Climate Change and Liveability of Cities: an Assessment of Possible Health Threats Associated With Increased Temperatures in Cities

Climate change is associated with extreme weather events such as heat waves, droughts, oods, hurricanes, storms, and wildres globally. Within cities, the impacts of climate change are quite conspicuous as the percentage of urban dwellers is expected to reach about 70% by 2050. As the planet warms up, temperatures in cities are likely to increase more than in rural areas. These dual challenges severely impact urban residents. This paper reports on a study on the impacts of climate change on the health and liveability of a set of 15 cities, in industrialised and developing countries from around the world. The assessment, based on the literature, examined the average temperature, maximum temperature and relative humidity of each city, and this data has been correlated with their liveability. It was complemented by a survey focused on residents of 109 cities from Africa, Asia, Europe, Latin America, North America Oceania. The ndings show that developing countries seem to be especially struggling to adapt to the threats caused by increasing temperatures. Moreover, cities in industrialised countries are not immune to climate change impacts. The paper also outlines some mitigation and adaptation measures, which can be implemented to improve the liveability in cities and the well-being of their populations, and to make them more sustainable.


Introduction
The current post-industrial era has brought about much prosperity to human society but is also associated with global climate change. Caused mainly by human activities, climate change is one of the main challenges currently facing humanity (Donkor et al., 2019). The burning of fossil fuels in industries and transportation releases a large amount of carbon-dioxide and other greenhouse gases in the atmosphere (WHO, 2018). This situation, in turn, traps heat in the lower atmosphere, increasing the average global temperature over time (WHO, 2018). Increasing average global temperature causes polar ice caps to melt, which then leads to a rise in the sea level. Climate change encompasses not only rising average temperatures but also frequent occurrences of extreme weather events, such as heavy rainfall, oods, heat waves, droughts and intense storms (Pereira et al., 2018).
Various studies have shown that increasing temperatures pose a serious threat to general public health and can also be directly related to high mortality (Mazdiyasni et al., 2017;Mitchell et al., 2016;Mora et al., 2017) and morbidity rates (Linares et al., 2017). This is especially true among vulnerable groups of people (Åström et al., 2011). Heat waves have a greater impact on people residing near cities. They cause a general thermal discomfort among people and can result in low productivity at work (Zander et al., 2015). Table 1. List of large cities in developing and industrialised countries with average, maximum temperature and relative humidity (Climate Data, 2010;Weather Atlas, 2010) A signi cant number of large cities around the world are located near coastlines. It is estimated that more than 600 million people live in coastal areas that are 10 meters or less above sea level. Moreover, nearly 40% of the world's population -or around 2.4 billion people -live within 100 kilometers of sea coastlines. Hence, sea level rise is a major danger resulting from climate change. As the concentration of people residing near coastal cities is ever increasing, they are prone to threats like coastal ooding, storms, and hurricanes (Chowdhury et al., 2021). These extreme events could impact the urban dwellers through loss of life, injuries, and damage to properties and infrastructures. Heavy rainfall that accompanies a storm can cause ooding in the cities.
Climate change is a major risk in the public health sector. There is an increasing number of inter-linkages between climate change and health, showing serious threats to human health (USGCRP, 2016). It is shown to either exacerbate pre-existing health conditions or introduce new ones. Cities around the world are also nding it very di cult to meet the demands for fresh water from their growing population. Some cities are already facing acute water shortages, which can also result in power failures. For instance, in 2015, the city of São Paulo, Brazil faced one of its worst drought periods, causing blackouts in the city (Watts, 2015). Some health-related studies have shown that in developing countries, droughts increase the risk of the breakout of water-borne diseases like diarrhea. Society can also face problems related to food insecurity and a rise in food prices as the requirements increase and the supply decreases (Revi et al., 2014 Secondly, a survey was conducted to identify the climate risks of tropical cities that are suffering from the global impacts of climate change. The survey for the sampled cities took place for one month, i.e., from the rst week of April 2020 to the rst week of May 2020. Different cities were selected from both industrialised and developing countries. The choice of samples was focused on tropical and densely populated cities, with more than 1 million inhabitants. Seven cities were selected from Asia, four cities from Europe, three cities from South America and one from Oceania, making a total of 15 cities ( Figure 1).
