Filtering by
- Member of: Phoenix Regional Heat and Air Quality Knowledge Repository
- Member of: MLFC Learning Futures Collaborative Collection
Maricopa County experiences extreme heat, which has adverse effects on community health and has been recognized as a serious public health issue. Therefore, the Maricopa County Department of Public Health (MCDPH) has conducted surveillance activities to assess morbidity and mortality due to extreme heat for the past 10 years. In 2016, MCDPH was interested in expanding their scope to include other climate-sensitive public health hazards. Subsequently, a network of stakeholders with an interest in the health effects of climate-sensitive hazards was established as the Bridging Climate Change and Public Health (BCCPH) stakeholder group. A smaller Strategic Planning Workgroup of key stakeholders from the BCCPH group was then convened over three sessions to work on a strategic plan for the group, which culminated in this document.
Practical Vision
The driving discussion question to identify the Strategic Planning Workgroup’s practical vision was, “What do we want to see in place in the next 3-5 years as a result of our actions?” The goal of this question was to help the group develop concrete outcomes that the BCCPH workgroup would like to achieve through activities included in the strategic plan. The following goals were identified:
A healthy community infrastructure design
Reframed messaging for multiple stakeholder needs
A coordinated multi-scale education effort
Improved health strategies and outcomes
A diverse network of partnerships for climate change adaptation and mitigation planning and development
New funding opportunities
Policy and research strategies, and private sector engagement.
Underlying Contradictions
The driving discussion question to identify underlying contradictions was, “What is blocking us from moving towards our practical vision?” The following challenges were identified:
People act out of self-interest vs. common good
Siloed effects lead to poor coordination
Political partisanship delays unified action
Conflicting information leads to biases
Culture and convenience impacts action
Vulnerable populations not represented, and normalization of climate change related negative effects
Strategic Directions
During the BCCPH Strategic Planning Workgroup meetings, participants identified five strategic directions for addressing environmental concerns affecting the health and well-being of the community. These strategic directions are in agreement with the climate and health adaptation strategies outlined in the Arizona Climate and Health Adaptation Plan. The strategic directions for Maricopa County are:
Fostering Environmental Action for a Healthier Community
Coordinating Research and Collaborative Efforts to Catalyze Change
Developing a Strategic and Targeted Communication Plan
Promoting Community Awareness and Public Education about Climate and Health
Celebrating Success and Champions
The City of Phoenix’s Cool Urban Spaces Report (2014) investigated the impact of the Phoenix Cool Roofs and Tree and Shade Master Plan initiatives on the city. The study evaluated how these heat mitigation efforts affect microclimates and human thermal comfort in the Phoenix metropolitan area. These findings are especially relevant as rapid and extensive urbanization has led to an urban heat island (UHI) effect that has increased steadily at approximately 0.9°F per decade. The city’s questions guiding this research were: 1. What are the cooling benefits achieved by increasing tree canopy from 10% (current) to 25% (2030 goal) and/or implementing cool roofs under existing conditions and projected warming? 2. What is the diurnal thermal benefit of tree canopy shade for a typical heat wave day during pre-monsoon summer?
The impacts of cool roofs and trees on near-ground air temperatures were modeled through 54 scenarios for a typical residential neighborhood in Phoenix. We ran the model for a combination of three tree-planting scenarios (no trees, current canopy cover and 2030 canopy goal) and three landscaping scenarios (mesic, oasis and xeric) with regular roofs and cool roofs under current climate conditions and two climate change projections. Two significant results of the tree and shade initiative are: 1. Increasing tree canopy cover to 25% leads to an additional temperature reduction of 4.3°F, which is a total cooling benefit of 7.9°F as compared to a bare neighborhood, and 2. Switching landscaping from xeric to oasis, i.e., adding grass patches to residential backyards, reduces average neighborhood temperatures by 0.4°F to 0.5°F.
The scenario with the lowest air temperatures is the residential neighborhood with mesic landscaping, 25% tree canopy cover and cool roofs under current climate conditions with an average neighborhood temperature of 99.5°F. In contrast, the xeric neighborhood with no tree cover and regular roofs under the high-emissions climate change scenario is the hottest. This indicates that the combination of increased tree canopy cover and cool roofs does lower temperatures as well as reduce the demand for air conditioning, thereby reducing anthropogenic heat. However, trees and cool roofs are only part of the solution and need to be included in a broader, more comprehensive mitigation and adaptation plan.
Across all climate and tree scenarios, the effect of cool roofs alone on local daytime temperatures is relatively low. Air temperature reduction only amounts to 0.5°F in the neighborhood. Regarding the city’s cool roofs initiative, results show little benefit for extending this project to commercial and residential properties based on its cooling impacts alone. Our research thus far indicates that there is no simple solution to mitigating the UHI, but a complex balance of strategies will be necessary so that efforts to lower the daytime temperatures do not increase nighttime temperatures or shift UHI impacts to more vulnerable populations.
