Health: European scale
Globally, the number of publications on the impact of climate change on health has strongly increased since about 2006. Still, the knowledge base is smaller than for other key sectors (e.g., agriculture) because of limited research investment in climate change and health (77).
Multi-hazard assessment 2100: Europe's most harmful extreme events
The seven most harmful weather-related extreme events in Europe due to climate change are heat waves, cold waves, droughts, wild fires, river and coastal floods, and windstorms. The occurrence and intensity of these disasters as well as demographic changes in Europe until the year 2100 have been estimated. This was done for business-as-usual climate and socioeconomic scenarios for the 28 European Union (EU) countries as well as Switzerland, Norway, and Iceland (EU+) (73). The results in this study are based on the assumption that current human vulnerability (in the reference period) remains constant throughout this century. One may expect people to adapt, however, and become less vulnerable than previously to extreme weather conditions because of advances in medical technology, air conditioning, and thermal insulation in houses. Therefore, the results could be overestimated. The results are summarized below.
50 times more weather-related deaths
Annual numbers of deaths were assessed in 30-year intervals relative to the reference period (1981–2010) up to the year 2100 (2011 - 2040, 2041 - 2070, and 2071 - 2100). Disaster records of previous years were combined with projections of climate change and socioeconomic (demographic) development. Climate change projection was based on a business-as-usual scenario (the so-called SRES A1B greenhouse gas emissions scenario). Human vulnerability to weather extremes was estimated on the basis of more than 2300 records collected from disaster databases during the reference period; it was assumed that human vulnerability stays the same between now and 2100, and that no additional measures will be taken to enhance human capacity to cope with future extreme climate conditions (73).
During the reference period (1981 - 2010), around 3000 Europeans lose their lives each year because of weather disasters. According to the results of this study two-thirds of the European population may be exposed to weather-related disasters due to climate change annually by the year 2100, compared with 5% during the reference period (1981 - 2010). Disaster-attributable deaths are expected to increase by roughly 50 times between now and 2071 - 2100 (by about 10 times in 2011 – 2040, and by about 30 times in 2041 – 2070). For the increased weather-related death toll, population change accounts for 10%, whereas climate change accounts for the remaining 90% (73).
Heat waves the most lethal, but drought fatalities are rare
Among these disasters, heat waves are the most lethal, accounting for 99% of the total future disaster-related mortality. During the reference period, about 2700 heat-related fatalities per year were reported in Europe by the disaster databases. Mortalities due to heat waves are expected to increase by 5400% in 2100. Urbanisation (18% increase in city dwellers in Europe by 2050) and urban heat island effects will augment the effects of heat waves (73).
Mortalities due to coastal floods are expected to increase by 3780%, due to wild fires by 138%, due to river floods by 54%, and due to windstorms by 20%, whereas mortality due to cold waves is projected to decrease by 98%. The effects of coastal flooding will be amplified by population growth in coastal flood-prone areas (14% more than total population growth) (73).
Droughts can be lethal in low-income and middle-income countries, mostly because of poor agricultural techniques and under-nutrition (74). On the contrary, people in high-income countries have diverse diets and guaranteed access to clean water for basic needs (75). Therefore, fatalities from droughts are rare in Europe and have not been reported in the observational period of this study (73).
Strong increase towards Southern Europe
Future effects show a prominent latitudinal gradient, increasing towards Southern Europe, where the premature mortality rate due to weather extremes could become the greatest environmental risk factor: for Southern Europe during the period 2071 - 2100 about 700 annual fatalities per million inhabitants (range: 482–957) due to heat waves have been projected versus 11 during the reference period. In addition, Southern Europe will experience an upsurge in drought conditions. By 2071 - 2100, about a third of the population in Northern Europe and almost all of those in Southern Europe could be exposed to a weather-related hazard annually (73).
Injuries and diseases
Direct injuries from flooding, windstorms, and wild fires could rise in the areas hit by the hazard. Because of more frequent and intense droughts in the future than at present, the number of people faced with reduced water resources for food production, domestic use, and other basic needs for human wellbeing could grow by more than 27 times between now (reference 1981 - 2010) and 2071 - 2100 (138 million people per year in 2100 versus 5 million now). The increasing number of heat waves might amplify cardiovascular, cerebrovascular, and respiratory diseases (73). Furthermore, mental health disorders associated with weather-related disasters, such as post-traumatic stress disorder and depression (76), could also increase.
Vulnerabilities - Overview
Based on a literature review a list of high-priority diseases has been identified likely to pose a threat in Europe under a changing climate (28):
- Vector-borne diseases: West Nile fever, dengue fever, chikungunya fever, malaria, leishmaniasis, tick-borne encephalitis (TBE), lyme borreliosis, Crimean-Congo haemorrhagic fever (CCHF), spotted fever rickettsioses, yellow fever and Rift Valley fever
- Waterborne diseases: fecal contamination of drinking and recreational waters, cholera, non cholera vibrios in marine waters, cyanobacteria
- Food-borne diseases: salmonella, campylobacter
- Extreme weather events: heat waves, extreme rainfall, strong winds / gales, hurricanes
- Air quality: respiratory tract infection
In other parts of the globe, in addition to these risks, climate change will negatively affect childhood undernutrition and stunting, through reduced food availability, and will negatively affect undernutrition-related childhood mortality and increase disability-adjusted life years lost, with the largest risks in Asia and Africa (98).
Vulnerabilities - Floods
Floods are the most common natural disaster in Europe. Climate change may strongly increase the annual damage and number of exposed people to coastal, river or flash floods. Several floods in Europe over the last years have shown that the health impacts of floods may be complex and far-reaching. In the first decade of this century, floods in the European Region have killed 1000 persons. More than 3.4 million were affected. The number of deaths from flooding was highest in central Europe and the former Soviet Republics (30).
Human health consequences of flooding include drowning, injuries, and an increased incidence of common mental disorders. Anxiety and depression may last for months and possibly even years after the flood event and so the true health burden is rarely appreciated (30,31). The summer 2007 floods in the UK, for instance, had a significant impact on people’s health and wellbeing. Many people suffered from illnesses, ranging from coughs and colds to bronchitis and heart attacks. Psychological impacts included increased levels of anxiety during periods of rainfall, and as a result of temporary living arrangements, dealing with insurers/builders and financial difficulties (32).
Known risk factors for flood-related mortality are: fast-flowing water, hidden hazards, water of unknown depth, driving and walking through flood-water, flood-water contamination (by chemicals, sewage and residual mud), exposure to electrical hazards during recovery and cleaning, unsafe drinking-water and food shortages and contamination, incomplete routine hygiene, CO poisoning, and lack of access to health services (30).
Outbreaks of infectious diseases are rare. Waterborne diseases on the other hand may be transmitted during flooding through contamination of drinking-water supplies, contact with contaminated floodwater and from sewage systems overloaded by floodwater. Drinking water can be contaminated by sewage, agricultural waste, industrial waste or chemicals (30).
Vulnerable groups within communities to the health impacts of flooding are the elderly, disabled, children, women, ethnic minorities, and those on low incomes (31).
Vulnerabilities - Air pollution
Fine particulate matter and ground level ozone (O3) are generally recognised as the two pollutants that most significantly affect human health in Europe. Of particular concern are particles with a diameter of 2.5 μm or less (PM2.5) since these could pass from the lungs into the bloodstream (58). Ozone concentrations are particularly high during heat waves, a study on the heat wave episodes of 2003 and 2014 in Europe has shown; ozone concentrations were closely related to increases in temperature (127).
Climate change affects surface concentrations of air pollutants, such as fine particulate matter and ozone (O3). Exposure to PM2.5 is associated with an increased relative risk of lung cancer, cardiopulmonary and all-cause mortalities (6) while O3 exposure is associated with increased incidence of cardiovascular, respiratory and all-cause mortality (7). PM2.5 is the fraction of the total particulate matter with an aerodynamic diameter less than 2.5 μm. In Europe, 400,000 (60) to over 600,000 (2,59) premature deaths each year from cardiopulmonary and lung cancer diseases are attributed to poor air quality, mainly anthropogenic PM exposure. The total external costs of the health impacts were estimated at EUR 330–940 billion (60).According to a model study of daily mortality due to heat and exposure to ozone during the European summer heatwave of 2003, possibly 50% of the deaths could have been associated with ozone exposure rather than the heat itself (11).
Projections of air quality changes over Europe under climate change are highly uncertain, however. This was shown for a scenario of global warming of 2°C above pre-industrial climate and for two indicators of air quality: the fraction of the total particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) and an indicator for ozone pollution (29). The results show that the simulated effects of regional climate change on the two air quality indicators are generally small and vary greatly from one model to another. The levels of fine particulate matter (PM2.5) are only slightly affected by regional climate change. These levels clearly increase over Spain and southern France, driven by changes in dust emissions, and decrease over southwestern Russia and the Ukraine, due to lower sulphate, nitrate and ammonium aerosol concentrations. Over the other parts of Europe, the projected changes of fine particulate matter are not clear. The impact of regional climate change on fine particulate matter mainly stems from changing natural emissions, such as desert dust (due to dryer soils and stronger winds over North Africa and Spain), sea salt and biogenic volatile organic compounds. Also climate-induced changes in ozone vary greatly from one model to another. In fact, no clear conclusion can be drawn about ozone changes in the future climate (29). In fact, heatwaves in a future warmer climate cannot necessarily be associated with a particular ozone concentration since future policy on reducing ozone precursor emissions may help to improve air quality (102).
