Climate Change:

Implications
for Cities

Key Findings from the

Intergovernmental Panel
on Climate Change
Fifth Assessment Report
 Rising temperatures:

The
The Intergovernmental Panel on Climate Change (IPCC)
Fifth Assessment Report (AR5) concludes that climate
change is unequivocal, and that human activities,
particularly emissions of carbon dioxide, are very likely
to be the dominant cause. Changes are observed in all

Physical
geographical regions: the atmosphere and oceans are
warming, the extent and volume of snow and ice are
diminishing, sea levels are rising and weather patterns
are changing.

Science Projections:
Computer models of the climate used by the IPCC
indicate that changes will continue under a range of
possible greenhouse gas emission scenarios over the

of
21st century. If emissions continue to rise at the current
rate, impacts by the end of this century are projected to
include a global average temperature 2.6–4.8 degrees
Celsius (°C) higher than present, and sea levels 0.45–0.82
metres higher than present.

Climate To prevent the most severe impacts of climate change,

parties to the UN Framework Convention on Climate
Change (UNFCCC) agreed a target of keeping the rise in
average global temperature since pre-industrial times
below 2°C, and to consider lowering the target to 1.5°C

Change
in the near future.

The first instalment of AR5 in 2013 (Working Group I on

the physical science basis of climate change) concluded
that by 2011, we had already emitted about two-thirds
of the maximum cumulative amount of carbon dioxide
that we can emit if we are to have a better than two-thirds
chance of meeting the 2°C target.

Impact of past emissions:

Even if emissions are stopped immediately, temperatures
will remain elevated for centuries due to the effect of
greenhouse gases from past human emissions already
present in the atmosphere. Limiting temperature rise will
require substantial and sustained reductions of greenhouse
gas emissions.

P2  Climate: Everyone's Business

About
this document
The Fifth Assessment Report from the PUBLISHED:

Intergovernmental Panel on Climate Change is May 2014

the most comprehensive and relevant analysis FOR MORE INFORMATION:

E-mail: AR5@europeanclimate.org
of our changing climate. It provides the scientific www.cisl.cam.ac.uk/ipcc
fact base that will be used around the world to www.iclei.org
www.europeanclimate.org
formulate climate policies in the coming years.
AUTHOR:
Rian van Staden
This document is one of a series synthesizing the most pertinent findings
of AR5 for specific economic and business sectors. It was born of the belief REVIEWERS:
that the cities sector could make more use of AR5, which is long and Debra Roberts
highly technical, if it were distilled into an accurate, accessible, timely, Jørgen Abildgaard
relevant and readable summary. Cambridge Project Team:
Nicolette Bartlett
Although the information presented here is a ‘translation’ of the key
Stacy Gilfillan
content relevant to this sector from AR5, this summary report adheres
David Reiner
to the rigorous scientific basis of the original source material.
Eliot Whittington
Grateful thanks are extended to all reviewers from both the science and
business communities for their time, effort and invaluable feedback on PROJECT DIRECTOR:
this document. Tim Nuthall

The basis for information presented in this overview report can be found PROJECT MANAGER/EDITOR:
in the fully-referenced and peer-reviewed IPCC technical and scientific Joanna Benn
background reports at: www.ipcc.ch
EDITORIAL CONSULTANTS:
Carolyn Symon, Richard Black

PROJECT ASSISTANTS:
Myriam Castanié,
Simon McKeagney

LAYOUT DESIGN:
Lucie Basset, Burnthebook

INFOGRAPHIC:
Carl De Torres Graphic Design

IMPLICATIONS FOR CITIES  P3

Key
Findings
Many emerging climate change risks are concentrated in
urban areas. Urban areas hold more than half the world’s
population and most of its built assets and economic activities.
They also house a large proportion of the population and
economic activities most at risk from climate change.

Climate change impacts on cities are increasing. Key issues

include rising temperatures, heat stress, water security and
pollution, sea-level rise and storm surges, extreme weather
events, heavy rainfall and strong winds, inland flooding, food
security, and ocean acidification.

