Climate change, as revealed by gradual changes in temperature, precipitation, atmospheric moisture, and wind intensity, as well as sea level rise and changes in the occurrence of extreme events, is already affecting cultural heritage sites. Accordingly, there is a rapidly increasing body of research reporting on the impacts of climatic stressors on cultural heritage and on the assessment of climate change impacts on cultural heritage assets. This review synthesizes the international literature on climate change impacts on tangible cultural heritage by developing hazard‐impact diagrams focusing on the impacts of gradual changes in climate on: (1) the cultural heritage exposed to the outside environment, (2) the interiors of historical buildings and their collections, and (3) a third diagram associated with climate change and the impacts due to sudden changes in the natural physical environment (e.g., storm surges, floods and landslides, wildfire) in addition to sea level rise, permafrost thawing, desertification and changes in the properties of the oceans. These diagrams, which depict the relationships between various stressors and their impacts on cultural heritage, will allow other researchers, stakeholders, and potentially decision makers to determine the potential impacts of climate change on a specific cultural heritage asset without a separate examination of the literature. This review thus provides the current state‐of‐the‐art on the impacts of climate change on the tangible, built heritage, that is, monuments, archeological sites, historical buildings, as well as their interiors and the collections they hold, highlights the limitations of previous research, and provides recommendations for further studies.This article is categorized under: Assessing Impacts of Climate Change > Evaluating Future Impacts of Climate Change

The use of inhibition chemicals holds the prospect of an efficient strategy to control crystallization in porous materials, thereby potentially contributing to the prevention or mitigation of the salt decay phenomenon in modern as well as historical building materials in a more sustainable manner. In this review, we first provide an essential background on the mechanism of salt crystallization and on the factors influencing this phenomenon; next, we illustrate the mechanism at the basis of the action of crystal growth inhibitors, and critically discuss the major advances in the development of different families of inhibitors, particularly focusing on their influence on salt transport and crystallization within the structure of porous media. Specifically, correlations between the crystallization inhibition processes in porous materials and variables, such as porous substrate composition and properties, contaminant salt type and concentrations, microclimatic conditions, inhibiting solution concentration and properties, and application methods, will be highlighted. Environmental aspects, limitations, and problems associated with some inhibition chemicals are also taken into account. Finally, a survey and a discussion on the most representative experimental techniques and instrumentation available to assess qualitatively and quantitatively the inhibitor effectiveness, as well as recently developed modelling tools are given out.

The purpose of this paper is to review the performance of the protective shelters installed over three archaeological sites in Malta over the past decade, and to draw some key lessons learnt that may be useful to others when considering whether to adopt a similar solution. The conservation threats to the Megalithic Temples of Malta are introduced and defined—these range from material issues (loss of surface) to structural issues (cracking and dislodgement of stones leading to structural instability and collapses). Causes identified specifically included fluctuating environmental conditions: wetting and drying cycles and thermal fluctuations, combined with the salt-laden Mediterranean island environment. The recognition during the late twentieth century of these issues as key factors in the deterioration of these structures, and the strategy that was developed in response, are outlined. A key component of this strategy was the installation of protective shelters over three of the main megalithic sites. The process through which the design requirements for the shelters were defined is reviewed. The performance of the shelters is then examined, through a critical review of unpublished reports and published studies. An evidence-based summary of the beneficial effects of the shelters is provided, and the possibility of any harmful effects discussed. A number of lessons learnt through this process are then identified. One key lesson is that the microenvironment in a newly-sheltered site is at a transitional stage that does not necessarily reflect longer-term trends, which therefore require long-term monitoring to be understood. The choice and number of environmental parameters to be monitored need to be informed by a careful consideration of their sustainability, both in terms of equipment and human resources. Any monitoring programme, however well-designed, needs to be open to re-evaluation and revision where needed. As more experience and data are accumulated from different sheltering projects, it will become more feasible to establish performance indicators in advance of a sheltering intervention, on the basis of which to evaluate its performance. The experience of these projects is then used to inform a checklist of key considerations for anyone considering whether to shelter an archaeological site. The foremost consideration is that every site requires a site-specific strategy tailored to its needs. The decision whether a shelter is desirable, and what its performance requirements should be, may only be taken in the context of such a strategy. This paper should help define the parameters for such a decision to take place.

The main building stone in the Maltese Islands is the Globigerina Limestone, of which the Lower member is commonly used. This occurs in two types, the durable franka and the more easily weathered soll. Two types of fresh franka (bajda -white- and safra -yellow-), as well as fresh soll stone blocks, were obtained, based on the identification by quarry owners. Their designation was confirmed by geochemistry. Physical and mechanical properties of the three were investigated, including uniaxial compressive strength, water absorption by capillarity, permeability and porosimetry. Porosimetry results confirmed outcomes of previous research work. Soll was found to have a lower overall porosity, but a high percentage of small pores with practically no large pores. Some of the tested stones were then treated with a non-toxic phospho-organic compound containing carboxylic moieties as a salt inhibitor and the corresponding non-phosphorylated compound, as aqueous solutions at different concentrations. Both treated and untreated stones were then subject to salt crystallization tests, using sodium sulphate in different concentrations. For the untreated stones, even after only one salt cycle, faster and more pronounced deterioration was observed for the soll samples as opposed to the franka ones. In the case of the treated stones, less deterioration with almost no damage was observed as opposed to non-treated ones. The presence of even very low concentrations of the inhibitor thus helps crystallization to occur on the stone surface and not within the pores. These encouraging results led to the conclusion that salt inhibitors can be used to treat salt-infested stone. Further research in this respect, also using NaCl/NaHCO3, is continuing.

Studies on original mortars can greatly assist archaeological interpretations, as elucidating the composition of such mortars gives clues on the origin of raw materials, manufacturing technology, and the construction phases of a site. This article presents the multi-analytical characterisation of 24 mortars and plasters from the Żejtun Roman Villa, Malta, to support archaeological hypotheses on the history of the construction of the site. The samples, belonging to at least three distinct phases included in the stratigraphy of the Żejtun archaeological site, were analysed using polarised light microscopy (PLM), scanning electron microscopy (SEM–EDS), X-ray diffraction (XRD), thermogravimetry (TGA/DSC), X-ray fluorescence (XRF), ion chromatography (IC), and stable isotope analysis (¹³C and ¹⁸O). The assessment of the results through correlations with archaeological evidence identifies five types of mortars with varying degrees of hydraulicity. These are associated with different development phases of the site and distinctive uses and were mainly produced using local resources, except in the Early Roman period when natural pozzolanic raw materials started being used. As there are no natural pozzolans on the Maltese Islands, it is hypothesised that the pozzolanic materials used as aggregate in the mortars were imported to the Islands from neighbouring volcanic regions. This volcanic aggregate was especially abundant in one of the mortar types, which was used mainly as a bedding mortar for floors.