Climate and weather-related variables, such as temperature and humidity for the 15 selected cities were also separately searched using online search engines. The databases that were mainly used for this purpose were Weather Atlas, Climate-data and Time and date. The data from these sources were then cross veri ed with each other to maintain reliability.
Thirdly, a questionnaire was designed to assess possible threats of climate change to the liveability of cities, as perceived by urban residents from many countries. Twenty-ve open-and closed-ended questions were divided into two categories 'demographic details' and 'climate change and liveability'. Final adjustments of the instrument were made based on feedback received from an international group of climate change scientists. Data were collected over approximately three weeks January -February 2021 through the online survey tool 'Google forms'. Statistical analysis and visualization of the obtained results were made in Microsoft Excel.

Literature review and survey on climate risks
Research has shown that urban areas are usually warmer than the surrounding rural areas (Macintyre et al., 2018). This is mainly due to the UHI effect, causing more hot days in metropolitan areas when compared to rural areas. Table 1 indicates that tropical cities of both developed and developing countries around the world are already experiencing high temperatures and high humidity in recent years. New Delhi recorded a maximum temperature of 48.0°C in June 2019.
This follows a rise in temperature trend in the city, which recorded maximum temperatures of 42°C in June 2018, 44°C in June 2017, and 42°C in June 2016 (Timeanddate, 2017). A similar rise in temperature trend is observed in Berlin, which recorded maximum temperatures of 39, 32, 30, and 35°C in the month of June in 2019, 2018, 2017 and 2016, respectively. Although Shanghai's maximum temperature (40.9°C) was recorded in July 2017, comparison with other years shows a consistent pattern in temperature rise, e.g., 40°C in 2016, and 38 and 39°C in 2018 and 2019, respectively (Timeanddate, 2019). Heat waves during this period have affected several people. For instance, during the heat waves of 1994 and 2004, the citizens of Berlin city suffered from more heat related stress and mortality than those in the neighboring state of Brandenburg (Gabriel and Endlicher, 2011). People living in the cities are vulnerable, as climate change worsens the UHI effect. Constant change in climate has increased the intensity and frequency of temperature uctuations, which intensi es the occurrence of heat waves and tropical nights (Lee et al., 2020), as supported by Table   1, which shows that the city of Berlin experienced hot summer days with temperatures reaching up to 39°C during summer of 2019. The humidity level also remained high during that period. During heat waves, cases of diarrheal diseases seem to peak in developing countries such as Bangladesh (Prince, 2017), along with respiratory and cardiovascular diseases (Dang et al., 2019).
Shanghai's population of 24.28 million inhabitants (Table 1) is exposed to the impacts of the UHI effect, and the temperatures are expected to rise further, causing an increased intensity of heat waves in the city's center when compared to its outskirts (Tan et al., 2010). Other densely populated cities like New Delhi, Ho Chi Minh City and Chennai are also highly exposed to the impacts of the UHI effect. According to Dang et al., (2019) and Ragettli et al., (2019), the main reasons for hospitalisation during hot summer months in Switzerland, South Korea, Vietnam and Bangladesh were respiratory and cardiovascular disorders and renal and infectious diseases. The deterioration of physical and mental health of the population has also been linked to the increasing temperatures. In Australia, an increase in hospital admission for mental disorders (e.g. anxiety) during heat waves has been documented (Nitschke et al., 2011). In Sweden, people with previous hospital admissions for a mental disorder were found to have the highest relative risk of death as the duration of the heat waves increased (Oudin Åström et al., 2013).
As speci ed in issue that has come to the, especially during pregnancy, as it creates additional heat stress problems. Respiratory and cardiovascular diseases, secondary to exposure to poor air quality, were found to have a greater impact on women due to their greater propensity for higher particulate deposition in the lung tissue (Ylipaa et al., 2019).
