Heat wave frequency trend in China for the last fifty years

Research highlights
Heat wave frequency has risen sharply in the last 25 years.
Heat waves are caused by a combination of several factors
The most severe heat wave in china in 50 years occurred in2013.
Most severe heat waves in China occur in the months of June and July.

Keywords: Heat wave frequency, High temperature days, Heat wave magnitude index, Annual heat wave frequency, Heat wave intensity duration index.

This paper seeks to analyze the trend in the increase in the frequency of heat waves and the various causing factors in china. In the last 50 years, China has experienced a surge in the frequency of the heat wave phenomenon.
This paper is structured and divided into five distinct chapters elaborating on the phenomena of heat waves and the causing factors. The first chapter of the research delves into the introduction and background part of the research. Under this chapter, an introduction to the heat wave frequency trend will be made extensively. The second chapter of the research gives a clear outline of the literature review into the development of studies in this particular field. The third chapter explains the methodology used to compare empirical data to ascertain the increase in the frequency of the heat waves. This paper makes a detailed analysis of heat wave trends in three major cities of China over 50 years to elaborate on trends and frequency of heat waves occurrence. The fourth chapter of this research makes a detailed analysis of the data obtained to arrive at conclusions. Additionally, the paper makes use of these past trends to predict probable future occurrences. Further, the paper discusses the possible causes of heat waves and trends observed.
The fifth chapter makes recommendations based on the findings of the report and further recommendations on how research into this field can be advanced. The last chapter makes a detailed conclusion based on the research work.

Table of Contents
Abstract 3
Chapter 1 6
1.1 Introduction 6
1.3 Justification of the study 9
1.4 Research objectives 10
Chapter 2 11
2.1 Literature review 11
2.2 Scope of the study 13
Chapter 3 13
3.1 Methodology and Data analysis 13
3.2 Data analysis 18
i) High-temperature day trend 18
ii) Heat wave frequency 19
iii) Heat wave magnitude index (HWMI) 20
Iv) Urbanization 20
Chapter 4 22
4.1 Discussions 22
4.2 Global warming 22
4.3 Atmospheric anomalies 23
4.4 Solar activities 23
4.5 Industrialization 23
4.6 Aerosols 24
4.7 Deforestation 24
4.8 Predicted future heat wave events in china 25
4.9 Impacts of heat waves in china 26
4.10 Limitations of the study 27
i) Lack of sufficient sample size data to carry out the research 27
ii) Inadequate literature on the topic 28
iii) Time constraints 28
iv) Data collection methodology limitations 28
v) Scope of the research 29
vi) Funding constraints 29
4.11 Assumptions 29
Chapter 5 31
5.1 Recommendations 31
5.3 Conclusion 35
References 38
List of appendices 39

