Passive subambient cooling and atmospheric water nexus

Review article https://doi.org/10.1038/s41467-026-74110-z Passive subambient cooling and atmospheric water nexus Received: 11 September 2025 Accepted: 27 May 2026 Sunmiao Fang 1,13, Saichao Dang 1,13, Kaijie Yang 2, Lyu Zhou3, Shakeel Ahmad1, Yan Zhang4, Qiong Li5, Qiang Li 6, Wenshuai Chen7, Khalid Hazazi8, Hussam Qasem9, Jiechen Wang 10, Yue Cao10, Pingfan Wu Hamad Saiari11, Issam Gereige11 & Qiaoqiang Gan 1,12 10 , Accelerating global warming has intensified the need for sustainable, lowenergy cooling strategies. Subambient radiative cooling is a compelling solution, passively dissipating heat to outer space via mid-infrared emission without external energy input. However, its performance depends on atmospheric conditions, especially low humidity and clear skies. Although its global potential is well-established, its performance under typical weather conditions and integration with sustainable water cycling technologies remain underexplored. This review examines how radiative cooling can be integrated with water-related technologies—including atmospheric water harvesting, sustainable agriculture, and radiative–evaporative cooling—to reduce thermal loads while improving water sustainability. 1234567890():,; 1234567890():,; Check for updates With accelerating global warming, ambient temperatures have consistently escalated in recent decades, setting increasingly alarming new records. According to the Copernicus Climate Change Service and the World Meteorological Organization, 2025 ranked among the warmest years on record globally, extending the recent sequence of exceptional heat1. In addition, regional trends are equally concerning; for instance, the United Arab Emirates recorded extremes exceeding 50 °C in late May 20252. High-latitude regions also experienced anomalous heat, with parts of the Arctic Circle exceeding 30 °C for over two weeks—temperatures 8–10 °C above seasonal norms3. This thermal escalation has pushed active air conditioning (which relies heavily on evaporative cooling towers and high electricity loads)4 to unsustainable levels of resource consumption. Consequently, there is an urgent need for passive alternatives that decouple cooling from the exhaustion of finite freshwater supplies. Among emerging strategies, daytime subambient radiative cooling (RC) has attracted considerable attention as a passive, energy-efficient alternative5. RC harnesses the natural process of thermal radiation, enabling surfaces to dissipate heat as midinfrared (MIR) radiation (8–13 µm) through the atmospheric transparency window and thus emit thermal energy directly into outer space without external power input (Fig. 1a)6,7. RC materials exhibit dual optical functionalities: they reflect most incoming solar radiation while enhancing thermal emittance in the MIR range8–10. However, RC performance is intrinsically constrained by local atmospheric conditions. For instance, optimal subambient RC typically requires clear skies, minimal cloud cover, and dry atmospheric conditions with relative humidity (RH) 1 Material Science and Engineering, Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia. Department of Environmental Science, Zhejiang University, Hangzhou, China. 3Department of Electrical & Computer Engineering, Texas Tech University, Lubbock, TX, USA. 4Shanghai Key Laboratory of Air Quality and Environmental Health, Department of Environmental Science and Engineering, Fudan University, Shanghai, China. 5School of Architecture, South China University of Technology, Guangzhou, China. 6College of Engineering, Huazhong Agricultural University, Wuhan, China. 7Key Laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin, China. 8EXPEC Advanced Research Center, Saudi Aramco, Thuwal, Saudi Arabia. 9Future Energy Technology Institute, King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia. 10Futurewei Technologies Inc., San Jose, CA, USA. 11Research and Development Center, Saudi Aramco, Dhahran, Saudi Arabia. 12Center for Renewable Energy & Storage Technologies, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia. 13These authors e-mail: contributed equally: Sunmiao Fang, Saichao Dang. 2 Nature Communications | (2026)17:5281 1 Review article https://doi.org/10.1038/s41467-026-74110-z a Total outgoing radiation Cold space Atmospheric window (8–13 μm) Patm Psun Prad Precipitation Evaporation Pnon-rad Condensation Earth Ocean 0.8 Blackbody radiation (300 K) 0.5 0.4 0.2 Solar irradiance (AM 1.5G) 0.3 0.6 1 8 2 3 5 Wavelength (μm) 13 16 22 0.0 25 c 100 90 Net cooling power (W m−2) 1.0 Ideal broadband cooler Ideal selective cooler Emissivity / absorptivity Atmospheric transmittance Normalized spectral irradiance b Tamb = 20 Solid: hcom = 0 W m−2 K −1 Dashed: hcom = 8 W m−2 K −1 60 Selective 30 0 −30 Broadband −20 −10 0 10 Temperature of emitter (°C) 20 Fig. 1 | Global cooling–water cycle nexus and theoretical analysis of subambient radiative cooling (RC). a Schematic of major physical components involved in the global cooling and water cycle nexus. RC technology enables passive surface cooling by emitting mid-infrared (MIR) radiation through the atmospheric transparency window (8–13 µm), which can be partially blocked by clouds. b Spectral features of ideal broadband (orange dashed curve) and selective coolers (green dashed curve). The yellow and blue backgrounds represent the solar spectrum and the MIR atmospheric transmittance spectrum, respectively. The 8–13 μm transparency window substantially overlaps with the thermal radiation spectrum of a 300 K blackbody (gray dashed curve). c Net cooling power of spectrally selective (green curves) and broadband MIR emitters (orange curves). All curves were calculated using a unified ambient temperature of 20 °C and the same atmospheric transmittance/skyradiance spectrum shown in (b). Solid and dashed lines correspond to non-radiative heat transfer coefficients of hcom = 0 W m−2 K−1 and hcom = 8 W m−2 K−1, respectively. preferably below ~40%11; however, such conditions are not prevalent in most inhabited regions. Consequently, the existing literature largely demonstrates RC efficacy under idealized weather scenarios12,13, while systematic assessments under realistic climatic constraints remain limited. This disparity presents a critical knowledge gap for reliable deployment depending on diverse local climatic conditions. This review addresses this gap by examining the nexus between subambient RC and atmospheric water, a strategically critical yet underexplored domain. The interplay between RC and water cycling offers advantages beyond passive thermal regulation, creating opportunities to enhance water sustainability, particularly in arid and surface water-stressed regions. We first outline the governing principles of subambient RC (...truncated)