Cooling for sustainable development

1 Cooling for Sustainable Development 2 Radhika Khosla*1,2, Nicole D. Miranda1,3, Philipp A. Trotter1,2,4, Antonella Mazzone1,2, Renaldi 3 Renaldi1,3 , Caitlin McElroy1,2, Francois Cohen1,2,6, Anant Jani1,5, Rafael Perera-Salazar1,5, Malcolm 4 McCulloch1,3. 5 1 6 2 7 University of Oxford, UK. 8 3 Energy and Power Group, Department of Engineering Science, University of Oxford, UK. 9 4 Chair for Operations Management, RWTH Aachen University, Germany. 10 5 Nuffield Department of Primary Care, University of Oxford, UK. 11 6 12 *corresponding author ([email protected]) Future of Cooling Programme, Oxford Martin School, University of Oxford, UK. Smith School of Enterprise and the Environment, School of Geography and the Environment, Institute for New Economic Thinking at the Oxford Martin School, University of Oxford, UK 13 14 Abstract 15 The unprecedented rise in cooling demand globally is a critical blind spot in sustainability debates. We 16 examine cooling as a system comprised of active and passive measures, with key social and technical 17 components, and explain its link to all 17 Sustainable Development Goals. We propose an analytical 18 and solution-oriented framework to identify and shape interventions towards sustainable cooling. The 19 framework comprehends demand drivers; cradle-to-cradle stages; and system change levers. By 20 intersecting cooling stages and levers, we discuss four specific, exemplary interventions to deliver 21 sustainable cooling. We propose an agenda for research and practice to transition towards sustainable 22 cooling for all. 23 24 1 25 Introduction 26 Cooling has been fundamental to shaping society in the twentieth century1–3 and will be even more so 27 in the coming decades. It enables thermal comfort of societies at high temperatures and is critical for 28 industrial production and for the preservation of food and medicine. Air conditioning is widely 29 considered to be an agent of modernity and a driver of the changing nature of life in the tropics, yielding 30 deep associations between cooling and civilization’s progress4. The trajectory of cooling is currently 31 undergoing an extraordinary change: as the economies and populations of the hottest parts of the world 32 grow, the demand for cooling for well-being has the potential to drive one of the most substantial 33 increases in energy and greenhouse gas (GHG) emissions known in recent history5. Under current 34 climate and socio-economic conditions, three-quarters of humanity will face health risks from deadly 35 heat6, with approximately two to four billion people requiring domestic space cooling to avoid these 36 risks, a number that exceeds the energy poverty gap indicated in the Sustainable Development Goals7. 37 The energy needed for space cooling alone is projected to triple by 2050, an equivalent of adding 10 38 new air conditioners (ACs) every second for the next 30 years8. This will require electricity generation 39 capacity akin to that of the US, EU and Japan today, implying myriad socio-economic, environmental 40 and political challenges8. 41 Despite the extraordinary projections for its growth, cooling is a blind spot in today’s sustainability 42 debates8. No cooling-related term (such as "cool", "cooling", "cold", "refrigeration", “freeze”, "ozone", 43 "heat" or "thermal") features in the text of the UN’s 2030 Agenda for Sustainable Development, the 17 44 goals, or their 169 targets. Two gaps in the literature are particularly salient. First, beyond selected 45 evident links to energy7,9, the extent of the relationship between cooling and the SDGs is neither well 46 understood nor systematically mapped. This is within the larger context of recent work acknowledging 47 the importance of describing the interrelationships between SDGs to design cross-cutting 48 interventions10–12. Secondly, there is a paucity of literature on cooling and a narrowness in its scope. 49 The literature that does exist is either limited to a technological13–15, behavioural16 or an extreme heat 50 impact focus17; or confines sustainability analyses to the environmental impact of refrigerants18,19, and 51 does not consider a holistic and systemic view to the provision of cooling. By contrast, extant studies 2 52 on heating buildings are orders of magnitude more numerous than those of cooling them20,21. As a 53 consequence, in order to structure the challenges and solution space to achieve sustainable cooling, we 54 argue that a novel, whole system perspective is needed. 55 In this Perspective, we first examine the linkages between each of the 17 SDGs and the provision of 56 cooling by assessing the literature. Second, to respond to the absence of considering cooling as a multi- 57 faceted system22, we develop an encompassing analytical framework that accounts for the interlinkages 58 between cooling and the SDGs with the objective of identifying, understanding and shaping intervention 59 pathways and cross-cutting solutions towards sustainable cooling. By ‘sustainable’ we mean striking 60 an adequate balance between natural and human-made capital, to maximise beneficial societal and 61 environmental outcomes23. Finally, we demonstrate how the framework can be used to categorise, 62 identify and distil a set of specific, high-potential interventions and propose an agenda for research and 63 action to facilitate the transition towards sustainable cooling for all. The framework and agenda are 64 solution-oriented by design and help respond to the urgent call for developing actionable 65 transformations to achieve the SDGs,24,25 especially the significant opportunities that are at risk of path- 66 dependent trajectories26. 