Crossing the Line – What the 1.5°C Breach Means for Global Health

Written by Emmanuel Urama, WHO CC Intern. Edited by Celine Tabche, Mona Kuroiwa. 

In 2024, the world crossed a crucial threshold in the climate crisis. According to the World Meteorological Organisation (WMO) and the EU’s Copernicus Climate Change Service, the global average temperature for the 12-month period ending in April last year was about ~1.5°C above pre-industrial levels (1). This moment is not merely a symbolic breach of the 1.5°C target set under the Paris Agreement, but an indication of a new and more dangerous era for human health. While its exceedance currently represents a single-year anomaly rather than a long-term trend, it serves as a stark warning that our climate is reaching critical limits (2). Now, more than ever, we must recognise the Paris Agreement for what it truly is: not just an environmental accord, but a public health obligation, and one that holds to the task of preventing widespread disease, infrastructure collapse, and loss of life as our planet continues to warm (3). The scientific evidence underpinning the 1.5°C goal is undeniable. Limiting global warming to this threshold could mean the difference between manageable risks and widespread catastrophe, according to the Intergovernmental Panel on Climate Change (IPCC) (4). Even a small increase, as much as half a degree, would bring about dramatic consequences (4). 

Figure 1. The difference between 1.5°C and 2°C is not academic – it is a matter of life and death. 

These climate shifts are not abstract, or even distant (5). They are unfolding now, in ways that threaten the very foundations of planetary, global, and public health (6). Take extreme heat, for example: Europe suffered more than 60,000 heat-related deaths in the summer of 2022 alone (7). These extreme heat events have become more prolonged and more frequent, causing cardiovascular failure, dehydration, and premature deaths (4). What’s more, climate change is also shifting the geographic range of infectious diseases, with mosquito-borne illnesses such as dengue and malaria now appearing in regions previously unaffected (4). 

These direct health risks are compounded by systemic pressures. As climate variability intensifies, agricultural yields are declining, exacerbating malnutrition in low-income regions (8). Changes in rainfall patterns are contaminating water sources and limiting access to clean drinking water, increasing diarrheal diseases and compromising hygiene (9). Air pollution, closely linked to fossil fuel combustion, contributes to respiratory and cardiovascular illnesses, already accounting for an estimated 7 million premature deaths annually, according to the WHO (10,11). Mental health is also under siege, meta-analyses showing a ~1% increase in suicide rates for every 1°C rise in temperature (12). Moreover, recurrent climate disasters – floods, wildfires, and droughts – inflict trauma, displacement, and chronic anxiety (13). The youth worldwide are reporting increased distress and anxiety about climate change, some questioning whether it is ethical to bring children into a rapidly warming world (14). 

And yet, the burden is not borne equally. Climate change is a magnifier of inequity, and the world’s richest 10% are responsible for over half of all emissions and two-thirds of global warming since 1990 (15,16). Yet, the most vulnerable are forced to pay the price – the low-income nations, small island states, indigenous communities, and children, disproportionately exposed to its consequences (16). The principle of ‘common but differentiated responsibilities’, embedded within the Paris Agreement, stresses the need for attuned support and adaptable strategies (17). Climate justice is not relegated to an optional add-on; it is central to protecting the right to health for all. 

The Paris Agreement represents the single most coordinated global effort to protect both the environment and human health (17). Yet its framing as an environmental treaty often obscures its direct implications for health systems, universal health coverage (UHC), and public health resilience (18). Without climate stability, health systems cannot function reliably. Hospitals and health infrastructure are already vulnerable to blackouts during heatwaves, flood-related failures, and supply chain disruptions, which strain health service delivery and workforce capacity (18). Rising disease burdens, we are seeing today, such as those from air pollution, poor diet, and physical inactivity, add further strain to already overstretched health workforces (19). As the WHO’s Operational Framework for Climate-Resilient Health Systems outlines, adaptation and mitigation measures must now be mainstreamed into national health policies and financing structures (20). 

Despite the daunting task ahead of us, the message must not be one of fatalism. There is still time to change course (21). Climate models show that swift and decisive mitigation, especially through phasing out fossil fuels, can stabilise global temperatures and preserve the health gains of the past century (21). This World Environment Day, we must reaffirm that climate action is not just about saving the planet; it is about saving lives. The Paris Agreement is our health treaty, whose success will define the well-being of current and future generations. Breaching the 1.5°c threshold should not merely trigger a global alarm, but must ignite coordinated, equity-driven health action. 

