This past decade was the hottest in recorded history. As the world warms due to climate change, cooling indoor spaces becomes a greater necessity and challenge. Today, almost 4 billion people—half of the global population—live in hot climates, and the majority of the other half of the population experiences high temperatures at some point during the year. Yet, in 2022, only 37% of the global population had access to cooling technologies. Over the next 25 years, 700 million more people will live in hot climates due to climate change, and the challenges for those already in hot climates will intensify.

Prolonged exposure to high temperatures and humidity has severe health consequences, causing, on average, half a million deaths per year. SEforALL estimates that 1.2 billion people are at high health risk from heat without adequate access to cooling. Increasing global access to cooling technologies is critical. We need to broaden access to a comprehensive range of cooling solutions to effectively manage heat impacts, for example, increasing shade, constructing well-ventilated buildings, and installing efficient air conditioning (AC) and fans.

Simultaneously, we must reduce global greenhouse gas (GHG) emissions and reach net-zero emissions by mid-century to limit the most severe impacts of climate change, including global heating. Today, buildings account for a third of global emissions. This is primarily due to the energy required for heating, cooling, cooking and powering appliances, as well as the energy consumed during building construction. Globally, 2,200 terawatt hours (TWh) of electricity (around 6% of buildings' energy use) powers fans, AC, and dehumidifiers that cool buildings. Decarbonizing the building industry, including cooling, is essential to slow global warming and limit rising temperatures to below 2°C in line with global climate agreements. 

The challenge is clear: we must simultaneously increase access to cooling while decarbonizing the energy used to provide it. Across the world, energy needed for cooling is likely to increase by 2.5 times by 2050, to over 5,000 TWh. In India alone, demand for cooling is expected to rise more than tenfold by 2050, requiring 15–20% of the forecasted electricity supply, up from 5–10% today.

In its latest major report, Achieving Zero-Carbon Buildings", the Energy Transitions Commission (ETC) delves into the various aspects of building decarbonization, including cooling. We believe it is feasible to meet global cooling demands while reducing greenhouse gas (GHG) emissions. It will require a combination of solutions, such as significantly increasing the use of electric cooling technologies (e.g., AC, fans, dehumidifiers) supported by a transition from fossil fuel power systems to clean renewable electricity. Equally critical is implementing passive-cooling techniques: building design methods that reduce indoor heat and humidity, such as external shading, white-painted roofs, and ventilating designs and materials. These non-energy-based solutions can, and must, make a substantial contribution.

Expanding Access to Air Conditioning Powered by Clean Electricity: a central pillar of global cooling

Air conditioning is set to become the world's leading cooling solution. ACs are electric, highly efficient, and compatible with a low-carbon future run on clean electricity. The International Energy Agency (IEA) expects the global stock of air conditioners to increase from around 2 billion today to 5–6 billion by 2050. Fans, which are a cheaper alternative cooling technology, currently outnumber ACs two to one.  However, by 2050, these numbers are expected to equalize as household incomes rise and ACs become more accessible. The massive increase in AC use will bring new challenges, including managing the resulting surge in demand for clean power and preventing the release of refrigerants from ACs into the atmosphere, where they contribute to global warming.

Improving AC efficiency is the most effective way to reduce this surge in energy needed for cooling. ACs on the market today vary greatly in efficiency, within and across countries. The market average model is much less efficient than best-in-class appliances. With the right policies, the global average AC efficiency could improve by 50%. For example, through the use of minimum energy performance standards (MEPS) and by introducing labelling regulations that indicate running cost implications to consumers. These types of policies could lower total annual global electricity requirements for cooling by 10–20% (500–1,000 TWh) in 2050.

Some countries are already experimenting with such policies. Since the US and EU introduced MEPS and efficiency labels, AC energy consumption has been cut in half. In China, tightening MEPS grew the market share of higher-efficiency ACs from 20% to 55% between 2019 and 2021. Better energy labelling and MEPS are keys to driving progress in other countries, like Thailand, where an AC over 600% efficient can cost the same as one less than 400% efficient.