The world’s urban population is forecast almost to double by

2050, increasing the number of people and assets exposed
to climate change risks. Rapid urbanisation in low- and middle-
income countries has already increased the number of highly
vulnerable urban communities living in informal settlements,
many of which are at high risk from extreme weather events.

Steps that build resilience and enable sustainable development

in urban areas can accelerate successful climate change
adaptation globally. Adaptation options exist in areas such
as water, food, energy and transport.

The greatest potential for mitigating greenhouse gas

emissions may lie in rapidly developing cities in industrialising
countries. City-based sectors with potential for mitigation include
buildings, energy, transport, and industry. However, many rapidly
developing cities lack the financial, technological, institutional
and governance capacity required for effective mitigation.

P4  Climate: Everyone's Business

Executive
Summary
By 2050, the global urban population is expected Risk levels for most key climate change hazards in
to have increased by 2.5–3 billion relative to 2009, urban areas will increase over the near-term, but a
corresponding to 64–69% of the world population. high level of adaptation can reduce these risk levels
Urban areas are a key driver of greenhouse gas significantly. Adaptation will become progressively
(GHG) emissions across multiple sectors and more difficult for every degree of temperature rise.
currently account for over 70% of global energy use.
Options for mitigating emissions in urban areas
Rising sea levels, inland floods, frequent and vary, and are likely to be most effective when
stronger tropical cyclones, periods of increased policy instruments are used together. For rapidly
heat and the potential spread of disease, as well as developing cities, options include shaping
increased drought, associated water scarcity and air urbanisation and infrastructure towards more
pollution, will have widespread negative impacts sustainable and low-carbon pathways. In mature
on people’s health, livelihoods and assets. Climate or established cities, options are constrained by
change may worsen access to basic urban services existing urban forms and infrastructure but there
and the quality of life in cities. Most affected are is potential by refurbishment and retro-fitting.
likely to be the urban poor in developing countries
where the population is growing rapidly. Three- Current findings suggest the need to increase
fifths of the world’s urban population is in centres the pace of mitigation in both developed and
with fewer than 1 million inhabitants and it is here developing world cities, focussing on emissions
that much of the growth in urban population is generated in sectors such as energy supply,
occurring. Climate change will also affect local transportation, buildings and industry. At the same
and national economies and ecosystems. As an time, a wide range of available urban planning and
example, over US Dollar (USD) 3 trillion in port development strategies can also reduce emissions.
infrastructure assets in 136 of the world’s largest
port cities are vulnerable to weather events.

Adaptation is possible, if complex, but cheaper in

the long run than doing nothing. An assessment
of present and future flood losses in some of the
world’s largest coastal cities shows the estimated
costs of adaptation are far below the estimated
losses in the absence of adaptation. The potential
for adaptation, and its effectiveness, depend
on the structure and development level of the
individual city.

IMPLICATIONS FOR CITIES  P5

Impacts of
Climate Change
water shortages, electricity shortages example, in the Sea of Japan it is
Rising (by affecting hydropower and plant currently rising twice as fast as the
temperature cooling), water-related diseases
(through use of contaminated water),
global average. Rising sea levels,
associated coastal and riverbank
and food prices and food insecurity erosion, or flooding in conjunction
By the mid-21st century, most of from reduced supplies. These may with storm surge could have
the world’s population living in the all contribute to negative economic widespread effects on populations,
largest urban areas will be exposed impacts and increased rural-to- property and coastal vegetation
to a minimum 2°C rise over pre- urban migration. An estimated 150 and ecosystems, and present
industrial levels, excluding urban million people currently live in cities threats to commerce, business, and
heat island (UHI) effects. By the late with perennial water shortage (i.e. livelihoods. Cities with extensive
21st century, some of the urban areas less than 100 litres per person per port facilities and large-scale
expected to be among the largest day for basic human needs). This petro-chemical and energy-related
in 2025 will be exposed to a rise number is projected to increase, industries are especially vulnerable
of up to 2.5°C over pre-industrial possibly up to 1 billion by 2050. to risks from increased flooding.
levels (excluding UHI effects), With a 0.5 m rise in sea level, the
especially in the high latitudes. population at risk could more
This implies that mean temperature
rise in some cities could be over Rising sea levels than triple while asset exposure
is expected to increase more than
4°C. Peak seasonal temperatures
could be even higher and the
and storm surge ten-fold. The value of assets exposed
in 2005 to flood risk from sea-level
increased frequency of hot days Sea-level rise represents one of the rise and storm surge in the world’s
and warm spells will exacerbate primary shifts in urban climate major port cities is estimated at
UHI effects, causing heat-related change risk, given the increasing USD 3 trillion – about 5% of global
health problems and, possibly, concentration of urban populations Gross Domestic Product (GDP).
increased air pollution, as well as an in coastal locations. In 2000, the By the 2070s, this is projected to
increase in energy demand for warm Low Elevation Coastal Zone (LECZ) increase to about 9% of global GDP.
season cooling, clean water, and comprised just 2% of the world’s land In fast-expanding and vulnerable
infrastructure damage. Each degree area but contained 10% of the global cities such as Ningbo (China), Dhaka
(Celsius) of warming is projected to population (600 million people), (Bangladesh) and Kolkata (India),
decrease renewable water resources including 13% of the world’s urban asset exposure may increase more
by at least 20% for an additional population (360 million). Two-thirds than 60-fold.
7% of the global population. of cities with populations above
5 million are located in the LECZ.