67 68 Cooling and the SDGs 69 We review the academic literature to identify the type and nature of relationships between cooling and 70 each of the 17 SDGs. We define a structured topic search query for each SDG and apply it to 12,000+ 71 peer-reviewed journals across disciplines. Search words were selected using a consensus-based expert 72 elicitation method and from SDG indicators and targets, combined with a common set of terms that 73 capture the literature on cooling (Supplementary Information). From 5.3 million documents (articles, 74 reviews, patents, and others) identified to contain SDG related topics, we find 0.43% or 23,093 75 documents to have mentioned cooling-related terms in their title, abstract or keywords (Figure 1). The 76 ratio of the total number of identified SDG documents compared to those which also include cooling- 3 77 related terms ranges from below 1.5 orders of magnitude for SDG 7 and SDG 12 to over 3 for SDG 4 78 and SDG 17. 79 The identified papers yield concrete and evidence-based examples of how cooling facilitates the 80 achievement of the SDGs (Table 1), demonstrating that cooling is directly linked to all 17 SDGs. 81 Table 1. Indicative examples of linkages between each SDG and the provision of cooling SDG SDG 1 SDG 2 SDG 3 SDG 4 SDG 5 SDG 6 SDG 7 SDG 8 SDG 9 SDG 10 SDG 11 SDG 12 SDG 13 SDG 14 Exemplary linkages between the SDG and cooling (see Table B.1 for references) No poverty Increased extreme heat without cooling provisions is linked to lower productivity from land and income, exacerbating poverty especially in developing countries. Reduced cooling from decreased urban green spaces is also linked to increased income poverty. Zero hunger Cooling enables food production and delivery via the cold chain as well as from cooling techniques that support food production in greenhouses and aquaponic systems. Good health Cooling reduces the health burden of severe exposure to heat, especially with climate and well being change impacts of rising temperatures. In addition, heat has an impact on infant wellbeing. Quality Cognitive faculties are impaired by extreme temperatures, and heat has a negative education effect on productivity and learning outcomes which are mitigated by cooling. Gender equality Household food-related activities are often women’s responsibilities, and the opportunities from cooling and refrigeration enable women to undertake small businesses and reduce time spent on daily food provision. Clean water Industrial processes (e.g. thermoelectric power plants) require vast amounts of water and sanitation for cooling with important implications and choices for water availability and quality. Affordable and Active space cooling and refrigeration have a very large electricity demand and clean energy influence clean energy system design (including via solar cooling technologies). Cooling is also required to generate clean energy, for instance via solar concentrated power. Decent work & Cooling reduces the negative health impacts on the economy and on worker economic productivity, especially in light of negative climate change impacts. growth Industry, Cooling in large quantities is vital for maintaining the resilience and sustainability of innovation & infrastructures, such as power plants and data centres, and creating adaptive infrastructure infrastructures in response to increasing urban heat island and population impacts. Reduced Sustainable cooling has the potential to reduce inequalities among and within inequalities countries and is proposed as a recipient of climate finance via multilateral funds for clean energy and climate investments, especially from OECD to developing countries. Sustainable The provision of active and passive cooling is key to the habitability and cities and sustainability of communities and cities in areas such as public and private transport, communities in homes, and in urban design and planning. Responsible Cooling consumption seriously burdens energy resources, and production of cooling consumption & technology has significant sustainability impacts across its life cycle (extraction to production disposal). Cooling from cold chains and refrigeration are also vital to reducing food waste. Climate action Cooling consumption drives large increases in GHG emissions driving climate change. Further, F-gases are a key by-product of refrigeration and air conditioning, which have amongst the highest global warming potential. Life below Cold chains and refrigeration practices are central to the fishing industry. Further, water industrial cooling processes affect underwater biodiversity (e.g., coastal water intake for cooling in nuclear plants affects jellyfish population). 4 SDG 82 Exemplary linkages between the SDG and cooling (see Table B.1 for references) Life on land Refrigeration at very low temperatures enables cryopreservation of endangered landSDG 15 living species. Furthermore, sustainable urban land use mitigates urban heat islands through evaporative cooling. Peace, justice Cooling is a focus of international agreements such as the Montreal Protocol, and SDG 16 and strong with rising visibility of its potential for Agenda 2030 and the Paris Agreement, institutions which aim for peace and justice across institutions. Partnerships for Cooling and refrigerants are part of the portfolio of global climate finance to SDG 17 the goals developing countries and plays a role in enhancing countries’ financing, technologies, and capacities for sustainable development. Note: Exemplary references for each link are provided in Table B.1 in the Supplementary Information B 83 84 As illustrated in the non-exhaustive list of examples in Table 1, the goals of zero hunger, good health 85 and wellbeing, and climate change are fostered by delivering cooling through cold chains for essential 86 food and nutrition, the supply of vaccines and protection against extreme heat, and reduction of GHG 87 emissions respectively. Performance of pupils in schools reduces considerably where hot weather 88 cannot be offset by the availability of cooling27. The reduction of inequalities (including gender) is a 89 social challenge that benefits from more just access to well-being-related resources such as cooling. 