Beyond efficiency, there are also regional variations in how ACs are used. Average annual energy consumption from AC use in households in Texas, USA is almost six times higher than use in Guangzhou, China, and Hyderabad. If households in India used their AC as much as those in Texas, electricity requirements for cooling would rise from ~400 TWh today to 2,700 TWh in 2050.

Alongside increasing global AC access, behaviours must adapt. For example, significant energy savings can be achieved with minimal impact on health and comfort by setting ACs no lower than 24°C and using them based on actual building temperatures rather than constant use. Some countries have implemented policies to encourage this type of AC use. For example, Belgium has cooling limits of 27°C in public buildings. Beijing deploys 'energy-saving inspectors' to ensure that ACs in commercial buildings (e.g., offices, hotels, malls) are not set below 26°C. The Indian government mandates default AC temperature should not be below 24°C, while Italy imposes fines of €500–3,000 for industrial buildings cooling below 25°C. The Japanese 'Cool Biz' (cool to 28°C) programme encourages dress codes that match varying office temperatures. Another consideration is that ACs contain refrigerants that contribute to global warming if leaked or vented. On average, 2–5% leaks annually and over 90% are vented at end-of-life. Global emissions from refrigerant leakage and venting (from cooling and heating technologies) are estimated at 0.5–1 gigatonnes of carbon dioxide (GtCO₂) today, which could rise to 3 (GtCO₂) in 2050 if the use of high global warming potential refrigerants continues; this is equivalent to 15% of today's annual emissions from buildings. New types of refrigerants can significantly reduce this impact, but proper AC installation, maintenance, and disposal are crucial to avoid increased warming. Policymakers should enforce regulations, incentives, and skills accreditation for proper refrigerant disposal.

The Crucial, and Often Overlooked, Complementary Role of Passive Cooling

Expanding access to air conditioners is vital, but today's reality is that ACs are unaffordable and inaccessible for many households. Currently, 55% of Africa's population (just over 10% of the global population) live in hot climates, yet they account for less than 5% of global cooling energy demand. This becomes even more significant when considering that between now and 2050, nearly half of the world's population growth will be in Africa. It is estimated that by mid-century, more than 40% of the population living in hot climates could still be unable to afford or power AC. Passive cooling methods that are low-cost and low-effort can have a big impact on internal building temperatures and increase the energy efficiency of cooling globally.

Passive cooling techniques minimize heat retention and maximize natural ventilation which reduces the need for active cooling. Techniques include orientating buildings against the sun, using materials and colours that reduce heat absorption, and building designs that balance light (through windows) and shade. Our research shows that global improvements in average AC efficiency combined with passive cooling techniques in new and existing buildings could shrink total energy used to cool buildings by mid-century by almost 50%, from 2,200 TWh to 1,200 TWh.

Reflecting sunlight with white paint on roofs is a cost-effective way to lower indoor temperatures by around 2–4.5°C. In one instance, painting a factory roof white in Indonesia reduced indoor temperatures by 10°C. Cities including New York, Los Angeles, Toronto, and now Hyderabad have launched roof-painting cooling programmes. Hyderabad's cool roof programme targets 300 million m² of roof area by 2028 and involves mandatory painting of all public, commercial, and residential building roofs over 500 m²; government support to paint roofs of social housing; and an outreach and awareness campaign including demonstrations, city-wide advertisement boards, and volunteering programmes to coat rooftops. Jodhpur, Bhopal, Surat, and Ahmedabad have similar cool roof community programmes targeting low-income communities where roofs are commonly made of heat-trapping tin sheets, cement sheets, plastic and tarpaulin. These programmes helped to lower inside temperatures by up to 5°C. Passive cooling techniques, such as external shading (from trees or awnings), reflecting heat, ventilation, and using heat-dissipating materials can theoretically reduce cooling energy needs by 25–40%. If optimal building design is combined with optimal urban design, energy demand reductions could reach as high as 75%.