Chapter 1
1.1 Introduction
Over the last half a century, heat waves have become increasingly common in China and the world. Although there is no consensus on the definition of a heat wave, there exists an agreed understanding of what constitutes a heat wave. A heat wave event has been described as a period of prolonged high temperatures than normal average temperatures for a period exceeding three days. For example, Beijing experiences an average daily temperature of 250c. However, at a particular period, the region receives high temperatures of 300c, 340c, and 380c. This phenomenon of sustained high temperatures for three days constitutes what is known as a heat wave.
In the past, heat waves have had severe effects on the planet and human beings. Some countries have been hit hard by these occurrences while others have been sparingly affected (Luo, & Lau, 2017). China has had its fair share of heat waves and the frequency trend has been on the rise in the last 50 years. It is at the backdrop of this realization that this research is carried out to expound on the increasing trend of heat wave phenomena occurrences in China. According to a report released by the China climate bulletin, most parts of China experienced slightly over 3.1 more temperature days in 2019 compared to the previous year. The northern parts of China were adversely affected by the heat waves compared to the southern regions. This disparity in the impact of the heat wave effects will be discussed in this research under geographical factors causing frequency trends of heat waves. However, the heat wave occurrence of 2019 in china was not only happening in China but also in other regions (Wang, et al. 2018). In the same period, temperatures around Europe reached a record high of 400c while other parts of Asia record temperatures as high as 500c.
The occurrence of these heat wave phenomena’s at the same time indicates a generally rising trend in heat wave frequency not only unique to China as a nation but as a global phenomenon. According to Wegner (1999), heat waves have a devastating effect not only on human beings but also on the environment, social aspects, the economy, and the general ecosystem. According to Guo, et al.(2017), the world meteorological organization has reported that over 126 million people have been affected by the increasing heat waves that have been experienced across the globe over the years. The organization further asserts that through the period from 2000-2016; the world has recorded the highest number of heat waves. Additionally, the report details that in the year 2003, Europe experienced extremely severe heat waves that claimed the lives of over 70,000 persons. In China, the 2013 heat wave resulted in over 5,700 heat wave-related illnesses with some leading to fatalities (Luo, & Lau, 2019). These statistics, therefore, point towards the tenacity and severity of heat waves over the years and the need to take proactive approaches in mitigating the impacts of the heat waves.
In the last 50 years, China has been subjected to more frequent heat waves than most parts of the world and the effects resulting from these heat waves have been catastrophic by all means. There have been huge losses of economic fortunes, environmental degradation, and as well as loss of human lives (Guo, et al. 2020). Several factors can be attributed to this worrisome trend. First, there are human-induced factors such as urbanization and industrialization. Urbanization refers to the processes of rapid development and growth of rural towns to urban centres. China is one of the strong emerging markets in the world. As a result, it has some of the most urbanized centres in the world. China has an overall urbanization rate of approximately 60%. This is a relatively high rate of urbanization and many amenities have to be sought to match this huge urbanization need. Additionally, to meet the growing population needs, China has invested heavily in the industrialization of the economy.
The last 50 years have seen high levels of industrialization since the inception of china’s economic recovery plan developed by Mao Zedong. Over the last century, China has been at the forefront of global industrialization (Wu, et al. 2021). As a result, the country has constantly emitted a large number of tonnes of harmful CO2 emissions and other harmful; gases in the process. However, there are reported natural phenomenon anomalies that have also led to the occurrence of these heat waves. In China, the presence of high subtropical pressure circulation has been attributed to the increase in the number of heat waves. All these causing factors of heat wave phenomena have combined to result in an increased frequency trend in heat waves across china. Therefore, this report will analyze these increasing trends and particular attention will be paid to Beijing, Tianjin, and Shijiazhuang. Additionally, the research will make recommendations on possible measures that can be taken to counter the negative adverse effects of heat waves.
1.2 Problem statement
China has experienced a surge in the heat wave frequency phenomenon in the last 505 years. However little research has been put into this field to try and explain the occurrence of these natural yet disastrous occurrences. In recent history (50years), china has experienced more heat waves than in the last 100 years preceding this period. Therefore these occurrences must be studied, discussed, and documented to advance knowledge in the area. In China, there is documented evidence of an increasing trend in the occurrence of these high-temperature day events. This documentation of climatic conditions for the last 50 years forms the basis of this research. Additionally, this paper will make a detailed analysis of heat wave trend frequency and research on the causing factors of this trend in China. The research seeks to discuss the leading causes of the increases in heat wave frequency in china (in particular within the regions of Beijing, Tianjin, and Shijiazhuang). Therefore the significance of this research cannot be understated as it will form a basis for understanding heat wave phenomena and lay a foundation for future studies into the event occurrences.
1.3 Justification of the study
There is little literature that exists on the topic of heat waveband the trend in the frequency of occurrence of these high-temperature events. This research is of great significance in expounding and explaining the factors that are contributing to the trend in the frequency of heat waves in waves in china. Additionally, this research will help in the consolidation of information on the topic for future studies. A clear understanding of the natural disaster is critical in developing a necessary measure to curb and limit the occurrences of the disaster. This study makes use of empirical data obtained from the national statically book of china and the urban development yearbook data. Temperature data is obtained from the normalized data set of 1970-2020 distributed by the china national meteorological information center. The study makes detailed findings and analyses that are crucial and vital in developing measures suitable to dealing with the increase in longer high-temperature days and a frequent occurrence of heat waves.
This research paper will also pay attention to the negative consequences of heat waves. Additionally, the paper will make realistic and achievable recommendations on the best possible ways to counter the current trend of rising frequency in heat waves.
1.4 Research objectives
Like other researches, this research embraces a multi-dimensional approach to arriving at conclusions. However, these research findings are guided by the project objectives which include the following;
i) To conduct an assessment of the trend to increased frequency in heat waves in China.
ii) To establish factors causing the change in heat wave intensities and frequency.
iii) To establish future projected heat wave trends.
iv) To establish the impacts of heat waves on Chinese populations.
v) To make recommendations on possible mitigation measures to curb the rising trend of heat wave frequency.

Chapter 2
2.1 Literature review
Up and until this moment there exists little literature on the frequency trend of heat waves. However several researchers and scientists have carried out elaborate studies in this field. Interestingly, there exists no single common definition of a heat wave from these previous researches but there is a consensus as to what constitutes a heat wave. There is a common concurrence that a heat wave comprises of an occurrence of high temperatures exceeding the average daily temperatures for three days or more in a row. In China, the trend has also been on the rise especially in the northern regions. Generally, there has been an increase in global temperatures over the years. As a result, other natural phenomenons such as heat waves have been on the rise (Seneviratne, et al.2007). Previous research findings have arrived at a similar position on the trend of deteriorating global climatic conditions. In the last few years, heat wave events have become frequent and more severe.
According to David (2018) heat wave phenomena have been there since the inception of the world, the magnitude and the severity of these occurrences have recorded a sharp rise in the 20th century through to the 21st century. In China, the severity of heat waves has become more intense and profound in the last half a century. The impacts have become more profound especially in the 21st century. From previous research findings, the years from mid-1995 have particularly been profound on the frequency and impacts of heat waves in china.
Other available literatures on this topic are forecasts and are meant to predict possible future outcomes. One such work has been done by David (2018). He addresses the possibility of continued future rise in temperatures and subsequent increase in the frequency of heat wave occurrences. His extensive works are based on the future frequency trends of heat waves in china. Unfortunately, further studies are pointing at the likelihood of escalations of heat waves in the north eastern region. In particular, the research by David (2018) has laid emphasis on the North China Plain. According to his findings, temperature levels are going to increase significantly in North China Plain. In his findings, he argues that the green house effect and excessive evaporations have negative impact on subsequent temperatures. in his research he warns that if drastic measures are not taken to limit the rise in global temperatures, it is likely that the NCP will be inhabitable in the next few years. He further argues that the NCP region is just but a representation of what is to be experienced in the wider nation. He however observes that the causes of general increase in temperatures in the NCP region is as a result of increased human cultivation of the land. In his conclusion he say, as a result of increased and intensive cultivation of crops, there has been a rise in the levels of evaporation, consequently leading to higher humidity. Additionally, the trapped moisture droplets create a net greenhouse effect leading the general increase in temperatures. As a result of increased temperatures, there is a corresponding frequency of the occurrence of heat waves.
2.2 Scope of the study
This research work is bound by the study of the frequency of heat waves in china and the contributing factors in the last half a century. The study will be confined to the analysis of data obtained from national institutes of data. Additionally, the study will focus on different factors that have increased general global temperature.