The demographic pro le of the respondents is shown in Table 3. The gender distribution of the residents included 40.1% female, 57.7% male and 2.1% did not answer to this question; almost 65.50% of the respondents were between 29 and 58 years old; nearly 2.9% had a high school degree and 89% had received a postgraduate degree. Moreover, 36% were professionals and 1.4% were unemployed; 33.1% received monthly income of above 3000 € and 10.3% had income of 1000 to 2000 €; almost 48.9% of the respondents lived in at and 15% lived in semi-detached house. The household participants of the respondents included 2 adults (52%), no children (50%) and 17% with 1 child (less than 18 years old). Temperature increase on a global scale is a big environmental threat all over the world. Rapid urbanization has raised the city's emission levels and has an effect on the temperature of the atmosphere. However, the COVID-19 pandemic and associated worldwide lockdown have recently lowered pollution levels. There are signi cant impacts that has been observed in the major megacity of the world. For example, the lockdown due to COVID-19 pandemic in the cities caused the pollution level of the city signi cantly improved (Sahani et al., 2020). As shown in Table 4, 17.8% of the participants stated that they have full lockdown. The results also show that 2.4% of participants experienced no lockdown and 16.7% have partial lockdown. Individuals, communities, and governments react to climate change in a variety of ways, which are also in uenced by public views of its causes, impacts, and broader implications (Demski et al., 2017). In the survey, we investigated respondents' opinions about rising temperature over the last decade, most of whom considered human activities and natural causes to be major contributors to climate change (49% and 2.2% respectively). Also, 44.5% of participants consider both of human activities and natural causes and 2.2% stated that there is no change in temperature of their city. Therefore, it can be concluded that the more people have knowledge on the raising weather temperature and the factors causes. According to Kashef (2016), human activities are the main derivers of climate change and have a signi cant impact on many aspects of human settlements. Human activities and natural causes, for example, can in uence human settlements through a variety of intermediary factors, including natural environmental change (Si et al., 2014), the socioeconomic system (Si et al., 2014), extreme weather/climatic events, and human health (Lo et al., 2019).
In the current survey, we considered basic descriptive for some of the phenomena that contribute to climate change in the city. These phenomes were displacements, ood, greater inequalities, higher vulnerability, health problems, increased food security problems, increased poverty. According to the survey, most of the respondents experienced higher vulnerability and health problems (23% and 22%, respectively). The ndings revealed that only 3% of people reported increased food security problems due to the climate change impacts. The factors of displacements and greater inequalities included approximately equal percentages (10%). These ndings are in line with Tiihonen et al. (2017) study as their results showed that increasing temperature caused by human activities can directly affect cities liveability.
In this survey, we discussed 7 items that could be positive steps to the reduction of climate change in cities. These items included buying organic foods, planting more trees, using public transport, participating in environmental campaigns, buying more energy-e cient devices, recycling waste and use less electricity. As the results of Table 4 show, 66.9% of the respondents stated that planting more trees is an effective way to decline climate change. The percentage of responses that included use public transport, buy more energy-e cient devices, recycle waste approximately were equal among participants (55%).
To determine the importance of different contributions to climate change, respondents were asked, "Which of the factors do you think has contributed the most to climate change?'' These factors were aerosols, deforestation, greenhouse gases, land use, and land cover change, and capitalism. Table 4 demonstrates that most people (48%) determined that greenhouse gases have the highest effect on climate change. In the next level, land use and land cover change were considered 28.8% as the second factor which contributes to climate change. The lowest contributors were for aerosols and capitalism with 18.7% and 1.4%, respectively. Table 4 shows respondents´ attitudes regarding to how climate change threatens on personal health and safety of residents in their city. According to the ndings of this study, 45% of respondents to some extent believed that climate change threatens the health of citizens and only 0.7% of people were not su ciently aware of this issue. In the survey, we investigated the natural hazards that most people have experienced. The items mentioned included oods, dry spells, storm surges, droughts, wild/bush, res, higher rainfall, heat, cyclones. Approximately 64% of respondents stated that they experienced oods, 56% dry spells and a lower percentage declared they experience droughts (0.7%) in their city.
Extreme weather conditions such as heat waves, droughts, and oods are expected to become more common and intense as a result of climate change (Donkor, 2020). These adjustments are likely to increase property and crop losses, as well as trigger costly societal disruptions (Béné et al., 2018). As shown in Table 4, 57% of the participants stated that poverty is the most important factor that leads to a direct socio-economic impacts of climate change. Following it, respondents regarded inequalities and marginalization to be the major socio-economic factor in climate change in their cities (51%).