Research indicates that 21st century climate change (under the moderate SRES A1B climate change scenario) increases global all-cause premature mortalities associated with PM2.5 by approximately 100,000 deaths and respiratory disease mortality associated with O3 by 6,300 deaths annually. The relative change in premature mortality as the percent change between “present” and “future” simulations is about a 4% increase in global all-cause mortality associated with PM2.5, and less than a 1% increase in respiratory disease mortality associated with O3. In the northern hemisphere, surface PM2.5 increases substantially near source regions (e.g., over East Asia, eastern United States, northern India, and Africa). These source regions are usually highly populated and hence, increases in PM2.5 will adversely impact human health. With climate change, surface PM2.5 concentrations decrease over western Brazil, parts of northern Europe, the Middle East and parts of North Africa, suggesting a potential “climate benefit” for air quality there (5,62).
Studies have shown that local-to-regional scale pollutant concentrations can be influenced by large-scale atmospheric circulation patterns, such as the North Atlantic Oscillation (3). The NAO commonly refers to swings in the atmospheric pressure difference between the subpolar and the subtropical North Atlantic. The NAO-Index (NAOI) is traditionally defined as the difference in the normalized sea level pressure anomalies between either Lisbon, Portugal, or Ponte Delgada, Azores, and Stykkisholmur/Reykjavik, Iceland. The NAOI is positive when the pressure contrast between the two centers of action strengthens, leading to a northward shift of the storm track (i.e., higher-than-average West-East transport) and more stable conditions over southern Europe. The NAOI is negative when the pressure contrast weakens and more storms enter the Mediterranean basin.
In winter months (December to March) the NAO dominates the atmospheric variability over Europe and PM concentrations are of most concern for public health, especially in southern Europe. The winter NAO has shown an upward trend during winter in the 1980s and 1990s; climate model predictions suggest that the positive trend in winter NAO will continue in the coming decades (4). Cities located in the Mediterranean area may be penalized by a NAO positive shift in a future climate, whereas central-northern and eastern Europe will benefit from such a shift. One of the areas most negatively affected by climate change is the Po-valley in Northern Italy, which is both heavily urbanized (e.g., Milan, Turin, Bologna) and also one of the largest industrialized regions in Europe. Because of its specific morphology, this area is also one of the most polluted regions in Europe, and climate change may aggravate this situation. Additional PM emission reduction measures may be necessary for those countries and cities in southern Europe, likely to experience NAO driven increases in mortality, in order to counteract these particular climate disbenefits (1).
Despite several pathways by which climate change may influence air quality, most model simulations show air pollutant emissions to be the main factor driving change in future air quality, rather than climate (61).
Health risk of wildfire smoke
Particles from wildfire smoke are more lethal than other - urban – particles because they tend to be more toxic and often occur in combination with other harmful environmental factors, particularly high temperatures (168). The risk of wildfires will increase as climate change worsens. These wildfires produce polluted smoke that can spread as far as 1000 km.
Several scientists have found adverse health effects of wildfire smoke in different world regions. On a global scale, it has been estimated that 339,000 deaths could have been attributable to wildfire smoke annually during 1997–2006 (169). Recently, a global study was carried out based on data for 749 cities from 43 countries and regions in the period 2000-2016. The study presents an update of wildfire smoke risk at the global scale, albeit with a dominate representation of urban populations (167).
In this study, mortality was related to daily exposure to wildfire related PM2.5. Data on daily counts of deaths for all causes, cardiovascular causes, and respiratory causes were used for this. Daily enhancements of PM2.5 concentrations by fires during the study period were estimated as the differences between simulations with and without fire emissions, calculated with a model and adjusted using ground-level measurements of PM2.5 and other predictors. From the relationship between the PM2.5 concentrations by fires and mortality, the fraction of annual deaths was calculated that could be attributed to short-term exposure to wildfire-related particulate matter (167).
The study included 65.6 million all-cause deaths, 15.1 million cardiovascular deaths, and 6.8 million respiratory deaths. Overall, 0.62% of all-cause deaths, 0.55% of cardiovascular deaths, and 0.64% of respiratory deaths were attributable to the acute impacts of exposure to wildfire-related particulate matter during the study period. The results show that wildfire smoke can affect health until 2 days after the exposure to the smoke. The exposure to wildfire related PM2.5 appears to have stronger effects on mortality than the exposure to urban PM2.5 (167).
Vulnerabilities - Pollen allergenic diseases
Allergenic diseases caused by pollen may appear earlier in the year (22) and may also increase. An example of the latter is the invasion of common ragweed (a native in North America) into Europe since the end of the nineteenth century (23). Model simulations for 2041–2060 compared with 1986–2005 under both a high-end (RCP 8.5) and a moderate (RCP 4.5) climate change scenario show that future ragweed airborne pollen loads are likely to increase in large parts of Europe owing to the synergistic effects of climate change on habitat suitability, pollen production, release and transport, and the infilling of existing suitable habitats due to seed dispersal. It was estimated that seed dispersal accounts for about a third of the future airborne pollen increase irrespective of climate change, whereas climate change explains the other two-thirds (23).
Vulnerabilities - Heat stress
Heat stress means that our body has difficulty in cooling itself during periods of exertion, or in extreme cases even while the body is at rest. Heat stress increases when rising temperatures reduce the difference between outside and body temperature. But it’s not just temperature that determines heat stress. Also air humidity is very important: a higher humidity makes temperature feel hotter than it actually is. In addition, for heat stress outdoors, the amount of radiation (e.g., direct sunlight adds to heat stress) and wind speed are important. In addition, local influences caused by humans such as urban heat island effects, black pavement, or other land surface modifications add to heat stress (57,166).
Indoors, heat stress can be quantified from a combination of temperature and humidity effects. This has been done on a global scale for mean monthly values of temperature and humidity over the period 1973 – 2012. The results indicate that heat stress has increased since 1973 over many land regions, consistent with and primarily driven by the increase in surface air temperature (57). Similar results were shown for the Mediterranean region for the period 1987-2016 (105). A further increase of heat stress is projected during this century (57,146).
Researchers have attributed 37% of deaths related to heat exposure around the world between 1991 and 2018 to anthropogenic climate change. The most affected areas included parts of southern Asia, southern Europe and central and South America (165).
Heat-related mortality is expected to increase by 59% EU-wide by 2050. The increase will be largest in already warm countries such as Cyprus, Greece, Italy, Portugal, and Spain, with smaller increases expected in Baltic and Eastern-European countries like Latvia, Lithuania, Poland, and the Czech Republic (124).
The tropics and parts of the mid-latitudes are most at risk
Human health impacts depend on both temperature and humidity. At low moisture levels the human body can efficiently loose heat through evaporative cooling, even on a hot day. When it’s hot and humid, however, the efficiency of evaporative cooling slows and the body may become unable to maintain a stable core temperature. When the effect of evaporative cooling is reduced such that the body accumulates heat, a threshold of human tolerance to heat stress is reached. Heat-humidity combinations then become dangerous (90).
Currently, some regions most at risk for extreme hot and humid weather, Northeast India, East China, West Africa, and the Southeast US, are some of the world’s most densely populated. In India and West Africa population density is expected to rise dramatically over the 21st century (91). In these risky regions, the number of people exposed to extreme heat will not only increase due to population growth combined with climate change. Also the continued urbanization will make the situation even worse. Due to the urban heat island effect (cities are generally several degrees warmer than their surrounding non-urban areas) more people will be exposed to extreme heat (90).
Future changes in the occurrence of these extreme heat conditions have been studied for a moderate and high-end scenario of climate change (RCP 4.5 and RCP 8.5) and several projections of population growth, based on a large number of climate models (GCMs) (90). The results suggest that exposure to extreme hot and humid conditions will rapidly increase throughout the 21st century and potentially beyond. By 2080 the relative frequency of these present-day extreme events could rise by a factor of 100-250 in the tropics and parts of the mid-latitudes, areas that are projected to contain approximately half the world’s population. In addition, population exposure to extreme conditions that exceed recent deadly heat waves may increase by a factor of five to ten. By 2070-2080, the threshold limit of human tolerance to heat stress will likely be exceeded for many people under the high-end scenario of climate change (RCP 8.5). Under the moderate scenario of climate change (RCP 4.5) this situation can be avoided (90).
Some of the most affected regions, especially Northeast India and coastal West Africa, currently have scarce cooling infrastructure, relatively low adaptive capacity, and rapidly growing populations. In the coming decades heat stress may prove to be one of the most widely experienced and directly dangerous aspects of climate change, posing a severe threat to human health, energy infrastructure, and outdoor activities ranging from agricultural production to military training (92). Research has shown, however, that relatively simple adaptation strategies such as early warning of heat waves, public education campaigns on the dangers of heat, and social check-ups on vulnerable people can drastically reduce the death toll on hot days (93).
The effect of changes in diurnal temperature range
In addition to heat extremes, the difference between the daily maximum and minimum temperatures known as the diurnal temperature range, may also affect human health. Data over the period 1985 to 2015 for several countries globally show that diurnal temperature range is associated with excess mortality (159).
