Health impacts of climate change

Climate change is a growing health crisis

How does climate change impact people’s health?

What are the implications for healthcare, life sciences, and employers?

How can the health sector respond to risks and opportunities?

The health sector both contributes to climate change and confronts its consequences:

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IMPACTS

IMPLICATIONS

RESPONSE

notes

This exhibit aims to illustrate some impacts of climate change on health and life sciences. The examples are not exhaustive, and do not aim to cover all impacts, geographies, organizations, or stakeholders.

FRACTURED MEDICAL SUPPLY CHAINS

DISRUPTED HEALTHCARE DELIVERY

HEIGHTENED WORKFORCE RISKS

INCREASED HEALTHCARE COSTS

US: Private insurers bore more than USD 180 million in health costs (~30% of the total health costs) from Hurricane Sandy in 2012. A major academic hospital in New York incurred flood damages, lost revenue, interrupted research, and staff safety costs amounting to USD 1 billion.

UK: After 2009 flooding destroyed several clinics in northern England, temporary health services cost NHS Cumbria almost GBP 7 million, as road closures and collapsed bridges quadrupled travel costs for community health teams. This represented more than the total spending on health facilities during the previous year.

Australia: Australia’s 2019-2020 wildfire season triggered AUD 2 billion in health costs from smoke-related premature deaths and hospitalizations. This is more than three times the previous record of nearly AUD 600 million from the 2002–2003 fire season.

Middle East: Construction companies have faced stakeholder concerns over the working conditions and health risks as workers, predominantly migrant labor, may be exposed to extreme temperatures and heat stress.

India: In 2015, labor hours lost due to extreme heat cost the services, manufacturing, agricultural, and construction sectors a combined USD 67 billion in potential earnings. This conservative estimate amounts to 4%-6% of annual GDP.

Canada: In 2017, wildfires in British Columbia forced 19 healthcare facilities to close, displaced 700 healthcare staff, and caused the evacuation of 880 patients.

US: In 2020, California wildfires forced nearly 1,000 staff from a Bay Area hospital group to evacuate and/or face road closures and delays, disrupting much-needed health services during the COVID-19 pandemic.

Honduras: In 2020, hurricanes Eta and Iota damaged 10 hospitals and more than 400 other healthcare facilities. Healthcare professionals were among the 9 million people affected, reducing health system capacity to cope with COVID-19 and other diseases.

Puerto Rico: In 2017, Hurricane Maria derailed the manufacturing operations of a major medical device manufacturer, causing USD 70 million in revenue loss. The disruption led to a months-long shortage of intravenous saline bags and workflow disruption at US hospitals, where nurses had to administer drugs manually to patients.

Madagascar: The island has more unique plant and animal species than the whole continent of Africa; more than 80% of these species are found nowhere else on earth. Climate change – among other factors – threatens this unparalleled biodiversity, which includes recently or yet-to-be discovered active ingredients for drugs.

China: In 2020, heavy flooding in eastern China disrupted PPE supply chains, delaying urgently needed shipments during the first wave of the COVID-19 pandemic.

CLIMATE CHANGE AFFECTS HEALTH WORLDWIDE

Climate change is worsening health risks and costs

Health impacts range from mild to severe, acute to chronic. They vary by race, age, gender, geography, and socioeconomic status.

Health harms happen directly as well as indirectly through complex, interdependent pathways.

Health and socioeconomic disparities widen as people and countries least able to cope are hardest hit.

Deaths

INJURIES

INFECTIOUS DISEASES

CHRONIC DISEASES

MENTAL ILL HEALTH

Health and life sciences organizations face:

More frequent and severe disruptions due to acute climate hazards

Accumulating strains on capacity and finances, due to chronic hazards and lasting or lagging effects of crises

payers

For healthcare and life sciences, climate change presents risks and opportunities

LIFE SCIENCES

HEALTH POLICYMAKERS

EMPLOYERS

PROVIDERS

Insurers and government

Pharma, biotech, medical devices

Local, national, international levels

Workplace, health and benefits

Hospitals, clinics, labs, care homes

The health sector can respond by (1) building resilience

Stakeholders have an obligation and opportunity to act now

Stakeholders are slow to act, believing impacts to be distant, complex, or uncertain, and deferring systemic solutions involving multiple actors

