As Global Warming Surpasses Limits of Human Survival, Non-Communicable Diseases Need to be on COP28 Agenda
A fire in a favela in Brazil: Poorer countries are least equipped to mitigate the health effects of the climate crisis.

The 28th United Nations climate conference, scheduled to open on 30 November in Dubai, has pledged to elevate health issues, but non-communicable diseases – which are set to become dramatically worse as temperatures rise – are nowhere on the agenda. Prevention of climate– and heat-related diseases need to be on the formal Conference of Parties (COP) 28 negotiating agenda – not just on the sidelines.

Humans are facing unprecedented health impacts from heat

Wildfires across Canada, Hawaii and Algeria, killer heat waves from Texas to India, China, southern Europe, and Morocco, and summer temperatures in the middle of the winter season in Argentina and Chile. The relentless, heat-related effects of climate change are more and more manifest – along with their human toll in terms of deaths and diseases from acute heat stroke to chronic kidney disease.   

As UN Secretary-General Antonio Guterres said recently: “The era of global warming has ended. The era of global boiling has arrived. The air is unbreathable and the heat is unbearable. And the level of fossil fuel profits and climate inaction is unacceptable.” 

And the impacts on health are mounting faster and faster. 

According to the latest report of the Intergovernmental Panel on Climate Change (IPCC), the world could see over nine million climate-related deaths annually by the end of the century in a high emissions scenario – more than any other disease risk factor we face today.

Amongst the growing list of climate-related health effects – which range from vector-borne diseases to hunger and undernutrition – non-communicable diseases (NCDs), particularly those linked to extreme heat, have received far too little attention. 

This is despite the fact that heat-related mortality, also linked to cardiovascular disease and other NCDs, will rise significantly by 2030 particularly under high emission scenarios, according to the IPCC.  Asia, North Africa and the Middle East will be most seriously affected – but Europe and North America will also be badly affected. 

The Intergovernmental Panel on Climate Change’s projection of climate-related deaths.

Extreme heat, NCDs and ‘wet bulb temperature’ survival threshold 

To understand how deeply and directly extreme heat affects health, it’s important to look at the basic physiology of how we humans function in “normal” temperatures and cope with temperatures that rise above our comfort levels.   

Our human thermometer is attuned to maintaining a body temperature of about 37 ℃.  We can tolerate higher temperatures for short intervals if we don’t exercise or work hard, have adequate shade and water and dress in clothes that permit sweating to self-regulate. 

This is how people have survived in tropical and desert regions for millennia. However, even in these regions, daytime temperatures remained, on average, around 32℃ – well below body temperature, with even lower night temperatures.  

Above a certain threshold, humans can only survive for a few hours since we cannot reduce our body temperature by sweating. This threshold, called the “wet–bulb temperature”, is a measure of the combination of temperature and humidity. Visually, imagine a wet cloth wrapped over a thermometer. 

Theoretically,  the wet bulb temperature threshold of survivability is defined as 35℃ – and this is for only a few hours of exposure. However, for healthy adults pursuing normal activity levels outdoors, the safe range is considered to be closer to 30–32.

The wet bulb temperature threshold also varies geographically in hot – dry and warm – humid climates so there is not one absolute defined threshold for human survival.

For instance, 37℃ in a relative humidity of 50% would be equivalent to a wet-bulb temperature of 28.3 C But with 99% humidity, air temperature of 37.5 C would be equivalent to a wet-bulb temperature of 37 C as well – above the survivability threshold. 

Another metric called the wet bulb globe temperature (WBGT) measures heat stress in direct sunlight. It is similar to the wet bulb temperature but also takes into account wind speed and solar radiation, and is often used to set heat exposure limits for outdoor workers.

What is clear, however, is that as the world warms, more tropical and temperate regions are seeing temperatures rise more frequently beyond the safety zone for more hours and days in the year.  This is now happening visibly, very much along the lines of scientific predictions.  

We have already breached the 1.5℃ target over land  

World Meteorological Organization, August 2023

The 2015 Paris Agreement set a global temperature limit of 1.5℃ above pre-industrial levels, based on knowledge of the harmful ecosystem and health impacts of temperatures rising above this threshold.  

Yet the average global temperature increase since pre-industrial times is already 1.15 ℃ according to the World Meteorological Organization (WMO). On land, we have already passed the threshold of 1.5℃ warming, with a mean temperature increase of 1.59 ℃ since pre-industrial times, according to the IPCC.

This last July was the hottest month ever on record, WMO recently warned. And with the arrival of El Niño, the warming phase of surface waters in the tropical Pacific Ocean, we are going to surpass the 1.5℃ threshold for parts of every year. 

“WMO is sounding the alarm that we will breach the 1.5°C level on a temporary basis with increasing frequency,” said WMO Secretary-General Petteri Taalas on 17 May. 

El Niño, he warned, “will combine with human-induced climate change to push global temperatures into uncharted territory. This will have far-reaching repercussions for health, food security, water management and the environment. We need to be prepared.”

