31

The rise of the sea level coupled with present day global warming put Venice at risk. It is necessary to improve our knowledge of the past history of the sea level rise, since the Little Ice Age, to establish better mitigation remedies. In general, paintings provide a qualitative image, but in the case of Venice, a quantitative evaluation of the apparent sea level rise (ASLR) is possible thanks to accurate paintings by Canaletto and Bellotto, with the help of the camera obscura. The paintings accurately present a high level of detail, including the algae belt. A methodology is discussed to assess the accuracy of paintings and how to distinguish a replica from originals. From the analysis of these paintings, compared with the algae level today, we can extend our knowledge about Venice submersion back in history for almost three centuries. Since Canaletto’€™s time, i.e. the first half of the eighteenth century, the ASLR=61 ±11 cm. In this period the average submersion rate of the city was .1.9 mm yr1. About half of the ASLR is due to land subsidence, the other to thermal expansion of oceanic water. A painting by Veronese, “The Presentation of the Family Coccina to the Virgin”€, gives us a unique opportunity to know the sea level in 1571. In the Coccina Palace, the number of steps clear of algae compared with the current situation gives ASLR =82 ±9 cm. In the period of time elapsed between Veronese and Canaletto, i.e. from 1571 to the first half of the eighteenth century, the average submersion rate of the city was 1.2 mm year, mostly due to land subsidence.