Urgent action is vital to minimize health harms and inequities for patients, staff, and societies – and to avert drastic and expensive changes in future

payers

Insurers and government

Pharma, biotech, medical devices

Local, national, international levels

Workplace, health and benefits

Hospitals, clinics, labs, care homes

LIFE SCIENCES

HEALTH POLICYMAKERS

EMPLOYERS

PROVIDERS

Select a disease burden category:

Climate change is worsening health risks and costs

Climate hazards are escalating. Shocks—such as extreme weather events—are becoming more frequent and intense. Stresses—such as sea-level rise—are worsening.

Health harms happen directly as well as indirectly through complex, interdependent pathways.

Health outcomes are likely to worsen across all major categories – deaths, injuries, and disease burden.

Spikes in urgent care needs

Reduced capacity as facilities, staff, services, or supply chains interrupted, damaged, or dislocated

Delays or loss of elective care, straining revenue and resources

Swell and change in disease burden due to lasting or lagging effects of crises and care delays

Research setbacks as sites, samples, or staff disrupted by extreme weather or critical infrastructure failure

Pricing and patent pressures as healthcare costs soar

Growth and change in disease burden and vulnerability

Disruptions to manufacturing and supply chains, damaging inventory, reducing capacity, and increasing operating costs

Biodiversity loss shrinks sources of existing and potential drugs

Spikes in urgent care needs and costs, coinciding with economic strain during crises

Increase in health and safety risks, productivity loss, healthcare costs

Reputational, legal, and regulatory risks as low-paid and migrant workers are more exposed to threats and less able to cope

Disruptions to on-site or other healthcare

Unpredictable and unmanageable liabilities as claims spike and swell

Severe cost pressure, particularly for payers covering poorer or aging populations

Growing regulatory and reputation risks for insurers as rising premiums widen already large protection gap

Asset stranding or volatility, such as for investments in high-carbon sectors or those exposed to physical or other transition risks

Spikes in urgent care needs and costs, coinciding with economic strain during crises

Increase in healthcare costs and productivity loss as determinants of health deteriorate

Widening health and economic inequalities, as well as intensifying pressure from climate migration

Financial burden of being lenders and insurers of last resort

Disruptions to healthcare and other critical infrastructure, services, and supply chains

Credibility risks as timely, quality, and equitable delivery of healthcare become increasingly important national issues

Make urgent and essential care affordable for everyone

Facilitate universal access to basic services and determinants of health – such as food, housing, healthcare, financial well-being

Ensure long-term viability. Public-private partnerships may be one way to pool risks and limit losses more effectively and sustainably

Model and mitigate climate-sensitive risks, and incentivize risk mitigation and resilience measures

Ensure continuity of care during crises

Prepare for changing needs

Design and select leave and health benefits to ensure all workers receive urgent and essential care

Assess and mitigate health risks through changes to worksites, schedules, practices, equipment, and exposures

Improve social determinants of health for workers – such as financial well-being, control and autonomy, health promotion programs

Provide guidance and training to increase workers’ resilience

Strengthen health systems for disaster preparedness, response, and recovery

Promote universal access to basic services and determinants of health – such as housing, healthcare, financial well-being

Implement policies with co-benefits for health – such as improving access to clean air, clean water, housing, healthy food, physical activity

Spur investment and innovation to monitor, avert, and respond to crises – such as disease surveillance to prevent pandemics, or vaccine platforms for rapid response

Build national and community resilience – integrate direct and indirect health impacts into disaster planning and risk reduction

Reconfigure operations and supply chains to increase resilience to climate shocks

A changing disease burden – for example, heat-related illness, tropical diseases

Ensure universal access and affordability for essential medicines and products

Invest in rapid response capabilities and partnerships – such as to repurpose drugs, devise tests, or discover vaccines for new infections

Devise adaptive service and staffing models – for example, telehealth and functional flexibility

Enhance community resilience – support public health measures to improve well-being and equity