Water security If GHG emissions continue to rise at

the current rate, sea level could rise
Risks to freshwater resources, such by almost one metre by the end of
as drought, can have many effects in the century. To compound matters,
urban areas, including increases in sea-level rise is not uniform. For

P6  Climate: Everyone's Business

 Many of the emerging global
climate risks are concentrated
in urban areas.

depend on the level of warming.

Inland flooding The variability of harvests is
also forecast to increase. All
By the end of the 21st century, aspects of food security are
Impacts and risks
changes in extreme rainfall potentially affected by climate
in the range 10–60% may • Rising temperatures could
change, including food access, exacerbate urban heat island
lead to changes in flood and utilisation, and price stability.
combined sewer overflow effects and thus increase heat-
Urbanisation changes land-use related health problems and air
frequencies and volumes of up cover, generally reduces the
to 400% depending on system pollution in cities.
amount of ecologically intact
characteristics. Inland flooding is land, and causes fragmentation • Warming is projected to decrease
often made worse by uncontrolled of the remaining land. Climate renewable water resources,
city development that builds change also affects the physical potentially compromising drinking
over natural drainage channels and chemical properties of the water supplies in many urban
and flood plains, increasing the ocean. Fish and shellfish are areas and increasing water-
speed and volume of runoff, or affected directly by changes in related diseases, food prices
by a failure to maintain drainage seawater temperature, pH and and food insecurity.
channels. The volume of sewage oxygen levels. Societies relying
released to the environment • Ocean acidification is a risk for
on fish for subsistence are likely marine resources.
by combined sewage overflow to be particularly disadvantaged.
spills and flooding is projected to A 2°C global temperature rise by • Sea-level rise, extreme weather
increase by 40% in some cities. 2050 is projected to cause global events and inland flooding
losses in landed catch value will result in threats to life
of USD 17–41 billion annually and livelihood, destruction of
Food security (relative to 2005 levels). Cities infrastructure, service provision
with a heavy reliance on local failure and governance issues.
Cities depend on their fishing for local food provision
surrounding areas as well as the • The value of economic assets in
would be significantly affected. coastal cities exposed to damage
rest of the world for food supply.
In many regions, there is likely to from floods is projected to rise
be a loss of food production and from 5% of global GDP in 2005
productive arable lands. Without to 9% by 2070.
adaptation, climate change is • Hazards such as floods and
projected to reduce yields of cyclones are a risk for half to two-
major crops such as wheat, rice, thirds of Asia’s cities with 1 million
and maize at local temperature or more inhabitants.
increases of 2°C or more above
present-day levels. After 2050,
the risk of more severe yield
impacts will increase, and will

IMPLICATIONS FOR CITIES  P7

 Climate Change - Everyone's Business Implications for Cities

Cities on the front line of a changing climate

Urban centres account for more than half of the world’s population,
most of its economic activity and the majority of energy-related
emissions. The role of cities in reducing emissions and protecting
their inhabitants is therefore central to effective climate policies.