90 The evidence across the goals makes clear that how cooling is provisioned for is critical to SDG 91 outcomes. It also suggests how overlooking the links between cooling and the SDGs poses risks to 92 sustainability outcomes. For example: meeting the growth in cooling energy demand with inefficient 93 technologies can pose severe burdens to the availability of clean and affordable energy (SDG 7) and to 94 global temperature rise from refrigerants and fossil-fuel based power (SDG 13); unsustainable cooling 95 technology production can seriously stress energy resources and have significant sustainability impacts 96 from extraction to disposal (SDG 12). Furthermore, often there are positive and negative feedbacks 97 between cooling and the SDGs, thereby enabling the delivery of some goals, while undermining others. 98 For instance, cooling has been essential to protect good health and well-being (SDG 3)28, and will 99 continue to be critical in this regard as extreme temperatures rise, but the manner in which it is predicted 100 to grow comes at the serious cost of climate action (SDG 13). Recognizing the absence of cooling 101 through the SDGs is a critical first step in addressing the missed opportunities, and potential perils, that 102 arise from this gap. 103 5 104 Framework for transitioning towards sustainable cooling 105 Given the scale, pace, and complexity of growing cooling needs, how can the solution space for 106 transitioning cooling towards sustainable development be identified? There are promising disciplinary 107 frameworks that can help answer this question. While not addressing cooling specifically, the wider 108 sustainability transitions literature provides alternatives, particularly with the lens of the Multi-Level 109 Perspective which combines technological, systemic and exogenous macro-level landscape elements to 110 place socio-technical systems at the centre of analysis22,29. However, frameworks proposed in this 111 literature explain how transition happen, not how they can be directed, and typically focus on 112 technological novelty, overlooking changes in the deployment and the mechanisms of uptake of 113 technologies30. Frameworks in the transition management literature focus on interventions for 114 sustainability, but are mostly confined to governance levers31. The Energy Cultures approach provides 115 another alternative, anchoring system dynamics in interactions between people and technologies, 116 behaviours and norms16. At the same time, it refers less to institutions, governance and market 117 arrangements which are important in shaping consumption trajectories. The literature on Technology 118 Innovation Systems provide yet another related line of enquiry32, and while valuable in tracing the arc 119 of technology growth, it is less applicable to non-technological scenarios which can be relevant 120 especially in the context of passive cooling. 121 To enable a systemic transdisciplinary approach to cooling as a system within the context of sustainable 122 development29, we draw from the different literatures discussed above and propose a solution-oriented 123 framework that integrates across analytical silos (Figure 2). The framework consists of macro-level 124 drivers that impact cooling demand dynamics. We also categorise the different stages of cooling 125 delivery across the value chain. Further, we identify five levers which act on the cooling system, 126 specifically on each of the stages of cooling delivery, to influence the trajectory of the future of cooling. 127 The intersection of stages and levers yields a set of twenty interconnected intervention points for system 128 change33. We elaborate on each of these framework components below. 129 6 130 Macro-drivers of cooling as a system. Macro-drivers or trends are key to understanding the external 131 conditions which shape the required output and operation of the cooling system. These drivers are 132 characterised as being external to the cooling system but with an influence over how it evolves. These 133 are illustrated on the left-hand side of Figure 2. 134 First, socio-economic trends of urbanization, economic development, population growth, especially in 135 developing countries with hotter climates, as well as changing energy and appliances prices34,35 are 136 leading to shifting and unprecedented demands for cooling. This is observed, for example, in Mexico 137 where increased income and heat exposure have driven a sharp rise in air conditioning demand5. Second, 138 technological trends influence the demand for new cooling systems, their availability, configuration 139 and controls. The increased access to cooling technologies, rise in data centres for increasing internet 140 traffic and data loads, and expanding electrification (aligned with SDG 7) especially in South and South- 141 East Asia and sub-Saharan Africa are materially influencing the uptake of cooling7. Third, 142 environmental trends driven by climate change are altering cooling demand, particularly in cities with 143 urban heat island effects. Increasing extreme temperatures are changing global requirements of thermal 144 comfort, increasing GHG emissions and the use of ozone-sensitive refrigerants (i.e. phase-out of 145 Hydrofluorocarbons (HFCs) and Chlorofluorocarbons (CFCs)). Fourth, geopolitics trends reflected in 146 international multilateral agreements, such as the Paris Agreement, Kigali Amendment to the Montreal 147 Protocol, the UN Urban Agenda, among others, comprise a global geopolitical governance driver, 148 which has bearings on how countries and the private sector develop cooling technologies and design 149 related policies. Each of these macro global trends directly and indirectly influence how the future 150 trajectory of cooling evolves. 