Weatherproof buildings and secure access to critical infrastructure and equipment

Ensure surge capacity for essential resources, including trained and psychologically supported staff

Plan for effective stakeholder coordination

Click on each stakeholder to explore implications

Click on each stakeholder to explore how they can respond to shocks and stresses

Handle claims and distribute funds swiftly and effectively during and after crises

The health sector can respond by (2) reducing emissions

If the health sector were a country, it would be the

emitter of greenhouse gases on earth

4.4%

56%

The sector climate footprint amounts to

of global net emissions

Sector emissions from top three countries/regions

Sector emissions driven by healthcare supply chain

71%

(from production, transport, and disposal of goods and services)

Healthcare will need to strike a balance between efficiency and resilience – cut emissions and costs without sacrificing quality or continuity of care

All stakeholders can reduce their emissions, and influence their sector and societies

Some changes will increase efficiency and resilience – for example, clean energy and low-carbon technologies can reduce emissions, protect public health, and keep health services running through crises

Other options present trade-offs, such as just-in-case capacity and stockpiles of essential supplies that boost resilience but also costs, resources, or emissions

Weak infrastructure exacerbates loss of life

When Hurricane Maria (a Category 5 storm) struck Puerto Rico in 2017, residents lost access to electricity, water, roads, and medical facilities. These critical infrastructure failures likely worsened the health impact: in the three months after the hurricane, disrupted or delayed medical care may have contributed to one-third of estimated deaths. Today Puerto Rico's underfunded healthcare system remains under strain and vulnerable to future crises.

8.2 million

Extreme heat will become a significant cause of death

More frequent and intense extreme weather events will increase mortality, particularly in places with weak health systems

The elderly, the chronically ill, the poor, and the very young are disproportionately vulnerable

annual excess deaths – or 73 deaths out of every 100,000 people – are forecast worldwide for 2100 due to extreme temperatures in a high emissions scenario. This mortality rate would match the current death toll from all infectious diseases.

300 million

More people will be exposed to increasingly frequent and severe disasters, with growing populations dependent on weakened ecosystems and infrastructure

people already live on land that will likely be underwater or annually flooded by 2050 due to sea-level rise, even in a low emissions scenario. Global coastal population may exceed 1 billion by 2050, exposing many more people to risk of injury.

Climate hazards could force mass migration or displacement, raising risks of conflict and violence

Rising temperatures correlate with an increase in self-harm and violence

500 million

Rising temperatures are expanding the transmission zones of vector-borne diseases

more people may be at risk of exposure to mosquito-borne diseases by 2050. Small increases in temperature can facilitate mosquitoes’ survival across a broader geographic and seasonal range, potentially increasing the burden of infectious diseases such as dengue and Zika.

Warmer temperatures could release long-buried pathogens or help new diseases emerge

Food/water insecurity and deteriorating air quality increase susceptibility to infections

USD 176 billion

Climate change and chronic disease share common drivers such as air pollution and meat-based diets

is the projected annual healthcare cost in 2060, of respiratory and cardiovascular diseases attributable to air pollution – an eight-fold increase from 2015. Climate change is making heat waves and wildfires more frequent and intense, increasing air pollution and worsening chronic disease burden.

Chronic conditions and related medications can make people more sensitive to climate hazards

Damage to the lungs or heart can last long after extreme weather events and account for the bulk of consequent costs

Trillions of dollars

Mental health outcomes and costs can outlast extreme weather events, potentially compounded by other gradual and perennial hazards

are the potential costs of mental ill health in a changing climate. Direct and indirect costs are likely to surpass USD 6 trillion by 2030 as climate hazards undermine psychological well-being and increase the prevalence of mental illness.

Pre-existing mental disorders and related medications can increase vulnerability to climate hazards

Disasters and economic hardship will likely increase mental illness in affected populations and subsequent generations

FRACTURED MEDICAL SUPPLY CHAINS

DISRUPTED HEALTHCARE DELIVERY

HEIGHTENED WORKFORCE RISKS

INCREASED HEALTHCARE COSTS

Tropical cyclones worldwide have already become more intense in the past four decades. Over the coming century in an intermediate emissions scenario, hurricanes in the Atlantic are likely to bring heavier rain and higher storm surges, further damaging critical infrastructure. Resilient healthcare facilities and infrastructure will be crucial in limiting the human cost of these extreme events.

