Climate Change, Cities and Urban Planning

Climate Change, Cities, and Citizens

Aliakbar Shamsipour; Associate Prof in Climatology, University of Tehran

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Green house gases in natural condition insulates the earth against extreme of temperature by limiting both incoming solar radiation & escape of reradiated heat in to space.This natural balance may be distorted by Green House Effect as gases such as carbon dioxide have built up in the atmosphere trapping more heat

Infra-red radiationSurface Temperature normal

Some reradiated heat reflected back to earth

Surface Temperature increases

More reradiated heat reflected back to earth

Less reradiated heat escapes in to space

Some reradiated heat escapes in to space

Naturally Moderated Green House EffectUnbalanced Green House Effect

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Causes of Global Warming

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China --> 9977 US --> 5233 EU --> 3487 India --> 2407 Russia --> 1812 Japan --> 1246 Germany --> 759 South Korea --> 616 Iran --> 611 Saudi Arabia --> 519 .WORLD TOP 10 CARBON EMITTERS - 2013Measure - million tonnes of CO2. Source: Global Carbon Project

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http://persian.euronews.com/2015/11/11/in-pictures-how-would-these-iconic-cities-look-at-2c-and-4c/

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The Kyoto Protocol is an international agreement linked to the United Nations Framework Convention on Climate Change, which commits its Parties by setting internationally binding emission reduction targets.

Recognizing that developed countries are principally responsible for the current high levels of GHG emissions in the atmosphere as a result of more than 150 years of industrial activity, the Protocol places a heavier burden on developed nations under the principle of "common but differentiated responsibilities."

The Kyoto Protocol was adopted in Kyoto, Japan, on 11 December 1997 and entered into force on 16 February 2005. The detailed rules for the implementation of the Protocol were adopted at COP 7 in Marrakesh, Morocco, in 2001, and are referred to as the "Marrakesh Accords." Its first commitment period started in 2008 and ended in 2012.

In Doha, Qatar, on 8 December 2012, the "Doha Amendment to the Kyoto Protocol" was adopted.

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URBAN HEAT ISLAND - REASONS

MOTOR EXHAUSTS

FACTORY & OTHER POLLUTION

DOMESTIC HEATING

DARK AND DRY TARMAC SURFACES

SMOG RESULTS FROM POLLUTIONHuman heat sources (domestic heating, cars, factories) all warm the air. Pollution by exhausts, factories and other dusts absorb radiation and prevent heat loss during the night. Dark surfaces have a low albedo. Dry surfaces reduce latent heat loss by evaporationIn humid conditions, this may result in smog which was common in pre-war London and still is in LA, Rome, Athens, Mexico City etc where surrounding hills prevent the escape of polluted air.

RUSH HOUR TRAFFIC THROUGH A HAZE OF FUMES

FOR INSTANCERainforest is close to the equatorDeserts are along the tropics and in the interior of major continentsIce is at high latitudesMICROCLIMATE

Global climatic regions relate to: Latitude Continental location (E or W)Regional climates relate more to: Altitude Ocean currents, winds Distance from seaColder - higher altitude, polar, and more continental.Warmer - southerly, lower altitude, oceanic, Warmer - southerly, oceanicWarmer - Gulf Stream takes warm water polewards

RAINFORESTDESERTDESERTNW Europe temperatures in JanuaryGLOBAL VEGETATION

Farmers alter albedo by plastic sheeting. Bare earth gains more radiant heat, but loses more heat through evaporation loss and wind at night. Prevention of frost at night can be crucial to early growth.Built-up areas are 2/3C warmer than rural areas, especially at night. This is an Urban Heat Island.MICROCLIMATE (2)On a smaller scale, weather and climate is affected by smaller scale variations in: Topography (relief) Albedo Aspect Urban Areas Vegetation Moisture and humidity Pollution, human activity

Low lying valleys and hollows collect cold and humid air (Frost Hollow); hilltops are exposed to wind; south-facing slopes (in Europe) are warmer, with longer days, effectively, than north-facing slopes (Aspect). East or west aspect may affect rainfall or snow coverThis in turn may affect vegetation, humidity, evaporation rates

The Greenhouse Effect due to human pollution is not intentional...

URBAN HEAT ISLANDThermal images of Atlanta show radiant energy being absorbed during the day (above) and retained during the day (below). The roads can be seen as tarmac absorbs radiation most effectively.

ATLANTAs heat islandThermal imaging of Atlanta shows the correlation of warmer temperatures and the built up area. The centre is warmest, outside the city is coolest. Bodies of water help reduce the effect.The location of the CBD and tarmac roads may be clearly seen. The effect is to warm major urban areas by 2-3C by day and night more than rural areas.

Why CitiesUrban Heat island phenomenon

Black FaadePaved SurfaceGasesLack of treesBlack roofsNon absorbable facades

Why CitiesUrban Heat island phenomenon

Why CitiesUrban Heat island phenomenon

Why CitiesUrban Heat island phenomenon

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London2143 hours28 July 2006Why CitiesUrban Heat island phenomenon

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Atlanta, Georgia, 11 May 1997Daytime air temperature 26.7o, Surface temperatures as high as 47.8oWhy CitiesUrban Heat island phenomenon

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New York City14 August 2002The cooling effect of urban vegetationWhy CitiesUrban Heat island phenomenon

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How do cities change climates?

Changes in albedo

Changes in particulate concentrations (aerosols)

Changes in gas composition (e.g., production of CO2, CH4, SO2, NOx) of atmosphere,

Changes in winds & air flow

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Albedo effectsDiffers between urban & rural

Very dependent on style and density of urban development

In North America, typical 4-6% decrease in overall albedo in urban areas vs. rural

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Magnitude of albedo effectsSummer temps over asphalt 10-25 C higher than air temps vs. bare soil, 1-5 C higher

Diurnal cooling greater for soil & vegetation than for asphalt

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Aerosol effects on thermal IRInterference with infrared wavelengths

Increased heating above urban area

Increased downward heat flux

Turbid layer thus contributes to atmospheric warming

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Aerosal effects on insolation: temperature inversions

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Aerosal effects on insolation: temperature inversions

Salt Lake City, Utahhttp://leggnet.com/labels/sky.html

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Changes in wind flow: Urban Canyon effect

Not only do buildings alter insolation and radiation they also interfere with wind

Typical net decrease in wind speed 15-30%

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Magnitude of urban influences on climate depends onSize of population

Nature and amount of energy consumption

Surrounding topography

Wind speed

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Socio-economic differencesLow per capita income cities (