151 152 Stages of cooling delivery. We conceptualize the cooling value chain in four distinct stages (Figure 2) 153 to isolate the different constituents of the cooling system. The initial stage, resources, relates to the 154 provision of natural raw materials including their extraction and pre-processing. This includes the 155 metals which comprise cooling equipment, or the materials which passive cooling technologies are 156 made of, and the refrigerants used in ACs. The production and assemblages stage describes how 7 157 resources are combined into a passive or active form of cooling, for instance the process of 158 manufacturing fans and air-coolers, or that of creating high-insulation bricks. This stage also entails 159 technology design and deployment (e.g. installation). The third stage, namely cooling activities, 160 encompasses purchasing, operating and maintaining the service of cooling to meet demand. This stage 161 is defined in broad terms, ranging from large-scale, industrial cooling to individual-level activities such 162 as wearing lighter clothes to stay cool. End-of-life as the final stage includes the removal or 163 decommissioning of forms of cooling, often leading to reuse (e.g. upcycle, full or partial recycle), 164 elimination or disposal. Examples of how active and passive technologies may pass through the 165 different stages of cooling are presented in Table 2. 166 Table 2. Examples of cooling delivery stages for active and passive technologies Active cooling examples36 District cooling neighbourhood Split mode room air- network with conditioner (AC) centralised chillers Passive cooling examples37 Plants in and Transparent phasesurrounding buildings changing window for shading and material to reduce heat providing cooling38 gains Resources Metals, refrigerants, petrochemicals, and water required to produce ACs components Metals to produce chillers, metal or plastic pipes for network and water as heat-transfer fluid Seeds/cuttings, soil, nutrients and water Phase-change material (PCM), glass and frame (e.g. metal & wood) Production and assemblages Manufacturing processes of AC in a factory, distribution and installation in internal and external walls Laying underground network pipes, installing chillers and building cooling plant Planting vegetation in adequate location and orientation to shield heat (e.g. next to windows/tree canopies on walls) Manufacturing glazed windows with phase changing material in a factory, distribution and installation in building envelope Cooling activities People’s AC purchase decisions, and people’s AC use decisions (e.g. controlling the temperature set point) Operating and maintaining chillers and the cooling plant; and people’s temperature and timing settings Maintaining the vegetation in indoor and outdoor environments with support of the building administration (e.g. pruning) People’s window purchase and installation activities; smart window systems that maximise thermal comfort End-of-life Remanufacturing and Decommissioning of recycling of viable cooling plants and AC components; safe distribution network disposal of refrigerant gases Removing of vegetation for building refurbishment purposes; or sustainable disposal of vegetation, e.g. biomass for heat Once PCM windows reach the end of use, disposal is carried out or re-manufacturing Stages of cooling 167 168 Levers for change. We identify an encompassing set of five levers capable of driving sustainable system 169 change. Viewing cooling as a system comprised of interacting social and technical constituents, we 8 170 argue that cooling demand is defined by socio-cultural behaviours16,39 and satisfied by a set of 171 technological solutions22 which enable the delivery of cooling-related value in accordance to 172 companies’ business models40, forming markets that are governed by policies and set in the context of 173 wider physical and intangible infrastructures29. We therefore identify five interconnected levers as 174 social interactions, technology innovation, business models, governance, and infrastructure design. 175 The first lever concerns social interactions. With new technologies available to consumers, people 176 frequently readjust and reinvent their needs and priorities, and new behavioural patterns are perpetually 177 created41. Collective values resulting in pro-environmental behaviours shape technological adoption, 178 which indirectly have an impact on cooling resources and production and assemblages. The systematic 179 repetition of specific behaviours creates 'cultures of cooling,' which differ across geographies and time. 180 Recurring behavioural choices and habits can be environmentally beneficial (e.g. nature-based/zero- 181 carbon practices) or detrimental, with the ability to be a powerful lever for large-scale impact on global 182 resources and the environment. 