An assessment has been carried out of changes in diurnal temperature range in a large number of countries and regions across the globe (based on a number of global climate models) towards 2100 (159). The results show two interesting effects. First, the projected diurnal temperature range increases under a high-end scenario of climate change (RCP 8.5) and stays constant or decreases slightly under a low-end scenario of climate change (RCP2.6). This suggests that mortality related to the diurnal temperature range may increase when global warming continues. Second, mortality for a certain diurnal temperature range may be higher at higher temperatures. In a warmer world the effect of the diurnal temperature range on mortality may thus be amplified. The combination of the effect of the change of diurnal temperature range on mortality and the amplifying effect of higher temperatures on this mortality is estimated to be 1.4% (low-end scenario of climate change) to 10.3% (high-end scenario of climate change) by the end of this century. This means that the excess deaths related to the diurnal temperature rangeare projected to increase in all studied countries or regions by 1.4 - 10.3% by the end of this century, compared with 1985 – 2015.
This assessment is based on the assumptions that population (size and composition) and temperature-related mortality risk do not change between now and 2100.
The impact of the Paris Agreement - Exposure to heat stress
The Paris Agreement makes a distinction between 1.5 °C and 2 °C global warming (above pre-industrial conditions). Warming should be limited to 2 °C global warming, but a limit at 1.5 °C is strongly preferred to avoid strong impacts of climate change. A recent study shows that the proportion of the population exposed to hot summers above the current record increases dramatically from 1.5 °C to 2 °C global warming (114).
This study looked at the population exposure to heat extremes in summers in Europe in the period 1950-2017. With this reference in mind, they quantified the exposure of the European population to historically unprecedented heat extremes in a 1.5 °C and 2 °C warmer world. Clearly, unprecedented hot summers are more likely in a 2 °C world than in a 1.5 °C world. In parts of southern and eastern Europe they are at least twice as likely at this 0.5 °C difference (114).
In the current climate in Europe, more than 45 million people are exposed to temperatures above the observed record. This number would increase to 90 million people in a 1.5 °C warmer world, and to 163 million people in a 2 °C warmer world. These numbers refer to 11% (1.5 °C) and 20% (2 °C) of the continent’s population, respectively (114).
The chance of having a summer with such widespread heat that at least 400 million people (or almost 50% of the continental population) experience a summer temperature exceeding the historical record is negligible in the current climate. In contrast, in a 1.5 °C warmer world such an event would occur on average once in 18 years, and in a 2 °C world once every seven years (114).
The impact of current policies compared with Paris Agreement
‘The costs of climate change are often estimated in monetary terms, but this raises ethical issues’, scientists state in a recent publication in the journal Nature Sustainability. These scientists, therefore, looked at the distribution of the global population in different climate zones and how this distribution changes under global warming. The historic distribution is the so-called ‘human climate niche’, into which people have adapted physiologically and culturally. Under global warming – and population growth – ever more people will be exposed to climate conditions outside this ‘human climate niche’. These conditions include ‘unprecedented heat’ (174).
They considered heat to be ‘unprecedented’ when mean annual temperature reaches or exceeds 29 °C. In 1980, only 0.3% of the global population experienced such conditions. Since then, the part of the global population exposed to this unprecedented heat started to increase markedly, reaching a tripling to 0.9% on average from 1980 to 2010. Therefore, they used the 1980 population distribution (total 4.4 billion) under the 1960–1990 mean climate as the reference state, and projected future changes in the ‘hot exposure’ of the global population compared with this reference (174).
Their future projections are based on the combined results of several climate models and four scenarios of global changes in population, socioeconomic conditions, and associated greenhouse gas emissions up to 2100. Their range of scenarios project a wide range of changes in hot exposure, reaching 8–40% of the global population – or 0.6–4.7 billion people – across these scenarios by 2090 (174).
The Paris Agreement aims to limit global warming to 1.5 °C. However, current policies are leading to around 2.7 °C global warming. The population exposed to unprecedented heat reaches 5% on average – or 0.4 billion – as global warming reaches 1.5 °C. Hot exposure further increases to 22% – or 2.1 billion – under 2.7 °C global warming. Thus, reducing global warming from 2.7 to 1.5 °C results in a ~5-fold decrease in the population exposed to unprecedented heat (174).
Several least-developed countries – including India, Nigeria, Sudan, Niger, Burkina Faso and Mali – will be left with large populations exposed to unprecedented heat, even if the world succeeds in significantly mitigating climate change. The authors of this study estimated the contribution of citizens from different countries to future global warming and then – in a next calculation step – estimated the contribution of these citizens to the increase of hot exposure. Since richer countries generally have higher emissions of greenhouse gasses, a citizen in a rich country will contribute more to the increase of hot exposure. They focused on the result of current policies, 2.7 °C global warming. About 2.7 citizens of the European Union emit enough carbon in their lifetimes to expose one future person to unprecedented heat. For the United States, this ratio is 1.2 to 1, and for Qatar even 1 to 2.8. Under current policies, the average contribution of a citizen of Qatar to global warming will lead to an exposure of almost three people to unprecedented heat by the end of this century (174).
Vulnerabilities - Heat-related versus cold-related mortality
Globally, 19 of the 20 hottest years in the last 100 years occurred after 2000. Frequency, intensity, and duration of heatwaves are increasing worldwide. As a result, the global annual numbers of cold- and heat-related deaths are changing. These changes have been quantified from daily time-series data on mortality and weather conditions from 750 locations in 43 countries or territories: two countries in Northern America, 13 in Latin America and the Caribbean, 17 in Europe, nine in Asia, one in Africa, and one in Oceania. These countries and territories account for about 46% of the world’s population (160).
The authors of this study refer to cold- and heat-related deaths as ‘mortality associated with non-optimal temperatures’. According to them, this is the largest investigation of the adverse impact of non-optimal temperatures on population health at the global scale. They used data on more than 130 million deaths from 43 countries or territories, located in five continents and covering the period 2000 to 2019 (160).
9.43% of global deaths in the period 2000 to 2019 were related to ‘non-optimal temperatures’, with 8.52% and 0.91% of deaths related to cold and high temperatures, respectively. Eastern Europe had the highest heat-related excess death rate and Sub-Saharan Africa had the highest cold-related excess death rate. The heat-related excess death rate in Eastern Europe was nearly five times higher than the global average. Europe was the only continent where both cold-related and heat-related excess death rates were higher than the global average. Little over half of all excess deaths occurred in Asia (160).
Remarkably, less people are dying now from ‘non-optimal temperatures’ as a result of global warming. In the period 2000 to 2019, the global cold-related excess death ratio decreased by 0.51% and the global heat-related excess death ratio increased by 0.21%, leading to a net reduction in the overall ratio. These results indicate that in the short run, global warming might slightly reduce the net temperature-related deaths. In the long run, however, climate change is expected to increase temperature-related mortality (160).
The increase in the number of people in Europe dying from high temperatures will start to exceed the reduction of the number of people dying from cold spells in the second half of this century, especially in the Mediterranean. This was concluded from projections of the future effect of climate change on temperature-related mortality in 16 countries across Europe (161).
In this study, the relation between temperature and mortality was quantified from data on daily temperature and mortality in the period 1998–2012. These relations were subsequently used to transform the daily temperature simulations from four climate models for a historical period (1971–2005) and a scenario period (2006–2099) into projections of temperature-related mortality. Changes in temperature-related mortality were quantified between the 30-year reference (1976–2005), mid-century (2035–2064), and end-of-the-century (2070–2099) periods. Future projections were based on a low-end (RCP 2.6), moderate to high (RCP 6.0) and high-end (RCP 8.5) scenario of climate change (161).
Of all deaths registered in the observational period 1998–2012, 7.17% were attributed to extremely high and low (‘non-optimal’) temperatures. Cold spells contributed much more to these deaths than heat: 6.51% vs 0.65%, a difference by a factor of ten. Differences across countries are large: In Germany, 4.85% of all deaths were related to non-optimal temperatures, in Italy 9.87%. A ten-fold difference in excess mortality atttributed to cold and heat was also found for 854 cities in Europe during the period 2000-2019: an annual excess of about 200,000 deaths attributed to cold versus about 20,000 attributed to heat (173).
In the course of this century, the percentage of the European population dying from cold temperatures will steadily decrease, while the percentage of the population dying from heat will increase. The latter increase will start to exceed the reduction of cold-weather related mortality in the second half of the 21st century, especially in the Mediterranean. As a result, mortality in Europe related to non-optimal temperatures will start to increase by the end of the century in a moderate scenario of climate change, and already by the middle of the century in the high-end scenario of climate change. These results are comparable with those reported elsewhere (172).
Mitigation policies to slow down climate change would be especially beneficial in the Mediterranean. Here, the benefits of less cold stress are much less than the adverse effects of a higher vulnerability to heat.
The vulnerability to cold and heat may be less now than the data over the period 1998–2012 suggest. Adaptation to extreme temperatures already seems to reduce the vulnerability to cold and heat (162), and hence both the decrease in cold-related mortality and the increase in heat-related mortality may be smaller than the results above suggest. Also, the European regions that will warm the most are also the regions that will dry faster. Heat stress not only results from high temperatures, but from high humidity as well. The projections above are based on a projected increase of high temperatures; an eventual decrease in humidity was not taken into account. Heat-related mortality in especially regions such as the Mediterranean may therefore be overestimated.