Chapter 3
3.1 Methodology and Data analysis
This research project makes use of simple and elaborate methodologies in the collection of empirical data from secondary sources. Once data has been collected from these secondary sources, it is thereafter keenly scrutinized and analyze. For this research, the report will put more emphasis on the study of climatic data for three urban regions (Beijing, Tianjin, and Shijiazhuang regions) and a further 4 rural stations to help in the comparison processes between urban centres and rural centres. This research appreciates the use of sampling as an effective tool to carrying out research to represent the bigger picture. The choice of these few regions is guided by the desire to have a detailed analysis of the trends in heat waves and probable causes of the same. Although having a large sample size is important when conducting a representative survey, in this case, a large data size will deny this research the opportunity to analyze, interpret and conceptualize factors that have been causing this surge in the frequency of occurrence of heat waves (Kang, & Eltahir, 2018). The outcomes contained herein shall be presumed to represent the wider nation-China. Data for this study is collected from the following state agencies;
i) China climate bulletin reports
ii) National statistical yearbook
iii) Urban construction yearbook and
iv) Normalized temperature data set of the years 1970-2020.
v) China national meteorological information centre.
vi) Ministry of natural resources.
The following section contains empirical data obtained from the various national agencies listed above.

Table 1 Basic Stations Information
Station name
Station Nature

116.20 E, 39.90 N

114.60 E, 38.30 N

14.020 E, 38.20 N

114.50 E, 37.70 N

117.10 E, 39.40 N

117.20 E, 39.00N

114.40 E, 38.00 N

Table 2 high temperature days in Beijing, Tianjin & Shijiazhuang

Apr 29
Sep 18

Apr 30
Sep 11

Apr 15
Sep23/Oct 1

Figure 1 Built-up area and Urbanization rate variations

Figure 2 Trend of high temperature days in Beijing, Tianjin and Shijiazhuang

Figure 3 The Man Kendal test for Beijing

Figure 4 Variations of Heat wave frequency and HWMI in Beijing over the last 50 years

Figure 5 Variations of Heat wave frequency and HWMI in Tianjin over the last 50 years

Figure 6 Variations of Heat wave frequency and HWMI in Shijiazhuang over the last 50 years

3.2 Data analysis
i) High-temperature day trend
High-temperature days refer to days that record relatively higher daily temperatures than the average daily temperatures. High-temperature days are a result of several factors combined. For the cities under study in this analysis, Shijiazhuang has a relatively higher number of high-temperature days. According to recent studies the average high-temperature days in Beijing, Tianjin, and Shijiazhuang start around the month of April and end at the start of the month of October. Interestingly, the difference can go as high as 20c in June and July. The three regions have an average of 10.5, 11, and 12.2 high-temperature days. AA majority of these days are experienced in the months of June and July with close to 65% of these events being recorded at this time.
A further 20% of the days are recorded in the month of August. The remaining high-temperature days are spread out across the other months. From records, it is observed that the onset of high-temperature days is delayed in rural areas as compared to the start in urban areas. Over the last 50 years, the average number of high-temperature days has been on the rise with an increased rate of between 2% to 3%. According to the Mann-Kendal test, the number of high-temperature days has been on a significant rise in Beijing. According to the MK test, in the late 1990s’ Beijing significance level exceeded the 0.05 limit and subsequent 0.01 level in the early 2000s’ (Xu, et al.2020). From empirical studies, it is established that the likelihood of occurrence of heat waves during these periods of high temperature days. In conclusion, the last 50 years have witnessed an increased early start to the onset of high-temperature days and an average increase in delays to the end of the same phenomenon.
ii) Heat wave frequency
From empirical studies, there is a clear correlation between heat wave frequencies and the number of high temperatures days. Years that have recorded a higher number of high-temperature days have subsequently had more heat waves and vice versa. In the last half of a century, heat waves in Beijing, Tianjin, and Shijiazhuang have increased significantly. Recorded frequencies for the three cities are 2.28, 1.78, and 2.67 respectively. Prior to the mid-nineties, heat wave events were relatively low. In comparison, Beijing recorded heat wave events of about 0.2, while Tianjin recorded 0.3, and 0.8 in Shijiazhuang. However, in the last 30 years, the number of heat wave events in these cities has more than tripled an occurrence that is likely to be attributed to the processes of industrialization and global warming.
Additionally, some years in these cities have experienced more than 10 heat wave events with extremes events being recorded in Beijing in 1999 (10) and 13 heat wave events in the year 2000. In comparison, heat wave frequencies for urban areas are relatively high compared to frequencies recorded in rural areas (Luo, & Lau, 2019). In addition to the urbanization and industrialization processes, it should be noted that cities with low altitudes tend to have a relatively high temperature. As a result, the regions are likely to receive more high temperature days and a subsequent higher number of heat wave events.
iii) Heat wave magnitude index (HWMI)
 The heat wave magnitude index is calculated by summing up the three days’ high temperatures and the value is normalized to a range of 0-1. In addition, for this study, the intensity, frequencies, and population exposure to heat waves will be investigated using heat wave intensity duration index (HWDI), annual heat wave frequency totals (N_HW), and the annual total of heat wave days (T_HW) under RCP4.5 and RCP 8.5 guidelines. According to data trend analysis, heat waves are projected to be on the increase, longer, and extreme over china. Additionally, Chinas higher altitude and latitude regions are expected to experience extreme heat wave conditions compared to the southern regions. Heat waves have a corresponding relationship with the general increase in global temperatures. Containing global warming levels to below 1.50c can help avert the extremes of HWDI, N_HW, and T_HW. In the last 50 years, Beijing, Tianjin, and Shijiazhuang have recorded HWMI of 1.8, 1.4, and 2.1. Additionally; this study will make use of statistical data from other relevant sources.
Iv) Urbanization
Urbanization in China is a leading factor that has led to a general increase in temperatures. Urbanization processes result in the emission of harmful greenhouse gases that in return lead to higher temperatures. Urbanization indices of Shijiazhuang, Tianjin, and Beijing indicate a rapidly growing trend for towns and cities in China. For instance, between the years 1980 -2010 the three towns recorded an urbanization rate of 62.3%, 83%, and 86% respectively. Compared to other regions of the world, these are relatively high rates of urbanization. Additionally, according to 2018 data, on urban built-up areas, the three cities under consideration recorded relatively high built-up areas with Beijing having a built-up area of 1485 km2. Tianjin has a built-up area of 1,103 km2 while Shijiazhuang recorded a built-up area of 291.8 km2.
Urbanization results in an increase in populations. In the last 50 years, Beijing has experienced a radical increase n its population. An increase in population has a corresponding increase in amenities required. Such amenities include transportation amenities. Transportation takes various forms; first, there is rail transport. Secondly, there is air transport and lastly road transport. Whichever mode of transport is adopted by the masses has one outright outcome. They all lead to a general increase in the amount of CO2 emissions from the combustion of oil products. An increase in CO2 levels has a corresponding increase in temperatures.

