Unique analysis shows air-con heat relief significantly worsens climate change
Researchers also discover major global inequality with Global South left behind by wealthier countries – despite needing air conditioning more.
While air-conditioning protects people from dangerous heat, it also significantly worsens global warming – by 2050 potentially producing more carbon dioxide than the current annual emissions of the United States, a new study reveals.
Scientists have combined climate science, energy modelling, and inequality analysis to create a unique framework using a set of well‑established global ‘storylines’ — Shared Socioeconomic Pathways and Representative Concentration Pathways (SSP and RCP scenarios) — a set of ‘futures’ ranging from strong climate action to high emissions.
The study reveals that, by 2050 air-conditioning use will more than double. Electricity for cooling could reach 4,493 TWh under mid‑range scenarios, and much more in high‑emissions futures. Emissions from air-conditioning could reach 8.5 GtCO₂‑eq per year in the worst‑case scenario — more the current annual emissions of the United States (5.9 GtCO₂‑eq).
Publishing their findings today (25 Feb) in Nature Communications, the international research group led by the University of Birmingham warns that most of this extra warming is caused by income-enabled growth in cooling consumption, more households adopting and using air conditioning, and not just rising temperatures.
Researchers estimate that air-conditioning use will add 0.03°C to 0.07°C of global warming by 2050, depending on the emissions pathway the world follows. This is the equivalent of around 74–183 billion transatlantic return flights. The predicted rise in temperature is a significant increase compared with the narrow margin left to keep warming below 1.5°C.
The paper also reveals a major global inequality - regions that need cooling the most, such as South Asia and Africa, have the least access to air-conditioning. Wealthier regions such as Europe and North America have lower cooling needs but higher air-conditioning usage.
Professor Yuli Shan from the University of Birmingham, the corresponding author, said: “Global warming is raising temperatures and causing more heatwaves, and as economic growth in some of the worst-affected countries means more people can offset extreme heat with air conditioning.
“As global temperatures rise, we risk being locked into an ‘arms race’ where defending ourselves against extreme heat is causing the issue to get worse. The world must transition quickly to cleaner, more efficient cooling technologies—while ensuring fair access to cooling, especially for vulnerable populations.”
As well as adopting a rapid transition to clean electricity, the research team recommends the fast adoption of low‑pollution cooling liquids in air-conditioning systems refrigerants and better building design – using insulation and shading more effectively. Researchers also advocate for behavioural changes such as turning the air-conditioning down and shifting cooling away from peak hours.
The study uncovers a fundamental development dilemma. Low-income limits regional access to cooling yet closing this gap to deliver equitable thermal comfort would generate substantial additional warming impact. Increasing demand resulting from rising incomes in low-income regions could have significant effects: an additional 94 million units at medium-income levels, 150 million units at high-income levels, and up to over 220 million units at the highest-income levels.
Dr Hongzhi Zhang, from Beijing Institute of Technology, the first author of this study, said: “The study reveals that if all low‑income regions gained the same access to air-conditioning as rich regions, related global emissions would jump dramatically - adding up to 0.05°C extra warming even in the most climate‑friendly scenario.”
Dr Hongzhi Zhang was a visiting PhD student at the University of Birmingham, supervised by Professor Yuli Shan.
Using their analysis framework, the researchers estimated how much cooling people will need as temperatures rise. They included humidity and weighted the results by where people live, as cooling needs matter more in areas with large populations.
They then fed these cooling‑need estimates into a global energy–economy model (GCAM) projecting how many air conditioners people will buy, how much electricity will be used, and how much greenhouse gas emissions the devices will produce.
The team ran GCAM under each of the five SSP‑RCP scenarios, so they could understand how air-conditioning use and emissions change in a sustainable world vs. a fossil‑fuel‑heavy world and how much warming comes specifically from air-conditioning use in each case. Researchers then compared regions by income and climate conditions, building an econometric model to reveal areas where people need air-conditioning but can’t afford it.
Finally, they measured how much extra warming AC emissions will cause, using a climate emulator called MAGICC, which estimates how emissions translate into additional warming.
Researchers at the University of Birmingham are using their wide-ranging pure and applied atmospheric research to provide solutions to the pressing problems of extreme weather and climate change which impact on our planet.