The impact of the Paris Agreement
Limiting global warming to 1.5 - 2 °C, the targets of the Paris Agreement, will have an impact on heat-related mortality. Potential health benefits of the Paris Agreement have been assessed for 451 locations in 23 countries across the globe. Changes in heat and cold-related mortality were quantified for 1.5 and 2 °C, and for 3 and 4 °C. This was done under the assumption of no changes in demographic distribution and vulnerability (106).
The projected impacts of a global warming from 1.5 to 2 °C on mortality are relatively small. Overall, a rise in heat-related mortality is largely balanced by a projected decrease in cold-related mortality. In Southern Europe, projected heat-related mortality rises by about 0.7 - 0.8%. A smaller, not significant, decrease of cold-related mortality was calculated for cooler areas such as Northern Europe. For Central Europe, no substantial changes in mortality were calculated (106).
Heat-related mortality increase is no longer balanced by a decrease in cold-related mortality in large parts of the world when global warming rises to 3 or 4 °C. Central and southern regions of America, Europe, and East-Asia are projected to experience increases in heat-related mortality ranging between + 3.5 and + 8.9% for 4°C global warming. For cooler regions in Europe and Asia, the reduction in cold-related mortality more or less equals the increase for heat; these changes are less than 2% (106).
The projected net temperature-mortality, the combined effect of changes in heat and cold-related mortality, shows the largest increase for the warmest regions. For Southern Europe, for instance, this increase is + 4.4%. For Central Europe this increase is + 2.6%. For Europe and Asia, the overall pattern shows moderate decreases in excess mortality in the colder areas of the north, nearly null changes or small increases in the temperate central areas, and larger increases in warmer southern regions (106).
Vulnerabilities - Heat stress versus Ozone
Both heat stress and ozone increase cardiorespiratory mortality. Current exposure to near-surface ozone in Europe is expected to cause around 56.000 premature deaths in Europe annually. Climate change and changes in the emission of greenhouse gases will substantially affect ozone and heat-related mortality and the ratio between them in the middle of this century in Europe. By 2050, ozone-related mortality is projected to be smaller, but heat-related mortality will strongly increase, making heat a larger health threat in the future. This was concluded from a study on future climate in 2046 - 2055 (centred on 2050) compared with the situation in 1991 - 2000. Future climate was based on an intermediate scenario of climate change (RCP4.5). This scenario leads to a 2 °C global average temperature increase by 2050, the threshold increase under the Paris Agreement (124).
Ozone-related mortality will reduce
Ozone is formed by the reactions of a mixture of pollutants from biogenic and anthropogenic sources. The rate of formation of ozone depends on sunlight, temperature, and other meteorological factors (mixing height, wind speed, and direction). Future near-surface ozone concentrations, therefore, depend on future changes in both anthropogenic emissions of pollutants from which ozone is being formed, and meteorological factors that determine the process of ozone formation.
On the one hand, anthropogenic emissions of those pollutants have decreased since the 1990s and are expected to continue decreasing in the future, both in North America and Europe (125). On the other hand, climate change will likely increase near-surface ozone concentrations in Central and Southern Europe (and decrease in Northern Europe) (126). The combined effect for Europe is probably a reduction of ozone-related mortality: 28% less ozone-related mortality could be expected EU-wide by 2050, according to this study. This reduction is not as large as it could be because of climate change and an increasingly susceptible population (124).
Vulnerabilities - Heat wave related mortality
The Russian heatwave in 2010 led to a death toll of 55,000 people and some US$15 billion of total economic loss (104) (others mention 50,000 heat-related fatalities (101)). The 2003 event caused 70,000 heat-related fatalities (99). The effect of heat waves on mortality is superimposed on the other factors that affect mortality. It is possible to differentiate the effects of heat waves from the other causes of human mortality. This was done in a new approach for 27 European countries for the period 1951-1980. The analysis demonstrates that many European countries are severely affected by heat waves. On average, around 28,000 people die every year in the 27 countries combined due to heat waves. An average of 0.61% of all mortality in the examined 27 countries is excess mortality caused by heat waves. This estimate goes up to 1.14% in the worst affected country, Portugal. Heat-related excess mortality may rise in the near future due to climate change. The effect of heat waves on human mortality varies significantly across countries, according to the results of this study. Some countries such as Spain and Greece suffer from higher mortality during individual high temperature events than other countries such as Germany or Switzerland. One reason for this is that the examined countries differ significantly with respect to the age structure of their population, their health care system, as well as their economic and institutional capabilities. Countries in Scandinavia are least affected in terms of total deaths (82).
Anthropogenic climate change is projected to increase heat-related mortality and decrease cold- related mortality, with an overall net increase in total mortality rates (70,78). Some previous assessments of health impacts of climate change build on the assumption that reductions of cold-related mortality will overcompensate increases in heat-related mortality at least for moderate levels of global warming. It has been argued that these assessments are based on flaws in previous analyses, are therefore not correct, and the net effect of moderate global warming is an increase of heat-related mortality due to the relative strong, dominating effect of the increase in heat-related mortality (78).
Humans can acclimatize and adapt to heat events. Heat sensitivity has decreased: the relative impact of heat events on human health has declined in recent decades (97). Due to acclimatization, current heat-mortality relationships are weaker in warmer cities (79), translating into relatively smaller heat impacts expected under climate change (80). Furthermore, there is some indication that deviations of temperatures in the cold range exert stronger effects in regions with relatively mild climates (81).
Although most Mediterranean populations are relatively acclimatized to high temperatures, an increase in the intensity and frequency of heatwaves, or a shift in seasonality, are significant health risks for vulnerable population groups, including those who live in poverty with substandard housing and restricted access to air-conditioned spaces (107). The degree to which heat-related morbidity and mortality rates will increase in the next few decades will depend on the adaptive capacity of Mediterranean population groups through acclimatization, adaptation of the urban environment to reduce heat-island effects, implementation of public education programmes and the preparedness of the healthcare system (108). Increased population life expectancies imply that the health protection of elderly people will become a major challenge for all Mediterranean countries under heatwave conditions. Indeed, increased mortality was found among people over 65 years in Athens, Greece, at high and very high temperatures (109).
Global future exposure to heat-related extremes: demographic change vs climate change
Worldwide the number of heat waves will increase. This will affect people’s well being and will increase heat-related mortality rates. More people will be exposed to heat-related extremes, not only due to global warming but also due to population growth. What effect is more important in determining future increase of people’s exposure to heat waves: climate change or population growth?
This was studied globally for climate model projections for the period 2061 - 2080 based on a moderate and high-end scenario of climate change (RCP4.5 and RCP8.5) and for a moderate and high-end scenario of population growth (SSP3 and SSP5). These results were compared with the period 1981 - 2005, representing present-day climate (96). As always in these studies, the definition of a heat wave is an important factor. In this study a heat wave day is defined as a day that meets two thresholds: daily mean temperature is greater than the 2% warmest days in the present-day climate (the period 1981 - 2005), and maximum daily temperature exceeds 35 °C.
The results show that the impact of climate change is a stronger determinant of exposure than demographic change in these scenarios. Exposure is quantified as the number of heat wave days times the number of people exposed to this heat, so called person-days of heat wave exposure. The moderate scenario of climate change, when compared with the high-end scenario, leads to a global reduction in exposure of over 50%. The slower population growth scenario leads to roughly 30% less exposure. Naturally, exposure reduction varies from one region to another. However, in almost all world regions, the impact of the climate change scenario dominates over the impact of the scenario of population growth (96).
The patterns of the spatial distribution of change in exposure are similar across all scenarios. Increases are largest in the equatorial/mid-latitude regions corresponding to the largest increase in heat wave days and high population growth areas such as India and large portions of Sub-Saharan Africa. Exposure increases in Eastern China in all scenarios, despite widespread areas of projected population loss. Across North America and Europe, increased exposure is most evident in urban areas (relative to rural) (96).
Of all world regions, Sub-Saharan Africa and South-east Asia would benefit most from mitigating climate change to the moderate scenario compared with the high-end scenario. The absolute reduction in heat wave exposure resulting from this mitigation is largest in Sub-Saharan Africa. In relative terms, however, South-east Asia stands to gain the most, experiencing roughly five times less exposure. The smallest reductions in exposure resulting from this mitigation occur in the cooler, slower-growth regions of Europe and North America, as well as Oceania (96).
The impact of the Paris Agreement
The likelihood of a heat-mortality event similar to the one of 2003 was estimated in a 1.5 °C and 2 °C warmer world for the cities of London and Paris. According to this study, stabilizing global warming at 1.5 °C rather than 2 °C would make a 2003 heat-mortality event 2.4 times less likely in London, and 1.6 times less likely in Paris (115).
Vulnerabilities - Urban heat island
The urban heat island effect is the difference between the temperature in the urban area and in the surroundings. This effect has been quantified from remote sensing for all cities in 38 European countries over the period 2006-2011. It was shown for daytime temperatures that this effect varies over the seasons, being maximum in summer (typically 2°C in July) and minimum in winter (1°C in February). Maximum values in summer were up to 3°C (8). For southern European cities annual averaged values for the urban heat island during 2001 – 2012 were quantified ranging between 0.74°C (Istanbul) and 1.83°C (Turin) (89). Global warming not necesarilly increases the urban heat island effect: a study on US cities shows that the surrounding rural areas may warm faster than the cities (103). Different results were obtained for European cities, however: an analysis for 37 European cities over the last 20 years, from 2000 to 2019, showned that the Urban Heat Island Effect is much stronger during heatwaves than during regular summer days. At night, when this effect is largest because cities release much less heat than rural areas do, the Urban Heat Island Effect was 0.7°C larger during a heatwave than during the rest of the summer (171). And the number of heatwaves is growing.