IMPACTS Sea-Level Rise Food Insecurity

Two-thirds of cities with populations above All aspects of food security are potentially
Climate change is expected 5 million are located in the Low Elevation Coastal affected by climate change, including access
to affect numerous aspects Zone. Rising sea levels and storm surge flooding to food, food utilisation and price stability. Climate
could have widespread effects on populations, change is likely to cause food production in some
of urban life. property, and ecosystems, presenting threats to regions (including the ocean due to warming and
commerce, business and livelihoods. acidification) to decline.

C E

E A B

Adaptation is possible if ADAPTATIONS ADAPTATIONS

complex, but cheaper in the Responses include: (A) improving early
warning systems, (B) strengthening
Local responses include support for urban and
peri-urban agriculture, (D) green roofs, local
long run than doing nothing. coastal infrastructure, a significant degree markets and enhanced social (food) safety nets.
How cities adapt to the of rezoning (including relocation of critical (E) Develop alternative food sources, including

effects of climate change services), (C) and evacuation and crisis

response management.
inland aquaculture, to replace ocean-based
resources under threat.
will vary enormously.

Mitigation efforts can have positive impacts for generations to come

Energy Supply Transport Buildings

Reductions in greenhouse gas (GHG) emissions Emissions can be reduced by avoiding journeys, Retrofitting existing buildings can reduce heating
can be achieved by the use of low-carbon shifting to low-carbon transport systems, enhancing energy requirements by 50–75% in single-family
technologies including renewables, nuclear, and vehicle and engine efficiency, and reducing the housing and 50–90% in multi-family housing at
carbon capture and storage. Switching from coal carbon intensity of fuels by substituting oil-based costs of about US Dollar 100 to 400 per square metre.
to gas can be a bridging solution. products with natural gas, bio-methane or biofuels, In contrast, substantial new construction in fast-grow-
or with electricity or hydrogen produced from low ing regions presents a great mitigation opportunity as
GHG sources. emissions can be virtually eliminated for new builds.
P8 Climate: everyone's Business
 Key Findings from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) For more information please visit cisl.cam.ac.uk/ipcc

Cities account for Urban infrastructure Over 64% of the world population New infrastructure and land-
37–49% of global accounts for over 70% to live in cities by 2050, significantly use policies could reduce GHG
GHG emissions of global energy use increasing energy use for infrastructure emissions by 20–50% by 2050

Extreme Weather Events Increased Temperatures Freshwater Availability

Changes in extreme rainfall could cause the The mean temperature rise in some cities could Risks to freshwater resources, such as drought,
amount of sewage released to the environment from be over 4°C by 2100, with peak seasonal temperatures can cause shortages of drinking water, electricity
combined sewage overflow spills and flooding to even higher. More hot days will exacerbate urban outages, water-related diseases (through use of
increase by 40% in some cities. Inland flooding is heat island effects, resulting in more heat-related contaminated water), higher food prices and increased
often made worse by uncontrolled city development. health problems and, possibly, air pollution. food insecurity from reduced agricultural supplies.

I J

F G H K

ADAPTATIONS ADAPTATIONS ADAPTATIONS

Responses include strengthening Development of urban planning heat manage- Options include (J) encouraging water
infrastructure, (F) localised migration, ment strategies, (H) including green zones, recycling and grey water use, improving
wastewater, stormwater and runoff wind corridors, green roofs and water features. runoff management and developing
infrastructure and management, and (I) Building codes will need to be improved, and new/alternative water sources, (K) storage
better emergency measures including the infrastructure used by vulnerable parts of the facilities and autonomously powered water
(G) stockpiling fuel, water and food. population will need to be made more resilient. management and treatment infrastructure.

