While cities promote efforts to limit the temperature increase to 1.5°C, the objective is still far-reaching. At the same time, cities already experience the compound effects of climate change (for instance droughts and heat waves). To this end, cities need to determine the critical pathways to improve their adaptation to climate change. They need also to work proactively with their stakeholders to build and invest in the infrastructure and incentives to cope with existing climate change impacts as well as those anticipated for the next decades.
The UIA Green-Blue-Gray project to Adapt Schools to Climate Change (GBG_AS2C)
Barcelona is a compact city of 1.6 million inhabitants with a hot and humid climate in the warm period of the year. The city is exposed to an excessive heat burden that is expected to raise in the following decades due to the increased frequency and intensity of heatwaves because of climate change.
The GBG_AS2C project implemented an innovative adaptation plan to climate change through the conversion of schoolyards to “cool islands” (termed as Climate Shelters) primarily with a mix of blue (water points), green (more shadow spaces and greenery in the courtyards), gray (interventions on the buildings and use of permeable materials) measures. The project has already converted 11 schools into climate shelters, whereas the City of Barcelona increased the number to 30 schools by exploiting another running program.
Urban greenery contributes to a considerable reduction of urban overheating through evapotranspiration and shading. It removes pollutants and contributes to the retention of stormwater runoff, and improves the health of urban residents.
Urban fabric (impermeable construction materials) influences the land surface and air temperature fields and reduces the cooling strength of rainwater evaporation. Several cities around the world have promoted programs for replacing typical urban materials with climate-friendly ones.
The blueprint of actions
Be part of an overarching climate strategy
Barcelona implements a thorough Climate Plan in view of both mitigation and adaptation to climate change. The main targets for 2030 are to reduce its levels of CO2 equivalent emissions by 40% per capita compared to those for 2005 (mitigation) and to increase the urban green space by 1.6 km2, in other words, 1 m2 for each current resident.
The Plan includes several medium and long-term targets and in particular promotes the transformation of communal spaces as a climate change tackling strategy.
Listen to the city
Cities are dynamic systems. Their land cover changes over time, thus influencing the state of the thermal environment and potentially the vulnerability of the city to climate change. Periodic updates of land cover are important for focused adaptation (Figure 1).
Figure 1. Land cover of Barcelona (source: Urban Atlas 2018). Dark red: continuous urban fabric; purple: commercial or industrial units; green: urban greenery.
Conduct a climate risk assessment
The definition of the state of the city environment as well as of the impacts of climate change at the local level are critical preconditions for the creation of a focused adaptation plan to climate change. In the event that the above preconditions are not met, the benefits from the application of the respective measures are considerably reduced.
In the GBG_A2CC, an analysis of the prevailing environmental and climatic conditions was performed and was further supported by estimates of future impacts of climate change on the city as described in the Climate Plan of Barcelona. Figure 2 presents the impacts of climate change on Barcelona and Figure 3 shows the spatial vulnerability of Barcelona to heat waves.
Figure 2. Impacts of climate change on Barcelona (source: Climate Plan 2018-2030, City of Barcelona).