ENDS
For more information, please contact the press office on +44 (0) 121 414 2772 or pressoffice@contacts.bham.ac.uk
‘Rising Air-Conditioning Use Intensifies Global Warming’ - Hongzhi Zhang, Yuli Shan, Ruoqi Li, Rui Xue, Junhua Ma, Jarmo Kikstra, Zongbo Shi, Zhaohua Wang, Bin Zhang, Bo Wang, Shuai Fang, Fan Yang, Klaus Hubacek is published by Nature Communications.
Notes for editors:
- Participating institutions include: University of Birmingham, UK; Imperial College London, London, UK; Beijing Institute of Technology, China; Digital Economy and Policy Intelligentization Key Laboratory of Ministry of Industry and Information Technology, Beijing, China; Nanjing University, China; Kunming University of Science and Technology, China; International Institute for Applied Systems Analysis (IIASA), Austria; Soochow University, Suzhou, China; La Trobe University, Melbourne, Australia; Aalborg University, Denmark; and University of Groningen, the Netherlands.
About the University of Birmingham
- As well as being ranked among the world’s top 100 institutions, the University of Birmingham is the most targeted UK university by top graduate employers. Its work brings people from across the world to Birmingham, including researchers, educators and more than 40,000 students from over 150 countries.
Journal
Nature Communications
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Rising Air-Conditioning Use Intensifies Global Warming
Article Publication Date
25-Feb-2026
Moist heatwave forecasts reduce health risks at major events
University of Reading
Forecasters could give India weeks of advance warning before moist heatwaves strike, allowing cricket matches and major gatherings to be rescheduled and reducing the risk of heat exhaustion and death.
Scientists have shown for the first time that India's summer monsoon actively controls the location and timing of moist heatwaves across the country. The findings reveal a striking regional pattern that forecasters could use to predict these events days or weeks ahead.
Unlike ordinary heatwaves, moist heatwaves are driven by humidity as much as temperature. When air is already humid, sweat cannot evaporate from skin, leaving the body unable to cool itself. This can lead to heat exhaustion and fatal heatstroke within hours.
Scientists from the University of Reading studied more than 80 years of weather data and found that, depending on whether the monsoon is active or running dry, the region of greatest risk can shift dramatically from one part of the country to another. The research is published in the journal Climate Dynamics.
Dr Akshay Deoras, who led the study, said: "We often find people being more aware of dry heatwaves in India given the scorching summer season, but moist heat remains less known and is therefore more dangerous. Outdoor public gatherings are notorious for causing heat exhaustion. Advance warning of a moist heatwave could allow organisers of public events, such as cricket matches and other large gatherings, to reschedule activities, extend drinks breaks, and strengthen on-site medical provision to protect both participants and spectators.”
"Our research shows for the first time that the monsoon is the key driver of where and when this deadly risk develops. Because we can forecast these monsoon patterns weeks ahead, this creates real opportunities to prepare and protect people.
“Advance warnings could also allow hospitals to increase staffing before moist heat-related admissions rise, enable city authorities to open cooling centres and adjust school hours, and help power grid operators manage infrastructure strain.”
Monsoon rains shift moist heatwave risk across India
When the monsoon brings heavy rain, northern India faces the risk of moist heat. As the rain subsides during dry spells, this danger shifts to the southern and eastern parts of the country. This happens because northern India is normally dry, so monsoon moisture pushes humidity to dangerous levels. In the south and east, humidity is already high, so dry spells and clear sky conditions trap heat instead.
Humidity matters more than temperature in making these conditions deadly. It is often the moisture in the air, not the number on a thermometer, that can cause moist heat related deaths. Over a billion people in India face this threat, particularly agricultural workers, labourers and elderly people.
Crucially, the study links moist heatwaves to a large-scale weather pattern that can be forecast two to four weeks ahead. During one specific phase of this large-scale weather pattern, heatwave occurrence over northern India rises by 125% above normal. Forecasters could use these patterns as early warning signs and save lives.
Journal
Climate Dynamics
Article Title
Anatomy of moist heatwaves in India during the summer monsoon season
Article Publication Date
26-Feb-2026
Access to safe water fails in the face of extreme heat, even in wealthy cities
Household water security is not universal in the Global North, leading to unequal capacities for coping with extreme heat
Universitat Oberta de Catalunya (UOC)
In a climate emergency in which high temperatures, heatwaves and droughts are increasingly common events, cooling systems and access to water have become some of society's greatest challenges and one of the major adjustments that people have to make in their homes. However, this access is neither guaranteed nor universal, even in cities in developed countries.
A team of experts led by a researcher at the Universitat Oberta de Catalunya (UOC) has highlighted the link between water security and the adaptability of homes in urban centres of the Global North, consisting of countries in North America and Europe, among others, to heat and high temperatures in the climate emergency.
