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CLIMATE CHANGE AND IMPACT ON BUILT ENVIRONMENT:
URBAN HEAT ISLAND AND PLUVIAL FLOODING
CLIMATE CHANGE
AND EXTREMES
METEOROLOGICAL EVENTS
GLOBAL CLIMATE CHANGE: DEFINITIONS
The term climate change refers to a change in the state of the climate that can be identified (for example, by
using statistical tests) by changes in the average values and / or by the variability of its properties, and that
persists for an extended period, typically decades or more.
Climate change may be due to natural internal processes or external forcing, such as changes in solar cycles,
volcanic eruptions and anthropogenic actions persistent varying the composition of the atmosphere or land use
[IPCC, 2014].
The Framework Convention on Climate Change of the United Nations (art.1) defines climate change as a
change "is attributed directly or indirectly to human activity that alters the composition of the global atmosphere
and which is in addition to natural climate variability observed comparable time periods"[UNFCCC, 1992].
The UNFCCC makes a distinction between climate change caused by human ability to change the composition
of the atmosphere, and climate variability attributable to natural causes.
GLOBAL CLIMATE CHANGE: IPCC SCENARIOS
GLOBAL CLIMATE CHANGE:
IPCC scenarios
The surface temperature is
likely to rise during the 21st
century in all the evaluated
emission scenarios
It is very likely that heat
waves will occur more often
and last longer, and that
extreme
precipitation
events will become more
intense and frequent in many
regions.
The ocean will continue to
warm and acidify, and the
average global sea level to
rise.
Projected changes in the climate system [IPCC, 2014b]
METEO-CLIMATIC VARIABLES AND EXTREME METEOROLOGICAL
EVENTS
METEO-CLIMATIC
VARIABLES AND EXTREME
METEOROLOGICAL EVENTS
Extremes
meteorological
events
Meteo-climatic
variables
Observed changes
(since 1950)
Probable impacts on
built environment and
population
Temperature
Reduction of days and cold
nights and great increase of
days and warm nights on a
global scale. Increased
periods of heat over large
regions.
Drought, erosion,
desertification, morbidity and
mortality, increases in
energy demand
Heavy rainfall
Precipitation
Significant increases in
intense precipitation events
(over the 95th percentile) at
the regional and sub-regional.
Flooding, landslides,
mudslides, mortality
Cyclones, tornadoes,
hurricanes
Winds
There were no relevant
changes for lack of evidence.
Damage to infrastructure and
public assets, mortality
Heatwaves
METEO-CLIMATIC VARIABLES AND EXTREME
METEO-CLIMATIC METEOROLOGICAL EVENTS
VARIABLES AND EXTREME
METEOROLOGICAL EVENTS
Heatwave
Heatwave is an Extreme Heat Event; EHEs conditions are defined by summertime weather that is
substantially hotter and/or more humid than average for a location at that time of year (US EPA, 2006). Is
an extended period of hot weather, which may be accompanied by high humidity, relative to the expected
conditions, of the area at that time of year.
The WMO didn’t expressed a standard definition of the phenomenon: in Italy (2003 heatwave) the heat wave
dangerous to human health is "a period of at least three consecutive days with maximum air temperature
above 30° C" (Greco, Biggeri et al. 2006).
Heavy rainfall
Is an “hazardous meteorological phenomenon, of varying but short duration (minutes, hours, days to a couple
of weeks) and of varying geographical extent, with risk of causing major damage, serious social disruption and
loss of human life, requiring measures for minimizing loss, mitigation and avoidance, and requiring
detailed information about the phenomenon (location, area or region affected, time, duration, intensity and
evolution) to be distributed as soon as possible to the responsible authorities and to the public” (WMO, 2004). Is
defined like rainfall/snowfall greater than or equal to 50 mm in past 24 hours (WMO-SWIC, 2015).
These events are meteorological events of small-scale
or short-term weather conditions, that may become an
hazard for built environment and population [C40, 2015].
