Climate Change Impact on Urban Environment

Author: Dr. Ujjwal Saha, Assistant Professor, IIEST-Shibpur

Contact: ujjwalsaha1980@gmail.com

Prologue

Upon my request, Dr. Saha first produced this summary article back in 30Oct2021. We tried the first version of Prodeeptika then, but that was not materialized. I have decided to publish this article now despite it's a bit old status, as "... with age comes wisdom" (Tibetan Guru of Johnny English). Hope the readers will enjoy its wisdom.

Abstract: In the recent times, global climate change has emerged as a great challenge to the sustainability of infrastructures of urban areas. Global climate change will affect every aspect of an urban environment through different mechanisms. Town planners, architects and civil engineers have to take into account the effect of climate change in their design of the urban infrastructures. In this review paper, all the possible impacts of climate change on urban environment have been discussed and possible solutions to this problem have been found out.

Keywords: Climate Change, Urban Environment, Adaptation, Mitigation

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Introduction

At present, worldwide urban areas provide shelter to approximately 53 % of total population (UN population division, 2014) and it is expected that nearly two third of world population will inhabit in urban areas by the year 2050. In case of India, the last census data indicates that above 31 % of people live in various urban conglomerates (Census of India, 2011) which are expected to increase little over 50% by the year 2050. This implies that over the next 35 years, Indian urban population will double. It will put tremendous pressure to the urban authorities to provide basic infrastructure to its entire citizen. On the other hand, climate change induced by global warming will bring unexpected weather phenomena such as intense heat wave or heavy rainfall induced flooding which will have immense impact on the future citizens or the urban areas. Hence, more attention is to be paid to the study of climate change impact on urban environment as the effect of climate change and urbanization are converging rapidly in a dangerous way in the Indian urban conglomerates. Generally climate change impact studies are carried out for different sectors separately such as water resources, bio-diversity, energy sector etc. But there is an urgent need for integrated climate change impact studies for Indian urban environment. The urban environment consists of human, urban infrastructures and ecology or bio-diversity.

In this review paper, at first, the cause of global climate change and how urban areas are contributing to the modification of global and local climate and the possible impacts of these changes to the above mentioned three urban environments are discussed. Then the various adaptation and mitigation options to tackle the double threat of climate change and urbanization are reviewed and conclusions are drawn.

Global Climate Change

The main source of the energy of the earth is the sun. The balance between the incoming and outgoing solar energy determines the temperature of the earth. The incoming solar energy when reaches the surface of the earth, it is either reflected back to the space or absorbed by the surface materials of the earth. The absorbed solar energy is released in the atmosphere in the form of infrared radiation. Various greenhouse gases (GHGs) such as water vapor (H2O), carbon dioxide (CO2), and methane (CH4) absorb the emitted infrared radiation and delays or prevent the loss of the heat energy into the space. Hence, over time, it increases the total trapped heat in the atmosphere causing the temperature of the earth to increase. This phenomenon is termed as “greenhouse effect”. The other two factors which affect the energy balance process are variations in the energy of the sun reaching earth and changes in the albedo of earth’s surface and atmosphere. Since the start of industrial age in the seventeenth century, human activities have contributed considerably to the increase of various heat trapping GHGs in the atmosphere. The main human activity affecting the rate and amount of greenhouse gas is the burning of fossil fuels. Human activities have also altered the earth’s reflectivity or albedo by altering the land use and land cover of the surface of the earth. The net result is the alteration of the energy balance of the earth and increase of the temperature of the surface and atmosphere of the earth. This process is known as “global warming”. The temperature is a dominant part of the climate of the earth. Hence, change in temperature will definitely affect the other climatic parameters such as rainfall, humidity etc which in turn will affect the life on the earth. The climate change is defined as the change in the long term mean and other characteristics of the properties or states of the climate. From the ongoing discussion, it is evident that the ongoing global climate change is the result of global warming which is caused by the various human activities in the post-industrial period (Oreskes, 2004).

Urbanization Effects on Local Climate and Global Climate Change

Urban areas are evolving constantly due to spatial interaction of the flow of economic, social, ecological and infrastructural systems (Gleeson, 2008, p. 2656). In urban areas, there is high concentration of industries, construction, transportation and households. In urban areas, construction of building structures is necessary to house people and for commercial activities and interaction between social and economic activities. Transport facilities are required for the movement of materials, goods and people from one place to another within or around city area. The city dwellers also require constant supply of food, clean water and sanitation, as well as heat, electricity, and light. This very nature of urban areas, which requires burning of fossil fuels, contributes hugely to the increase of greenhouse gases, thereby leading to the climate change. As per the estimate of UN (UN, 2007), worlds urban areas generate approximately, 75% of total greenhouse gas emissions.

The process of urbanization replaces the natural vegetated surface with impervious hard artificial surface affecting the evaporative cooling, shading, rainwater interception, infiltration and runoff generation processes. Due to this change in the urban features, it affects the local climate in different ways which is discussed next. Concrete, tarmac, asphalt, and other surfacing materials absorb heat energy from the sun, resulting in modification in the local energy balance to create an urban heat island, which is characterized by higher air temperatures in the urban area by several degrees than in the surrounding rural areas. The hard surface also reduces infiltration, thereby increasing storm runoff and reducing ground water recharge causing more chance of flooding to occur and depletion of underground water storage. Population densities in urban areas increase air, water, land and sound pollution and put pressure on water supplies and other natural resources.

