As the true impact of anthropogenic global warming sets in, the need for vigilance among the world’s coastal cities grows. A UNESCO World Heritage Site and home to over 250,000 residents, Venice, Italy knows this more than most.
“When you are this close to the upper limit of the tidal range, any meteorological event can be hazardous and cause an extreme flood. Small increases can have a large impact,” explained Piero Lionello, a researcher at the Università del Salento.
Lionello and a group of international researchers have just published a review of the threats Venice faces in a special issue of Natural Hazards and Earth System Sciences. They focus on three key areas – relative sea level rise, the occurrence of extreme water heights, and the prediction of extreme water heights and floods.
Relative sea level rise in the region surrounding Venice can be hard to estimate, with forecasts ranging from 17 to 120 centimeters by the end of the century.
“There are important feedbacks in the climate system, for instance related to polar ice sheet dynamics, that we need to understand and better simulate to make more reliable projections,” explained study co-author Davide Zanchettin.
Fighting back against extreme water heights is dependent on accurate forecasts. For nearly a year, Venice has been protected by the Modulo Sperimentale Elettromeccanico, or MoSE, a series of barriers and gates located at several key inlets to the lagoon. These gates are opened or closed four to six hours ahead of the tidal maximum.
“The MoSE system will be operated on the forecast,” said study co-author Georg Umgiesser. “If the forecast is wrong, the operation of the MoSE becomes wrong – and that is very important both economically and ecologically.”
According to Lionello, we could stop global warming completely by stopping the use of fossil fuels and the sea level would continue to rise in spite of this, though at a much reduced pace.
Given that this goal seems to be a decade or so off, he warns: “the present evidence is that we will need to change our adaptation strategies. It’s clear that we need to be prepared to act.”