CITY CLIMATE HAZARDS
CITY
CLIMATE
HAZARDS
City climate hazard taxonomy
[C40, 2015]
Precipitation
Wind
Meteorological
Lightning
Fog
Extreme temperature - cold
Extreme temperature - hot
Climatological
Water scarcity
Drought
Wild fire
Forest fire
Land fire
Flood
Hydrological
Rain storm
Heavy snow
Severe wind
Tornado
Cyclone (hurricane/typhoon)
Tropical storm
Electrical storm
Fog
Extreme winter conditions
Cold wave
Extreme cold weather
Heatwave
Extreme hot weather
Wave action
Chemical change
Mass movement
Geophysical
Hazard group
Lightning/thunderstorm, derecho
Ice, hail, freezing rain, debris avalanche
Cold snap, frost
Cold days
Lack of precipitation and seasonal melt (snow,
glacial)
Bush fire, grass fire, pasture fire, scrub fire
Landslide
Avalanche
Rockfall
Lahar, mud flow, debris flow
Debris avalanche, snow avalanche
Insects and microorganisms
Vector-borne disease
Hazard
City climate hazard
Air-borne disease
Insect infestation
Chemical change
Wave action
Wild fire
Water scarcity
Drought
Subsidence
Landslide
Hot days
Glacial lake outburst
Subsidence
Insects and micro-organisms
Flood
Flash/surface flood
River flood
Coastal flood
Groundwater flood
Storm surge
Salt water intrusion
Ocean acidification
Water-borne disease
Biological
Monsoon
Snowstorm/blizzard
Dust storm/sandstorm
Extratropical cyclone
Waterlogging
Seiche
Sudden subsidence (sinkhole), logn-lasting
subsidence
E.g. cholera, typhoid, legionnaires’ disease
E.g. malaria, dengue fever, yellow fever, west nile
virus, bubonic plague
E.g. pneumonic plague, influenza
E.g. pine beetles, killer bees, termites
Rockfall
Avalanche
Subsidence
Landslide
Subsidence
Landslide
Insects and micro-organisms
Flood
Chemical change
Flood
Extreme temperature – hot
Flood
Related natural hazards
CLIMATE – RELATED HAZARDS
CLIMATERELATED
HAZARDS
Extreme events are often but not always associated with disaster. This association will depend on the particular
physical, geographic, and social conditions that prevail. Non-extreme physical events also can and do lead to
disasters where physical or societal conditions foster such a result. [IPCC, 2012].
Hazard may overlap and trigger different phenomena of high magnitude associated with the conditions of
vulnerability, exposure and sensitivity of the exposed elements [Pescaroli, 2015].
The two hazards of heatwave and heavy rainfall can lead to secondary, but not less important, phenomena
through a cascading relationship (related natural hazards) [C40, 2015], generating multiple direct and indirect
effects. At such weather natural events must be added the anthropic contribution and the characteristics of
the built environment, that can generate at the urban level phenomena such as the UHI and pluvial flooding.
The risks deriving by climate change are the result of
interaction between climate-related hazards and exposure
and vulnerability characteristics of natural systems and
human affected, that produce different impacts on the built
environment and population.
CLIMATE – RELATED IMPACTS
CLIMATERELATED
IMPACTS
Climate-related impacts referred generally to effects on people, buildings, health, ecosystems, facilities,
infrastructures, livelihoods, economic, social and cultural resources due to interaction between climate
change and hazardous climatic events that occurred within a specific period of time and to vulnerability of
society
In the 5th Report of the IPCC - WGII, the term impact is mainly used to refer to the effects of extreme weather
events and of climate change on natural and human systems.
The impacts of climate change on geophysical systems, including floods, droughts and rising sea levels, are a
subset of impacts called physical impacts [IPCC, 2014a].
RISK OF CLIMATE – RELATED IMPACTS
RISK OF
CLIMATE-RELATED
IMPACTS
Interaction of climate-related hazards with the vulnerability and exposure of human and natural systems
[IPCC, 2014a]
Hazard
:The potential occurrence of a natural or humaninduced physical event or trend or physical
impact that may cause loss of life, injury, or other
health impacts, as well as damage and loss to
property, infrastructure, livelihoods, service
provision, ecosystems, and environmental
resources. In this report, the term hazard usually
refers to climate-related physical events or
trends or their physical impacts [IPCC, 2014a].