In this survey, we considered six actions that can be taken to mitigate climate change impacts and make cities more liveable including: climate-resilient urban planning; enhanced economic development; environmental regulations to curve carbon emissions and pollution; promote renewable energy; sustainable public transportation; waste management through recycling/reuse. According to Table 4, most of the participants (76.8%) in this survey stated that climate-resilient urban planning is an essential action to address climate change impacts in cities. Besides, promoting Page 12/22 renewable energy (59%) was the second most important factor for people. Nearly, 46.5% of the respondents had the same attitude about reducing climate change through sustainable public transportation and waste management.
For the question of who the main responsibility should have to tackle climate change impacts in the city, most people declared that central government has the highest responsibility (79%). After that, individuals and stakeholders, and local government were considered (62%) ( Table 4). Concerning the question of what institutions are working to reduce climate change impacts in the city, most of the respondents declared that environmental groups have the greatest responsibility (73.9%). Table 4 exposes respondents awareness level of the socio-economic burden of public health hazards due to climate change. Based on the ndings of this study, 30% of people had a moderate attitude and 21.4% of people were su ciently aware of this issue.

Conclusion
The ndings of this study emphasise that, after the recent deadly heat waves, there is clear pressure in many countries to introduce plans, and so their development was necessarily rapid. As such plans are being introduced by an increasing number of countries, we recommend that the contents of these plans be consistently developed as information on the effectiveness of interventions accumulates. More importantly, the notion of gradual acclimatisation to heat in elderly groups to build up their physiological defenses is a potentially valuable concern that has been given little attention.
Although evidence supports the advice to stay in an air-conditioned setting, avoiding outdoor temperatures and strenuous exercise could deprive elderly people of the opportunity to train their sweat glands.
The bottom line is that we also need to take action to make our communities less vulnerable to the already ongoing impacts of climate change. Many communities have programs to address health issues that are climate sensitive. Based on the ndings of this study, there are a few approaches for managing the health threats associated with extreme heat, as follows: By communicating heat wave risks and suggesting protective actions, heat wave early warning systems can protect individuals. These warning systems are much less costly than heat illness treatment and coping strategies.
Encouraging people to hydrate during heat warnings and avoiding strenuous outdoor exercise.
Easy access to public drinking fountains, swimming pools and spray pads, which can help keep individuals cool during periods of extreme heat.
Urban forests might mitigate urban heat islands, including street trees and wooded areas, reducing local air temperatures.
Stricter mitigation policy should also be implemented, to reduce greenhouse gas emissions. Many studies have shown that lower greenhouse gases are related to lower mortality rates during extreme heat events, especially in tropical cities.
Moreover, mitigation measures are also linked with health co-bene ts. A case in point is how the promotions to use cleaner alternatives such as public transportation, walking or cycling for daily commute can bring about reductions in climate-altering pollutants in the air, causing direct health bene ts for people. Similarly, diets that restrict foods with high carbon footprints, such as meat and dairy products, not only reduce carbon emission but also offer health bene ts by lowering the risk of cardiovascular diseases.
Adaptation measures from public health and health care services should also be pursued, especially in the tropical cities of low and middle-income countries. This helps to promote health and reduce the disease burden during increasing temperatures. Some public health interventions include infectious disease surveillance, early warning systems, vulnerability mapping and resilient health care services (Smith et al., 2014). It is suggested that outdoor activities should be reduced during those periods. Vulnerable groups of people should be especially protected. Finally, smart technologies for cooling can also be used to reduce indoor heat and improve the health and well-being of the urban population in developing countries. These include upgrading the housing infrastructure with cooling methods such as ventilations, fans and renewable air conditioning (Lundgren Kownacki et al., 2019). There are some limitations in this study as it covers a small number of cities around the globe. Moreover, the research only uses data gathered after 2010, hence providing a picture of current trends and limited insights on past trends.
Funding: There is no source of funding.
Ethical approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Figure 1 World map, highlighting the sampled cities (created with Datawrapper). Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.