183 Technology innovation, the second lever, influences ways of generating sustainable cooling through 184 new technologies and by responding to dynamic cooling needs. Technological advancement can foster 185 energy-efficient and affordable passive and active cooling. For instance, this lever can significantly 186 change the impacts of cooling by improved efficiency of the incumbent AC technology, i.e. vapour 187 compression cycle42. Similarly, improved phase change materials and radiative cooling can fulfil or 188 reduce space cooling demand. Technology innovation occurs across the stages of cooling and applies 189 to space, food and processes to meet changing cooling needs in a sustainable fashion. 190 The third lever, business models, shapes companies’ key business processes and how these are linked 191 internally and with external actors to provide cooling. Business models are critical to adopt and 192 implement both established and new cooling technologies, connecting technological innovations and/or 193 regulatory changes with user needs to deliver on their cooling demand. They consist of three critical 194 dimensions40, namely the firm’s value proposition, its value capture approach (how the value 195 proposition is realised and monetised), and value networks to support the value proposition. Sustainable 196 cooling-based value propositions could entail, for example, a socially responsible way of extracting raw 9 197 materials required for cooling, delivery of a food cold chain with net-zero emission or guaranteeing 198 high recycling rates of AC components. 199 The fourth lever of governance is key to align the multitude of actors and steer the direction of the 200 cooling transition via policy design and implementation. This lever comprises overarching policy 201 strategies for the future of cooling which are guided by the SDGs and individual actors’ objectives; 202 economic, regulatory and information instruments which implement the policy strategies; and 203 associated multi-level governance processes43. Sustainable cooling policies can comprise international 204 agreements as well as national guidelines and local, adaptation-focused instruments8. Deep 205 decarbonisation is likely to require a broad set of policy instruments44. For example, regulations are key 206 to effectively encouraging the deployment of the more efficient ACs which are often subject to energy 207 performance standards45. Expanding carbon pricing creates financial incentives to support efficient 208 ACs. A growing number of national cooling action plans provide an integrated policy vision towards 209 cooling across sectors. 210 Finally, the lever of infrastructure design for cooling encompasses both the broader context in which 211 cooling services are supplied and demanded. Infrastructures, such as the physical built environment and 212 the electric power system (or hard infrastructures), and equally, the degree of spatial interconnectedness 213 and human capabilities (or soft infrastructures) shape and enable different solutions for cooling. Cooling 214 and infrastructure need to provide urban resilience in light of climate change and increasing urban 215 populations. We assign a focal role to infrastructures because they predetermine the available action 216 space and provide an opportunity for choices and behaviours that are associated with sustainability46. 217 For example, for every ton of milk distributed, twenty times more is lost in sub-Saharan Africa than in 218 Europe as milk transport covers vast rural areas with no access to electricity infrastructure to power 219 cooling47. Designing and adjusting infrastructures offers significant potential for reshaping the 220 possibilities of cooling supply and demand. The choice of infrastructures and how they are combined 221 and used create path dependency and lock-in. In this way, careful selection of long-lived infrastructure 222 assets is critical for influencing future patterns of behaviour, organisation and development12. 10 223 Each of these five levers influences each stage of the four stages of cooling, with the potential to trigger 224 interventions that can shift the trajectory of cooling towards achieving sustainability outcomes. 225 226 Interventions to transition cooling towards sustainability 227 In this section, we demonstrate how the framework can be used to identify and map the solution space 228 of cooling interventions which have considerable potential to enable sustainable development. 229 Interventions at the intersections of each cooling stage and each lever of the framework are influenced 230 by one or several macro-drivers and can impact the entire cooling system so as to build momentum 231 towards sustainability transitions. By emphasizing the potential for purposeful intervention in complex 232 and inter-connected systems, our approach builds on the studies of social transitions and sensitive 233 intervention points33. Changes induced by any one of these interventions can be non-linear, path- 234 dependent, amplificatory, or recursive. We discuss four interventions with the potential to shift the 235 balance between natural and human-made capital towards more sustainable outcomes. While these 236 exemplify different intervention points in Figure 2 (namely, in turn, B3, I2, G1 & G4, and S3), the 237 interconnected nature of the cooling system implies that the realisation of the interventions’ full 238 potential can depend on supportive actions across adjunct intervention points. Table C.1 in the 239 Supplementary Information C lists the respective relevant drivers, stages of cooling and levers of these 240 four interventions. 