Vulnerability
The propensity or predisposition to be adversely
affected. Vulnerability encompasses a variety of
concepts and elements including sensitivity or
susceptibility to harm and lack of capacity to
cope and adapt. In the field of disaster risk, this
includes the characteristics of a person or group
that influences their capacity to anticipate, cope
with, resist, and recover from the adverse effects
of physical events [IPCC, 2014a].
Exposure
The presence of people, livelihoods, species or
ecosystems, environmental functions, services,
and resources, infrastructure, or economic,
social, or cultural assets in places and settings
that could be adversely affected [IPCC, 2014a].
Risk refers to potential for consequences where something of value is at stake and
where the outcome is uncertain, recognizing the diversity of values. Risk is often
represented as probability of occurrence of hazardous events or trends multiplied by
the impacts if these events or trends occur. Risk results from the interaction of
vulnerability, exposure, and hazard [IPCC, 2014a].
CLIMATE VARIABILITY IN EURO – MEDITERRINEAN AREA
CLIMATE VARIABILITY IN
EURO-MEDITERRANEAN
AREA
Projected change in Mediterranean climate over the Euro-Mediterranean domain
[Alessandri et al., 2014]
Euro-mediterranean area
climate-change hot spot
particularly sensitive area
to climate changes
[Giorgi, 2006]
The emerging trends expect that the
MED zone expands into other warm
temperate climates (WarmTemp to MED)
which will experience a greater wintersummer difference in rainfall in
accordance with the typical MED
seasonality.
Moreover, there was a reduction in
average precipitation in summer and
winter and an increase in average
summer temperatures especially in
southern Italy, where the transition to the
arid climate is increasingly evident
[Alessandri et al., 2014]. In addition to
changes in the average values, the
increase of the maximum values it may
increase the probability of occurrence of
extreme events [Castellari, Venturini et
al., 2014].
CLIMATE VARIABILITY IN EURO – MEDITERRANEAN AREA
CLIMATE VARIABILITY IN
EURO-MEDITERRANEAN
AREA
Atlantico: accresciuto rischio di erosioni e alluvioni
costiere, stress dei sistemi biologici marini e perdita
degli habitat; aumento della pressione turistica sulle
coste; grandi aumenti nel rischio di tempeste invernali
e vulnerabilità dei trasporti ai venti.
Boreale: eutrofizzazione di laghi e zone umide,
aumento delle alluvioni e dell’erosione costiera,
aumento del rischio di tempeste invernali; riduzione
della stagione turistica.
Tundra: scioglimento del permafrost; diminuzione
della tundra; aumento dell’erosione costiera e delle
alluvioni.
Centrale: aumento in frequenza e intensità delle
alluvioni estive; aumento della variabilità dei raccolti;
aumento di problemi sanitari da ondate di calore;
gravi incendi nelle aree a torba drenate.
Montagne: scomparsa dei ghiacciai; riduzione del
periodo di copertura nevosa, spostamento verso l’alto
del limite della vegetazione arborea; severe perdite
della biodiversità, riduzione della stagione sciistica;
aumento delle frane.
Mediterraneo: reduction in the availability of
water; increased drought; severe loss of
biodiversity; increase in forest fires; reduction of
summer tourism; reduction of suitable areas for
cultivation; increased summer energy demand;
reduction in the production of hydroelectric
power; increased loss of land deltas and
estuaries; increased salinity and eutrophication
of coastal waters; increase in heat waves.
Steppa: diminuzione dei raccolti agricoli; aumento
dell’erosione dei suoli; aumento del livello del mare
nel caso di oscillazione nordatlantica; aumento della
salinità delle aree interne.
Expected impacts of climate change during the 21st century in the main European biogeographic regions [LIMES, 2007]
INTERNATIONAL POLICIES ON ENERGY AND CLIMATE CHANGE
INTERNATIONAL POLICIES
ON ENERGY AND CLIMATE
- Green Paper (2007)
and White Paper (2009) on the Adaptation: strategies to strengthen the
CHANGE
resilience of territories
- European Adaptation Strategy (2013): planning guidelines for adaptation and mitigation and their
local spread
- Climate Energy Package 20-20-20 (2009): -20% Co2 emissions compared to 1990; +20%
renewable energy; +20% improving energy efficiency
-Paris Conference on Climate (2015): 195 countries; universal and legally binding agreement on
climate (keeping the increase in global average temperature below 2°)
- Elements for a National Adaptation Strategy to Climate Change (2013)
- Report on the State of scientific knowledge on Impacts, Vulnerability and Adaptation to
Climate Change (2014)
URBAN
CLIMATE
CHANGE
URBAN CLIMATE CHANGE
URBAN
“Before human development
began
CLIMATE
disturbing natural habitats, soil and
CHANGE
vegetation constituted part of a balanced
ecosystem that managed precipitation and
solar energy effectively. In natural areas,
much of the rainwater infiltrates into the
ground or is returned to the atmosphere via
evapotranspiration,
thus
absorbing
rainwater and performing a cooling function
for excess solar loads” [Getter e Rowe,
2006].
