© Crown copyright Met Office Climate Change, Cities, and the Urban Heat Island Mark McCarthy, Martin Best, Richard Betts, Maggie Hendry

© Crown copyright Met Office

Climate Change, Cities, and the Urban Heat IslandMark McCarthy, Martin Best, Richard Betts, Maggie Hendry


Contents

This presentation covers the following areas

• Human exposure to climate stress.

• A simple coupled urban-climate model.

• Energy use and the urban environment.

• Cities in a regional climate model.


Majority of population residing within urban areas

Figure from the UN department of Economic and Social Affairs


Human Exposure to climate stress

• Population dynamics and urbanisation will contribute to future exposure of humans to climate stress.

• Can we design climate models that are useful impacts and adaptation tools despite uncertainties?


A simple urban climate model•Mark McCarthy


A simple urban scheme for a climate model

Ground

Atmosphere

C(dT/dt)+G=Rn-H-LE-Qf

H LE LWSW

Best et al. 2006: Boundary layer Meteorology 118: 503-525


Subgrid heterogeneity

•Urban parameters:

•Albedo

•Roughness length of heat and momentum

•Heat Capacity

•Anthropogenic heat release

•Impervious surface

Essery et al. 2003: J. Hydrometeorology, 4, pp.530-543


Urban Heat Island responds to climate feedbacks but not forcings in a 2XCO2 experiment

Diurnal Temperature Range


Energy use•Mark McCarthy


Energy use and urban heat islands.

Energy use data courtesy of London Energy and CO2 inventory 2003


Change in average temp.

Change in 95th %ile temp.

Global mean change

Global mean change

2*CO2

2*CO2 + UHI

2*CO2 + UHI + 60Wm-2

2*CO2 + UHI + 20Wm-2


Energy use and climate.

Load data courtesy of EDF energy


Energy use-climate-urban feedbacks

• Urban climates can change in response to climate change.

• Urban climates can change in response to local anthropogenic forcing.

• Local anthropogenic forcing can change in response to climate.


Cities in a regional climate model•Mark McCarthy


Urban heat islands in HadRM3 – offline ‘v’ coupled

Obs

Model

London Weather CentreSt James Park

HeathrowNortholt

2oC


Seasonality and magnitude of a heat island simulated by RCM

LWC – WisleyObservations

SJP – WisleyObservations

HadRM3 London


Anthropogenic heating and extremes.

• Avg annual no. of hot nights (>20oC):

• Present day Climate:

• No urban = 0.45

• Coupled urban = 2.9

• Coupled urban + 25Wm-2 = 4.2

• Coupled urban + 75Wm-2 = 4.4

• With 2.5oC Climate Change:

• No urban = 3.5

• Coupled urban = 14.6

• Coupled urban + 25Wm-2 = 16

• Coupled urban + 75Wm-2 = 22


Summary.

• Forcings and feedbacks between climate, local heat release, and the urban heat island require coupled climate-urban models.

• Met Office UM provides one such framework.

• Simple scheme captures UHI.

• Warming similar for vegetation and urban surface in HadCM3

• Local heating is significant additional driver of change

• Feedbacks are important in 25km regional model

• Important for capturing extremes in night time temperatures.


Objectives.

• Improved quantification of urbanisation and anthropogenic heating in climate change.

• Urban model development, assessment and uncertainty (Maggie Hendry – 9am Weds)

• Collaborations to develop urban planning tools and impact assessments:

• SCORCHIO (SCORCHIO - Sustainable Cities: Options for Responding to Climate cHange Impacts and Outcomes.

http://www.sed.manchester.ac.uk/research/cure/research/scorchio/

• CIRCE – Climate Change and Impacts research: The Mediterranean environment

http://www.circeproject.eu/







Documents

© Crown copyright Met Office Climate Change, Cities, and the Urban Heat Island Mark McCarthy, Martin Best, Richard Betts, Maggie Hendry