Toward Sustainable Urban Adaptation and Mitigation

Transcription

1 Toward Sustainable Urban Adaptation and Mitigation Matei Georgescu, Assistant Professor School of Geographical Sciences & Urban Planning Senior Sustainability Scientist, Global Institute of Sustainability Arizona State University Fall Meeting Roof Coatings Manufacturers Association 14 October, 2015

2 Living In an Increasingly Urban World Late 2000 s denoted a landmark juncture for humanity. Extensive conversion of natural to engineered landscape is projected through 2030 and beyond. How much expansion? Georgescu, M., et al. (2015), Environmental Research Letters, 10(6),

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4 Consequences of (Unchecked) Urban Expansion Heat Stress Air quality Energy availability Water supply/quality

5 Modeling Our [Climate] System Incoming solar radiation Atmospheric scattering Atmospheric absorption Turbulence Cloud growth and various forms of precipitation Vegetation & Soil properties

6 Navier-Stokes Equations + Physics

7 Modeling [Our] Urban Climate System Balance of incoming and outgoing energy fluxes: Surface energy budgets of urban areas and their more rural surroundings differ because of variability in (1) land cover and surface characteristics, and (2) level of human activity (e.g., anthropogenic heat).

8 Sky View Factor and Morphological Characterization What percentage of the sky is visible? Enormous complexity of cityscapes and view factors B. Holmer et al. (2001), Theoretical and Applied Climatology

9 Real Urban Areas Vancouver, Canada Uppsala, Sweden Toyono, Japan Akure, Nigeria Phoenix, Arizona University campus of Szeged, Hungary Adapted from: Stewart and Oke, (2012) Bull. Amer. Meteor. Soc. According to UN 2012 (world population forecast) more than 70 definitions of what urban means: no consensus globally on what urban means.

10 Defining Urban in Models Urban land use/land cover in WRF model can be characterized as: A single class (i.e., bulk parameterization ) MODIS LULC/Urban using SLUCM (or multi-layer model) NLCD 3-class LULC/Urban using SLUCM (or multi-layer model) Urban representation as city and/or metro specific morphological characteristics. Ching, J. et al. (2009), National Urban Database and Access Portal Tool. Bull. Amer. Meteor. Soc., 90,

11 How do we tackle solutions? 1. Utility of process-based models (i.e., based on fundamental physical principles), in conjunction with suitable observational data. Process understanding is mandatory. 1. Scenario-based assessment (i.e., alternative, and in principle realistic, futures) permits process evaluation associated with differential trajectory paths (i.e., not just the what, but the how as well). 2. Uncertainty assessment quantification and tradeoffs examination is permitted. Adaptation Mitigation Urban solutions require incorporation of essential elements of both Adaptation and Mitigation approaches.

12 How do we tackle solutions? Adaptation Adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities. Source: IPCC AR4 Mitigation An anthropogenic intervention to reduce the anthropogenic forcing of the climate system; it includes strategies to reduce greenhouse gas sources and emissions and enhancing greenhouse gas sinks. Source: IPCC AR4 Adaptation Mitigation Urban solutions require incorporation of essential elements of both Adaptation and Mitigation approaches.

13 Common Urban Adaptation Strategies Cool Roofs/materials Green Roofs Source: Henry Builders Trees Chicago City Hall (Source: National Geographic) Phoenix Civic Space Park is located in downtown Phoenix. The city is attempting to increase vegetation cover to 25% across Phoenix, by (Source: Phoenix Park and Recreation Department)

14 Integrated Climate Land Use Scenario: A Scenario-based Assessment Urban: 2000 c ICLUS_A2: 2100 c Bierwagen et al., (2010), Proc. Natl. Acad. Sci., 107(49), Expansion is consistent with SRES GHG emissions storylines rather than independent, locally generated projections, that may be in conflict with adjacent socioeconomic development (and may therefore be unrealistic).