In Italy urban settlements are home to over
90% of the population [Filpa, 2013]: this
action of expansion and construction of the
city by man has been a disturbing factor for
the natural system, with a changes in the
emission characteristics of surfaces (Urban
Heat Island) and in the hydrological
system, with an increase in the volume of
water runoff (pluvial flooding).
In relation to the extreme heat and
precipitation events, these phenomena
constitute aggravating factors.
URBAN CLIMATE CHANGE
URBAN
CLIMATE
CHANGE
40
50
60 70
80 90 100 110
Temperature (F)
Urban Heat Island
Is defined as a temperature difference
between an urban area (warmer) and
the surrounding rural areas (cooler).
It is the result of the interaction between
urban structure and environmentalclimatic components, or between solar
radiation
and
urban
physical
characteristics (geometry, dimensions,
materials, colors, vegetation).
Mapping the temperature of the air of a
city with isotherms, the city center with
higher temperatures, appears a '"island"
in the sea of surrounding rural areas,
characterized by lower temperatures. In
general, the urban areas characterized
by high population and building density
represent the "peaks" of the island in the
mapping of isotherms, while the surfaces
are characterized by water or by
vegetation, are, on the contrary,
characterized from lower intensity [Oke,
1982].
Atlanta, Urban Daytime Thermal View of the Heat Island, 1998 [NASA, 2010]
URBAN CLIMATE CHANGE
Urban Heat Island
It can be distinguish two main type of UHI
[Oke, 1995]:
Surface Urban Heat Island (SUHI)
Thermal gradient that occurs between a
urban surface exposed to solar radiation
and a shaded area or characterized by
higher humidity, such as a lawn.
Atmospheric Urban Heat Island (AUHI)
Thermal gradient between temperature of
the air of an urban area and that of a near
rural area. It is divided in:
- Canopy Layer Urban Heat Island
(CLUHI); heat island layer of urban
cover, relative to air closest to the
surfaces, below of the average height
of the buildings;
- Boundary Layer Urban Heat Island
(BLUHI); relative to air in the layer
above the average height of the
buildings and trees, up to the portion in
which the urban conformation not
influence more the atmospheric
characteristics.
Climatic analysis levels [Voogt, 2006]
URBAN CLIMATE CHANGE
URBAN
CLIMATE
CHANGE
The urban factors that influence Urban Heat Island are:
CITY FORM
Settlement factors
- Location and weather conditions
- Topography
- Population density
- Building density
- Urban shape and frame (Rugosity, Urban Canyons reduce Sky View Factor and increase surface area and
multiple reflection)
Surfaces characteristics
- Impermeable surfaces increase waterproofing
- Absence of trees, shrubs
- Loss of land evapotranspiration
-Albedo, emissivity, surface temperature, rugosity
Thermal properties of materials
- Building envelope (U-value, Φ, Fa)
CITY FUNCTION/ANTHROPIC ACTIONS
 High energy consumption
 Pollution
URBAN CLIMATE CHANGE
Pluvial flooding
URBAN
CLIMATE
CHANGE
Is caused when precipitation ponds or
flows over the ground before it enters
a natural or man-made drainage
system or watercourse, or when it
cannot enter the drainage system
because the system is already full to
capacity [SEPA, 2015].
Pluvial flooding occurs when rainfall that
is usually converted into run-off, which
can be evacuated by the drainage
system, remains on impermeable
surfaces and flows overland or into local
depressions and topographic lows to
create temporary ponds.
This is usually associated with shortduration storms (of up to three hours)
and with rainfalls > 20–25 mm/hour.