241 Cooling as a Service (CaaS) business model (intervention point B3). Only a fraction of global cooling 242 demand is currently met, with climate change driving the need for more cooling globally in general, 243 and in many hot and low-income countries in sub-Saharan Africa and South Asia, specifically. This is 244 likely to exacerbate the cooling access gap. The “Cooling as a Service” (CaaS) business model 245 innovation is an approach to overcome these challenges. Its value proposition is to make 246 environmentally sustainable cooling more broadly accessible. Rather than pursuing the traditional way 247 of selling AC units, CaaS companies capture value by retaining ownership and operation of cooling 248 assets and charge customers for ensuring thermal comfort in their homes48. Critically, the often times 11 249 prohibitively large upfront investment burden is either shared or entirely taken away from end-users, 250 making access to cooling more attainable for low-income households. While CaaS has not been 251 implemented at scale in low-income countries, its asset ownership retention approach is similar to pay- 252 as-you-go (PAYG) business models for solar home systems which was instrumental in providing first- 253 time electricity access to roughly 30 million people worldwide in 2019 alone49. Similarly to off-grid 254 energy regulations in some African countries, CaaS can be combined with government regulations that 255 curb end-user prices for cooling services. Environmentally, deploying highly energy-saving cooling 256 systems, which are more expensive but have lower lifecycle costs per unit of cooling, becomes more 257 attractive, implying its potential for contributing to more sustainable cooling. In addition, the CaaS 258 business model endogenises proper maintenance of cooling systems (which can reduce electricity 259 demand by up to 20%50). The Rwandan government is the first to have implemented a financial support 260 mechanism for CaaS operators offering space cooling and food refrigeration services. Early-stage 261 finance is a key barrier for asset bundling at scale. Companies could look to various green finance 262 vehicles as a potential and currently underexplored source. Where CaaS is used for food cold chain 263 applications such as in Rwanda, green finance can save additional, substantial carbon emissions from 264 reducing food waste. 265 Embedding passive and energy-efficient sustainable cooling in urban infrastructure (intervention 266 point I2). Given that projections of world population living in towns and cities are set to reach 66% by 267 2050, these will become the epicentre of cooling demand51. The production and assemblage of 268 infrastructure locks-in long-term physical assets and types of cooling consumption. Passive and energy 269 efficient city designs7 provide benefits to large populations by reducing urban heat islands52, reducing 270 cooling loads and improving thermal comfort in both indoor and outdoor environments. A key means 271 through which city planners can introduce passive cooling is increasing vegetation through street trees, 272 green façades and green roofs53. For example, in Xiamen Island, the integration of green roofs reduced 273 average land surface temperature by 0.91°C54. Passive technologies have longer lifetimes than 274 mechanic-electrical components of active technologies, hence benefits will be delivered in the longer- 275 term. Urban infrastructures can furthermore be designed to ease the application of energy-efficient 12 276 bundled cooling networks. However, to apply these multifunctional solutions, it is necessary to 277 overcome political economy complexities, as observed in the green infrastructure planning of New York 278 city55. In addition to policy-makers, municipalities, construction sector professionals (e.g. builders, 279 architects), organisations with high cooling demand and individuals are required to agree on the design 280 of infrastructural spaces and technological choices with sustainable cooling strategies such as green and 281 blue spaces and phase changing materials. 282 Linking cooling to climate action and refrigerant phase-down across global environmental 283 agreements (intervention points G1 & G4). Active space cooling and refrigeration is based on the use 284 of a chemical coolant to absorb and release heat. Hydrofluorocarbon (HFC) functions as an excellent 285 chemical coolant within both; however, HFCs are 10,000 times more potent than CO2 in contributing 286 to climate change. If F-gas use continues on its current trajectory it is estimated to contribute 20% of 287 global climate pollution by 205056. Changing the current HFC trajectory requires coordinated global 288 action -- and global agreements are a key intervention to do so especially when free markets with 289 external environmental costs fail to exert sufficient pressure on producers and consumers. The Montreal 290 Protocol, one of the most successful global environmental agreements57, reduced nearly 98% of ozone 291 depleting substances. The Kigali amendment to the Montreal Protocol entered into force in 2019 and 292 aims to replicate this success and reduce HFC consumption by 80% by 2047. Critically, the Kigali 293 amendment defines progress as reducing the total tonnes of CO2 equivalent, opening up a multitude of 294 solution avenues while still increasing the provision of cooling necessary for wellbeing. Combining this 295 HFC phase out with improved energy efficiency of cooling has the potential to reduce the global 296 temperature increase in business-as-usual scenarios by up to 1 °C in the coming decades48. But 297 achieving this sustainable balance for cooling and climate at scale requires further policy and 298 technological innovations. Greater coordination is required from the institutional frameworks for 299 phasing-out F-gas and improving the energy efficiency of cooling by linking the SDGs to the Montreal 300 Protocol at the global level as well as to regional and national cooling plans. Within this institutional 301 framework there is also scope to address market and technology orientated solutions. Further, such new 302 governance measures that address the cooling-climate interface can also limit end-of-product-life F-gas 13 303 leakages and enable practices towards a circular cooling economy. This requires a network of aligned 304 policies to address all the stages of cooling: from the production of sustainable cooling (as with the 305 Biarritz Pledge for Fast action on Efficient Cooling from the 2019 G7) to the design of anti-dumping 306 policies to prohibit the import of inefficient technologies. 