Tropical nights on the Spanish Mediterranean coast 1950-2014

The increase in the number of tropical nights (TN; minimum temperature double dagger 20 degrees C) constitutes important evidence of the global warming process throughout the Mediterranean region. A significant increase in the number of these events has been recorded since the second half of the 20th century. From the meteorological observations in the period 1950-2014 in the regions of Valencia and Murcia, in the central sector of the Spanish Mediterranean coast, we analyse the evolution of the number of tropical nights, the length of the episodes and their frequency. Our results indicate that the study regions experienced a significant increase in tropical nights within the last 3 decades due to climate change and the increase in sea surface temperatures (SST) in the central Western Mediterranean. We also discuss the relationship of the number of tropical nights with the increase in the Mediterranean Sea surface temperatures in the neighbouring sectors, as well as the possible implications of the combined effects of this with the urban heat island effect. Tropical nights are a cause of thermal discomfort, and thus there is a need to adapt buildings and manage urban planning to ameliorate this, and to be prepared for more frequent events in the future.