Chapter 4
4.1 Discussions
High temperature weather has a direct bearing on the frequency of heat wave events in a particular region. However, heat waves are not only a result of high temperatures but as a result of several factors combined together. Therefore, understanding the phenomenon of heat waves requires a broader perspective. This paper makes a detailed analysis of heat wave incidences and heat wave indices for three major cities in china for a period of 50 years. The findings made in this report for the temperature patterns in the three cities are consistent with findings on the general trend in temperature rise across China (Sun, et al.2017). Heat wave events and frequencies are consistent with the rise in global temperatures. Other factors evaluated for the purposes of this study include; urbanisation effect on temperatures, anomalies in atmospheric circulations, climate warming, and solar activity.
4.2 Global warming
Global warming is undoubtedly the leading factor causing an increase in heat wave events. The last 25 years under consideration in this research are coincidentally the warmest years in China’s modern history according to data obtained from the national temperature centre. It is not a coincidence that the last 25 years have been the warmest years of China’s history and at the same time with the highest number of high-frequency events (Luo, & Lau, 2019). it is therefore correct to conclude that higher global temperatures are responsible for the general increase in the number of heat waves being experienced in China, for instance in Beijing it is correctly documented that every year with a recorded higher annual average temperature has a corresponding increase in the number of heat waves. This, therefore, serves to explain the significant influence and impact of global warming on the frequency of occurrence of heat wave events. Additionally, research has shown corresponding increases in heat events with general climatic anomalies.
4.3 Atmospheric anomalies
 Studies carried out have established that atmospheric pressure anomalies are also a leading factor in the development of heat waves. In this argument, hot air is trapped beneath a high pressure system. Air usually circulates from the lower regions to the upper regions for cooling and precipitation. However, this is not always the case. At times the air is held trapped within the earth’s atmosphere for a relatively longer duration. As a result of this retention, the mass of air gets heated from the sun’s rays and from the radiations of the earth’s surface, leading to an increase in temperatures of heat retained. If no prevailing winds blow over the trapped mass of air, heat waves are developed with catastrophic consequences.
4.4 Solar activities
Research on solar activities is not yet well-formed. However, it is believed that some solar activities have resulted in the formation of heat waves around the world. Sunspots are solar activities that generate a relatively high amount of solar energy. As a result, the high cosmetic energies are transmitted to the earth’s atmosphere where they result in increased temperatures leading to the formation of heat waves. Additionally, solar star collisions have been recorded to produce a relatively high amount of energy. Once the energy gets to the earth’s atmosphere through radiation, there are possibilities of temperature flare-ups. Lastly, the disintegration of atmospheric atoms has been shown to emit radioactive elements leading to temperature flare-ups and subsequently heat waves.
4.5 Industrialization
According to data analyzed, it is evident that in pre-industrialization, the frequency of heat wave events was relatively low compared to post urbanisation era. Urbanisation leads to an increase in emissions of harmful gases to the environment. Therefore, the gases get trapped in the ozone layer of the atmosphere. As a result, the dense ozone layer forms an artificial greenhouse effect over the regions (Guo, et al, 2020). Subsequently, heat from the sun gets trapped in the atmosphere leading to a general rise in the surface temperatures. To better understand the impact of urbanisation, there is a need to study the frequency of heat wave occurrences in rural areas and compare them against urbanised areas. From statistical data obtained for the pearl delta river of southern China, it is established that the region experiences less number of high temperature days. Subsequently, the region has a relatively lower number of heat wave occurrences. This glaring disparity can be attributed to the differences in the levels of urbanisation.
4.6 Aerosols
Although the effect of aerosols on heat waves is not fully documented, there is substantial evidence that is linking aerosols in the atmosphere to the general occurrence of heat waves. Areolas have the capability to weaken and scatter radiations. An observation made in Beijing in the year 2017, the urban heat intensity UHI was recorded to be positive and increased with a corresponding increase in PM2.5 concentration. However, the UHI weakens at maximum temperatures and even records a negative value. From this observation it can be concluded that a high PM2.5 Concentration and high UHI have an ultimately negative impact on the development of high temperature days. Therefore the effect of aerosols pollution hinders the development of high temperature days. Therefore in the absence of these aerosols, the frequency and occurrence of high temperature days may become rampant and more profound.
4.7 Deforestation
 The regions of Beijing, Tianjin, and Shijiazhuang have experienced a general decrease in forest cover. Vast tracts of land have been deforested to create room for urbanisation and the processes of industrialization. Consequently, there has been a corresponding increase in temperatures. Forest cover plays an important role in helping in the circulation of air. Additionally, plants remove carbon (IV) oxide emissions from the atmosphere and replace them with oxygen. Removal of CO2 from the atmosphere has a corresponding net effect of lowering the environmental temperatures. As such, plants play an important role in reducing temperatures and subsequently leading to fewer heat waves.
4.8 Predicted future heat wave events in china
According to research work conducted by David (2018), China may be heading to the brink of its existence by the end of the century. Chin, considered as the world population headquarters may become a vast land of inhabitability by the end of the 21st century due to the increased frequency of heat wave events. Scientific research has shown that beyond a certain level of humidity and temperatures human life cannot be in existence. According to David (2018), there is an urgent need for mitigation measures to be taken to remedy the situation. One of the most likely regions to experience this devastation is the North China Plain (NCP).
This region is an agriculturally fertile region and over the years has had intensive cultivation of crops. As a result of the extensive irrigations and use of chemicals, the region at the moment is experiencing higher temperatures than normal. Extensive irrigation leads to high rates of evaporation resulting in a hot and humid atmosphere that is inhabitable. In this research, the area around NCP and equating to 4000 km2 was mapped against a temperature model obtained from empirical data of over 30 years. Temperature data of 30 years over the region was then mapped on the model to derive a correlation of time versus temperature increases. Thereafter, the developed model was used to predict future temperatures on two possible scenarios. (i) The model was used to determine future temperature readings over a period of 30 provided the conditions remained constant (intensive and mechanised farming using chemicals). (ii) The second scenario involved predicting future climatic conditions over a period of 30 years with moderate efforts to reducing farming intensity and emissions. The two findings on the possible future scenarios had similar outcomes of the general increase in temperature but in different intensities. (i) Presented a general increase in temperature by 0.5oc in the NCP region. (ii) Although the second scenario showed a relatively lower temperature increase, it did concur with the researcher’s assertions that current activities have a huge bearing on the future of global temperature and subsequently increase in heat waves. The research came to the conclusion that if the NCP does not embrace strategies to limit their current emissions to the atmosphere, the region might become the first inhabitable area in the world. Mapping the same scenario to the rest of the country show that china will become inhabitable by the end of the century. This is because increases in temperatures will have a corresponding increase in the frequency of the occurrence of heat waves. Heat waves are known to have severe consequences on human health and have resulted in mortalities in the past. Therefore, caution and care should be exercised n china and in the world as to how temperature increases are handled.