307 The role of lifestyles and behaviours for access to sustainable cooling and resilience (intervention 308 point S3). Lifestyle, social and behaviour changes are important determinants of consumption 309 patterns39. For cooling, these include using alternatives to active cooling (e.g. achieving thermal comfort 310 through changes in clothing, beverage intake or shading) or by altering habits (e.g. reducing standard 311 AC temperatures for big consumers such as hotels and commercial buildings). Cooling-related lifestyles 312 vary: the average US-American consumes over six times the energy for space cooling compared to 313 people in the European Union, and over 28 times compared to people in India8. Further, socio-cultural 314 and psychological factors influence consumption, driving differentiated attitudes towards thermal 315 comfort. In Singapore, the use of ACs is deeply rooted in everyday practices58, while in Japan, despite 316 most households having AC, people prefer natural ventilation59. A deep understanding of cultures and 317 household dynamics is central to driving such sustainably-oriented behaviours. While not always easy 318 to achieve, lifestyle and behaviour changes -- such as changing temperature set-points, changing 319 dressing codes, changing times of work, prioritizing passive cooling activities and infrastructures – can 320 be fostered by anchoring them in shared ideologies such as global wellbeing, environmental protection, 321 as well as social justice movements and moral standpoints33,60. Behavioural science and environmental 322 psychology offer key insights on how humans make choices, which can be used for designing 323 sustainability-promoting instruments61 and triggering social tipping points62. When behavioural change 324 occurs, follow-on measures can sustain the change over time63. 325 326 Transitioning Cooling towards Sustainable Development: Agenda for Research and Practice 327 The unprecedented predicted growth in cooling, its absence from mainstream sustainable development 328 debates, and the range of potential interventions to transition the system towards the SDGs begs a 14 329 critical question: Where should cooling research and practice focus to underpin a shift towards 330 sustainability? As this issue swiftly gains prominence, the implications of cooling decisions on other 331 SDGs will gain purchase. Climate change presents one such example: meeting the internationally 332 agreed aspiration of net-zero GHG emissions by mid-century will have serious implications for cooling 333 technological and infrastructure decisions (and vice versa) which are set to rapidly grow in the same 334 timeframe. How should countries, companies, organizations and individuals navigate their immediate 335 and growing requirements of cooling with the much larger and longer-term implications of their 336 decisions? There remains a pressing and unanswered field of enquiry that investigates if, how, and for 337 whom, cooling contributes to the goals of sustainable development. 338 To advance answers to this question, in analysing the cooling and sustainable development nexus as 339 well as of defining an action-oriented framework to foster sustainable cooling, we define an agenda for 340 research and practice by highlighting three areas of prioritisation. Knowledge, analysis and decision- 341 making around each of these can effectively facilitate a transition towards sustainable cooling over the 342 short and long-term. Connecting the expertise across disciplinary boundaries will be key to addressing 343 these issues and understanding the various inter-relationships that cooling presents. This is especially 344 relevant as the academic literature is limited, as established in this Perspective, whereas professional 345 practice in this area is advancing at a faster pace14,56. As a result, the co-production of knowledge by the 346 often-scattered academic and professional communities who are at the frontier of the relevant areas of 347 science and practice will be key to a holistic and integrated understanding of the relationships between 348 sustainable development and cooling. Such inter- and trans-disciplinary approaches that link research 349 with empirically evidenced impact have become an important trend in approaching advancements of 350 science particularly in fields where on-ground experience is crucial for testing and calibrating new 351 findings, such as in urban science and architecture64. Equally, the need for a transdisciplinary approach 352 is well identified to establish demand-side climate solutions – to which cooling is central – and 353 investigate their mitigation potential, detail policy measures and assess their implications for human 354 well-being and sustainable development39. With this context, we propose three overarching outcome- 355 oriented themes to guide the agenda for research and practice. 