The urban heat island effect is most pronounced during calm nights with clear skies (63,171). In these situations this effect at night can be up to 7°C (for London and Rotterdam) (64,65) or even 10.5°C (Hamburg) (66).
The impacts on health of more frequent heat extremes probably greatly outweigh benefits of fewer cold days (9).
Causes of the urban heat island
Urban heat is a function of human caused alternations within urbanized surface influencing the local microclimates. These alternations include differences in the surface energy budget (118). The areas build up from asphalt or concrete exhibit higher thermal conductivity and increased heat capacity (119). Dark surfaces (e.g. roads, parking lots or rooftops) may warm about 8 °C above the temperature of surrounding air (120). The urban land surfaces magnify the absorption of solar energy, and together with reduced presence of vegetation, contribute to overall lowered evaporative cooling and local soil moister (121). However, other additional sources of heat can be found within urban systems, such as released heat waste that can be attributed to traffic, power plants, energy used to warm/cool the buildings (122), or even human metabolism (223).
Amplyfied by heat waves
The urban heat island effect is highest during the nighttime and early morning (prior to sunrise) hours: for New York City a difference between urban and rural temperature at night as high as 8°C was observed during a heat wave in 2016. During daytime, however, urban and rural temperatures were more or less the same (71). This clearly illustrates that cities stay hot during the night due to increased thermal storage (72). The built surfaces that dominate the urban environment have high thermal inertia and hence have high heat storage capacity.
The observations in New York also illustrate that heat waves amplify the heat island effect: the urban-rural temperature difference at night may be up to 3°C higher during heat wave days compared to regular days. This is due to that fact that the high-pressure weather system during a heat wave inhibits the heat of the city to be transferred to the upper atmosphere. Thus, the heat stays close to the surface thereby amplifying the near surface air temperature. In addition, the soil in the city dries out during a heat wave. Higher surface soil moisture means more evapotranspiration to cool the urban environment. The high soil desiccation during a heat wave, however, limits the moderating impact of evapotranspiration (71).
Vulnerabilities - Global assessment urban heat island in 2050
In future decades, urban heat islands will create more heat stress for more people for three reasons: ever more people are living in urban areas and are thus exposed to the urban heat island effect, the effect itself will increase when cities expand, and this is an extra effect on top of global warming. By 2050, there will be an additional 2-3 billion people living in urban areas, where surface temperatureshave already been rising faster than the global mean (129). How much will heat stress increase for the urban population between now and 2050, due to urbanization and climate change? This has been assessed at the global scale (summarized below).
Urbanization and global warming
A study has been carried out on the projected global urban land expansion and heat island intensification through 2050 (128). A distinction was made in arid, tropical, temperate, and cold climate zones. Trends of historical urban expansion were extrapolated into the future, based on scenarios of socioeconomic development used by the IPCC (the so-called Shared Socioeconomic Pathways (SSP) (130)). Projections of future urban land areas were combined with data onpopulation growth, to estimate both the change of the urban heat island effect and the number of people exposed to this. These data were integrated with projected global warming under a moderate scenario of climate change (the so-called RCP 4.5 scenario).
Urban land expansion
It is expected that globally urban land will expand by 78% - 171% between 2015 and 2050. More than two-thirds of this urban expansion will occur in Asia (46% - 49%) and Africa (16% - 25%), where the majority of urban population growth will be concentrated. More than 70% of the new urban lands will concentrate in the more humid temperate and tropical zones (128).
Stronger urban heat island effect
This urban land expansion will result in average summer daytime and nighttime warming in air temperature of 0.5 °C - 0.7 °C, and up to about 3 °C in some locations. During winter, the additional urban heat island warming will be weaker: on average 0.4 °C - 0.6 °C (up to about 2 °C). This additional urban heat island warming is on average about half, and sometimes up to two times, as strong as that caused by global warming under the moderate scenario of climate change (128).
The additional warming induced by urban expansion varies significantly across and within climatic zones. The effect is strongest in temperate and cold climates, on average 0.8 °C - 1 °C. Urban areas in the tropical and arid climates will experience weaker but still substantial additional warming due to urban expansion: on average 0.2 °C - 0.3 °C (128).
The magnitude of expansion and the subsequent warming are the most prominent in temperate urban areas.
Tropical zones most vulnerable
Regions most vulnerable to the increasing urban heat island effect are those with low economic capacities but substantial warming caused by urban land expansion. The majority of these risk-prone urban areas will be in the tropical zones. In total, about half of the world’s urban population will live in the most risk-prone regions by 2050 (128).
Implications for human health
Studies have shown that in the coming decades, global warming will increase the temperature-related mortality rates by 3%-13% in tropical zones but will reduce those by up to 1% in temperate/cold zones (131). The additional warming induced by urban expansionwill exacerbate heat-related health risks, and probably increase mortality rates. In addition, there will be a negative impact of rising humidity (128).
Implications for energy consumption
The use of air conditioning, and thus energy consumption, will increase. As a result, the waste heat of the more widely adopted AC systems enhance the urban heat island effect, which further increases cooling energy use (132). Wintertime warming can result in energy savings byreducing heating requirements in the temperate and cold zones. The energy savings on heating are not likely to outweigh the extra costs on cooling, however (128).
The extra warming in 2050 due to urban expansion will be as significant as, and at places even stronger than, that caused by global warming. This effect will expose billions of urban dwellers to greater extreme heat risks. This enormous urban land expansion and the subsequent warming are likely to occur in a relatively short time window of three decades (128). According to the authors of this study, interventions are needed to restrict or redistribute urban expansion or to mitigate urban heat, in order to reduce the wide ranges of impacts on human health, energy systems, urban ecosystems, and infrastructures (128).
Vulnerabilities - Tick-borne diseases
Lyme disease (Lyme borreliosis) is the most important vector-borne disease in temperate zones of the northern hemisphere in terms of number of cases. Tens of thousands of cases are reported in Europe every year and prevalence is greater eastwards (40,41,42). Central Europe is the region with the highest incidence of Lyme disease (39). Countries with annual incidences of over 20 per 100,000 citizens include Lithuania, Estonia, Slovenia, Bulgaria, and the Czech Republic (40). The number of cases in Europe has increased steadily: more than 360,000 cases having been reported over the last two decades (39). Over the last years there were approximately 65,500 patients annually in Europe. Its geographical distribution is still increasing, especially towards higher altitudes and latitudes (43).
Lyme disease is caused by the Borrelia bacteria and is transmitted by the tick Ixodes ricinus (42). This tick occurs throughout Europe, west to east from Ireland to the Urals, and north to south from northern Sweden to North Africa (44). In Europe, the overall mean prevalence of the Borrelia bacteria in ticks that causes Lyme disease is 13.7%. Central Europe (Austria, Czech Republic, Germany, Switzerland, Slovenia and Slovakia) has by far the highest rates (>20% in adult ticks), according to a publication in 2011 (43).
The tick is sensitive to climatic conditions, requiring a relative humidity of at least 80% to survive during its off-host periods, and is therefore restricted to areas of moderate to high rainfall with vegetation that retains a high humidity (i.e. litter layer and soil remain humid during the day). Suitable habitats typically include deciduous and coniferous woodland, heathland, moorland, rough pasture, forests and urban parks (42).
Tick-borne encephalitis (TBE)
Other important tick-borne diseases are encephalitis (TBE) and tick rickettsiosis (Rocky Mountain Spotted Fever). Those diseases are also transmitted by the tick Ixodes ricinus, just like Lyme disease (42).
In 1993 the incidence of tick-borne encephalitis (TBE) showed a sharp rise in Central Europe and has remained high since (34). The main risk areas for TBE are in Central and Eastern Europe and the Baltic and Nordic countries. The areas extend to the west of Europe as far as Switzerland and the French region of Alsace, and to the south of Europe as far as northern Italy and the Balkan countries (33). In 2013, TBE was reported to be endemic in 27 European countries (34). Approximately 5000 – 12,000 cases of TBE are reported in Europe each year (35). It is estimated that TBE is one of the most serious neurological diseases transmitted by tick bites in Central Europe, Eastern Europe and Russia, and that it has a significant impact on public health in these geographical regions (34).
The incidence of TBE appears to be increasing; this could be due to several reasons: improvements in the diagnosis and reporting of TBE cases, increased recreational activities in areas inhabited by infected ticks, and changes in climatic conditions affecting tick habitats (36). Some regions, such as Scandinavia, have seen an increasing trend in TBE cases (37). In Sweden, mild winters with increased daily minimum temperature are correlated with higher numbers of ticks. Between the early 1980s and mid-1990s in Sweden a northward expansion of the geographic distribution limit of the disease-transmitting tick Ixodes ricinus and an increased tick density has been reported. Researchers related this expansion to climatic changes (45,56).
Link with climate change?
