| Protecting heritage in a changing climate
In August 2002, the historic city of Prague was devastated by a catastrophic flood. Old theatres, libraries, churches, museums and synagogues suffered around 80 million euros worth of damage. In the same year, the attic wall of the Cloth Hall, a World Heritage Site in Cracow, Poland, was partially destroyed by a severe storm. Protectors of Europe’s cultural heritage may be feeling uneasy. Such extreme weather conditions are set to increase, if global climate change goes as predicted. And with a future of warmer, wetter weather, the slow deterioration of stone, clay and wood that heritage organisations spend millions battling against might also be about to get worse.
|Salt and moisture damage to a wall painting in Klodzko, Poland, as a result of floods in 1997.|
The NOAH’S ARK project is addressing these issues for the first time, by studying exactly how predicted scenarios of climate change translate into conditions that damage the built environment. It aims to highlight areas of Europe where cultural heritage is likely to suffer most, and to offer mitigation strategies specific to different materials and structures.
The three-year project began in 2004. It brings world-class climatologists together with specialists in the protection and conservation of cultural heritage. There are ten partners: research institutes from Italy, Sweden, Poland, the Czech Republic, Spain and Norway; two British universities; an insurance company specialising in churches and historic buildings and a small environmental assessment company from Spain.
The partners have spent the first year of the project engaged in a vast number-crunching exercise, persuading the Hadley Centre climate models reported by the Intergovernmental Panel on Climate Change (IPCC) to provide information that is relevant to the effects of weather on buildings and monuments. “When we started this project, we expected to be able to extract the important variables from the Hadley models easily, for different parts of Europe,” explains project coordinator Cristina Sabbioni, of the National Research Council’s Institute of Atmospheric Sciences and Climate in Bologna, Italy. “But instead we needed a completely new climatological perspective. This meant a lot of work.” For example it is not the absolute temperature that affects masonry, but the range of temperatures, and the time period over which that range occurs. Rapid cycles of freeze and thaw damage buildings. Similarly, from the point of view of archaeological remains or cultural artworks, what’s important about heavy rain is how hot and dry the weather is afterwards, because it is the drying out process that is damaging.
The partners have now generated the crucial variables, which include relative humidity, the number of days with high wind speed, and predictions of heavy rainfall and storm events for three time periods: the present (1961-1990), the near future (2010-2039) and the far future (2070-2099). These databases will form the basis of a vulnerability atlas of Europe, showing areas where changes in conditions will pose a threat to cultural heritage.
The team are also modelling future levels of air pollution, long understood to impact on buildings and monuments. Some pollutants, such as sulphur dioxide, are decreasing as a result of effective mitigation strategies. But particulates are escalating. Crucially, particulates with high organic and nutrient content may increase. Combined with changes in temperature and rainfall, this could alter the way biological communities of lichens, bacteria and fungi on the surface of buildings and stoneworks interact with their substrate, a process known as biodeterioration. The two Spanish partners are specialists in this field.
|Attic wall of the Cloth Hall, a World Heritage Site in Cracow, Poland, destroyed by a storm in 2002.|
The project will determine on how different materials are affected by different conditions in future climate scenarios. Wood, for example is highly affected by thermal or humidity shock. Clay based materials suffer from changes in moisture content, whilst metals like iron, steel and bronze are vulnerable to corrosion. How will the Eiffel Tower be bearing up in 2099? Estimates of damage will be translated into risk maps, showing the type of risk that is most prevalent in each region.
In assessing how to adapt to climate change, the team will concentrate on two particular areas of concern. First, they will study the effects of drying out on buildings in different parts of Europe. One of Poland’s World Heritage designated medieval wooden churches, at Debno, will form one of the case studies. Secondly, they will study the effect of high wind velocities on buildings. Mathematical models of how winds create pressure differentials in buildings of different shapes will help to assess which buildings might be vulnerable to damage.
The outcome of all this research will be a set of mitigation and adaptation guidelines, targeted by monument type and building material, which will be made available for public use at the end of the project in 2007.
“What our project reveals is how much work there is to be done on the impact of climate change on cultural heritage” insisted Sabbioni. She hopes NOAH’S ARK is building the foundations for future research. “Cultural heritage is part of our identity in Europe, and must be preserved in the future. There has been a huge amount of research on the deterioration of buildings and materials in the present and in the past, but there will be serious new challenges in the future. We have a duty to arm conservators with the information they need to face them.”