Energy Demand Low Carbon Cities Policy Instruments

Increasing the efficiency of buildings, appliances Options for rapidly developing cities focus on Approaches include co-locating high residential with
and distribution networks will reduce energy shaping their urban and infrastructure development high employment densities, achieving high land-use
demand. Changes in the awareness and trajectories. For mature cities, options lie in urban mixes, investing in public transit. The best plans for
behaviour of residents can also reduce demand. regeneration (compact, mixed-use development that advancing sustainable urbanisation and low carbon
Projections suggest demand may be reduced by shortens journeys, promotes transit/walking/cycling, development, especially in fast-growing parts of the
up to 20% in the short term and 50% by 2050. and adaptive reuse of buildings) and rehabilitation world requires political will and institutional capacity.
and/or conversion to energy-efficient building designs.
IMPLICATIONS FOR CITIES P9
Resilience
Urban governments are at the heart
Steps that build
resilience and of successful urban adaptation because Funding
enable sustainable so much of this depends on local
development can assessments and integrating adaptation Large cities with strong economies and
accelerate successful into local investments, policies administrative capacity can best attract
climate change and regulatory frameworks. Well- external funding and raise internal funding
adaptation. governed cities with universal provision for adaptation. Less prosperous and smaller
of infrastructure and services provide a urban centres and cities with fragmented
strong base for building climate resilience if governance structures or administrations
processes of planning, design and allocation lacking in capability have weaker prospects.
of human, capital, and material resources are Types of financing that can be used to
responsive to emerging climate risks. facilitate adaptation include local revenue
raising policies (taxes, fees, charges), the
Urban adaptation provides opportunities use of local bond markets, public-private-
for a shift towards resilience and sustainable partnership (PPP) contracts and concessions,
development via multi-level urban risk national or local financial markets, national
management, alignment of policies and (or state/provincial) revenue transfers
incentives, strengthened local government or incentive mechanisms, market-based
and community adaptation capacity, investments and grants and concessional
synergies with the private sector, and financing (such as an Adaptation Fund).
appropriate financing and institutional
development. Although the many rapidly
growing cities provide good opportunities Housing
for such developments, there is limited
evidence of this being realised in practice. Good quality, affordable, well-located
housing provides a strong base for city-wide
climate change adaptation that minimises
Planning current exposure and loss. Possibilities for
adapting the existing building stock rest
There is no single approach to urban with owners and public, private and civil
adaptation planning because of the society organisations.
complex, diverse and context-dependent
nature of climate change adaptation and
of cities themselves. Although top-down Rising temperatures
and bottom-up approaches are widely
recognised, in practice adaptation entails In response to increased temperatures,
a combination of both. Local governments cities may develop urban planning heat
can play a central role addressing the management strategies, including green
challenges of adaptation planning and zones, wind corridors, green roofs and water
implementation in close partnership with features. This implies improved building
the public, low-income groups, and civic codes and the proofing of infrastructure used
and private sectors. Closer integration of by the weakest population groups against
disaster risk management and climate high temperatures – especially schools,
change adaptation, with the incorporation retirement facilities, and hospitals.
of both into local, sub-national, national
and international development policies
can provide benefits at all scales.

P10  Climate: Everyone's Business

 The Fifth Assessment Report (AR5) of the
Intergovernmental Panel on Climate Change
(IPCC) is the most detailed assessment of
climate change ever.