The increase in the number of tick-borne diseases is not necessarily due to climate change (10), although recent climate change has likely increased global risks from undetectable to moderate for Lyme disease (163). The upsurge of the incidence of tick-borne encephalitis (TBE) in the 1980-90s in Central and Eastern Europe, for instance, has been attributed to socio-economic factors (human behavior) rather than temperature (46). The increasing popularity of outdoor recreation is believed to be one of the most important causes of the increase of the number of cases of Lyme disease (47). In addition, biotic factors, such as increases in deer abundance (48) and changing habitat structure, may play a role in some countries (49).
In the Alps and Scandinavia increased winter mean temperatures at higher altitudes and latitudes and an extended vegetation period may have permitted roe deer to spread to and inhabit previously inhospitable areas. Such deer movements may have allowed this tick to be transported northwards on the Scandinavian Peninsula, resulting in a significantly increased tick range during the last 30 years (50). Changes in forest and wildlife management probably also played a role (51). In Sweden, the northward spread of this tick to many previously tick-free localities was particularly rapid and extensive. This was probably due to a combination of the expansion of the roe deer population and the warmer climate (mild winters and extended spring and autumn seasons) (50).
In the Netherlands there is evidence of an increase in tick bites amongst humans (52). Possible contributory factors suggested are an expansion of nature reserves, an increased abundance of wildlife, a reduction of pesticide use in agriculture and forestry, and climate change.
According to the IPCC, changes in the latitudinal and altitudinal distribution of ticks in Europe and North America are consistent with observed warming trends, but there is no evidence so far of any associated changes in the distribution of human cases of tick-borne diseases (10). Instead, climate-related changes in land use and socio-economic influences on human behaviour are more likely to have a strong impact on the distribution and abundance of ticks and infection risk of diseases such as Lyme disease and tick-borne encephalitis (43,53).
But climate change will increase future infection risk
In the future, the distribution of the tick I. ricinus is projected to expand in Northern Europe as winter seasons become shorter and milder, and deciduous woodland expands. In southernmost regions of Europe ticks will probably get active year-round (as opposed to seasonal) by the end of this century (43). Tick density and infection risk will probably also increase due to an increase in the density of wild and domestic vertebrates, paralleled with the expansion of suitable habitats for the host animals of ticks (43).
Vulnerabilities - Mosquito-borne diseases
Recent climate change has likely increased risks from undetectable to moderate for dengue, and may begin to increase incidences of West Nile fever. The impact of climate change on malaria hasn’t been detected yet, but this is probably just a matter of time. Overall, the risk of malaria is projected to increase with additional warming, but risk reduction may occur in some regions that become too hot and/or dry for the mosquito that spreads malaria. The latter may also be the case for dengue fever. Although the impact of climate change on malaria hasn’t been detected yet at the global scale, the impact could be evident within another half degree of warming and rise steadily with additional warming (163).
For 2025 and 2050, the areas with elevated probability for West Nile infections (linked to climate change) (110), will probably expand and eventually include most Mediterranean countries (111). During recent years, dengue fever cases were reported in several Mediterranean countries, such as Croatia, France, Greece, Italy, Malta, Portugal and Spain. Although most cases were probably imported, in 2010 local transmission of dengue was reported in Croatia and France. During the hot summer of 2017, outbreaks of chikungunya were reported in France and Italy (112). Today, there is an apparent threat of outbreaks, transmitted by Aedes mosquitoes, in the European Mediterranean countries (113).
This century, the suitability of the climate for malaria and dengue will increase for the Eastern Mediterranean region (164).
Vulnerabilities - Sand-fly-borne diseases
Leishmaniasis is a protozoan parasitic infection caused by Leishmania infantum that is transmitted to human beings through the bite of an infected female sandfly. Sandfly distribution in Europe is south of latitude 45⁰N and less than 800 m above sea level, although it has recently expanded as high as 49⁰N. Currently, sandfly vectors have a substantially wider range than that of L infantum, and imported cases of infected dogs are common in central and northern Europe. Once conditions make transmission suitable in northern latitudes, these imported cases could act as plentiful source of infections, permitting the development of new endemic foci. Conversely, if climatic conditions become too hot and dry for vector survival, the disease may disappear in southern latitudes. Thus, complex climatic and environmental changes (such as land use) will continue to shift the dispersal of leishmaniasis in Europe (28).
Future climate change could have an impact on the distribution of leishmaniasis by affecting the abundance of vector species and parasite development. Recent modelling indicates that the central European climate will become increasingly suitable for Phlebotomus species of sandflies (84). One modelling study concluded that, by the end of the 2060s, France, Germany, western Poland and southern United Kingdom could be colonised by sandfly species, principally Phlebotomus ariasi and Phlebotomus pernicious, while the entire Mediterranean Basin, Balkan Peninsula and Pannonian Basin would all be potentially climatically suitable habitats for many Phlebotomus species (85). Such expansions of sandfly species would increase the risk of leishmaniasis (86).
Vulnerabilities - Infectious diseases
Evidence about future risks from climate change with respect to infectious diseases is still limited (14). The effect of climate change on the risk of imported or locally-transmitted (autochthonous) malaria in Europe has been assessed in Spain (15), France (16) and the UK (17). Disease re-emergence would depend upon many factors including: the introduction of a large population of infectious people or mosquitoes, high levels of people-vector contact, resulting from significant changes in land use, as well as climate change
Vulnerabilities - Foodborne parasites
The impact of climate change on foodborne parasites is complicated and provides no easy answers. How the different projected changes may interact and impact upon a diversity of foodborne pathogens is almost impossible to predict. The success of many parasites is due to a number of factors, including their adaptability to different hosts and environments. While some pathogens may suffer under some conditions of climate change, being unable to locate the “right” host, or incapable of surviving inhospitable conditions, many parasites are likely to persist and adapt. Besides, other factors not necessarily related to climate change may also affect the transmission and impact of foodborne parasites (19).
Ocean acidification and human health
The oceans acidify
Of all the CO2 we release into the atmosphere, around 25% is taken up by the oceans where it interacts with seawater and forms carbonic acid (148). The oceans acidify. The average surface pH of the ocean has already decreased by 0.1 unit since the beginning of the Industrial Revolution, and a further 0.3 - 0.4 unit decrease is expected by the end of the century (149). As pH is measured on the logarithmic scale, this corresponds to a doubling in acidity by 2100. These changes are happening at an unprecedented scale and speed, rapidly exposing marine ecosystems to conditions they have not experienced over millions of years.
When marine ecosystems are affected, so are we. After all, oceans provide many ecosystem services, such as nutrition, medications, and mental and physical health benefits. Ocean acidification is an emerging human health issue of ‘substantially greater complexity, and possibly scale, than currently appreciated’, scientists conclude from a review of studies carried out in recent years (147).
Seafood quantity and quality changes, causing malnutrition
More than 4.5 billion people obtain at least 15% of their animal protein intake from fish (150). In some countries, the share of protein from fish can be greater than 50% (151). Ocean acidification not only affects the available seafood, but the nutritional qualities of this food as well: when the food source of fish species changes, the species that are harvested for consumption also change.
Direct negative effects are damage to the survival of eggs and early larval stages for some fish species, and the survival, growth, development, and reproduction across different groups of organisms (152). The culture of shellfish in coastal waters is already experiencing decline in some regions because of the reduced carbonate saturation and mortality of juveniles unable to grow shells (153). Many aquaculture species and systems are thought to be less susceptible to ocean acidification, however.
Indirect effects of ocean acidification can be driven by changes in food source, especially phytoplankton, which form the foundation of the marine food web. Also, degradation or loss of coral reefs or macro algal forests will induce ecosystem effects that alter the characteristics of dependent fisheries (154). Many fish and invertebrates rely on structures such as coral reefs for ecosystem services, including the provisioning of habitat and feeding grounds. The persistence of these dependent species will likely be threatened under ocean acidification as coral reefs bleach and transition to more simple habitats. Tropical fisheries will, therefore, likely be degraded by ocean acidification, with profound consequences for the people that depend upon them.
Pollutants accumulate in human tissue
Ocean acidification affects the propagation of contaminants through the marine environment. These contaminants, such as heavy metals, pharmaceuticals, and active ingredients in personal care products, mainly enter the environment via municipal effluent discharges, aquaculture, animal husbandry, horticulture runoff and waste disposal. They can be taken up by organisms and then transferred through the food chain, accumulating in tissues of organisms at higher trophic levels, including humans. Ocean acidification may intensify this bioaccumulation (155).
Natural toxins also accumulate
Ocean acidification can modify the abundance and chemical composition of harmful algal blooms. These algae are food to shellfish, their natural toxins accumulate in shellfish, and this may in turn negatively affect human health. Ocean acidification has been found to lead to an increased algal growth rate (156), a change that could accelerate the production of toxic algae. Moreover, the toxicity of the blooms is likely to increase. These toxins not only enter the human body through food, but also trough the air. They can be releases and mixed into seawater aerosols when the algae are broken up in the surf (157).
Loss of habitats impacts mental health
The livelihoods of approximately 300 million people depend on marine fisheries. In the past, the collapse of regional fishing industries in Europe has caused unemployment, financial pressures, societal stress, and a decline in the mental health of individual fishers and the fishing community. The oceans also provide nature-based recreation and exercise opportunities that promote “nature-connectedness”, all of which have been shown to be a fundamental of mental health (158). The anticipated loss of (access to) habitats due to ocean acidification reduces recreation opportunities and the formation of associated social connections.