As a result of three workshops within each community, the residents brought forth ideas that they want to see implemented to increase their thermal comfort and safety during extreme heat days. As depicted below, residents’ ideas intersected around similar concepts, but specific solutions varied across neighborhoods. For example, all neighborhoods would like to add shade to their pedestrian corridors but preferences for the location of shade improvements differed. Some neighborhoods prioritized routes to public transportation, others prioritized routes used by children on their way to school, and others wanted to see shaded rest stops in key places. Four overarching strategic themes emerged across all three neighborhoods: advocate and educate; improve comfort/ability to cope; improve safety; build capacity. These themes signal that there are serious heat safety challenges in residents’ day-to-day lives and that community, business, and decision-making sectors need to address those challenges.
Heat Action Plan elements are designed to be incorporated into other efforts to alleviate heat, to create climate-resilient cities, and to provide public health and safety. Heat Action Plan implementation partners are identified drawing from the Greater Phoenix region, and recommendations are given for supporting the transformation to a cooler city.
To scale this approach, project team members recommend a) continued engagement with and investments into these neighborhoods to implement change signaled by residents as vital, b) repeating the heat action planning process with community leaders in other neighborhoods, and c) working with cities, urban planners, and other stakeholders to institutionalize this process, supporting policies, and the use of proposed metrics for creating cooler communities.
ASU faculty and students share research at Phoenix City Hall regarding urban heat, including causes, consequences, and potential solutions.
Presentation by David Sailor, professor in the School of Geographical Sciences and Urban Planning and director of the Urban Climate Research Center at ASU. Sailer's presentation addresses how to define urban heat islands (UHI), and decisions about why and how to measure these complex ecosystems.
Shade plays an important role in designing pedestrian-friendly outdoor spaces in hot desert cities. This study investigates the impact of photovoltaic canopy shade and tree shade on thermal comfort through meteorological observations and field surveys at a pedestrian mall on Arizona State University’s Tempe campus. During the course of 1 year, on selected clear calm days representative of each season, we conducted hourly meteorological transects from 7:00 a.m. to 6:00 p.m. and surveyed 1284 people about their thermal perception, comfort, and preferences. Shade lowered thermal sensation votes by approximately 1 point on a semantic differential 9-point scale, increasing thermal comfort in all seasons except winter. Shade type (tree or solar canopy) did not significantly impact perceived comfort, suggesting that artificial and natural shades are equally efficient in hot dry climates. Globe temperature explained 51 % of the variance in thermal sensation votes and was the only statistically significant meteorological predictor. Important non-meteorological factors included adaptation, thermal comfort vote, thermal preference, gender, season, and time of day. A regression of subjective thermal sensation on physiological equivalent temperature yielded a neutral temperature of 28.6 °C. The acceptable comfort range was 19.1 °C–38.1 °C with a preferred temperature of 20.8 °C. Respondents exposed to above neutral temperature felt more comfortable if they had been in air-conditioning 5 min prior to the survey, indicating a lagged response to outdoor conditions. Our study highlights the importance of active solar access management in hot urban areas to reduce thermal stress.
We generated 5-meter resolution SVF maps for two neighborhoods in Phoenix, Arizona to illustrate fine-scale variations of intra-urban horizon limitations due to urban form and vegetation.
This established model is applied here to show the relative effects of four common mitigation strategies: increasing the overall (1) emissivity, (2) percentage of vegetated area, (3) thermal conductivity, and (4) albedo of the urban environment in a series of percentage increases by 5, 10, 15, and 20% from baseline values.
Here, 201 surveys were distributed in Metropolitan Phoenix to determine the social impacts of the heat warning system, or more specifically, to gauge risk perception and warning response.
Context:
With rapidly expanding urban regions, the effects of land cover changes on urban surface temperatures and the consequences of these changes for human health are becoming progressively larger problems.
Objectives:
We investigated residential parcel and neighborhood scale variations in urban land surface temperature, land cover, and residents’ perceptions of landscapes and heat illnesses in the subtropical desert city of Phoenix, AZ USA.
Methods:
We conducted an airborne imaging campaign that acquired high resolution urban land surface temperature data (7 m/pixel) during the day and night. We performed a geographic overlay of these data with high resolution land cover maps, parcel boundaries, neighborhood boundaries, and a household survey.
Results:
Land cover composition, including percentages of vegetated, building, and road areas, and values for NDVI, and albedo, was correlated with residential parcel surface temperatures and the effects differed between day and night. Vegetation was more effective at cooling hotter neighborhoods. We found consistencies between heat risk factors in neighborhood environments and residents’ perceptions of these factors. Symptoms of heat-related illness were correlated with parcel scale surface temperature patterns during the daytime but no corresponding relationship was observed with nighttime surface temperatures.
Conclusions:
Residents’ experiences of heat vulnerability were related to the daytime land surface thermal environment, which is influenced by micro-scale variation in land cover composition. These results provide a first look at parcel-scale causes and consequences of urban surface temperature variation and provide a critically needed perspective on heat vulnerability assessment studies conducted at much coarser scales.