CMIP6 better constrain projections of 21st century Antarctic sea ice loss?

<p>Results from CMIP5 have previously suggested that ensemble regression techniques or model selection may provide solutions to the challenge of making projections of future Antarctic sea ice area (SIA) in the presence of large historical biases. Here, we revisit and extend such analysis incorporating the CMIP6 ensemble, which shows modest improvements in some aspects of sea ice simulation and in particular a reduction of inter-model spread in historical SIA. We focus on the strongest forcing scenarios analysed, CMIP5 RCP85 and CMIP6 SSP5.85.</p><p>In summer (February) the historical climatology of SIA is a strong linear constraint on projections of SIA in both generations. This is because the strong forcing leads to the loss of the majority of summer SIA in each model, so that the models that start with greater SIA exhibit greater reductions. Differences between CMIP5 and CMIP6 are largely explained by the fact that, compared to CMIP6, CMIP5 contains many more models that have very large positive biases in historical SIA and do not lose the majority of ice.</p><p>In winter (September), a much smaller proportion of SIA is lost, but inter-model spread in SIA climatology still explains just under half the variance in projections of SIA change, in both CMIP5 and CMIP6. The mean historical winter climatology is similar between generations, as is the regression slope of SIA change against SIA climatology.  However, there is a greater reduction of SIA in CMIP6 than CMIP5. We find this to be statistically related to greater global mean warming in CMIP6 than CMIP5, and therefore potentially to the larger climate sensitivity in the CMIP6 ensemble.</p><p>These findings imply that, depending on season, a different balance of local (SIA climatology) and global (GMST change) drivers can be used to explain the inter-model and inter-generation spread in projections of SIA loss. They also firmly tie our ability to project Antarctic SIA loss to our understanding of the fidelity of higher CMIP6 climate sensitivity. Questions remain about whether models are correct in their simulation of Antarctic SIA sensitivity to global surface temperature.</p>

Droughts in Bern and Rouen from the 14th to the beginning of the 18th century derived from documentary evidence

Droughts derive from a precipitation deficit and can also be temperature driven. They are dangerous natural hazards for human societies. Documentary data from the pre-modern and early modern times contain direct and indirect information on precipitation that allow for the production of reconstructions using historical climatology methods. For this study, two drought indices – the drought index of Bern (DIB) and the drought index of Rouen (DIR) – have been created on the basis of documentary data produced in Bern, Switzerland, and Rouen, France, respectively for the period from 1315 to 1715. These two indices have been compared to a third supra-regional drought index (SDI) for Switzerland, Germany, France, the Netherlands, and Belgium that was synthesised from precipitation reconstruction based on historical climatology. The results of this study show that the documentary data from Bern mainly contain summer droughts, whereas the data from Rouen rather allow for the reconstruction of spring droughts. The comparison of the three above-mentioned indices shows that the DIB and the DIR most probably do not contain all of the actual drought events; however, they detect droughts that do not appear in the SDI. This fact suggests that more documentary data from single locations, such as historical city archives, should be examined in the future and should be added to larger reconstructions in order to obtain more complete drought reconstructions.

New documentary data on the climate in Southern Spain from 1792 to 1808

This work presents a new source of documentary data on the Spanish climate from 1792 to 1808 coming from the periodical Correo Mercantil de España y sus Indias, in which weekly summaries of Spanish weather conditions were published. The potential of this data source for historical climatology studies is analysed, focusing on information related to the south of the Iberian Peninsula.