Loss of potential medical resources
The vast biodiversity of the oceans offers opportunities for medicines and other natural products to counter the impacts of environmental stressors on human health. So far, the exploration of these opportunities has been limited. As ocean acidification is expected to negatively impact biodiversity, it will also impair our ability to prospect for new medications in such areas (147).
How to deal with health effects of ocean acidification
For the sake of our health it is important to conserve and restore biodiversity and ecosystems. This starts close to our homes, where outputs from industry and wastewater facilities, agricultural discharge, and urban runoff deteriorate the water quality of receiving marine ecosystems and thereby reinforce the effects of global changes, such as ocean acidification. Monitoring and managing water quality at a local scale reduces the effects of these global-scale changes. In addition, marine-protected areas, for instance, could encourage the resistance and resilience to the loss of species due to acidification (147).
It looks like we have to adapt to some disturbance of ecosystems and biodiversity due to ocean acidification. One way to adapt is to boost the human consumption of species that benefit from ocean acidification, such as fast-growing macro algae. This may compensate for the loss of parts of the seafood diet and help satisfy future demands. Still, changes in the availability of fish species may lead to malnutrition and increase inequalities in societies. Those who are able to afford the price of an increasingly rare resource will still have access, many others will not (147).
Economic impacts of climate change on health
Without adaptation the costs of heat-related mortality in Europe at 2 °C global warming are estimated to be EUR 11 to 41 billion/year by the middle of the century (current prices, undiscounted; potential reduction in cold-related mortality not included), with around two-thirds of the increase due to the climate signal alone (87). Values vary widely according to whether current adaptation and future acclimatisation are included or not. Projected impacts are highest for the Mediterranean (Cyprus, Greece and Spain) and some eastern EU Member States (Bulgaria, Hungary and Romania). Compared with these heat-related mortality impacts, additional impacts, including food-borne disease, extreme events (deaths and reduced well-being as a result of coastal flooding) and occupational health (outdoor labour productivity) are low (88).
Health adaptation to climate change: a global assessment
The Lancet Countdown on health and climate change monitors global developments on health adaptation to climate change. 35 academic institutions and UN agencies from every continent are involved in this initiative. The report of November 2019 presents the situation in 2018 (133). The main results are summarized below. We've also added the main conclusions of the 2022 update (170).
Exposure to heat-related health impacts increases, especially in cities
The vulnerability to heat extremes continues to rise among older populations in every region of the world. Overall, Europe remains the most vulnerable region to heat exposure, due to its ageing population, high rates of urbanization, and high prevalence of cardiovascular and respiratory diseases, and diabetes. From 1990 to 2018, populations in every world region have become more vulnerable to heat and heat waves, with Europe and the Eastern Mediterranean remaining the most vulnerable (133).
Extreme heat is generally much higher in cities than in the surrounding rural landscape. Climate change contributes much more to heat-related health impacts in cities than one would expect from global average temperature rise. Human populations are concentrated in the areas most exposed to warming. From the 1986-2005 baseline to 2018, city dwellers have experienced a mean summer temperature change that is four times higher than the global average (133).
Older people are exposed to heat waves more often. Globally, for people aged 65 years or older, over 220 million additional exposures to heat waves have occurred in 2018, compared with 1986-2005. The increase was highest in India and across northeast Asia. 31 million of these additional exposures were in the EU. Data since 1990 show no statistically significant global trend in the number of people affected by heat waves, extreme temperature, and drought-related disasters, however (133).
Higher temperatures also continue to affect people’s ability to work. In 2018, 45 billion additional potential work hours were lost globally due to rising temperatures, compared with the year 2000 (133).
Extreme weather events: health care improvements pay off
Globally, in 77% of the countries the population experienced an increase in their exposure to wildfires from the period 2001-2014 to 2015-2018. The health effects of wildfires range from direct thermal injuries and death, to the exacerbation of acute and chronic respiratory symptoms due to exposure to wildfire smoke (134).
Since 2000, the number of precipitation extremes, resulting in flood and drought, has increased in especially South America and South-East Asia. Floods are particularly problematic for health, resulting in direct injuries and death, the spread of vector-borne and water-borne diseases, and mental health issues (135).
Since 1990, the number of flood-related and storm-related disasters has increased in Africa, Asia, and the Americas. This has not led to an increase in the number of people affected by these disasters, however. This could be due to improved disaster preparedness (including improved early warning systems) as well as increased investments in health-care services (136).
Less vulnerable to climate-sensitive diseases
Global health trends in climate-sensitive diseases from 1990 to 2017 show an improvement, except for dengue fever. Socioeconomic development, improved access to health care, and major global health initiatives in sanitation and hygiene, and vector control, have all contributed to these improvements in health outcomes (137). Mortality from dengue fever continues to rise, particularly in South-East Asia.
More people are undernourished
Globally, crop yield potential for maize, winter wheat, and soybean has reduced in concert with increases in temperature. Research has shown global yield reductions of the four key crops maize, wheat, rice, and soybeanrespectively by 6%, 3.2%, 7.4%, and 3.1%, globally for each 1°C increase in global mean temperature (138). However, improvements in nutrient and water management, as well as expansion of agricultural areas in lower income countries are currently increasing global food production (139). Still, the number of undernourished people worldwide appears to have been increasing since 2014, driven by challenges to access, availability, and affordability of food (140).
Revenue fisheries and aquaculture under pressure
Fish provide almost 20% of animal protein intake to 3.2 billion people, with a greater reliance on fish sources of protein in low-income and middle-income countries (141).Climate change threatens fisheries and aquaculture in a number of ways, including through sea surface temperature rise, change in intensity, frequency, and seasonality of extreme events, sea-level rise, and ocean acidification (142).
Health adaptation to climate change is widespread
Notably, the world is beginning to adapt. Most countries are aware of the need to adapt their health sector to climate change, and development planning is underway. In 2018, half of the 101 countries surveyed for the Lancet Countdown declared that a national health and climate change plan was in place. However, only about 20% of the surveyed countries have allocated resources to take actions to address most of their key priorities. In addition to these countries, also 489 cities participated in the survey. In 2018, 54% of them expected climate change to seriously compromise their public health infrastructure, with 69% of them actively developing or having completed a comprehensive climate change risk or vulnerability assessment (133).
Global spending on health adaptation to climate change is still relatively small compared to total spending on climate change adaptation. It has increased though, from 4.6% in 2015-2016 to 5.0% in 2017-2018 (133).
Air conditioning: a double-edged sword
Use of air conditioning as an adaptation measure is a double-edged sword: on the one hand, global air conditioning use in 2016 was estimated to reduce heat wave related mortality by 23% compared with the complete absence of air conditioning; on the other hand, it also contributes to climate change, worsens air pollution, adds to peak electricity demand on hot days, and enhances the urban heat island effect. Between 2000 and 2016, the global number of air conditioning units (residential and commercial) more than doubled to 1.62 billion units and the proportion of households with air conditioning increased from 21% to about 30%. In the EU this proportion was 14% in 2016. In 2016, air conditioning accounted for 10% of global electricity consumption and 18.5% of electricity used in buildings. These figures are projected to increase to 16% and 30% in 2050, respectively (143).
Most cities hot spots of air pollution
The world is becoming increasingly urbanized, with almost 70% urbanization of the global population expected by 2050 (144). Many cities have become hot spots of air pollution. 83% of the cities exceed the WHO’s recommended safe concentrations for fine particulate matter (145). The highest measured concentrations currently have been reported in south and east Asia. A positive exception to this trend is China, where many highly polluted cities have improved air quality because of their ambitious emission control efforts. Cities in Europe and the USA have seen slowly decreasing concentrations of fine particulate matter with effective implementation of air pollution control legislation and regulation. In 2016 there were 2.9 million premature deaths globally that were associated with high concentrations of fine particulate matter. The situation has improved slightly in the European region (133).
Lancet countdown update 2022
Each year the Lancet, one of the world’s leading medical journals, publishes a report on the global status on health and climate change. We’ve summarized some of the most relevant findings in the 2022 update for you (170).
- Number of heat-related deaths is increasing: During the last 40 years, the number of heatwave days has steadily increased. Vulnerable populations – adults older than 65 years and children younger than one year of age – were exposed to 3.7 billion more heatwave days in the period 2012-2021, annually, compared with the period 1986–2005. The number of heat-related deaths increased by 68% between 2000-2004 and 2017-2021.
- Number of work hours lost due to heat is increasing: The increase of the number of heatwave days also effects labour productivity. Since 1999, the number of work hours lost because of excessive heat exposure increased by 5.6 billion hours each year. In 2021 this loss had accumulated to 470 billion work hours – an increase of 37% compared with the end of last century. Two thirds of all labour hours lost globally in 2021 were in the agricultural sector. This proportion was highest in the least developed countries.
- Exposure to wildfires and droughts is increasing: The human exposure to days of very or extremely high wildfire danger has increased in 61% of countries from 2001-2004 to 2018-2021. On average, 29% more global land area was affected by extreme drought for at least one month in a year in the period 2012-2021 compared with 1951-1960. The Middle East and north Africa was particularly affected, with some areas experiencing more than 10 extra months of extreme drought.