Climate Action is Health Action – What We Can Still Do

Written by Emmanuel Urama

In light of mounting evidence of climate impacts, every action to combat climate change is also an action to protect health. From reducing carbon emissions to creating greener cities, the measures we take today can prevent illness, reduce suffering, and save lives tomorrow (1,2). Climate change is not a distant environmental threat, it is a present-day public and planetary health emergency (3). But it is also a window of opportunity: to rebuild our systems, reimagine our cities, and re-centre health equity on a global scale.

Individuals

Change begins with choices we make every day. Adopting a predominantly plant-based diet, for example, not only reduces greenhouse gas emissions, but also lowers the risk of chronic diseases such as diabetes, heart disease, and certain cancers (4,5). Choosing to walk, cycle, or use public transport improves air quality and promotes cardiovascular fitness, and reducing household energy use, through more efficient insulation, renewable energy choices, or conscious consumption, cuts emissions and improves energy resilience (6–8). Importantly, staying involved and vocal, by advocating for climate-responsible policies, voting for green leadership, and discussing the links between climate and health, helps shift public discourse and drive political will (8).

Communities

But the actions of a few are not enough. Communities and cities have tremendous influence over how climate change is experienced and addressed (9). Urban centres, which produce over 70% of global emissions, are on the front line of both risk and innovation (9,10). Expanding urban green spaces not only helps mitigate heat, but also promotes psychological wellbeing, reduces air pollutants, and fosters social cohesion (11,12). Investing in climate-resilient infrastructure (ranging from flood defences to heatproof schools and hospitals) saves lives and reduces costs in the long-term (13). For instance, local food systems and community gardens can strengthen food security while helping to reduce transport emissions. In addition, public education and outreach initiatives, integrated climate-health school curricula, and climate-resilience capacity-building programs can all build and bolster a community’s capacity to cope with and adapt to the impacts of climate change (14).

Governments

Governments, however, must lead the charge. Effective climate policy is health policy. National action plans should integrate health at every stage, from emissions reduction strategies to disaster response systems (15). For example, enforcing clean air regulations and investing in reliable public transport reduce the prevalence of pollution-related diseases (15). Fiscal policies, such as carbon pricing that accounts for health-related costs, can support sustainable transitions while simultaneously protecting vulnerable populations (15). Health ministries must be active participants in climate negotiations and national climate adaptation strategies, as recommended by WHO’s Health and Climate Change Country Profiles (15).

The Health Sector

It is equally imperative that the healthcare sector itself not be exempt. Paradoxically, if it were considered a country, the global health sector would be the fifth-largest emitter of greenhouse gases (16). Hospitals, clinics, and related services must decarbonise through sustainable procurement, renewable energy use, low-carbon healthcare technologies, and waste reduction (16). Fortunately, the WHO’s guidance on climate-resilient and low-carbon healthcare provides a practical roadmap for what such a transformation could look like (17).

The Case for Change

Figure 1. Synergies and trade-offs between climate action and the Sustainable Development Goals (SDGs) by Nerini et al. (2019) (18).

One of the most compelling reasons to act is the impressive range of co-benefits, policy measures that simultaneously reduce emissions and improve global priority health outcomes. Clean air reduces asthma, chronic obstructive pulmonary disease (COPD), and cardiovascular deaths; active transport infrastructure reduces traffic injuries and sedentary lifestyle-related illnesses; and increased access to green spaces lowers rates of depression and anxiety (11,19,20). Healthier diets, cleaner environments, and reduced exposure to pollutants also all contribute to better health outcomes, particularly for children, the elderly, and people with chronic disease (21,22).

The economic case is just as strong, because inaction is costly. As one notable example, the mental health burden linked to climate-related hazards and air pollution is estimated to cost over USD $500 billion by 2050 (23). By contrast, investing now in mitigation and adaptation reduces future healthcare costs, improves workforce productivity, and strengthens public trust in institutions (24). Strikingly, the World Bank found that investing USD $1 trillion in climate-resilient infrastructure in developing countries could generate a potential USD $4.2 trillion in benefits (13).

Yet, for all our scientific understanding and policy frameworks, one ingredient remains essential: a sense of possibility; not just belief, but action. And we’re already seeing what’s achievable. Cities such as Denmark’s Copenhagen are working towards carbon neutrality through smart infrastructure and strong cycling-friendly policies (25). Hospitals in the UK are transitioning toward 100% renewable energy by expanding on-site solar installations (26). Youth-led movements are pushing for climate justice, reframing climate change not only as a climate crisis, but a chance to rewrite the future (27). So, this World Environment Day, let’s remember that the health of our climate is the health of our future. The food we grow, the air we breathe, the heatwaves and floods we face – they all affect how well we live. Climate change is a health issue. But so is climate inaction. Together, with science as our guide and equity as our compass, we can shape a world where people and planet thrive in concert.