4.9 Impacts of heat waves in china
Impacts on human health
Heat waves negatively impact the health of individuals. From previous findings heat wave-related complications have resulted in mortality. This is because heat waves have a correspondingly high temperature. Human beings have an optimum body temperature of 370c. However, when subjected to extreme temperatures the body cells start to lose shape and eventually degenerate. As a result, people experiencing severe heat wave complications such as heat strokes are likely to succumb to their complications. Additionally, heat waves may lead to severe dehydration among individuals. Consequently, the severe dehydration may result in death (Guo, et al.2020).
Environmental impacts
Heat waves have a negative consequence on the environment. During periods of high temperatures, excessive evaporations on water bodies take place. As a result, the regions become highly humid. High humidity in the atmosphere is not good for the existence of life. As a result of the high rates of evaporations these regions receive heavy floods triggered by the excessive evaporations as a result of the heat waves.
Additionally, heat waves lead to occurrences of droughts. From time to time droughts have been known to result in massive reductions in agricultural produces. Reduced agricultural produces will ultimately lead to food scarcity. Therefore, there is a great need to understand heat waves and their patterns to help farmers’ plan better in the future to minimize losses.
4.10 Limitations of the study
Findings made in this report should be considered to be a true reflection of data obtained from the relevant authorities. However, the findings herein are not without limitations. Although the limitations affected the process of data collection and analysis, the processes made true reflections and findings on the causes of heat waves and the increase in the frequency of the same.
i) Lack of sufficient sample size data to carry out the research
Although statistical data from the various agencies was provided, there exist comparative data gaps for the regions under observation. Comprehensive and comparative data is of great essence in making firm deductions. To arrive at an elaborate and conclusive research study, sufficient data is needed to reduce biases. Additionally, the nature of the study restricted data methodologies to the sampling of empirical data acquired from secondary sources. Therefore, if any error was committed in the data collection stages was likely to have been carried on in this research. However, this research made a careful analysis of the data obtained from the national institutions on statistics was carefully analyzed and evaluated throughout the study of this research.
ii) Inadequate literature on the topic
Studies on heat wave frequency trends in china are limited. There is no sufficient information concerning this topic. Most previous researches cantered on the health impacts of heat waves in China. The lack of well established literature on the topic made this research more complicated as it had few pieces of research to compare with. Availability of prior literature is an important aspect to making any research work easy and possible. Researchers build on concepts from previous works and make advancements to the same. Where there is sufficient literature on a topic, research becomes relatively easy and vice versa is true. However, this research paper joins the limited pool of the existing literature. Future researchers will borrow from this research to build on concepts advanced herein. None the less, this research made prudent use of the available works to come up with elaborate models, detailed analysis and arrive at exhaustive conclusions.
iii) Time constraints
Although a reasonable amount of time was allocated towards this research, it was not sufficiently adequate. This research required a relatively longer period to compare more data and make a highly detailed analysis. Nonetheless, the research was completed within the allocated time and meaningful findings and conclusions arrived at in the best manner possible. In the future, the study should be allocated a fairly sufficient amount of time to make it possible to analyse all the statistical historical data in detail.
iv) Data collection methodology limitations
This study made extensive use of empirical data provided by secondary sources. Although the sources provided substantial data for the study, they also acted as a barrier to the effectiveness and accuracy of the research. The methodology gives little room for correction of errors that might have been made in the processes of recording the information. Therefore, errors made during the stages of collecting and recording may be propagated to secondary researchers. However, that notwithstanding, detailed analysis of the data was conducted to ensure that there was no room for error. This research suggests that future researchers should not only rely on empirical data provided by the various state agencies but also go out of their way and document first-hand impacts of the severities of heat waves.
v) Scope of the research
This research study is limited in its scope. Emphasis is on the trends of heat wave frequency and changing factors in nearly 50 years. However, to bring this particular topic into proper perspective a wider set of data is required. However, the data is not readily available. Nonetheless, the 50-year analysis has resulted in the demonstration of heat wave frequency trends. Additionally, the study is limited to heat wave trends whereas it does not lay emphasis on other aspects of heat waves.
vi) Funding constraints
 This area of study is largely underdeveloped. Current researches including this research are forming the basis for future research works. Therefore, conducting extensive research work requires huge funding. Additionally, financing plays an important role in the kind of outcomes that are to be realised. This research work endured the dynamics of strained resources and the studies had to be made using a tight budget. Nonetheless, this research made valuable findings on the causes of increased trends in the frequency of heat waves. Additionally, the research has presented sound recommendations on the possible measures that can be taken to remedy the situation. According to David (2018), there is an urgent need for China to take proactive measures to prevent the possible extinction of the population by the end of the century.
4.11 Assumptions
While making future heat wave frequency predictions, it is assumed that the current controlling factors shall remain constant and that other entrant factors shall have no effect.
The research makes a general assumption that the empirical data relied upon from these secondary sources is correct and factual. Owing to the nature of this study, it can only be presumed that the data borrowed from these national institutions is factual and consistent. This is because; collecting personal data to study climatic conditions requires relatively long durations. Nonetheless, the outcomes arrived at are in concurrence with the general trend in the occurrences of heat waves in China. For instance, the data has accurately pointed out the occurrences of frequent heat wave trends in the months of June and July. Therefore, this gives credibility to the data
This research further makes the assumption that the collision of atmospheric atoms does not cause a significant increase in temperatures. Therefore, if the main causing factors of temperature rise are controlled atomic collisions shall not form the next major frontier to temperature changes.
Lastly, this research makes the assumption that Heat waves are caused by the general increase in global temperatures and not as a result of extraterrestrial activities.

