For centuries, often millennia, Europe's monuments have withstood earthquakes, fire and plundering. Now cultural treasures ranging from the Colosseum to Westminster Abbey could face new threats from climate change, a new study says.
Increased rains in northern Europe could wash away layer after layer of ancient stone, while rising heat in southern and central Europe could lead age-old monuments to crack and disintegrate, says the EU-funded study by research institutes in seven European countries.
Experts have long warned that a rise in sea levels attributed to global warming threatens low-lying areas, including treasures like Venice or sites located in flood-prone regions.
But the three-year study didn't look only at the catastrophic impact of sudden storm surges, landslides and floods. It also took into account the slow erosion that Europe's cultural heritage could suffer at the hands of climate change, said Cristina Sabbioni, the study's coordinator.
"We needed to put this problem on the table, because so far it has been politically ignored," said Sabbioni, who is a physicist with Italy's National Research Council.
Climatologists, aided by chemists, geologists and biologists used projected climate data to predict up to 2099 how marble, limestone, wood and other materials commonly used in ancient buildings would fare in future weather patterns, Sabbioni said, speaking last week on the sidelines of the study's presentation in Rome.
Researchers produced a "Vulnerability Atlas" of Europe, with maps that indicate which areas will suffer an increase or decrease in various risk factors, from damage caused by salt crystals to corrosion of Medieval stained-glass windows.
According to the study, lower humidity during the summer in Britain, France, northern Spain and central Europe will increase the amount of salt deposited on fragile monuments.
This is especially dangerous for the region's Gothic cathedrals, whose elaborate carvings are made in soft porous stone which absorbs sea salt present in liquid form in the air's moisture. Once the water evaporates, the salt crystallizes and puts pressure on the surrounding stone, Sabbioni said.
"If the salt is deposited on the surface the damage is aesthetic, and this is a dramatic problem for frescoes," she said. "But if it is absorbed we have internal breakup of the material."
Less rain in southern Europe will force authorities to spend more money to clean monuments blackened by pollution, while an expected rise of precipitation in northern Europe could wash away an increasing amount of ancient stone each year.
Monuments built in marble and limestone, such as the Colosseum in Rome and the Parthenon in Athens, will also suffer due to increased temperature fluctuations which cause such materials to dangerously expand and contract, causing fractures and breakage. Central Europe, southern Spain and Greece will be the areas most affected due to the drier climate and rising temperatures, the study says.
Even more recent monuments like the iron-built Eiffel Tower, completed in 1889, could face trouble as the study predicts warm weather and pollution will increase corrosion of metals in northern Europe.
Researchers said that problems caused by rain, salt crystallization and thermal stress are already known to conservation experts. For example, the baroque facades and statues of the southern Italian town of Lecce, carved in soft stone, have long been eroded and damaged by rain, pollution and salt.
But the study indicates these threats will move to areas where they were previously unheard of, said Joseph King, an official with the International Center for the Study of the Preservation and Restoration of Cultural Property, a U.N.-backed intergovernmental organization based in Rome.
"Climate change touches a lot of things, and cultural heritage is among them," said King, a conservation expert who did not take part in the EU study. "The problems we are going to have are the same ones we have now; the difference is in the intensity and where they are going to occur."
Not all the study's predictions are negative. Glass corrosion is expected to decrease across Europe and reduced moisture will help bricks in historical buildings stay dry.
Sabbioni warned that the effects of climate change could be ultimately worse, as the climate model used for the study was a "moderately optimistic" one chosen among those used by the U.N.-sponsored Intergovernmental Panel on Climate Change. The IPCC issued a spate of reports this year, drawing on the studies of some 2,500 scientists, which predict grim consequences of global warming if swift action is not taken.
Although no specific research was done on single monuments, the maps produced by the $1.6 million "Noah's Ark" study on climate change and cultural heritage can help policymakers plan conservation efforts based on which risk factors threaten their area, Sabbioni said.
The study offers guidelines to help limit the effect of climate change on monuments, from increasing the frequency of repairs to installing barriers on buildings to reduce salt deposits.
Researchers didn't produce an estimate of the cost of climate change on cultural conservation, but the study says that, ultimately, Europe may have to accept some losses to its heritage.
"Priorities will have to be established," Sabbioni said. "We cannot hope that everything will last forever."