It can also occur following lower
intensity rainfalls (~ 10 mm/hour)
over longer periods, especially if the
ground surface is impermeable by
being developed, saturated or frozen
[Houston et al., 2011].
Glasgow, National Pluvial Flood Map for Scotland , 2011 [Lardet at al., 2010]
URBAN CLIMATE CHANGE
URBAN
CLIMATE
CHANGE
Pluvial flooding
The urban factors that characterize pluvial flooding or can influence the severity of pluvial flooding are (Falconer,
2009; Houston et al., 2011):
Infrastructural factors
- Road or rail embankments can be barriers to surface flow and cause deep ponding
- Road or rail underpasses may be vulnerable and can create deep ponding
Topographic factors
- Roads and open spaces with high slopes can increase velocity of surface flows
 Surface and underground drainage capacity
- Impermeable surfaces increase stormwater runoff
- Lack of capacity of urban drainage system
URBAN CLIMATE
CHANGE EFFECTS
URBAN CLIMATE CHANGE EFFECTS
URBAN CLIMATE
CHANGE EFFECTS
Urban Heat Island
The generated effects on the built
environment and population can be:
Direct; increased energy consumption,
increased heat loads in outdoor
spaces, high inputs of atmospheric
pollutants and greenhouse gases,
reduce quality of life and comfort of the
individual, aggravated by the events of
the heatwaves.
Indirect; increased vulnerability of
survivors and deterioration of water
quality; surfaces, floors and roofs which
reach temperatures higher than those
of the air transferring this excess heat
to the rainwater that, because of the
phenomena of surface runoff, is
transported, together with the
pollutants, to the surface or
groundwater water bodies.
URBAN CLIMATE CHANGE EFFECTS
URBAN CLIMATE
CHANGE EFFECTS
Pluvial flooding
The generated effects can be [Houston
et al., 2011]:
Direct; immediate, may cause physical
damage to the buildings (structural
elements or finishing) and infrastructure,
and consequent costs for restoration or
reconstruction, health problems for those
affected (death, physical trauma and / or
mental), and deterioration of water
qualityThe runoff can cause transport to
water bodies (surface and underground)
of pollutants in the area, both urban and
rural.
Napoli, 12/10/2012
Indirect; not immediate, they are longer
lasting and affect the interruption of
economic and social activities (loss of
industrial and agricultural production) or
services (transport
infrastructure,
school activities, health care, etc.) and
the increased vulnerability of survivors.
Palermo, 27/11/2015
Salerno, 01/09/2014
URBAN CLIMATE CHANGE EFFECTS
- Rising global temperatures (average and maximum)
- Increased frequency of extreme weather events (heatwaves, heavy rainfall, dryness)
- Reduction in annual average rainfall
And then:
- Ideal southward shift
- Thirty years 2080/99: increase of 5-6° in global average temperatures (without a massive reduction
in greenhouse gas emissions)
Napoli, 12/10/2012
Palermo, 27/11/2015
Salerno, 01/09/2014
CITIES AS VULNERABLE PLACES TO CLIMATE
CITIES AS VULNERABLE
PLACES TO CLIMATE
Central role of cities in fighting the climate change effects
- Open spaces of cities become unlivable places during the warmer months, mostly for vulnerable
groups, causing discomfort and mortality
- Big cities are home to 50% of the world population and it is expected in 2030 will host 70%
Predicting what might happen in the future:
- Reducing the environmental impact of the construction industry
- Surrounding Co2 emissions during the entire life cycle
- Buildings and urban spaces as environmental relievers
(designed to withstand extraordinary events and able to limit their current and future effects)
Napoli, 12/10/2012
Palermo, 27/11/2015
Salerno, 01/09/2014
DESIGN FOR CLIMATE CHANGE
DESIGN FOR CLIMATE
CHANGE
- URBAN REGENERATION
Read and face the change improving the environmental (living?) comfort through adaptation strategies and solutions
and mitigation of climate change
- RESILIENT ACTIONS
Able to adapt to change and to mitigate the future effects
Preventive actions of urban spaces regeneration and of Co2 emissions reduction, to start the recessive process
advocated by the EU
Napoli, 12/10/2012
Palermo, 27/11/2015
Salerno, 01/09/2014