After 2024 became the warmest year on record, with temperatures rising 1.5 °C above pre-industrial levels for the first time ever, humanity is “moving into the unknown,” said Andy Haines, professor of environmental change and public health at the London School of Hygiene & Tropical Medicine.

“We are now above the Paris Agreement’s preferred target of 1.5° Celsius [above pre-industrial levels), and six of the nine planetary boundaries have already been transgressed,” Haines said, speaking in late May at an event on the margins of the World Health Assembly.

“These environmental thresholds interact in ways we don’t fully understand, meaning we will encounter surprises, nonlinear changes, and tipping points with irreversible consequences in human lifetimes.”

The nine planetary boundaries are a scientific guideline that outlines the safe limits of Earth’s natural systems. They mark the thresholds that humanity shouldn’t cross if it wants to avoid lasting harm to the environment and serious risks to human well-being.

Crossing these boundaries—such as climate change, biodiversity loss, and others—could lead to sudden or irreversible shifts in the Earth’s systems.

Just six weeks on, his words seem all the more prescient, given the unprecedented flooding in Texas and unbearable heat waves seen since in Europe. Meanwhile, the World Meteorological Organization (WMO) has forecast that last year’s record heat levels will continue for the next five years, exceeding the 1.5°C threshold yet again at least once.

Rare moment of constructive dialogue amidst geopolitical tensions

Haines’ stark warning opened a unique gathering of about 100 climate and health experts from around the world. The session on “Climate Change and Health, Adaptation and Resilience in a Changing World, at the Geneva Health Forum’s 2025 conference, offered a rare moment of constructive dialogue amid rising geopolitical tensions.

As Haines and other participants underlined, climate change is having a cumulative series of impacts going far beyond heatwaves, and it must be treated as an environmental or economic crisis, as well as a defining human health emergency.

Haines also cautioned that efforts to adapt to climate change – an emphasis in many low- and middle-income countries that lack resources to transition to clean and renewable energy sources – will not be enough to avert disaster.

“We can’t adapt our way out of this crisis. We have to do both—adaptation and mitigation—in an integrated way,” Haines stressed.

He highlighted that decisions made now will shape the health futures of generations. “Children born in 2020 will experience drastically different lifetimes than those born in the 1960s,” Haines said. “About 90% of them are expected to live their lives exposed to extreme climate conditions, especially heat.”

Planetary boundaries

In the past, climate change was traditionally seen through the lens of rising heat and more extreme weather, including storms. But today, there is a growing understanding of how warmer temperatures are stressing other ecosystems essential to human life on this earth. And at the same time, as more of those planetary boundaries are breached, these also exacerbate the effects of climate change.

The nine planetary boundaries are climate change, ocean acidification, stratospheric ozone depletion, biogeochemical flows in the nitrogen cycle, excess global freshwater use, land system change, the erosion of biosphere integrity, chemical pollution, and atmospheric aerosol loading. They were first identified in 2009 by a team of 28 international researchers.

“Planetary health is bigger than climate change,” Haines stressed. “So, we’re actually facing multiple planetary level threats. Six of the nine planetary boundaries have been exceeded, have been transgressed, and these planetary boundaries interact in all sorts of complex ways we don’t fully understand.”

Adaptation vs mitigation

Climate adaptation involves taking action to prepare for and adjust to the current and future impacts of climate change. In contrast, climate mitigation refers to efforts to reduce or prevent greenhouse gas emissions from human activities, thereby slowing or reversing the effects of global warming.

Countries most vulnerable to climate impacts prioritize adaptation, while major emitters focus on mitigation.

“It’s often true to say that we tend to put adaptation and mitigation in separate boxes. I want to argue that we need to do both in an integrated way,” Haines said.

“We shouldn’t pose one against the other. We shouldn’t say, ‘Well, we’re going to adapt, so we don’t need to mitigate. We’re going to mitigate so we don’t need to adapt.’ That’s not true. We can’t adapt our way out of this crisis. We have to do both,” he continued.