- Risk infectious diseases is increasing: The changing climate is affecting the spread of infectious diseases such as malaria and dengue, putting populations at higher risk of emerging diseases and epidemics.
- Food insecurity for more people: Increased temperatures have shortened crop growth seasons of staple crops maize, rice and wheat, and reduced food security. 720–811 million people were hungry in 2020. An additional 98 million more people were exposed to moderate or severe food insecurity in 2020 compared with the annual average for 1981–2010 – probably because of extreme heat.
- Gap health impacts and adaptation is increasing: According to the experts who wrote this Lancet 2022 report, ‘the pace and scale of climate change adaptation, planning, and resilience is far from what is necessary to reduce the health impacts of climate change.’ Of all the urban centres they looked at, only 27% had enough trees to be called ‘moderately green’, and just one out of three countries reported having heat-related early warning systems for health. The experts conclude that the gap between the health impacts of climate change on the one hand and the investments in adaptation and implementation on the other continues to increase.
- The poor suffer the most: 84% of global economic losses due to climate-related extreme events in 2021 affected the richest countries. The population of the poorest countries suffered the most, however, since in these countries almost none of the losses were insured. In 2021, extreme weather events caused damage worth US$ 253 billion. The annual monetised value of global heat-related mortality (in 2021) and premature mortality due to air pollution (in 2020) was estimated to be US$ 144 billion and US$ 2.3 trillion, respectively.
- Hope for the future: The experts see ‘emerging glimmers of hope’, however. The coverage of health and climate change in the media is strongly increasing and reached a new record high in 2021, and this increasing attention is also reflected by country leaders. The interest in renewable energy generation is also increasing in response to the extremely high energy prices, and public health will benefit from this.
The most effective adaptation measures for health in the near-term are programs that implement basic public health measures such as provision of clean water and sanitation, secure essential health care including vaccination and child health services, increase capacity for disaster preparedness and response, and alleviate poverty, and climate-specific measures to protect health, including enhanced surveillance and early warning systems (10,27).
It is crucial that healthcare professionals receive appropriate and focused training. Environmental and/or community-based interventions— such as removing mosquito-breeding sites or checking on vulnerable groups during heat waves—could have the most value in a warmer world, despite a lack of good-quality evidence to date (27).
A noticeably increase in mortality during Europe’s mega heat wave of June 2017 was not reported by the media, arguably due to (i) an efficient implementation of early warning systems following the lessons learned from previous high-impact European mega heat waves, such as that of August 2003, and (ii) the use of air conditioning systems (100).
For Canadian cities, four major categories of mitigation strategies and measures have been identified (21):
- Greening measures: all measures that can increase the total vegetation index of the city, including planting trees along streets and open spaces with green-roofed buildings that offer more cooling potential.
- Urban infrastructure-related measures (architecture and land use planning): measures that act on buildings, road infrastructures, and urban morphology.
- Storm water management and soil permeability measures: measures that increase the soil’s moisture which helps to reduce the temperature.
- Anthropogenic heat reduction measures: measures that reduce heat produced by human activities, including heat-health warning systems that encourage types of behavior that can help reducing heat mortality.
Road pavements: In a review on climate change and transport infrastructures (117) a number of options is inventoried of alternative road pavements to combat urban heat islands: reflective concrete and porous asphalt or porous concrete. Conventional asphalt pavements absorb 95% of solar energy, while cement concrete has minimum solar reflectance equal to 40%. In pavements composed of porous materials, the voids fill up and store the water when it rains; when the pavement temperature increases, the water evaporates. The evaporation process subtracts heat to the pavement and therefore reduces its surface temperature. Vegetative permeable pavements add the transpiration benefits to the evaporation ones. The presence of vegetation into the modular blocks, which compose the pavement, allows plant transpiration from the road pavement to the atmosphere. Both pavements mitigate the UHI, but their implementation is limited by mechanical and functional characteristics of the materials. Indeed, for the same thickness, porous pavements have a service life lower than traditional structures. Furthermore, the high level of discontinuity of vegetative modular pavements reduces their use to parking lots, sidewalks and low vehicle movement zones. Other cooling solutions consist of: solar heating reflective coating layer, using white materials (e.g., pigments, binders, light aggregates, white topping, reflective paints) for surface layer of road pavement, circulation of a fluid in the pavement to remove the excess heat.
A study examining well-established interventions to reduce the urban heat island effect (replacing bitumen and concrete with more heat-reflective surfaces, and introducing more green spaces to the city) estimated these would reduce heat-related emergency calls for medical assistance by almost 50% (12). Urban green spaces lower ambient temperatures, improve air quality, provide shade, and may be good for mental health (13). The heat island effect is smaller in green areas than in areas with sealed surfaces (63,65).
A comparison of recent insights from scientific studies on often-advocated measures such as green roofs, planting more trees, and increasing the albedo of roofs and pavements, showed that green roofs (such as a mat of sedum) on cooling the city might not be that effective (24). Observations of green roofs in Chicago, for instance, did not alter temperatures in the surrounding areas significantly (25). A modeling study simulating 25% of the roof area along a street in the centre of Arnhem in the Netherlands as green roofs had no effect on street-level temperatures for conditions such as the 2003 European heat wave: the wind blew away the cooler air before it could reach the ground (26). Instead, whitening roads and roofs (cool roofs), and thus increasing the city’s reflectivity or albedo, planting trees and converting paved areas to grass seem to be more effective (24).
Researchers recently created a cooling paint that can coat just about any surface, lowering its temperature by 6°C. This could drop cooling costs by up to 15% in some climates. White paints typically reflect only about 80% of visible light, and they still absorb ultraviolet (UV) and near-infrared (near-IR) rays, which warm buildings. The new paint reflects up to 99.6% of light, including IR, visible, and UV. The paint also emits additional heat at wavelengths that the atmosphere does not block, thus shedding excess heat into space without warming the surrounding air (116).
Open water dampens the diurnal cycle: in summer, the suburbs close to the inner-city water bodies experience advective cooling during the day and warming at night. The advection of warm air from adjacent water bodies at night may enhance the urban heat island effect (67). Water bodies within built-up areas hinder cooling at night especially in summer when cooling is most needed, for instance during heat waves (68). Heat risk for the urban population will increase more than for their rural counterparts due to local urban forcing (69).
At nighttime, the urban heat island effect is dominated by two factors: (1) ability of materials to store solar radiation during the day, and (2) the rate at which this energy is released at night (additional energy in the form of anthropogenic heat is negligible (95). Thus, the increase of radiating surface area of cities is the main contributor to the nocturnal urban heat island. Efforts to mitigate this in the development of future urban structures should aim at minimizing the enveloping surface of urban structures (94).
A survey of national infectious disease experts in Europe identified several institutional changes that needed to be addressed to improve future responses to climate change risks: ongoing surveillance programs, collaboration with veterinary sector and management of animal disease outbreaks, national monitoring and control of climate-sensitive infectious diseases, health services during an infectious disease outbreak and diagnostic support during an epidemic (18). The implementation of entomological and sentinel clinical surveillance networks (early detection of the mosquito vector and index of human cases) has proven to be valuable in identifying disease hotspots and in limiting disease spread when appropriate health responses (case isolation and treatment) are promptly implemented (27).
Tick-borne diseases: Lyme and encephalitis (TBE)
An early warning system for tick activity has been developed in the Czech Republic for tick-borne encephalitis (TBE). Since 1971, all reported TBE cases are laboratory confirmed. The incidence of TBE demonstrated a significant increasing trend in the country since the early 1990s (54). This led the Centre for Epidemiology and Microbiology (CEM) at The National Institute of Public Health (SZU) in Prague in collaboration with the Czech Hydrometeorological Institute (CHMI) to develop an early-warning system for tick activity and disease risk. It consists of forecasts that predict daily tick activity several days to a week in advance, published twice a week at the websites of CEM and CHMI (55).
Other ways to protect against tick-borne diseases is preventing tick bites, by avoiding tick risk areas, being informed about how to remove ticks and recognize early symptoms, using insect repellent on skin and clothing when in risk areas, and wearing protective clothing with long sleeves, and long trousers tucked into socks or boots (35).
The best way to protect against TBE is vaccination. Austria is among the most strongly affected countries in Central Europe, but the annual number of cases has strongly declined due to vaccination. In Austria, the high vaccination coverage (more than 80% of the total population has received at least one TBE vaccination) has led to a substantial decline in the number of annual cases (38). The incidence in the unvaccinated population, however, remained constant at about 6 per 100,000, suggesting no major changes in the countrywide overall risk of human exposure to TBE virus-infected ticks.
There is currently no vaccine available on the European market for Lyme disease (43). Since ticks do not have a high probability of transmitting the Borrelia bacteria that causes Lyme disease until 12–24 hours after ticks begin to feed on the blood of their host, immediate removal of ticks is one of the most effective ways of avoiding Borrelia infection (43).
Usual monitoring systems focused on food safety hazards may miss – or pick up with delay – the occurrence of hazards related to climate change because they did not occur previously. A better exploitation of warning systems to alarm on the development of food safety hazards related to natural disasters may therefore be needed (20).
For extreme weather events, appropriate infrastructure, accurate forecast and timely alerts for at-risk populations are likely to be the best adaptation and preparedness options. An example of this is heat–health warning systems (HHWS) currently implemented in several European countries (27).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Europe.
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