More frequent and severe heat waves increase mortality

15% of people in South Asia are already exposed to dangerous levels of heat and humidity, and severe heat waves cause thousands of deaths in India and Pakistan.

During 2021–2050 in a low emissions scenario, India may experience nine times as many severe heat waves, lasting three times longer and, exposing 15 times more people to heatwave days each year, relative to a 1985–2015 baseline. By 2100, 75% of South Asia’s population may be exposed to dangerous heat and humidity in a high emissions scenario; extreme heat may cause 200 excess deaths per 100,000 people in poor, hot countries like Pakistan and Bangladesh. Heat stress is also likely to erode labor productivity and economic growth, reducing societies’ capacity to adapt to climate change.

An increasingly erratic South Asian monsoon fails?

Flash floods and prolonged droughts could lead to crop failure and destitution for hundreds of millions of farmers, who often lack irrigation and insurance. Related risks include famine or soaring food prices for more than a billion people, as well as mass migration and conflict over resources.

Vulnerable populations suffer most from extreme heat

While rising global temperatures reduce the risk of death from extreme cold for populations in northern latitudes, far more people – particularly the elderly – will be vulnerable to more frequent and intense heat waves.

In 2018, Japan recorded 32 million incidents of heatwave exposure among people older than 65 – equivalent to almost every elderly citizen experiencing a heatwave that year. The health impacts were stark: an intense summer heatwave led to 70,000 heat-related hospitalizations, of which nearly half were the elderly. This age group also accounted for 80% of related deaths.

Climate-driven malnutrition increases mortality among children

In 2019, floods, cyclones, and drought contributed to food crises across east and southern Africa. Of 33 million people facing starvation, more than 16 million were estimated to be younger than 18. Even a short period of undernutrition can stunt children and increase their risk of contracting and dying from common infections.

In an intermediate-to-high emissions scenario, in 2030 climate change in eastern and southern Africa may cause nearly 30,000 deaths of children under the age of five due to stunting. This is up 8% from a scenario with no climate change.

In a low emissions scenario with moderate population decline and no adaptation, during 2031–2080, Japan may see a 50% increase in heatwave-related excess deaths, relative to the 1971–2020 baseline. This figure increases to 80%–100% in an intermediate or intermediate-to-high emissions scenario.

Rising ocean temperatures degrade coral reefs that ordinarily dissipate energy from sea waves and protect low-lying coastal areas from coastal erosion, storms, and floods. The loss of this natural defense could further expose millions of people to the impacts of tropical storms, which are likely to become more intense under continued global warming. Catastrophic losses from storm surges, such as the 6,300 deaths and more than 28,600 injuries in the Philippines after 2013 typhoon Haiyan (Yolanda), may become more likely.

In a high emissions scenario, coral reefs near the Philippines, Indonesia, and Malaysia could experience annual severe bleaching by 2045. Across these three countries, this would put 26 million people currently protected by coral reefs at greater risk of injuries during storm surges.

Climate change affects health directly and indirectly

Climate change will increase mortality, particularly for vulnerable populations

Coral reef degradation increases injury risk from storms

Rising temperatures escalate the risk of violence

Hotter days, especially in temperate or warm places, are associated with more violence at the individual, community, and national levels. For each standard deviation of increase in average temperatures, the frequency of interpersonal violence increases by 4% while that of intergroup conflict increases by 14%. Possible explanations for this increase range from climate-induced resource strain to psychological responses to heat.

By 2050 in a high emissions scenario, there may be 9,000 to 40,000 more suicides in the US and Mexico. From 2020 to 2099, there may be cumulatively 2.3 million or 3.2 million more violent crimes in the US, costing an additional US$341 billion or US$496 billion, in an intermediate or high emissions scenario respectively.