require the construction of safety nets. Improving the efficiency

Basic services storm surge protection (barriers, of urban markets, promoting
floodgates, dikes) and a significant farmers’ markets, investing in
Reducing basic service deficits and degree of rezoning and upland infrastructure and production
building resilient infrastructure expansion, as well as the relocation technologies may all moderate food
systems (water supply, sanitation, of critical services. Improved early price increases. Food security may
storm and waste water drains, warning, evacuation, and crisis be enhanced by support for street
electricity, transport and response management will reduce food vendors, access to cheaper
telecommunications, health care, the health and livelihood risk to food and measures like cash
education, emergency response) residents, as will the development transfers (e.g. Brazil’s Bolsa Familia
can significantly reduce hazard of alternative intra-coastal Programme) or, for older groups,
exposure and vulnerability to transport routes and modes and pensions. Initially rural in focus,
climate change, especially for non-coastal, distributed energy cash transfer programmes have
those most at risk or vulnerable. generation capacity. expanded in urban areas, in some
places reaching much of the low-
income population. Changes in the
Water security Extreme weather availability of key resources from
ocean-based sources may require
Increased freshwater demand due to and inland cities to develop alternative food
increased temperatures will require
cities to look at water management flooding sources and strengthen logistics for
the acquisition and distribution of
infrastructure and planning. alternative foodstuffs. This might
Cities can react to challenges Extreme weather events will require
that cities develop distributed, also include the introduction of
in freshwater availability and inland aquaculture.
pollution by creating strengthened, resilient energy, healthcare and
distributed, autonomously powered command-and-control services.
water management and treatment This will include strengthening
infrastructure; by encouraging public transport infrastructure,
water recycling, the use of grey and potentially stockpiling fuel,
water and improved runoff water and food. Improved building
management; and by developing standards can be used to strengthen
new/alternative water sources and built infrastructure, with a special
expanding storage facilities. Energy focus on poorer communities.
generation may also be affected, Wastewater, stormwater and runoff
requiring cities to expand water- infrastructure could be improved.
independent generation capacity.

Food security
Rising sea levels Adaptation measures concerning
and storm surge urban food security can reduce
climate vulnerability especially
Risk through sea-level rise and for low-income urban dwellers.
storm surge may lead to cities Adaptive local responses can include
strengthening coastal infrastructure, support for urban and peri-urban
especially ports and electricity agriculture, widespread green roofs,
generation capacity. This will local markets, and enhanced social

IMPLICATIONS FOR CITIES  P11

 Mitigation
Potential
Energy supply  Significant reductions
Sectoral strategies in cities’ GHG emission from energy
production can be obtained by (for example)
The long lifetime of the built environment switching from coal burning to Natural
limits the speed at which emissions Gas Combined-Cycle (NGCC) power plants
in some sectors (such as buildings and (provided that fugitive methane emissions
transport) can be reduced. Large amounts are controlled) or Combined Heat and Power
of primary resources are used in their (CHP) plants. Low-carbon options include
initial construction, which contributes to carbon dioxide capture and storage (CCS),
lifecycle emissions. Energy use in human nuclear and renewable energy technologies.
settlements mainly concerns urban areas. These may have co-benefits for cities, for
Cities account for about 71% of energy- example in reducing urban air pollution.
related CO2 emissions, but only 37–49% of Initiatives that encourage companies to
global GHG emissions (other sources of GHG exchange ideas and techniques for reducing
emissions are predominantly associated material and energy use, such as eco-
with rural areas). industrial parks and regional eco-industrial
Energy demand  Increasing the efficiency networks, can reduce emissions.
of buildings, appliances and distribution Transport  Emissions from transportation
networks will reduce energy demand. can be reduced by avoiding journeys where
Changes in the awareness and behaviour of possible, a modal shift to low-carbon transport
residents can also reduce demand. Projections systems, lowering energy intensity by
suggest demand may be reduced by up to 20% enhancing vehicle and engine performance,
in the short term and 50% by 2050. and reducing carbon intensity of fuels by
Buildings  Retrofitting existing buildings substituting oil-based products by natural gas,
can lead to potential reductions in heating bio-methane or biofuels, or with electricity or
energy requirements of 50–75% in single- hydrogen produced from low GHG sources.
family housing and 50–90% in multi-family
housing at costs of about USD 100 to 400
per square metre. In contrast, substantial
new construction in dynamically growing
regions presents a great opportunity from
a mitigation perspective as emissions
can be virtually eliminated for new builds.
Both approaches are generally cost-effective
but barriers remain to their widespread
implementation.