15 356 Place planetary stewardship and meeting people’s needs at the heart of cooling decisions. In order to 357 be compatible with the SDGs, cooling must protect both people and the planet. The provision of cooling, 358 however, can posit trade-offs between people and the planet. There is strong potential for an unintended 359 feedback; for instance, the cycle of higher temperatures leading to increased cooling and energy 360 consumption, which leads to a rise in GHG emissions and, in turn, fuel higher temperatures. Preserving 361 human well-being, along with stability of the environment will be essential to a long-term cooling 362 trajectory that is sustainable. Our framework suggests that doing so will require better understanding 363 context-specific societal needs, innovation and deployment of technologies to enable equitable quality 364 of life, governance practices that account for the externalities to the environment and providing adequate 365 physical and intangible infrastructures for sustainable cooling to be feasible, across the stages of 366 cooling. 367 Prepare for and mitigate climate change impacts which will demand cooling in varied geographies. 368 There is clear evidence that as the planet warms the negative impacts, vulnerabilities, and risks to life 369 and infrastructure will increase in almost all geographic locations. The frequency and intensity of 370 extreme heat events, for example, is a well identified global trend that is already changing the 371 geographies of cooling. For instance, in Europe with its milder climate, 15% of the increased electricity 372 demand between 1990 and 2016 is attributable to space cooling65. A large burden of cooling falls on 373 warm-climate low and middle-income countries with, as this Perspective suggests, considerable 374 bearings on the various SDGs. Other, often cooler climate regions that do not traditionally account for 375 extreme heat events will have to start adapting long-term plans, processes, infrastructure and 376 capabilities. Analogously, warm-weather regions will need to prepare extensively for the likely high 377 costs of such extreme events. Urban heat action plans and early warning systems are gaining 378 prominence as a starting point to reduce the imminent negative impact on people and the planet. 379 Embedding the anticipated economic and non-economic costs of a changing climate and its implications 380 of cooling throughout development and resilience planning, across scales of governance, will be 381 necessary to prepare for the exponential increase in cooling consumption. 16 382 Promote long term sustainable cooling solutions over existing unsustainable business-as-usual 383 alternatives. The dominant active cooling technologies are well-established, with large supply chains, 384 high performance and lower upfront costs, but can come with long-term negative impacts on energy 385 demand (e.g. competing for use of renewables) and emissions (e.g. leaks of refrigerants). However, 386 there are numerous passive cooling technologies and designs that deliver thermal comfort with no or 387 substantially lower energy consumption as they harvest local, naturally-occurring and renewable 388 resources (e.g. materials with high thermal mass, wind for ventilation, vegetation for shade, sea and 389 lakes as heat sinks). Their benefits include lower maintenance and longer life-spans, and more flexibility 390 to adopt and adapt to local knowledge in the form of vernacular cooling. Being strongly interlinked 391 with building design, passive cooling may have higher upfront capital costs. However, it is a strategic 392 investment that offers long-term cooling solutions with lower running and planetary costs. More 393 research and more action are needed for adequate policy strategies and instruments to foster passive 394 cooling technologies, as well as context-specific interactions of passive cooling with physical 395 infrastructures and social behaviours. 396 397 In this Perspective, we lay forth the multiple inter-relationships between cooling and sustainability, 398 arguing for cooling to be considered as central to achieving all SDGs. We also provide a 399 transdisciplinary conceptual framework to identify, shape and influence the interventions by which the 400 current trajectory of cooling can deliver sustainable development. With a world positioned at the brink 401 of unprecedented cooling demand, this Perspective offers a way forward while being acutely aware of 402 the extraordinary opportunity the current moment provides to use cooling as a lens to look to the 403 sustainability of our future. 404 405 References 406 1. 407 Cooper, G. 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The Future of Cooling - Opportunities for energy efficient air conditioning. https://www.iea.org/reports/the-future-of-cooling (2018). 544 545 Acknowledgments 546 We are grateful to the support provided by the Future of Cooling Programme at the Oxford Martin 547 School, University of Oxford. 548 Author contributions 549 R.K. led the manuscript conception, design and writing. N.M. led data acquisition and analysis on the 550 links between cooling and the SDGs. R.K., N.M. and P.T. wrote the introduction and the section on 551 cooling and SDG links. A.M. developed the framework visuals. N.M., P.T., A.M., R.R. and C.M. 552 contributed to the framework writing. A.J., P.T. and M.M. contributed to the future agenda. R.K., P.T., 553 F.C., M.M. and R.P.S. revised the manuscript. All authors contributed towards the design of the work 554 and the editing of the manuscript. 555 Competing interests 556 The authors declare no competing interests. 23