However, passive cooling solutions vary in cost, ease of installation, and effectiveness. For example, techniques such as designing in natural ventilation and using building materials that are heat reflective are difficult to retrofit. This variability makes it challenging to estimate total possible energy demand reductions. Nevertheless, it is clear that passive cooling solutions can significantly contribute to addressing the global cooling challenge. Unfortunately, these techniques are often ignored today. In many cases, lack of know-how and awareness among developers and weak regulation stand in the way of adoption. Higher-standard building codes and training and awareness programmes for developers could help to realize some of the low-hanging fruit opportunities.

Global Collaboration and Learning: key to decarbonizing and expanding access to cooling

Collaboration and partnerships are vital to meet the rising cooling demand. For example, the UNEP and Rocky Mountain Institute, are working in partnership with India's Ministry of Housing and Urban Affairs under the Cool Coalition framework, to develop an urban cooling programme for India's cities. They draw from stories and best practices from around the world to deliver local assistance for meeting cooling demand and improving energy efficiency and emissions from cooling. Ensuring access to cooling and managing the resulting energy demand will be two major challenges in the coming decades, but solutions exist and risks can be managed. A single solution will not work for the diversity of local conditions, building types, and people's needs so there is a lot to learn by sharing the diverse suite of existing solutions from across the world and encouraging adoption of solutions at the local level. Successful policies such as the cool roofs programmes, and air-conditioning efficiency standards and labelling demonstrate what is possible. Sharing transition stories and working collaboratively can help achieve healthier lives and a cooler planet.

Bibliography

CLASP. 2023. China's MEPS lead to major AC market transformation. Details available at <https://www.clasp.ngo/research/all/chinas-meps-lead-to-major-ac-market-transformation/>

Cool Coalition. 2023. Indonesia's cool roofs champion.  Details available at <https://coolcoalition.org/indonesias-cool-roofs-champion/>

International Energy Agency (IEA). 2019. Helping a warming world to keep cool. Details available at
<https://www.iea.org/commentaries/helping-a-warming-world-to-keep-cool>

International Energy Agency (IEA). Space Cooling. Details available at <www.iea.org/energy-system/buildings/space-cooling>

International Energy Agency (IEA). 2018. The Future of Cooling. Details available at <https://www.iea.org/reports/the-future-of-cooling>

International Energy Agency (IEA). 2023. Keeping cooling in a hotter world. Details available at < https://www.iea.org/commentaries/keeping-cool-in-a-hotter-world-is-using-more-energy-making-efficiency-more-important-than-ever>

International Energy Agency (IEA). 2022. Africa Energy Outlook. Details available at
<https://www.iea.org/reports/africa-energy-outlook-2022>

United Nations. Global issues: population. Details available at <https://www.un.org/en/global-issues/population>
Government of Telangana. 2023. Telangana Cool Roof Policy 2023-28 

Ministry of Power. 2024. BEE notifies New Energy Performance Standards for air conditioners. Details available at <www.pib.gov.in/PressReleasePage.aspx?PRID=1598508>

NDRC. 2021. Cool roofs: Community-led initiatives in four Indian cities. Details available at <https://www.nrdc.org/bio/anjali-jaiswal/cool-roofs-community-led-initiatives-four-indian-cities>

 Systemiq analysis for the ETC; IEA (2023), World Energy Outlook 2023; BNEF (2023), New Energy Outlook 2022

UE EIA (2020), Residential Energy Consumption Survey; Odyssee-mure (2023), Sectoral profile – households;

Lawrence Berkeley National Laboratory (2004), A Tale of Five Cities: The China Residential Energy Consumption Survey; Guo et al. (2022), Extreme temperatures and residential electricity consumption: Evidence from Chinese households; Energy Informatics (2022), Investigation on air conditioning load patterns and electricity consumption of typical residential buildings in tropical wet and dry climate in India

World Meteorological Organization (WMO). 2024. Climate change impacts grip globe in 2024. Details available at <https://wmo.int/media/news/climate-change-impacts-grip-globe-2024#:~:text=The%20year%202024%20is%20set,more%20heat%20for%20the%20future.

https://www.iea.org/data-and-statistics/charts/share-of-population-living-in-a-hot-climate-2022-and-penetration-of-air-conditioners-2000-2022>  #