P12  Climate: Everyone's Business

 travel times, enabled by multiple modes of
Urbanisation is
a global trend
Urban form and transportation. There is robust evidence
and is associated infrastructure that following these guidelines in urban
development reduces city emissions.
with increases in
income, and higher Urban form and infrastructure Urban mitigation options are likely to be
urban incomes are significantly affect GHG emissions. They most effective when policy instruments are
correlated with higher are strongly linked to the use of materials bundled. These can include instruments
consumption of energy and energy in a city, waste generated, and that help decrease emissions such as land
and GHG emissions. system efficiencies of a city. use regulations, density regulations, urban
Mitigation options vary by city type and containment, building codes, parking and
development. The options available for design regulations, land management and
rapidly developing cities include shaping their acquisition regulations and increasing
urbanisation and infrastructure development green space and urban carbon sinks.
trajectories. For mature, built-up cities, Market-based instruments include property
mitigation options lie in urban regeneration taxes, development taxes, fuel prices and
(compact, mixed-use development that transportation costs.
shortens journeys, promotes transit/walking/ Income and scale exert important influences
cycling, and adaptive reuse of buildings) and on the mitigation potential for technologies.
rehabilitation/conversion to energy-efficient While lock-in may limit the rate of mitigation
building designs. in mature cities, the opportunity exists in
An area of special focus is infrastructure, rapidly growing cities to leapfrog to new
especially in terms of density, land-use mix, technologies. For mature cities, technology
connectivity and accessibility. Connectivity is important for R&D and knowledge
and accessibility are tightly related. While concentration, and access to capital that
individual measures of urban form have facilitates the development and early
relatively small effects on vehicle miles deployment of low-carbon technologies.
travelled, they become more effective when AR5 highlights two key knowledge gaps
combined. There is consistent evidence that important in relation to mitigation that
co-locating higher residential densities with can be addressed by cities and their
higher employment densities, coupled with local governments. These are the lack of
significant public transit improvements, emissions data at a local level and the lack
higher land use mixes, and other supportive of consistency and comparability on local
demand management measures can lead to emissions accounting methods, demanding
greater emissions savings. Highly accessible the development, standardisation and active
communities are typically characterised use of GHG inventories in cities.
by low daily commuting distances and

IMPLICATIONS FOR CITIES  P13

Conclusion
The next two decades The urban population is projected to increase Linkages between urbanisation and
present a window from 3.4 billion in 2005 to 6.3 billion in GHG emissions trends are complex
of opportunity for 2050. Urban population growth will be and involve many factors including the
mitigation in urban concentrated in Asia and Africa. The rural level of development, rate of economic
areas, as a large population is projected to begin declining growth, availability of energy resources
portion of the world’s around 2020. and technologies, and urban form and
urban areas will be infrastructure. Transition from coal-based
developed during The full likely impact of climate change energy supply to low-carbon electricity
this period. on cities has yet to be determined, and is could help mitigate the fast-increasing
dependent on location, level of development, CO2 emissions associated with rapid
size, resources and the ability and political urbanisation. Other options for cities
will to adapt. Case studies and regional include good-quality, affordable, well-located
reviews assessing urban vulnerabilities housing, providing a strong base for city-
to climate change have revealed diverse wide climate change resilience. International
physical and societal challenges and large financial institutions provide limited support
differences in levels of adaptive capacity. for transformation in urban areas. Local
Well-governed cities with universal fiscal policy itself can restrict mitigation
provision of infrastructure and services have efforts to support pursuing more compact
a strong base upon which to build climate city strategies. Overcoming the lack of
resilience. However, even high levels of political will, restricted technical capacities,
successful adaptation in well-governed cities and ineffective institutions for regulating or
cannot address all risks in the longer term planning land use will be central to attaining
without both effective global mitigation low-carbon development at a city scale.
and horizontal learning between cities for
adaptation and mitigation. Both developed and developing cities are
under pressure to build up the skills and
resources to contribute directly to reducing
local emissions in close co-operation with
regional and national bodies. Action in
urban centres is essential to successful global
climate change adaptation and mitigation,
as these areas hold more than half the
world’s population and most of its built
assets and economic activities.