Haines noted that while many adaptation strategies may seem intuitive, they must still be evaluated for long-term impact. For example, installing air conditioning to deal with heat might appear helpful, but it releases hot air outdoors and increases fossil fuel consumption.

“So, we’ll then have to move towards passive ventilation – green roofs, green space in cities,” Haines said.

“But even when we’re thinking about cities and nature, we need to be careful which trees we choose. So if you choose some very allergenic trees, you make health problems worse,” Haines said.

He added that adaptation must not be oversimplified: “We need to have better science, better understanding, and a more nuanced approach to adaptation.

“Implementation science is not given the respect it deserves in academia,” Haines said. “But understanding what happens when we apply interventions at scale is critical. Do we get the co-benefits we expect? Do we inadvertently harm people?”

Other challenges of adaptation – nutrition and health services

Similar questions arise when considering how to adapt to shifting food systems, said Jessica Kronstadt of the Planetary Health Alliance at Johns Hopkins University.

“How do food systems change because of different concentrations of CO₂ in the environment, because of changing precipitation?” she asked.

“What are the implications of the loss of pollinators and other biodiversity loss?” Kronstadt continued. “What are the implications of pollution, and how does this affect aquaculture? So again, as we think about adaptation, what are all the environmental changes we’re adapting to, and what are all the health impacts?”

Good nutrition is central to climate resilience as well as health equity, added Sandro Demaio, Director of the WHO’s Western Pacific Regional Office, who described how countries in his region are actively working to ensure that healthy food remains accessible to all in a warming world.

Across Asia “there is such an incredibly rich food culture that we should be proud of, and we should hold on to, including the indigenous food knowledge across the region,” Demaio said.

At the same time, in isolated Pacific Island states, climate change poses severe risks to food systems and other vital health infrastructure, he noted.

In many Pacific Island countries, for instance, around 60% of health services are located within half a kilometer of the ocean, and are increasingly threatened by rising sea levels and extreme weather.

Better assessment of adaptation measures

For Yonhee Kim of the Department of Global Environmental Health at the University of Tokyo, the key concern is more effective assessment of adaptation measures.

“There are many ideas, and there are many interventions,” she said. However, leaders must evaluate which strategies best suit particular settings and contexts.

“We need to think about the real-world setting,” Kim emphasized.

She also pointed out that while there is growing evidence about the physical impacts of adaptation strategies, there is still insufficient research on their effects on mental health. For instance, one typical response to urban heat is establishing cooling centers, but psychological barriers may prevent some individuals from utilizing them.

“We need to think of what we might overlook, and we may need to consider the kinds of unique characteristics that individuals with mental health conditions may have,” Kim said.

Cultural values and human behavior are primary drivers of environmental change and will ultimately shape how countries approach adaptation and mitigation, she pointed out.

“What are the values that we need to both try to prevent some of the changes, to begin with, but also make sure we’re adapting?” Kronstadt asked.

On the road to COP30 in Brazil

The WHA session took place ahead of a long lineup of summer and autumn climate events climaxing in the United Nations Climate Conference in Belém, Brazil in November (COP 30).

“We need to go further, faster, and fairer,” said UN Climate Change Executive Secretary Simon Stiell at the close of the intersessional Climate meetings in Bonn on 27 June, where delegations from around the world made only incremental progress on a range of thorny issues, from the weak-kneed national climate commitments to a new goal on climate finance.

That followed an event earlier in June, where the WHO’s European Regional office launched the Pan-European Commission on Climate and Health (PECCH) – to tackle the growing threat climate change poses to public health.

This week, a Global Climate and Health Summit hosted by the Physiological Society and supported by Wellcome is taking place in London.

That is to be followed by the more policy-focused Global Conference on Climate and Health, 29-31 July, in Brasília, Brazil, hosted by the Government of Brazil, the World Health Organization, and the Pan American Health Organization (PAHO).