Chapter 5
5.1 Recommendations
It is without a doubt that in china there has been an increase in the occurrence of heat wave phenomena over the last 50 years. This claim is supported by the elaborate data available on climatic changes. Recommendations made in this research are double faceted. First, this research makes recommendations on ways in which factors accelerating heat wave occurrences can be mitigated. The second set of recommendations are geared towards ensuring that future research in this field is made better
This research recommends that strategies be put in place to curb the rising trend of global warming. Global warming has emerged as one of the leading factors in the increase in the frequency of heat waves. As a result of increased temperatures cases of heat, flare-ups have been on the rise. China as a nation has contributed immensely to this end. Over the last 50 years, China has experienced rapid growth. The rapid growth has been accompanied by immense negative impacts on the environment. One of the most effective strategies that the government can use is to abide by the international conventions on environment conservations and commit to keeping emissions to relatively lower levels. A reduction in global temperatures will have a net effect of a reduction in the frequency of occurrence of heat waves.
This research recommends that the government intensifies efforts to craft better reforestation strategies and curb the rapid rates of deforestation. Deforestation has been flagged as another causing factor of an increase in the frequency of heat waves. Over the period of last 50 years, China has experienced a massive reduction in forest cover. In the late 20th century massive deforestation took place to pave way for urbanization. Additionally, the demand for timber products has been quite high in the period under consideration. As a result trees and other forest covers have been cleared to meet this demand. According to statistics, china lost close to 2,500,000 Ha of forest cover between the years 1990 and 2010. This massive clearance of forest cover translates to a rate of approximately 1.5% per year. If not checked, the situation may lead to more adverse negative consequences including an increasing the frequency of heat waves. Therefore, to counter this negative occurrence, there should be concerted efforts by a multiagency team to speed up the process of reforestation to ensure that there is an increase in forest cover. This method poses unique advantage in that it is easy to implement and has relatively low capital requirements to realise.
Additionally, this research recommends that china puts in place better control measures in its industrialization processes. Industrialization is undoubtedly Chinas trademark in the period lasting over 50 years. China has seen a massive economic turnaround resulting from industrialization. The massive industrializations have positioned china among the great emerging economies of the world. However, these gains have come at great environmental costs. For the period under study, China has continuously made use of coal power to run the industries. Coal power is a leading pollutant in the atmosphere. Combustion of coal products results in massive carbon (IV) oxide emissions. In addition, there has been a general lack of a framework to guide the processes and requirements of emissions to the environment. As a result, these emissions have contributed immensely to the greenhouse effect. This research recommends that China adopts several approaches as elaborated herein to tackle this ever-rising concern. First, the government should ensure strict adherence to international conventions on tackling climate change. This will ensure that relevant authorities are compelled to play their roles effectively in curbing rising global temperatures. Secondly, legislation on safe emissions to the atmosphere should be enforced with strict adherence. There exist mechanisms through which industrial emissions can be cleaned to effectively remove environmental pollutants leading to the emission of relatively clean air. Lastly, China should aim at discontinuing the use of environmentally unfriendly means of powering the industrial plants. At the moment, coal is a popular source of energy. According to a 2019 report, coal use accounted for over 55% of all energy supplies in china. This is a significant percentage and efforts should be channeled towards reducing this huge reliance on coal as a means of power production. There exist numerous clean sources of energy. For instance, China is yet to fully exploit its potential in hydro energy production despite being endowed with numerous water sources. Additionally, wind energy is an emerging trend in sourcing power. Adoption of clean power sources to drive the industrialization agenda will lead to a significant drop in the tones of harmful emissions generated annually. As a result, the general increase in temperatures will be reducing. Consequently, a reduction in global temperatures has a corresponding decrease in heat wave occurrences.
Urbanization has impacted negatively on the general atmospheric temperature. To illustrate this tabulated temperature data from Beijing is compared with data from other rural centres within China. The comparison makes a glaring finding that Beijing has relatively higher temperatures and has experienced more heat waves as compared to these rural centres. Mapping this finding on the entire nation proves the dire situation that the country finds itself in. According to global urbanisation rankings, at 60 % urbanisation index, china is among the leading countries in the world with a high urban population. This leads to the conclusion that urbanization has resulted in negative impacts on the prevalence of heat waves. Nonetheless, this research appreciates the fact that China is a densely populated country and in touch with civilization. However, there is a need to come up with more stringent measures that will regulate urbanisation processes to ensure the process does not result in negative consequences on the general atmospheric temperatures.
5.2 Recommendations on possible measures to improve on future research  
