Climate Change & Cities

James Voogt

Department of Geography

Western University

President: International Association for Urban Climate

CO2 – Now above 400 ppm

280 Pre-industrial CO2 level

Where are we going?RCP = “Representative Concentration Pathways”

To keep temperature change <2°C relative to pre-industrial levels requires

atmospheric concentrations in 2100 of about 450ppm CO2eq (high confidence)

These scenarios include substantial cuts in anthropogenic GHG emissions by

mid-century.

How will climate change?

IPCC AR5 WG1 (2013)

Near term warming – all scenarios

Increasing rate of warming – high emissions scenarios

Temperature Projections: North America

IPCC WG1 2013

Hig

h E

mis

sio

ns

Lo

w E

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IPCC: Warming in the Great Lakes region is projected to be about 50% greater than

that of the global mean warming; more warming further north; mean warming over

land will be larger than over the ocean (very high confidence)

Projected Hot Days

MOE (2009)

IPCC AR5: “a current 20-year high temperature event will occur more frequently by

the end of the 21st century (at least doubling its frequency, but in many regions

becoming an annual or two-year event) and a current 20-year low temperature

event will become exceedingly rare”

Toronto

Urban Impact: Shift in demands for cooling (increases) and heating (decreases)

Trends in the Number of Annual Heat Wave Days

Smith et al. (2013)

15 Heat Wave Indices and their change 1979-2011

Days p

er

Year

Data suggest heat

waves are already

increasing

Very Likely to change

further by late 21st

Century

Heatwaves and Cities

The urban heat island can

magnify heat wave effects

Toronto

Russian Heat Wave: 70,000 deaths

European Heat Wave: 55,000 deaths

Heat is the deadliest of weather

hazards (US Data)

Future Climates and Heatwaves

Schär et al. (2004)

the probability of a summer experiencing mega-

heatwaves will increase by a factor of 5 to 10

within the next 40 years

Chicago: Deaths from heat

waves per year for 7 climate

models run for 3 emissions

scenarios

Peng et al. (2010)

Higher temperatures in polluted

regions trigger feedbacks that

increase ozone and particulate

matter pollution

Precipitation

Evaporation increases in a warmer world

Warmer air contains more moisture

IPCC WG1 AR5 2013

High Emissions Scenario

RCP 8.5Low Emission Mitigation

Scenario

RCP 2.6

Precipitation in North America

IPCC WG1 2013

High latitudes – more precipitation

Subtropics – decreases in precipitation

Change since 1950 in Top 1% Heaviest Rainfall Events

US National Climate Assessment (2013)

IPCC: likely

increases in either

frequency or

intensity of heavy

precipitation

Extreme Precipitation High moisture content in atmosphere

Poleward movement of storm tracks

IPCC: Over most of the mid-latitude land masses extreme

precipitation will very likely be more intense and more

frequent in a warmer world

The Canadian Press / Winston Neutel

Toronto Rain Event 2013

Ontario’s most costly “natural” disaster

$850 million - insured losses

$1.2 billion – estimated total losses

TELLING THE WEATHER STORY | 14

By 2050, a 1990’s 1-in-20 year annual

maximum daily precipitation amount is likely

to become a 1-in-10 year event.

ABOUT TWICE AS MANY HEAVY

SUMMER STORMS.

More heavy precipitation events in 2050

Toronto Rain – 2005 - $624 m

Calgary Rain/Wind – 2010 – $1B

Calgary Rain/Wind – 2009 – $362 m

SW Ontario Rain/Wind –2009 – $482 m

Calgary Hail – 1991 – $885 m

CBC

Flooding

High River AB, June 23, 2013 (REUTERS/Andy Clark)

Character of rainfall is changing: more intense; overall precipitation less frequent

Spatial changes to precipitation

More precipitation from extratropical cyclones in winter

Hydrology changes – timing/amount of runoff

Human modifications

TELLING THE WEATHER STORY | 17

Severe Weather

Goderich Tornado: Aug 21 2011(AP/CP/Geoff Robins)

A trend towards environments that favour more severe

thunderstorms

Fires in BCMONTHS OF IMPACT$5B + DAMAGES30+ DEATHS

Ice Storms1998 Eastern Canada Ice Storm

2013 Southern Ontario Ice Storm

$200 million in insured losses

Alex Urosevic for National Post

“by 2046-2065, days with freezing rain are

projected to increase by 35% to 55% for

Toronto and Windsor, by 50% to 70% for

Montreal and Ottawa, and by 70% to 100%

for Kenora, Thunder Bay, and Timmins.”