P14  Climate: Everyone's Business

Glossary
ADAPTATION GREENHOUSE GAS RESILIENCE
The process of adjustment to actual A gas in the atmosphere, of natural The capacity of social, economic,
or expected climate and its effects. and human origin, that absorbs and and environmental systems to cope
In human systems, adaptation seeks emits thermal infrared radiation. with a hazardous event or trend or
to moderate or avoid harm or exploit Water vapour, carbon dioxide, nitrous disturbance, responding or reorganizing
beneficial opportunities. In natural oxide, methane and ozone are the in ways that maintain their essential
systems, human intervention may main greenhouse gases in the Earth’s function, identity, and structure.
facilitate adjustment to expected atmosphere. Their net impact is to trap
climate and its effects. heat within the climate system. SUSTAINABLE DEVELOPMENT

BIOFUEL MITIGATION Development that meets the needs of

the present without compromising the
A fuel generally in liquid form, A human intervention to reduce the ability of future generations to meet
produced from organic matter or sources or enhance the sinks of their own needs.
combustible oils produced by living greenhouse gases.
or recently living plants. URBAN AGRICULTURE
OCEAN ACIDIFICATION
CLIMATE CHANGE Small areas (e.g. vacant plots,
A reduction in the pH of the ocean over gardens, verges, balconies, containers)
Any significant change in climate an extended period, typically decades within the city for growing crops
that persists for an extended period, or longer, which is caused primarily and raising small livestock or milk
typically decades or longer. by uptake of carbon dioxide from cows for own-consumption or sale
the atmosphere. in neighbourhood markets.
CLIMATE IMPACT
PERI-URBAN AGRICULTURE URBAN HEAT ISLAND
The effects of climate change on
natural and human systems. Farm units close to town which operate The relative warmth of a city compared
intensive semi- or fully commercial with surrounding rural areas.
CO-BENEFITS farms to grow vegetables and other
horticulture, raise chickens and other WATER SECURITY
The positive effects that a policy or livestock, and produce milk and eggs.
measure aimed at one objective might Secure access to an acceptable
have on other objectives. PROJECTION quantity and quality of water for health,
livelihoods and production.
FOOD SECURITY A potential future evolution of a quantity
or set of quantities, often computed by a
Secure access to sufficient amounts model. Projections involve assumptions
of safe and nutritious food for normal that may or may not be realized, and
growth, development, and an active are therefore subject to substantial
and healthy life. uncertainty; they are not predictions.

FUGITIVE EMISSIONS

Emissions of gases or vapours from

pressurised equipment due to leaks and
other unintended or irregular releases of
gases, mostly from industrial activities.
IMPLICATIONS FOR CITIES  P15
“The IPCC’s Working Group II report is a clear signal to local governments
of the urgent need to ramp up the adaptive capacity of the world’s
urban areas. This summary document is a critical tool in helping local
governments determine the extent of the challenge and the scope of
the opportunities that such foresighted adaptation action requires.”
DEBRA ROBERTS, DEPUTY HEAD: ENVIRONMENTAL PLANNING AND CLIMATE PROTECTION,
DURBAN, SOUTH AFRICA.

Disclaimer: About us:

This publication has been developed and released The University of Cambridge Institute for Sustainability
by the European Climate Foundation (ECF), ICLEI - Leadership (CISL) brings together business, government
Local Governments for Sustainability (ICLEI) and the and academia to find solutions to critical sustainability
University of Cambridge’s Judge Business School (CJBS) challenges.
and Institute for Sustainability Leadership (CISL). Cambridge Judge Business School (CJBS) is in the
This project was initiated and financed by ECF and business of transformation. Many of our academics are
endorsed by CJBS and CISL. leaders in their field, creating new insight and applying
the latest thinking to real-world issues.
The family of summaries, of which this report is part,
ICLEI - Local Governments for Sustainability (ICLEI)
is not meant to represent the entirety of the IPCC’s Fifth
– is the world’s leading association of more than
Assessment Report (AR5) and they are not official IPCC
1000 metropolises, cities, urban regions and towns
documents. The summaries have been peer-reviewed by
representing over 660 million people in 86 countries.
experts both from the business and science communities.
The English version constitutes the official version.

For more information: Reproduction and use:  The materials can be freely used to advance
discussion on the implications of the AR5 and consequences for business.
E-mail: AR5@europeanclimate.org The report is made available to any and all audiences via the Creative
www.cisl.cam.ac.uk/ipcc Commons License BY-NC-SA. This document is available for download
www.iclei.org from the CISL website: www.cisl.cam.ac.uk/ipcc
www.europeanclimate.org