Research in this field is far from being exhaustive and conclusive. This position is evidenced by the little literature that exists on the topic. Additionally, the lack of a general consensus and definition of a heat wave further elaborates on the green areas that exist in this topic. In the last 50 years, the study of heat waves has not received the due attention that it requires. As a result, there has been little study into the field. In the mid 20th century, heat waves were often confused for a general increase in temperatures. These heat waves were of lesser magnitudes as compared to heat waves experienced in the last 25 years. Therefore, little effort was put into understanding the phenomena. However, recent trends in an increase in heat wave frequencies have pointed out a growing concern that should be addressed in the most elaborate manner possible. Therefore, this report recommends the following to improve on the study of this topic;
Increased funds allocation to the study of this topic. Proper understanding of trends in heat wave frequency is an important aspect of securing the future of mankind. Over the last 50 years there has been a constant increase in the number of heat waves recorded in china. Therefore, this is an indicator of the possibility of experiencing more heat wave events in the future if all factors are held constant, heat waves have a dire consequence on human life and in extreme cases has led to mortalities. Therefore it is quite important that more studies are carried out in this field to ensure that there is credible information about the causes of the heat waves, frequency of occurrences, and possible measures that can be used to mitigate the severity of these heat wave events.
Increasing the scope of the area of study. Heat waves are a result of many combined factors. Therefore, the study in this area should be broadened to include other studies to determine the relationship that exists between this field and those other areas. This will additionally lead to an increase in the literature available for this area of study.
5.3 Conclusion
This research paper makes a detailed analysis of three regions in china and the general heat wave frequencies in china. The analysis details the heat wave trends and frequencies over the period of 50 years from 1970-2020. The paper further quantifies contributions made by other factors leading to higher temperature events that have ultimately resulted in heat wave occurrences (Guo, et al.2020). Findings in this research are in concurrence with the general pattern in climatic conditions. It has been established that there is an increase in the number of heat wave events occurrences in the three cities under study and in the other parts of the country.
From this research work, it can be correctly adduced that high temperature days occur in the periods from June through July and account for over 60% of the total heat waves in these regions under study. It is during these high temperature day events that heat waves are experienced. Therefore, it has been established that heat wave consequences are more severe in china in these two months. Additionally, the research has established that the occurrence of more high temperature days can be traced to have increased significantly from the mid-1990s’. Data from previous years show a relatively fewer number of high temperature day events as compared to the years after 1995. Intrestingly, it is observed that in the last 50 years the duration of high temperature days has significantly increased. The high temperature phenomena days have been observed to be starting early and coming to an end late compared to the periods before the last 50 years under consideration. As a result, the heat wave events have increased significantly. This means that Chinese citizens are exposed to more heat waves than the previous generations. From scientific findings heat waves have been shown to have net negative impact on the genetics of human beings. As a result, prolonged exposure to heat waves may lead to undesired consequences among the Chinese population in the future. Therefore, there is need to study more on the causes of heat waves to minimize possible future negative consequences on the population.
From the findings above it is established that global warming is one of the factors that have led to a general increase in high temperature events phenomenon. Global warming is commonly referred to as the greenhouse effect. In this case, emissions from industrial activities result in the emission of hazardous gases into the atmosphere. These gases form a blanket over the atmosphere and at the ozone layer. Therefore, heat energy from the sun and radiation energy from the earth is trapped in the atmosphere resulting in an increase in temperatures and subsequently heat waves. However, there are a number of factors that cause global warming apart from emissions of hazardous gases into the atmosphere by industrial parks. For instance, deforestation and subsequent reduction in forest cover have resulted in a corresponding increase in temperature. This is because plants are essential in the process of air circulation and removal of CO2 from the earth’s atmosphere to replace it with oxygen through the processes of photosynthesis.
Additionally, the research findings have established that atmospheric anomalies such as atmospheric pressure anomalies have contributed immensely on the frequency of occurrence of heat wave events. That notwithstanding, the research has established that atmospheric anomalies have limited effect on the frequency of heat wave trends. Aditionally, through research findings, it is established that the heat waves resulting from atmospheric anomalies are less frequent and take place over relatively small geographical areas (Guo, et al. 2020).
 The research paper makes sound recommendations for the advancement and future of the study of this area. In the recommendations, it is observed that there is insufficient funding to help advance research in the trend of frequency of heat waves. As such, more commitment should be emphasised in this regard to ensure that the area is exhaustively expounded and more information is made available to the public.