This will push nearly one-third of humanity outside the earth’s “human climate niche” by the end of the century with “high temperatures linked to issues including increased mortality, decreased labour productivity, decreased cognitive performance, impaired learning, adverse pregnancy outcomes, decreased crop yield, increased conflict and infectious disease spread,” says Professor Chi Xu at Nanjing University in China. 

While until now, most land areas of the earth have been habitable, even if conditions may sometimes be harsh, but by the end of this century, large areas of the populated world will be virtually uninhabitable. 

The drought in the Horn of Africa has impacted approximately 4.5 million Somalis, and around 700,000 people have been forced to leave their homes.

Heat-related increases in chronic disease 

So what are the health impacts of the temperature rises that we are seeing? In acute instances, extreme heat can lead to sudden organ failure and death

Anecdotally, we’ve already seen many more such cases during this year’s summer in the northern hemisphere. A 13-year-old girl cycling home from school, was one of 15 people that perished in extreme heat in Japan and the Republic of Korea in the first weekend of August. 

In June, the deaths of a 14-year-old boy and his stepfather in Big Bend National Park in Texas in 48°C heat also gained a lot of attention in US media. 

But the stories that hit the headlines are only the tip of the ‘heat–berg’. Uncounted numbers of outdoor workers, such as farmers and construction workers, are likely to have died from heat-related conditions over the past months and weeks. A 44–year–old road worker in Milan and two construction site workers in Jesi and Brescia were among the workers who died from heat this summer, for example. 

Over time, however, chronic extreme heat exposure also can trigger or exacerbate a range of NCDs such as kidney disorders, hypertension, and chronic cardiovascular and respiratory diseases – leading to more premature deaths.

And as usually happens, it is the elderly, children, pregnant women and outdoor workers – a large proportion of which are also poor and marginalized – who are among the worst affected

Heat and workers’ health 

With regards to outdoor workers, few countries have yet paid sufficient attention to heat-related health. In the US, for instance, the federal Occupational Safety and Health Administration (OSHA), lacks any kind of official labour standard for heat and health standards to protect workers. 

In some cases, laws have even moved backwards. The Texas State Legislature recently passed a bill nullifying local ordinances in the cities of Austin and Dallas that required employers to give construction workers water breaks of 10 minutes every four hours. The bill was signed into law in late June, just as a deadly heat wave gripped the state. 

Indeed, by any public health standard, this is the opposite of the direction in which we need to move to create decent work and workplaces in the climate change era. Indirectly, as well, heat waves pose a particular threat to livelihoods, socioeconomic output and reduced labour productivity – affecting mental health, nutrition and other health determinants. 

Heat stress among workers, if not properly managed, can also lead to injuries and significant losses of productivity. 

A construction worker in Texas, where the state legislature recently removed some health protections for outdoor workers.

Other NCD risks related to climate change 

Heat is not the only climate-related driver for NCD morbidity and mortality – which is in turn responsible for 74% of the total global deaths. 

Climate change depletes food supplies, increasing hunger and malnutrition in multiple pathways. These include direct damage to crops, livestock and fish catches from rising land and ocean temperatures, as well more complex ecosystem events – for example, pest invasions such as the massive locust swarms seen over the past couple of years in the Horn of Africa.

Increasingly, low-income countries in Africa and elsewhere are also experiencing a triple burden of undernutrition and malnutrition, including micronutrient deficiencies; overweight and obesity, as a result of increased consumption of sugary drinks and other industrialized, ultra-processed foods, and decreased consumption of fresh, indigenous food varieties. As a  result, more people living with diabetes, hypertension and cancers in developing countries.

Due to rising sea levels, freshwater systems in vulnerable Small Island Developing States (SIDS) are threatened by the increased salinity of groundwater supplies, which is increasing daily salt intake of island inhabitants – and thus risks of hypertension and related NCDs. 

A multi-year drought in Uruguay has had severe consequences for the freshwater supply, leading the authorities to add brackish water to the drinking water supply, enhancing dangerous salt levels. 

People living with NCDs also are at particular risk during and after extreme weather events such as floods and storms, which interrupt routine healthcare services and access to life–saving medication, such as insulin. The displacement and trauma of extreme weather also exacerbate mental health conditions – a factor highlighted at the recent Ministerial meeting on SIDS.

Addressing the heat and health crisis 

While rich countries are affected as well, it is often the same low- and middle-income regions most vulnerable to the effects of climate change that are also the least prepared to cope with its health impacts – including heat-related ones. 

Of the 17 million premature deaths annually from NCDs, some 86% already occur in low- and middle-income countries.  

So what can we do to combat and counter these trends?  We must act both in climate forums like COP28, as well as in global health forums and national health systems and across sectors nationally, regionally and globally. 

Stronger health systems : NCD diagnosis, prevention and treatment are poorly integrated into primary health care and universal health coverage (UHC) of many low- and middle-income countries, and these interventions are often not considered part of UHC. 