Drought is a threat multiplier for conflict and displacement

From 2007 to 2010 Syria experienced an unprecedented drought, the likes of which have been made two to three times more likely by climate change. Agriculture and livestock losses drove the migration of up to 1.5 million people from rural to urban areas, which was likely one contributing factor – among others – to the outbreak of the 2011 Syrian civil war. Now in its tenth year, the civil war has killed 380,000, displaced 12 million, and injured many. More than half of all health facilities are defunct.

In a high emissions scenario with rapid fossil fuel-based economic growth, from 2050 to 2100 the Mediterranean may see a 14% decline in monthly rainfall. This could drive longer and more intense droughts, and increased risk of injuries from violence, conflict, and displacement.

Rising temperatures and sea levels trigger water wars?

Water scarcity and compounding effects on food security could spark conflicts among states, within countries, or between local populations and extractive businesses. Tensions between groups are especially likely if some perceive privileged access, profligate use, or contamination of scarce resources.

Mosquito-borne diseases expand in range

Dengue, a mosquito-borne viral disease most commonly found in the tropics, is likely to present a growing public health challenge due to climate change. Rising temperatures lengthen transmission seasons and expand mosquitoes’ geographic range, facilitating the spread of dengue to temperate regions previously unfavorable to the disease. Public health measures to combat outbreaks may become strained if climate hazards weaken economies and living standards.

By 2050 in an intermediate-to-high emissions scenario, much of southeastern US – currently a low-risk area – may become suitable for dengue transmission. In the same period under a high emissions scenario, Latin America and the Caribbean could see 11.8 million dengue cases per year, a 175% increase from the 1961–1990 baseline.

New diseases could emerge from microbes adapting to climate change

The fungus Candida auris may be among the first microbes to become dangerous to humans after adapting to higher temperatures; it is now a cause of serious infections and sometimes death. Since the first reported infection in 2009, it has emerged on six continents including Europe, which has detected nearly 1,000 cases from 2013 to 2019. C.auris has become a serious global health threat, as it is often drug-resistant, difficult to identify, and prone to spreading in healthcare facilities.

Many microbes cannot survive in the warm-blooded human body. As more microbes adapt to rising temperatures and develop greater heat tolerance, new fungi, viruses, bacteria, and parasites could infect humans.

6-7

Rising temperatures increase risk of zoonotic disease outbreaks

From 2014 to 2016, the Ebola outbreak in West Africa infected nearly 29,000 people and killed 11,000. Another 10,600 people died because of conditions left untreated due to Ebola's strain on health services in Guinea, Liberia, and Sierra Leone.

By 2070 in an intermediate-to-high emissions scenario, an Ebola epidemic infecting more than 1,500 people could occur every ten years, as compared to the present average of every 17 years. Climate change, among other factors, is also increasing the risk of new pathogens spilling over from animals to humans.

Thawing permafrost can release long-buried pathogens

In 2016, a heatwave brought temperatures in the Arctic to 35°C, causing permafrost to thaw and release frozen anthrax spores into nearby water and soil. This led to the region's first anthrax outbreak in 75 years: 2,300 reindeer (an important food source) and one person died, and at least 20 people were infected.

By 2050 in an intermediate emissions scenario, nearly four million people in polar regions such as Alaska, Canada, and Russia may be exposed to near-surface permafrost thaw. This trend could revive dormant pathogens such as anthrax, smallpox, or the influenza strain that led to the 1918 pandemic.

Exposure to air pollution worsens COVID-19 outcomes

Poor air quality increases people's risk of infection and death from COVID-19. In the US, a small increase in long-term exposure to fine particulate pollution (PM2.5) is associated with an 11% increase in the COVID-19 death rate.

Climate change and air pollution reinforce each other in a negative feedback loop. Air pollution causes climate change; in turn as temperatures rise, wildfire seasons are likely to grow longer, generating more smoke. Heat waves can also coincide with and worsen extreme air pollution episodes. This feedback loop can worsen communities’ risk of infection, severe disease, and death from respiratory illness.