The Brasília conference hopes to come up with a set of concrete inputs to the draft Belém Health Action Plan as well as a strategy for promoting health as a “core pillar of climate action” at COP30, taking place in Belém, 10-21 November.

And on 1-2 November, just ahead of COP30, Beijing’s Vanke School of Public Health will commemorate the 10th anniversary of the Paris Agreement at its World Health Forum, with the theme : Climate Change & Health: Responsibility, Governance, and a Shared Future for Mankind,” notes Vanke Dean, Margaret Chan, former WHO Director General (2006-2017), who moderated the WHA side event in May.

“The scientists’ discussion about ‘planetary limits’ is real,” Chan said, who, in her remarks  stressed the urgency of equipping younger generations to tackle climate-related health threats, and noted a Vanke School initiative to develop a Chinese edition of a textbook on planetary health limits.

Speaking later with Health Policy Watch, Chan recalled how she was “initiated very early on about climate and health issues,” when she first first joined WHO in 2003 as the Director of the Department of Public Health and Environment, which was synthesizing at the time, the early research on the issue. In 2008, as a new WHO Director General, Chan presided over the passage of the first World Health Assembly Resolution on Climate Change and Health.

Europe and Asia are both heat hotspots

While nearly half of humanity already lives in areas highly susceptible to climate change weather extremes, a third of the world’s heat-related deaths occur in the European Region – with an estimated 100,000 heat-related deaths in 35 European countries in 2022-23 alone, according to WHO.

Asia, meanwhile, is warming at twice the rate as the rest of the world, according to another recent WMO report; glaciers that feed vital freshwater reserves used during the dry season also are melting faster.

In 2023, the Lancet Countdown report found that global deaths from heat exposure have surged by 65% since the early 2000s, from around 188,000 annually to 310,000 in the 2020s.

The Intergovernmental Panel on Climate Change’s medium emissions scenario, which predicts 2.4°C warming by 2100, projects that between a million and 1.7 million additional temperature-related deaths will occur annually by the end of the century.

The health argument: A longstanding refrain still ignored

“Health can be the most powerful argument for climate action. Health is the argument for climate change,” said Dr Maria Neira, director of WHO’s Department of Climate, Environment and Health, at the May event.

Her remarks are a longstanding WHO refrain that come amid growing scientific consensus that climate change is “the greatest 21st-century health threat,” according to a recent analysis in the BMJ, which called for more focused local data and funding for climate and health priorities.

“Substantial and growing evidence shows its harmful effects on health through various pathways, including heat stress, drought, and shifting infectious disease patterns,” wrote the authors from Australia, Norway and Denmark, echoing remarks by Haines and others at the GHF conference.

Neira said that reducing climate pollutants would also reduce air pollution, which now causes as many as seven million premature deaths each year.

“Everybody should understand that they are not just negotiating with the percentage of emissions of greenhouse gases. They are negotiating with our lives because the decisions they are going to take will have an impact on how many cases of asthma, lung cancer, and cardiovascular diseases we are going to have.”

“What we are seeing are politicians, with the best intentions, treating climate change as if it were an economic or an environmental issue,” Neira added.

Cunrui Huang of the Vanke School of Public Health at Tsinghua University in China echoed Neira’s message, emphasizing the need to prioritize people and public health in climate action.

He said climate change multiplies health risks and stressed the importance of strengthening cross-sector partnerships, particularly between the environment, health, and energy sectors.

“We need to bring health to the center of climate discussions, and we need to break the silos of health, energy, environment,” Huang said. “We need to work together.”

Linking adaptation and mitigation seamlessly

One area where such cross-sector partnerships can foster more seamless adaptation and mitigation strategies is in the health sector itself, said Neira.

She pointed to the Alliance for Transformative Action on Climate and Health (ATACH). The initiative focuses on two primary goals. The first involves decarbonising health systems, which account for around 5% of global emissions. The second involves bolstering health systems’ resilience and response to extreme weather and climate-related events through channels ranging from early warning systems to better health services coverage for climate-sensitive diseases.