Primary healthcare facilities lack simple diagnostic technologies to measure blood pressure, blood glucose levels, and peak expiratory flow (an indicator of respiratory diseases). 

They also lack basic medicines listed in WHO’s Package of Essential NCD (PEN) interventions. Investments must be strengthened to cope with today’s already large NCD burden – and prepare better for tomorrow – including more heat–related diseases. 

Additionally, facilities in many low-income countries lack even a minimum functioning infrastructure for energy, clean water, sanitation and waste. Ensuring these services is essential to ensure the uptake of modern technologies for the prevention, detection and control of NCDs. Next month’s UN High-level meeting on UHC is an opportunity to strengthen the commitments.

Early warning, heat action plans and workers’ health: During California’s recent heat waves, the City of Los Angeles opened “cooling centers” to protect people who lacked adequate home cooling. 

With emergencies now becoming routine, more cities and countries need to consider the development of heat and health guidelines and action plans. 

As part of this, occupational health standards should be assessed and strengthened, to protect workers better from climate-related and particularly heat-related diseases. and particularly for outdoor workers. WHO may be called upon to support this process with evidence-based guidelines with regard to safe temperature thresholds for outdoor work, and relief measures such as the provision of shade, water, and cooling breaks and devices.  

Advocacy at COP28 

At COP28, we in the health sector need to advocate for increased recognition of the health problems associated with climate change – problems which the recent series of extreme heat waves may be finally raising to the top of our political awareness. 

This needs to go beyond rhetoric and lead to greater access for the health sector to international climate financing, such as the Green Climate Fund, and the Loss and Damage Fund, as well as through the World Bank and regional development banks.

Investments in policies to reduce greenhouse gas emissions should be recognized and assessed in terms of their co-benefits for health as well as to climate – such as transforming food systems to make them more sustainable and resilient as well as healthier. 

We need to retool tax and financial incentives for linked climate and health actions. This includes the removal of harmful subsidies not only on fossil fuels but on agricultural commodities like sugar and intensive livestock production. 

Two years ago, the COP26 Health Programme and the Alliance for Transformative Action (ATACH) were launched by WHO and partners outside the formal COP agenda. It established building blocks to protect the health of people from climate change, such as addressing the barriers faced by countries to access finance to address climate change and health. 

Proactive climate measures can improve health 

Well-designed climate mitigation measures can not only avoid increases in NCDs but can even reduce existing NCD risk factors, blunting the epidemic increase in such diseases.  For instance, measures to ensure clean energy and transport will reduce air pollution; policies to promote walking and biking may reduce weight and lower blood pressure. 

Policies supporting the production and consumption of healthy, locally produced fresh foods, particularly plant-based foods, and discouraging excessive red meat consumption, would lower greenhouse gas emissions in agriculture and result in healthier diets. 

In addition, planting trees and shrubs with crops could both increase the resilience of crops to droughts and excessive rainfall runoff, reduce CO2 emissions as well as improve health.

We have illustrated some of the ways in which climate change and NCD are interlinked and suggested that actions to manage them must be aligned. These two crises have one thing in common: they can be prevented. 

Going beyond ‘health’ rhetoric to action  

But this requires strong and deliberate policies by brave political leaders – as well as more explicit recognition of the health impacts of climate change and the co-benefits of mitigation and adaptation in all aspects of climate action. 

It appears long forgotten, but Parties to the UNFCCC are committed to considering the public health implications of their climate policies. We need formalized discussions on how to fully integrate health-incentivising climate policies into countries’ nationally determined contributions (NDCs) under the Paris Agreement, and the reporting requirements for National communications. This should include the systematic quantification of health co-benefits of climate change mitigation and adaptation commitments – which would reduce the huge burden of NCDs. 

Only after such health impacts and benefits are fully counted, can health also have the seat it deserves at the table of climate funding and investment decisions.  

During the seven years we have left to fulfil the 2030 Sustainable Development Agenda and to achieve the target of a one-third reduction in premature deaths from NCDs, which is intertwined with our climate agenda, we need to see a lot more courage from national governments and leaders than we have seen in the past 30 years. 

Human health is in fact the lynchpin in the two processes.

The declaration of a COP “Health Day” and a Health Ministerial Meeting at the Climate Conference are important steps. But this needs to be followed by concrete action to reduce and reverse our planet’s spin into an abyss of worsening climate and human health impacts – including NCDs, which constitute the biggest global health epidemic of our time.

Dr Bente Mikkelsen

Dr Bente Mikkelsen is WHO’s Director of the Department of Non-communicable Diseases.

Dr Maria Neira is WHO’s Director of the  Department of Environment, Climate Change and Health 

Marit Viktoria Pettersen is a consultant for the WHO’s Integrated Service Delivery in the Department of Noncommunicable Diseases.

Image Credits: Denys Argyriou/ Unsplash, UN-Water/Twitter , Josh Olalde/ Unsplash, WHO, World Economic Forum, Maria Neira.

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