“Water is the 'air conditioning' of the most socioeconomically vulnerable groups.”
"Water is a vital but underrecognized tool for adapting homes to extreme heat, especially for people who cannot afford air conditioning," explained Hug March, the study's principal investigator and the joint leader of the TURBA Lab group, affiliated to the UOC-TRÀNSIC research centre and a full professor in the Faculty of Economics and Business at the UOC, with Katie Meehan, of King's College London, Elena Domene and Mar Satorras, of the Institut Metròpoli, and David SaurÃ, of the Universitat Autònoma de Barcelona.
This study, which has appeared in open access format in the journal npj Urban Sustainability, published by the Nature group, provides a critical analysis of access to safe and acceptable water for a thriving life, a key factor in adapting to extreme and chronic heat, especially in cities. This access is not always available in all cities, not even in the wealthiest ones.
Water – an essential tool for heat adaptation
Access to water is taken for granted in the countries of the Global North; however, this is contradicted by the facts on the ground. This is primarily because water is a critical resource for adapting to high temperatures, especially for people who have no alternative due to energy poverty or a lack of stable housing. "Access to water acts as 'air conditioning' for the most vulnerable groups, as it plays a key role not only in hydration, but also acts as a cooling mechanism for the body," March said.
In fact, low-income households, made up of marginalized communities, people with chronic illnesses, or elderly people living in precarious conditions, suffer from "systemic cooling poverty". "Household water security is not universal in the Global North, which means that people's ability to cope with extreme heat is uneven," March explained.
Increased household water insecurity
According to the authors, extreme heat is a phenomenon that is now "here to stay." Water is even more essential for ensuring heat adaptation in cities, in both public spaces and in the home.
For example, the authors point out that in areas in southern Europe such as the city of Barcelona, apart from drinking water, practices such as showering, going to public swimming pools and using public fountains are among the most widely used strategies for coping with extreme heat in socially vulnerable areas.
"Financial pressure forces vulnerable households to limit their water consumption by taking shorter showers, as they prioritize saving money over relief from heat. As a result, ignoring water insecurity can compromise people's ability to adapt to extreme heat among the most socioeconomically vulnerable groups, and further exacerbate social and spatial inequalities in cities," warned March. For example, in the city of Portland, in the United States, water and sewerage rates are forecast to reach $2,400 by 2030.
Proposals and strategies for adapting to heat
In order to contribute to improving water security in urban environments, the experts put forward several proposals and strategies, including the development of a genuinely transformative agenda for heat justice. This programme must address issues related to water security, and include data and mechanisms to provide access to water resources, especially for homes, where household water security is taken for granted as guaranteed and universal, but becomes critical in times of climate emergency.
The authors pointed out that as droughts and difficulties related to water become more common in many cities, alternative resources are being adopted, including desalination, thereby increasing fees and costs related to access to water. If it is not implemented according to criteria of socio-environmental justice, this increase in costs will aggravate water insecurity among the poorest members of society.
"A transformative agenda for heat justice must have water security as its cornerstone, since without safe, affordable and reliable water, the ability to adapt to chronic and extreme heat is fundamentally compromised, and this deepens existing social and spatial inequalities, particularly among vulnerable urban populations," concluded March in the article, which was funded by the Catalan Institution for Research and Advanced Studies (ICREA) and UKRI Horizon Europe Guarantee.
This study falls within the UOC's research missions on Planetary health and well-being and Digital transition and sustainability, and supports the UN Sustainable Development Goals SDG 6, Clean Water and Sanitation, and SDG 11, Sustainable Cities and Communities, in the context of community adaptation to heat.
Journal
npj Urban Sustainability
Method of Research
Commentary/editorial
Subject of Research
Not applicable
Article Title
Why water security matters to cities under extreme heat in the Global North
Heat and pregnancy
About The Article:
Climate change is increasing the frequency and intensity of heat waves and the exposure of pregnant individuals to extreme heat. This article summarizes current evidence about risks to maternal health from ambient heat (hot weather, high indoor temperatures, and occupational exposures) and how these risks can be managed.
Corresponding Author: To contact the corresponding author, Sari Kovats, PhD, email Sari.kovats@lshtm.ac.uk.
To access the embargoed study: Visit our For The Media website at this link https://media.jamanetwork.com/
(doi:10.1001/jama.2026.0001)
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
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JAMA
