Urban adaptation can roll back warming of emerging megapolitan regions

Abstract

Modeling results incorporating several distinct urban expansion futures for the United States in 2100 show that, in the absence of any adaptive urban design, megapolitan expansion, alone and separate from greenhouse gas-induced forcing, can be expected to raise near-surface temperatures 1-2°C not just at the scale of individual cities but over large regional swaths of the country. This warming is a significant fraction of the 21st century greenhouse gas-induced climate change simulated by global climate models. Using a suite of regional climate simulations, we assessed the efficacy of commonly proposed urban adaptation strategies, such as green, cool roof, and hybrid approaches, to ameliorate the warming. Our results quantify how judicious choices in urban planning and design cannot only counteract the climatological impacts of the urban expansion itself but also, can, in fact, even offset a significant percentage of future greenhouse warming over large scales. Our results also reveal tradeoffs among different adaptation options for some regions, showing the need for geographically appropriate strategies rather than one size fits all solutions.sustainability | mitigation | land-use change | urbanization | urban climate

A Global Geospatial Ecosystem Services Estimate of Urban Agriculture

“…Consequently, Africa will make up an increasingly larger fraction of total urban land (Güneralp & Seto, 2013). Such recognition of anticipated urban expansion has implications for prioritization of strategies guiding sustainable urban development (i.e., retrofitting relative to planning of future cities), which have largely focused on reduction of greenhouse gas emissions and on land-based solutions such as green and cool roofs (Georgescu et al, 2014;Sailor, 2008), increased vegetation fraction (Krayenhoff et al, 2014;Middel et al, 2015), and local engineering-based solutions (Meggers et al, 2016). In addition to potentially beneficial aspects of landscape configuration (Connors et al, 2013), deployment of natural capital within built environments may provide considerable additional human and environmental cobenefits.…”

Citywide Impacts of Cool Roof and Rooftop Solar Photovoltaic Deployment on Near-Surface Air Temperature and Cooling Energy Demand

“…Many studies reveal that the large-scale deployment of roofing technologies is an effective means of reducing energy consumption (e.g., Akbari et al 2009;Oleson et al 2010;Menon et al 2010;Salamanca et al 2012a;Cotana et al 2014;Georgescu et al 2014). Cool roofs, by virtue of increased reflectivities, absorb less incoming shortwave radiation than dark roofs, thereby promoting a lower skin temperature.…”

“…In wintertime, the potential penalty associated with cool roofs is in general outweighed by the summer benefit and can be annulled if the roofs are typically covered with snow during the cold season (Bretz and Akbari 1997). However, energy savings are more limited for areas that do not have extensive wintertime snow pack, such as the Mid-Atlantic states of the USA (e.g., Georgescu et al 2014). Various studies have documented the direct benefits of large-scale cool roof deployment in urban areas.…”

“…Green roofs can more efficiently partition available energy into latent heat and reduce sensible heat transmission into the urban environment. Although regional differences exist between cool and green roof technologies (e.g., Georgescu et al 2014), and their assessment must extend beyond the examination of near-surface temperature impacts, this recent work has demonstrated that green roofs (assuming abundant soil moisture) can be nearly as effective as cool roofs at reducing near-surface air temperature.…”

How cities can beat the heat

“…"If we don't have that, then we don't have precipitation, " says Georgescu. In a modelling study 7 , he found that if cool roofs were widely implemented in urban areas from Florida to the northeastern United States, daily summertime precipitation could decrease by 2-4 millimetres by 2100.…”