Abstract
Understanding public perceptions of climate is critical for developing an effective strategy to mitigate the effects of human activity on the natural environment and reduce human vulnerability to the impacts of climate change. While recent climate assessments document change among various physical systems (e.g., increased temperature, sea level rise, shrinking glaciers), environmental perceptions are relatively under-researched despite the fact that there is growing skepticism and disconnect between climate science and public opinion. This study utilizes a socio-ecological research framework to investigate how public perceptions compared with environmental conditions in one urban center. Specifically, air temperature during an extreme heat event was examined as one characteristic of environmental conditions by relating simulations from the Weather Research and Forecast (WRF) atmospheric model with self-reported perceptions of regional and neighborhood temperatures from a social survey of Phoenix, AZ (USA) metropolitan area residents. Results indicate that: 1) human exposure to high temperatures varies substantially throughout metropolitan Phoenix; 2) public perceptions of temperature are more strongly correlated with proximate environmental conditions than with distal conditions; and 3) perceptions of temperature are related to social characteristics and situational variables. The social constructionist paradigm explains public perceptions at the regional scale, while experience governs attitude formation at the neighborhood scale.
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Notes
Gallup’s findings on America’s increasing skepticism about climate change were challenged by a Stanford poll that asked slightly different questions and found a solid majority of the public (75%) believes that the earth has been heating up over the last 100 years and human behavior is responsible (Krosnick, Op Ed in the New York Times, June 9, 2010). Editor in Chief of the Gallup Poll, Frank Newport, replied that a variety of other national polls “show demonstrable drops in Americans’ acknowledgement of and concern about global warming” (Newport, Letter to the Editor in the New York Times, June 17, 2010) Surveys conducted by the Yale Project on Climate Communication showed a shift over time toward less concern and more disbelief among the American public that climate change is happening. The percentage of the public who were alarmed or concerned in the 2008 survey was 51%, which slipped to 39% in 2010. Those who were doubtful or dismissive increased from 19% in 2008 to 31% in 2010 (Leiserowitz et al. 2010).
The average size of the Census Block Groups sampled in this study was 0.45 square miles (or 1.2 square kilometers); the average population count was 2,085 people per CBG.
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Acknowledgements
This study is based upon research supported by the National Science Foundation (NSF) under grant Nos. DEB-0423704 Central Arizona - Phoenix Long-Term Ecological Research (CAP LTER), SES-0345945 Decision Center for a Desert City (DCDC), and GEO-0816168 Urban Vulnerability to Climate Change. Any opinions, findings, and conclusions or recommendation expressed in this study are those of the authors and do not necessarily reflect the views of the NSF.
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Appendix 1: A technical note on the WRF simulations
Appendix 1: A technical note on the WRF simulations
This study employed WRF version 3.0.1.1 to simulate spatial and temporal distribution of T 2m in the Phoenix metropolitan area during the extreme heat event 15–19 July 2005. The WRF run was started at 00 UTC (1700 LST) allowing 24 overlapping hours for model spin up for 72 h simulation periods. 2-way nested WRF model runs with four domains and resolutions of 27, 9, 3 and 1 km, respectively were performed. In the simulations, 41 vertical levels were used with the first five vertical levels of ~25, 35, 45, 60 and 80 m AGL. The innermost domain included the Phoenix metropolitan area, surrounding desert and agricultural land.
WRF initial and boundary conditions were provided by NCEP ETA analysis data that are available with a 40 km resolution at a 3-h time-step. Planetary boundary layer processes were included via the Mellor-Yamada-Janjic scheme (Janjic 2002), microphysics through the WRF Single-Moment 3-class simple ice scheme (Hong et al. 2004), convection for the domains with 27 km and 9 km resolutions by the Kain-Fritsch scheme (Kain 2004) and the long and short wave radiation processes were included through the Rapid Radiative Transfer Model (Mlawer et al. 1997) and Dudhia scheme (Dudhia 1989), respectively. The Noah UCM and the Noah Land surface model (Noah LSM; Chen et al. 1997) were applied to the fraction of a model grid cell with built and natural surfaces, respectively.
An anthropogenic heat flux, Q F , derived by the Sailor and Lu (2004) method was added to the sensible heat flux in WRF. Hourly Q F values are based on the monthly energy consumption and average vehicle kilometers traveled per person. The average energy and fuel consumption data are spatially and temporally allocated based on the spatial distribution of the working and residential population densities (Grossman-Clarke et al. 2005). For this particular urban area, which is mostly suburban and not very densely settled, Q F values are small in comparison to the other heat fluxes. Maximum values for the built-up urban, xeric, and mesic residential areas are ~30, 35 and 20 W m−2 and occurred during the evening rush hour (LST 1700). Values during other day time hours are between 5 and 25 Wm−2.
The standard procedure for obtaining initial soil moisture for WRF is by interpolating the NCEP ETA model soil moisture values to the WRF spatial resolution. The initial soil moisture data reflect conditions in the native desert surrounding Phoenix but not the soil moisture content as influenced by specific local irrigation practices. Therefore the standard WRF cannot account for effects of irrigation on latent heat fluxes and subsequently air temperatures.
Irrigation occurs in the region year round to sustain agricultural productivity and non-native plant species that are predominantly used in urban landscaping. Most plants cannot survive extended periods of water stress, particularly during the hot summer months. Flood irrigation of agricultural fields is the preferred irrigation practice. For example, approximately 10–15 cm of water are applied to agricultural fields on a weekly basis via flooding during the summer months. This provides soil moisture conditions at field capacity to a depth of about 90 cm. Therefore, to account for flood irrigation in the WRF simulations, the initial soil moisture content of all soil levels was set to the reference soil moisture which corresponds to field capacity (USGS LULC category 3). The Noah LSM soil model has four layers with thicknesses of 0.05, 0.25, 0.70 and 1.50 m. The predominant soil categories in the region are “sandy loam” and “loam” with field capacities of 0.383 and 0.329 m3 m−3 and wilting points of 0.047 and 0.066 m3 m−3. In the course of the simulations the soil moisture content for the sandy loam dropped to 0.35, 0.36, 0.32 m3 m−3 for soil layer one to three and stayed at field capacity for layer four. Plants did not experience significant water stress. In comparison the climatological soil moisture content as obtained from the NCEP ETA model initial data are 0.10, 0.11, 0.12 and 0.14 m3 m−3.
Drip irrigation (the placement of drippers close to the plants’ stems to allow water to drip over an extended period of time into the soil) is the preferred irrigation practice for urban vegetation in Phoenix (Martin 2001; Martin et al. 2003). This irrigation technique ensures that there is sufficient water available in the root zone of plants to fulfill the transpiration demand, but very little water is “lost” by soil evaporation because the soil surfaces in between plants are usually dry. In WRF, the root depth of the urban and agricultural vegetation extends to 1 m (layer 3). To account for the drip irrigation practice and to avoid high evaporation rates from bare soil surfaces that are usually dry in urban landscaping in Phoenix, the initial soil moisture content was increased for the 3 sub-surface layers for the urban land use categories but not for the top soil layer. This ensured that vegetation in the model did not experience water stress and was able to transpire according to the atmospheric demand. The initial soil water content of the top soil layer was left at the value provided by the NCEP ETA model.
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Ruddell, D., Harlan, S.L., Grossman-Clarke, S. et al. Scales of perception: public awareness of regional and neighborhood climates. Climatic Change 111, 581–607 (2012). https://doi.org/10.1007/s10584-011-0165-y
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DOI: https://doi.org/10.1007/s10584-011-0165-y