15 Scenario-based U.S. Megapolitan Expansion Naming Convention (CONUS simulations) Experiments: Climate (3 ensemble members) Horizontal Resolution: 20-km Δx, Δy 1. Control: Baseline urban (2000) 2. A2_ICLUS: Maximum urban expansion for B1_ICLUS: Minimum urban expansion for A2_GreenRoofs: As A2 with green roofs deployment 5. A2_CoolRoofs: As A2 with cool roofs deployment 6. A2_GreenAlbedo: As A2 with hybrid reflective and evapotranspiring properties. Each scenario represents 24 years of simulations (8 years X 3 ensemble members) In total: 144 years of CONUS simulations (~2 million grid cells)

16 Cool Roofs ENERGY STAR Qualified products. Source:

17 2m Temp difference ( C): JJA [A2_ICLUS Control] For all regions, each urban adaptation strategy completely offsets urban-induced warming. Cool roofs are more effective at cooling than green roofs, but geography matters (e.g., Florida relative to California). Hybrid strategies reveal an urban adaptation saturation effect. Georgescu, M., P. Morefield, B. G. Bierwagen, and C. P. Weaver (2014), PNAS, 111 (8),

18 Near Surface Temperature: Urban relative to GHGs Georgescu, M., P. Morefield, B. G. Bierwagen, and C. P. Weaver (2014), PNAS, 111 (8),

19 Hydroclimatic tradeoffs: JJA [A2_CoolRoofs Control] Georgescu, M., P. Morefield, B. G. Bierwagen, and C. P. Weaver (2014), PNAS, 111 (8),

20 Multi-scale Assessment: California c c Georgescu, M. (2015), Journal of Climate

21 Multi-scale Assessment: California [JJA] c Impact of Urban Expansion [ C] Georgescu, M. (2015), Journal of Climate

22 Multi-scale Assessment: California [JJA] c Impact of Green Roofs Deployment [ C] Georgescu, M. (2015), Journal of Climate

23 Multi-scale Assessment: California [JJA] c Impact of Cool Roofs Deployment [ C] Georgescu, M. (2015), Journal of Climate

24 Multi-scale Assessment: California Urban Expansion: Nighttime temps increased (~2 C); minimal changes during daytime hours Green Roofs deployment: Nighttime temps increased slightly (<1 C); minimal changes during daytime hours Cool Roofs deployment: Nighttime temps unchanged; significant decrease of temps during daytime hours (~4 C) Georgescu, M. (2015), Journal of Climate, 28(7),

25 Air Quality Implications Daytime Nighttime Urban Expansion Green Roofs deployment Cool Roofs deployment Georgescu, M. (2015), Journal of Climate, 28(7),

26 Assessment Report on Climate Change and Cities (ARC3-2) Chapter Teams at ARC32 Midterm Workshop Urban Planning and Design Mitigation and Adaptation Equity and Environmental Justice Economics, Finance, and the Private Sector Urban Climate Science Disasters and Risk Urban Energy Water, Wastewater, and Sanitation Urban Solid Waste ARC3-2: Assist cities around the world to address the causes and consequences of climate change (Cambridge University Press). It will be presented at COP21 in Paris in 2015.

27 How do we begin to Address Solutions? 1. Time to recognize 1-size-fits-all solutions are not possible and place-based approaches matter. Exclusive focus on near-surface temperatures (as has been done until recently) is NOT the answer. 2. By recognizing that appropriate solutions fall within a broader sustainability framework, that include elements of both adaptation and mitigation, we can comprehensively and quantitatively examine co-benefits, tradeoffs, uncertainty, and unintended consequences e.g., solutions to decrease urban heat should not be deployed to target areas of high heat exposure, but rather areas of high heat exposure sensitivity (i.e., embedded within socioeconomic awareness). 2. At what value(s) of reflectivity do cool roofs still lead to benefits without leading to unintended consequences, and how does this vary geographically? THANK YOU!