20-21

Food insecurity makes children more susceptible to infection

In 2016, a drought began in the Horn of Africa that pushed 15 million people into severe famine. Malnutrition, displacement, and lack of clean water and sanitation left people more vulnerable to infectious diseases. Somalia saw 23,000 measles cases at the height of the drought — six times as many as in the previous year — mostly affecting children.

While projections vary, there is consensus that climate change is likely to reduce crop yields in eastern Africa. In a high emissions scenario, by the 2090s rising temperatures could cause an 8%–35% decline in major crop yields – maize, rice, wheat, sorghum, and soybean – across most of the region, potentially increasing food insecurity and the impact of infectious disease outbreaks.

Mega-storms overwhelm critical infrastructure in a major coastal city?

Storm surges and large-scale flooding could disrupt healthcare, transport, power, and even water-treatment facilities – which could trigger a cholera outbreak, as happened after Hurricane Matthew in Haiti in 2016. Untreated cholera kills half its patients; such death tolls could destroy trust in overwhelmed health systems and governments.

Climate change may expand the warm, wet habitats of wild bats and primates, the animal vectors thought to transmit Ebola – potentially bringing them into contact with more human populations. Urban sprawl and deforestation may further increase the likelihood of human-wild animal contact and disease transmission.

Wildfire-linked water pollution brings cancer risk

In 2016, the Fort McMurray fire in Canada contaminated more than 250 watersheds with dissolved organic carbon. Such pollution can generate carcinogens that technicians at many water treatment plants lack the expertise to handle, increasing risk of cancers. Residents had to boil water as a precaution for three months, and annual water treatment costs remain 50% higher than before the fire.

By 2050 in an intermediate-to-high emissions scenario, area burned annually by wildfires in Western Canada and Alaska could more than triple. This would threaten water security and health of residents in the region – such as the 2.4 million people in Alberta, more than two-thirds of the provincial population, who rely on drinking water originating in forested watersheds.

Sea-level rise increases hypertension prevalence

Saltwater is contaminating drinking water in Bangladesh, potentially putting 20 million people at risk of high blood pressure, the leading global risk factor for attributable disease burden. In coastal areas with moderate salinity exposure, 45–84% of surveyed residents have high blood pressure, compared to the national average of 24%.

By 2050, in an intermediate emissions scenario, 80% of river area in southwest coastal Bangladesh could exceed salinity levels suitable for drinking water, a 21% jump from 2012. Freshwater areas may be lost entirely in an area currently home to 5 million people. Increasing prevalence of hypertension will result in increased risk of cardiovascular disease, the top cause of death worldwide for people 15 and older.

Air pollution worsens health outcomes for asthmatics

Ground-level ozone is the main ingredient in smog. In 2015, 61% of China's population was exposed to ozone pollution exceeding the WHO’s recommended limit. People with asthma are particularly vulnerable to ozone pollution, as it can aggravate their condition and make asthma attacks more frequent.

By 2050 in an intermediate emissions scenario, more intense air stagnation events and heat waves could worsen air quality for more than 85% of China’s population. In an intermediate-to-high emissions scenario, higher temperatures and greater humidity could increase ozone pollution and the likelihood of high-ozone periods in eastern China, home to most of the country's population. Such trends pose a health risk to the 4.2% of China’s adult population currently suffering from asthma.

Medications can amplify health risks from heat

Commonly used medications – such as for blood pressure or heart disease – can harm the body’s ability to regulate heat by preventing sweating, reducing a sense of thirst, or increasing fluid loss. During 2001–2013 in Australia, people who began taking commonly used medications – such as diuretics and ACE inhibitors for blood pressure – had significantly higher risk of hospitalization for dehydration or heat-related illness.

In a high emissions scenario, Australia may see double the number of heat waves between 2020 and 2039, compared to the 1990 – 2009 baseline period. This could mean nine to 11 heat waves each year across northern and southern Australia, increasing the risk of heat-related illness for the 11% of Australian adults who take medications for high blood pressure.

Heat waves increase heart attack risk for diabetes patients

Pre-existing conditions such as diabetes can reduce the body’s ability to cope with heat. Short-term heat exposure spiked the relative risk of heart attacks in Germany from 1987 to 2014, particularly among diabetes patients.

