The rising temperature of the Planet results in increasing changes and impacts on Earth and particularly in urban areas, putting people’s lives at risk with increasingly intense and frequent floods, heat waves, prolonged periods of drought, high winds and causing damage to infrastructure, public spaces and buildings.
The heat
Rome has seen significant changes in recent years in terms of rising temperatures and changes in precipitation patterns.
Istat data show a rising temperature trend between 1971 and 2021, with the highest values recorded in the last decade.
Climate stripes: the colors of global warming in Rome
Climate stripes are a graphic depiction of the changing climate invented by scientist Ed Hawkins of the University of Reading. The stripes for Rome, developed by CMCC with advanced high-resolution climate models, represent for each year the difference between the annual surface atmospheric temperature and the average value of the same temperature calculated over the period 1981-2010 in the City of Rome. If the stripes are red it means we are above the average value for the period 1981-2010 (warmer than average), if they are blue we are below average.
Rome, even the capital of heat
In Rome, the increase in heat is more pronounced than in all other Italian regional capitals: the average temperature for the 2011-2021 period marks higher values over Rome (17.7°C), averaging +1.7°C over the 1981-2010 period, respectively.
In particular, the number of summer days (i.e., those with maximum temperatures greater than 25 degrees) and tropical nights (with temperatures not falling below 20 degrees) are on the rise, which were 20 more and 24 more in 2021 than in the 1981-2010 period, respectively.
The capital also leads among Italian cities for the highest anomaly with respect to the indicator duration of heat periods (heat waves) in 2021, with +40 days compared to the 1981-2010 period. And, in parallel, the number of days with frost (-9) in the same time frame has decreased.
The urban heat island effect
Urban heat islands occur when temperatures in cities are significantly higher than in surrounding green and agricultural areas. This effect is caused by building density, the presence of impermeable surfaces such as asphalt and concrete, sparse vegetation, and heat accumulation in buildings.
The map shows in dark red areas with higher density of buildings, little greenery, and soil sealing with asphalt surfaces where there is a more significant urban heat island effect that can lead to temperatures more than five degrees higher than in the areas in blue in the map.
More abnormal heat, more urban ailments and risks
Epidemiological surveys (i.e., investigations into the frequency with which diseases occur and the conditions that promote or hinder their development), on the other hand, highlight the consequences of exposure to conditions of high temperatures and heat waves, with effects on mortality among the oldest and most vulnerable people.
In addition, the cross-referencing of statistical analysis with urban mapping highlights with increasing clarity the areas of the city and neighborhoods where major impacts that put people, buildings, and infrastructure at risk are most frequently encountered.
The rains
Rainfall patterns are also changing, with rainy years alternating with low rainfall years, the lengthening of rainfall-free days and, at the same time, the intensity of rainfall on some days.
The total annual precipitation averaged 807 millimeters during 1971-2000, then decreased to 783 during 2011-2021. 2017 and 2020 were the least rainy years with 527 mm and 601 mm, respectively, while 2014 was the rainiest year with 1,116 mm.
A comparison between the year 2021 and the average of the period 1981-2010, shows that days with very heavy rainfall (greater than 20 millimeters) increase by 4 days, while the rainfall indicator on very rainy days (which measures the concentration of the phenomenon) is in Rome equal to +47mm compared to the average of the period 1981-2010, demonstrating how rain is increasingly concentrated on very rainy days, with negative consequences of management of the phenomena.
Inconvenience and damage to the city caused by water
Rome is also the municipality in Italy that according to statistics is suffering the most from the impacts related to the increased frequency and intensity of floods and heavy rains.
The consequence can be seen in the flooding from heavy rains that periodically block underpasses, regional trains, and surface public transport and that stop traffic in underpasses and streets, with civil defense interventions to secure places and people. And also in the increasingly frequent days with high winds, as well as tornadoes and storm surges on the coastal shoreline.