ATACH already has membership from 94 member states, which have set goals for their health systems in line with local needs and capacities.

“As the health professionals, we can decarbonize our own health system, of course, keeping with the top quality of care,” Neira said. “We can also reduce the amount of plastics and the amount of procurements.”

Leveraging renewable energy is a key component of the initiative, she said, leading to more accessible and affordable electricity for clinics in remote and rural areas of Africa and Asia – while also putting them on a low-carbon trajectory.

At the same time, designing the physical infrastructure of clinics to better withstand heat and storms, can simultaneously make them more resilient and more energy-efficient.

“We are solarizing as many healthcare facilities around the world as possible,” said Neira.

‘Sponge’ cities to combat urban heat impacts

Urban planning is yet another domain where the use of integrated adaptation and mitigation strategies can bolster the health and climate resilience of a city’s residents, Neira added.

More urban green spaces not only reduce climate impacts, but can improve mental health, ease traffic congestion, and encourage more active lifestyles, in turn reducing the burden of non-communicable diseases and their associated conditions.

John S Ji of China’s Vanke School of Public Health at Beijing’s Tsinghua University pointed to the tensions that have arisen in traditional forms of urbanization between climate, health and development goals.

For example, in many developing countries, including China, urbanization has been associated with longer life expectancy due to better access to health services.

“Is urbanization causing longer life expectancy?” Ji asked. “Maybe, but at the same time, it’s causing the urban heat island effect,” he explained, referring to the phenomenon where large expanses of urban asphalt heat up cities more than around their periphery.

“In downtown centers, the temperature can be up to 5° C higher as compared to rural areas. So the urban heat island is an issue.”

To address this, some communities have implemented a “sponge city” concept, which enables the coexistence of water, green spaces, and dense urban development.

“But how do we implement this effectively?” Ji asked. “How do we do it without vector-borne diseases, such as mosquitoes, and also allergies from certain choices of trees? These could be major issues going forward.”
China leads ‘climate health literacy’

Despite the growing impacts on daily life of heat and extreme weather, the general public remains poorly informed about the relationship between climate and health, said Jian Zhou of the Institute of Energy, Environment and Economy at Tsinghua University.

“I think it is the critical moment and essential for us to set up something that we label as the climate health literacy,” Zhou said.

China’s leadership in climate and health education

Under the guidance of Chan, who has continued to carry forward the climate message ever since leaving WHO in 2017, the Vanke School of Public Health, which is part of Tsinghua University, has launched a new climate and health literacy initiative.

The programme features two core courses on climate and health run by the Global University Alliance, which recruits students from around the world for a six-month program. After completing the courses, students return to their universities and local communities to share their knowledge with peers.

In 2024, the program reached students from more than 400 universities in 79 countries.

Vanke’s World Health Forum in November will meanwhile bring together international organizations as well as government officials, academic experts, and industry leaders from around the world, Chan told Health Policy Watch. “This forum, directly addresses the growing health risks posed by escalating climate crises, aiming to promote the deep integration of emission reduction targets and population health benefits. It will also contribute to the implementation of the Paris Agreement and advancing the United Nations Sustainable Development Goals (SDGs).

“Global climate governance has entered a critical stage of deepening global cooperation and collaboration,” Chan said, adding “Climate change has become the most pressing global challenge of the 21st century.”

–Elaine Ruth Fletcher contributed reporting and editing to this story

Image Credits: WMO, Maayan Hoffman, London School of Hygiene and Tropical Medicine, Daria Devyatkina/Flickr, Stockholm Resilience Centre, WHO/Bill & Melinda Gates Foundation, GHF, WHO/V. Gupta-Smith, E Fletcher, Health Policy Watch, European State of the Climate 2024 report, Health Care Without Harm , Sergio Calleja/Flickr , Vanke School of Public Health .