From 2021–2050 in an intermediate-to-high emissions scenario, Germany may see more than 650 excess deaths each year from coronary heart disease and heart attacks related to heat waves – double the 1971–2000 baseline. As temperatures rise, populations age, and diabetes prevalence increases, patients will be increasingly vulnerable to heat waves.

Warmer temperatures increase risk of allergies and asthma

In 2013, 13.5 million people in Europe suffered from allergies to the ragweed plant. This allergy costs Europe €7.4 billion each year in medical treatment and productivity loss. Rising temperatures and CO concentration are likely to increase allergy incidence, severity, and costs through the spread of allergenic plants, longer pollen seasons, and increased pollen production and dispersion into the air.

In an intermediate emissions scenario, over the 2041–2060 period, 77 million people in Europe could be at risk of allergies and asthma from ragweed, a 130% increase from the 1986–2005 baseline. The greatest increases in risk are projected in currently less affected parts of Europe such as Germany, Poland, and France.

Bushfire smoke threatens lasting health harms

In 2019, smoke from record-breaking bushfires in Australia adversely affected 80% of the population, far more people than those directly exposed to the fires. Healthcare costs amounted to AU$2 billion. It may take years for survivors to recover, and some could suffer lasting health effects such as cancer and respiratory or heart disease.

In the next few decades, fire seasons are expected to lengthen in southern and eastern Australia, where most of the population lives now. By 2030 in a high emissions scenario, these regions could see a 20%-50% increase (compared to 1995) in days per year with severe fire danger, followed by smoke-related disease burden and costs.

An aging population with pre-existing conditions is exposed to prolonged heat waves and forest fires, during a new hottest summer on record?

Besides vast numbers of early deaths as in Europe’s 2003 heat wave, soaring hospitalizations for respiratory and cardiovascular complications could cost billions during and after the event.

Extreme heat intensifies mental ill health

Extreme temperatures increase health risks for patients with mental ill health. In Toronto during 2002–2010, emergency room visits for mental and behavioral disorders increased by 29% in the week after a hot day (defined as ambient temperature of 28°C). The patterns were similar for schizophrenia, mood disorders, and neurotic disorders.

In a high emissions scenario, the number of annual hot days (with a maximum temperature above 30°C) is likely to increase. Relative to the 1986-2005 baseline, Canada on average may see 2.6 more hot days each year by 2050, and 13.2 more each year by 2100. This trend poses a risk to the one in three Canadians affected by mental illness in their lifetime.

Climate-driven economic hardship worsens mental health

During 2000–2019, drought in Australia decreased average annual farm profits by 22% (AU$18,600), harming the livelihoods as well as mental health of farmers and farm workers. Male Australian farmers have about double the suicide rate of the general male population. Mental ill health can also affect the next generation: Children in drought-hit farming communities struggle with increasing workload, adversity, and stress.

In a high emissions scenario, the climate cycle that triggers severe drought in Australia could become more frequent, from once every 17 years during the 1900s to once every six years this century. This would exacerbate economic hardship and resulting mental health burden.

9-10

Violence takes a toll on mental health of migrants

2019 was the fifth consecutive year of drought in Central America's Dry Corridor, leaving 1.4 million people facing starvation. Crop shortages, poverty, and hunger have contributed to surges in Central American migration to the US. Nearly 80% of migrants screened by Doctors Without Borders in Mexico experience or witness violence en route, including threats, abuse, assault, torture, or murder. As a result, most people (56% of those screened) experience moderate or serious symptoms of anxiety, depression, and post-traumatic stress.

Decreasing rainfall is likely to spur more climate migration and displacement. In a high emissions scenario, by 2050 Mexico and Central America could see up to 3.9 million people displaced from their homes. Many of them will suffer serious psychological consequences from exposure to violence.

Climate refugees face escalating mental health risks

Rapidly rising sea levels have already submerged eight islands in the Western Pacific, with more to come. In a survey of 100 residents of Tuvalu, an island nation midway between Hawaii and Australia, almost two in three people reported psychological distress at levels that affect daily tasks. Similarly, nearly all of 57 surveyed residents in the Solomon Islands reported fears and worry due to rising sea levels.