Wang, P., Tang, J., Sun, X., Wang, S., Wu, J., Dong, X., & Fang, J. (2017). Heat waves in China: Definitions, leading patterns, and connections to large‐scale atmospheric circulation and SSTs. Journal of Geophysical Research: Atmospheres, 122(20), 10-679.
Luo, M., & Lau, N. C. (2019). Amplifying effect of ENSO on heat waves in China. Climate Dynamics, 52(5), 77-389.
Wu, X., Wang, L., Yao, R., Luo, M., & Li, X. (2021). Identifying the dominant driving factors of heat waves in the North China Plain. Atmospheric Research, 252,
Luo, M., & Lau, N. C. (2017). Heat waves in southern China: Synoptic behavior, long-term change, and urbanization effects. Journal of Climate, 30(2), 73-720..
Wang, P., Tang, J., Wang, S., Dong, X., & Fang, J. (2018). Regional heatwaves in china: a cluster analysis. Climate dynamics, 50(5), 191-917.
Guo, X., Huang, J., Luo, Y., Zhao, Z., & Xu, Y. (2017). Projection of heat waves over China for eight different global warming targets using 12 CMIP5 models. Theoretical and applied climatology, 128(3-4), 50-322.
Luo, M., & Lau, N. C. (2019). Characteristics of summer heat stress in China during 1979‒2014: climatology and long-term trends. Climate Dynamics, 53(9), 75-388.
Guo, E., Wang, Y., & Bao, Y. (2020). Assessing spatiotemporal variation of heat waves during 1961–2016 across mainland China. International Journal of Climatology, 40(6), 36-305.
Wu, X., Wang, L., Yao, R., Luo, M., & Li, X. (2021). Identifying the dominant driving factors of heat waves in the North China Plain. Atmospheric Research, 252,.
Fischer, E. M., Seneviratne, S. I., Lüthi, D., & Schär, C. (2007). Contribution of land‐atmosphere coupling to recent European summer heat waves. Geophysical Research Letters, 34(6).
Kang, S., & Eltahir, E. A. (2018). North China Plain threatened by deadly heatwaves due to climate change and irrigation. Nature communications, 9(1), 1-99.
Xu, F., Chan, T. O., & Luo, M. (2020). Different changes in dry and humid heat waves over China. International Journal of Climatology.
Luo, M., & Lau, N. C. (2019). Amplifying effect of ENSO on heat waves in China. Climate Dynamics, 52(5), 37-328.
Sun, Q., Miao, C., AghaKouchak, A., & Duan, Q. (2017). Unraveling anthropogenic influence on the changing risk of heat waves in China. Geophysical Research Letters, 44(10), 58-505.

List of appendices
Figure 7 Annual high temperature days from 1970-2020

Figure 8 Main contributing factors of increase in heat waves

Figure 9 June 2017 Beijing heat wave