Canada in a Changing Climate 2014

Current Climate Future scenario

City [D = City on a delta]Population in

2005

Exposed

population

Exposed

assets

Exposed

population

Exposed

assets

Mumbai, India 18.2 2.8 46 11.4 1598

Guangzhou, China [D] 8.4 2.7 84 10.3 3358

Shanghai, China [D] 14.5 2.4 73 5.5 1771

Miami, USA 5.4 2.0 416 4.8 3513

Ho Chi Minh City, Vietnam [D] 5.1 1.9 27 9.2 653

Kolkata, India [D] 14.3 1.9 32 14.0 1961

New York-Newark, USA 18.7 1.5 320 2.9 2147

Osaka-Kobe, Japan [D] 11.3 1.4 216 2.0 969

Alexandria, Egypt [D] 3.8 1.3 28 4.4 563

New Orleans, USA [D] 1.0 1.1 234 1.4 1013

Tokyo, Japan [D] 35.2 1.1 174 2.5 1207

Tianjin, China [D] 7.0 1.0 30 3.8 1231

Bangkok, Thailand [D] 6.6 0.9 39 5.1 1118

Dhaka, Bangladesh [D] 12.4 0.8 8 11.1 544

Amsterdam, Netherlands [D] 1.2 0.8 128 1.4 844

Sea Level Rise: Top 15 world port cities ranked by population exposure under the current

climate and future climate scenario.

Population – millions; Exposed Assets: $US billions

Nicholls et al (2008)

EFFECTIVE CLIMATE CHANGE ADAPTATION

A MORE VIBRANT WORLD

More than half the global

population now lives in

urban areas and this is

increasing (64-69% by

2050).

In 2006, urban areas

accounted for 67 – 76 % of

energy use and 71 – 76 %

of energy-related CO2

emissions.

Urban-Global Links CO2

Data from UN in Oke et al. forthcoming

It is important to see the urban climate effect as embedded in the general climate. The accumulated contributions of all the cities of the world does have an impact on global climates. Changes in the global/regional climates have an affect on cities.

Cities and Climate Change

Mills (2010)

GHG Emissions Vary with Climate and City Layout

Oke et al. (forthcoming)

Surface Controls on Urban Climates

Photo: J. Voogt

Form: Geometric structure

Land Cover(impervious, vegetated)

Metabolism

(emissions of water,

heat, pollutants)

City Size

Materials(radiative, thermal,

moisture, aerodynamic)

At the building scale:

Solar radiation management

Shading

Reflectance (surface properties)

Greater use of daylighting

Facilitation of air movement

Application of urban vegetation:

roof and walls

Application of water

Building material properties

On-site generation of energy

Where we are going: a (sobering) update

Friedlingstein et al. (2014)

“Two thirds of the CO2 emission quota consistent with a 2°C temperature

limit has already been used, and the total quota will likely be exhausted in

a further 30 years at the 2014 emissions rates.”

The window of opportunity to limit global average warming to < 2°C is

rapidly closing. Significant mitigation efforts are needed immediately.

Take Home Messages

Anthropogenic climate change is occurring and effects will

become more clear with time

Cities are important sites related to both emissions of GHG

(climate forcing) and receiving impacts of climate change

Urban areas further modify climates: e.g. water balance

changes and heat islands that exacerbate climate change in

cities

More compact and densely occupied cities generally generate

less GHG per capita. Policies to reduce emissions in cities

should consider technology and fuel-switching, but also the

potential for moderating the urban contribution of GHG

through more efficient urban form, transport and land-use mix.

Risk Level withCurrent Adaptation

Potential forAdditional Adaptation to Reduce Risk

Risk Level withHigh

Adaptation

Risk-LevelVeryLow Med

VeryHigh

4°C

2°C

Present

Long Term(2080-2100

Near Term (2030-2040

Increased Risksfrom Wildfires

Heat-RelatedHuman Mortality

Damages from River and Coastal Urban Floods

NORTH AMERICA

IPCC North America: Risks

Pledges to Emissions Cuts made in Durban 2011

ClimateActionTracker.Org (as shown in Tollefson 2011)

emissions

concentrations

temperature

sea level

IPCC (2002)

Climate Change Commitments

A summary of the tools/strategies (in black) employed at the building, building group and settlement scales to achieve climatic objectives at those scales. The application of tools at each scale has a climate impact at (red), and places limits on decisions made at (blue), the other scales.

Urban Scales, climate objectives and design tools

Objective Impacts Limits

Buildings Building Groups Settlement

Indoor comfort Shelter

Buildings Location Materials Design (e.g. shape, orientation, etc.)

Access to light, solar energy, wind. Air quality

Building codes

Outdoor comfort Outdoor health

Building groups

Local climate change: Emissions Materials/surfaces Building dimensions – flow interference & shadow areas

Building placement. Outdoor landscaping, materials and surfaces. Street dimensions & orientation

Guidelines on Densities Heights Uses Green-spaces

Energy use Air quality Protection from extremes

Settlement Energy efficiency Air quality Urban climate effect

Mode and intensity of traffic flows. Energy efficiency Air quality Urban climate effect

Zoning Overall extent and shape. Transport Policy