In a high emissions scenario, most atolls may be uninhabitable by the 2040s because of sea-level rise that damages infrastructure and freshwater security. The threat of displacement will cause increasing harm to the mental health of those living on these islands and other low-lying coastal areas.

Mental health impacts outlast extreme weather events

In late 2013 and early 2014, England experienced heavy and prolonged rainfall that flooded 6,500 properties. Nearly 4,000 households experienced increased psychological distress, with an estimated £25 million to £67 million in public health and welfare costs. Mental health impacts such as depression and post-traumatic stress disorder lasted at least three years for some flood victims.

By the 2080s, in a high emissions scenario with no population growth and current adaptation levels, 3.5 million people in the UK could be exposed to high flood risk, almost doubling from 1.8 million today. Double the number of emergency service providers may also face high flood risk by then.

The threat or reality of displacement takes a psychological toll on hundreds of millions of people?

In some places on the front lines of climate change, more than half the population exhibits signs of mental ill health (see case studies). This is more than double the global period prevalence, and a glimpse into the future for other parts of the world.

Climate change is a threat multiplier for health and healthcare

CLIMATE CHANGE AFFECTS HEALTH WORLDWIDE

Disclosure: The following content, which touches on self-harm, may be disturbing to some readers.

Disclosure: The following content, which touches on the correlation between rising temperatures and an increase in self-harm and violence, may be disturbing to some readers.

Climate change is a risk multiplier for injuries from sea-level rise, extreme weather, conflict, and violence

Climate change increases existing communicable disease risks and creates new ones

Climate change increases non-communicable disease risks and costs, and worsens outcomes for people with pre-existing conditions

Climate change increases risks and costs of mental ill health, already a leading driver of disability

Climate change is worsening health risks and costs

Health impacts range from mild to severe, acute to chronic. They vary by race, age, gender, geography, and socioeconomic status.

Health harms happen directly as well as indirectly through complex, interdependent pathways.

Health and socioeconomic disparities widen as people and countries least able to cope are hardest hit.

This map and these examples are not exhaustive, and do not aim to fully represent the health impacts of climate change or their geographic distribution within or across countries and regions. Instead, the selected examples aim to illustrate the geographic breadth of impacts on the major categories of disease burden.

This map and these examples are not exhaustive, and do not aim to fully represent complex climate and meteorological processes or their impacts on health. Instead, the selected examples present a snapshot of the complex environmental, societal, and health interactions through which climate change directly or indirectly affects health.

Insurers, employers, and governments can prefer or reward sustainable providers, develop policies to reduce unnecessary care, reflect climate risks in pricing to encourage risk reduction, and channel investments into green assets

Use purchasing and investing power to incentivize others to go green

Providers can become energy efficient and switch to renewable sources, avoid unnecessary care, and use low-carbon modalities such as telehealth or electric-vehicle fleets

Pharma and medical device manufacturers can reduce use of energy and water, minimize packaging waste, and reconfigure supply chains to reduce emissions from transport

Cut emissions by reducing energy use and waste, and switching to green suppliers and technologies

Clinicians and public health experts can use their trusted voices to educate their staff and communities on climate risks, and advocate solutions

Policymakers can integrate public health into climate action, and drive mitigation and adaptation efforts for immediate and long-term health benefits

Protect public health by supporting transition to low-carbon economies

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notes

RESPONSE

IMPLICATIONS

IMPACTS

Refer to Notes for details on different emissions scenarios

Scenarios

References

Acknowledgments

The map is for illustrative purposes and does not imply the expression of any opinion on the part of Marsh McLennan, concerning the legal status of any country or territory or concerning the delimitation of frontiers or boundaries

Refer to Notes for details on different emissions scenarios

largest

Ensure continuity of care during crises

Prepare for changing needs

Ensure continuity of care during crises

Prepare for changing needs

Ensure continuity of care during crises

Prepare for changing needs

Ensure continuity of care during crises

Prepare for changing needs

More frequent and severe disruptions