Impacts Of Climate Change on Urban Environment

According to Inter Governmental Panel on Climate Change (IPCC, 2007), at the end of this century, the global surface temperature is likely to rise in the range of 1.1 – 6.4°C compared to 1990 values, and rise of between 18 to 59 cm in the global mean sea level. This combined with local changes due to urbanization will have significant impacts on the urban environment. The main effects of climate change on urban environments are summarized in the following subsections.

Sea level rise

Thermal expansion of ocean water as it is subjected to increased temperature and melting of ocean and polar ice is the main causes of global sea level rise. Most of the cities (Mumbai, Chennai, New York, London etc) with share of over 50% of the world’s population are situated or near or on sea and so will be affected by the rise in sea level (Nicholls 2006). The rise in sea level will directly increase flooding, inundation and damage, increased salinity in the ground water aquifers, coastal erosion, and indirectly affect the coastal ecosystem and tourism industry of the city.

Extreme Climatic and Weather Events

The impacts of the extreme climatic and weather events are shown in the Table-1 (UN- HABITAT, 2011).

Table-1: Impacts of Extreme Weather and Climate Events on Urban Areas

Climatic Phenomena	Likely Impacts
Reduced number of cold days and cold nights	For heating requirement, the demand of energy will be lesser
More frequent and warmer hot night and days and over most land areas	Demand for cooling will increase
Warmer temperatures	Fewer occurrence of disturbance of transport due to snow. Winter tourism will be affected due to lesser ice.  Alteration in permafrost
Increase of frequency of Heat waves/ Warm spells over most land areas	Energy consumption for air conditioning will increase. In warm areas, the quality of life of people who do not use air conditioning will reduce. The general health of elderly, poor and very young will deteriorate including significant loss of human life
Increase of frequency and duration and amount of heavy rainfall events over most land areas	Flash flooding will disrupt the normal functioning of transport, commerce, and settlements, societies. Loss of human life and property. Pressures on infrastructures. Water borne disease may increase. The rainwater can be used in hydropower generation.
Increase in drought affected areas	Shortage of water will affect households, industries and services. Potentials of generation of hydropower will reduce.
Increase in activity of intense tropical cyclone	Flood and high speed wind will damage property and life and public services. Private insurance companies may withdraw risk coverage or increase premium. Migration of population.
Tsunamis	Damage or loss of property and buildings and resources. Injury and death of human and living beings. Migration of population to safer places

The potential impacts of climate changes on different aspects of urban environments are summarized in Table 2 (UN- HABITAT, 2011).

Table-2: Potential Impacts of Climate Change on Urban Areas

Issues	Likely Impacts
Human Health	Due to heat stress, higher mortality rate in summer time while in winter lower mortality rates due to decrease in cold waves. Asthmatic disease due air pollution. Damage to plants and buildings. De-hydration and discomfort.
Bio-diversity	Urban wetland habitat will be disturbed. Breeding will be impaired. Competition will increase between different species for survival. Spread of Invasive species, including both animal and plant species. Strengthening of disease pathogens. Due to rise in sea level rare salt marsh habitat will be threatened. Earlier occurrence of spring seasons and longer duration of frost-free season will affect timing of bird egg-laying, flowering and leaf emergence of plants.
Infrastructure and Building	Thermal discomfort will reduce the productivity of the worker. On clay soils, higher chance of building subsidence. Underground pipes and cables will be affected in winter due to movement of ground.
Transportation Sector	Higher occurrence of extreme weather will disrupt transport systems. Passenger comfort will be reduced due to higher temperature. Damage to road infrastructure. Disruption related to cold weather will be reduced.
Economic Activity	Insurance industry will have more claims of damage. The premium of flood insurance cover will increase. The terms and condition will become stringent. Risk management may provide significant business opportunity.
Tourism and Lifestyle	Higher temperatures in hot places could attract more visitors to the places where temperature is low for frequent breaks or holidays. Open and green spaces will be utilized more intensively. Outdoor dining, living, and entertainment will become more popular.

The IPCC TAR (IPCC, 2001) suggested that vulnerability or potential damage in the urban areas depends on three main factors: (1) Location of the city (cities near sea and river are at higher risk) (2) Size and population (densely populated and unplanned cities have higher risk). (3) Economic condition (Cities dependent on weather phenomena at most risk).

Mitigation Options

The engineering solution to tackle the impacts of climate change in urban areas can generally follow two paths: Mitigation and Adaptation. Mitigation strategies aim to reduce the emission of greenhouse gases and enhance natural process or invent artificial process to capture and remove greenhouse gases from the atmosphere (Hunt, J., 2004). Whereas adaptation solutions aim at taking action to minimize the harmful effects of the climate change before and as soon as they happen (Walsh et al., 2011). Both adaptation and mitigation solutions seek to reduce or avoid the potential damage caused by the climate change. Mitigation is long term solution on global scale whereas adaptations are local scale immediate solutions. The various mitigation options available to the different sectors relevant to the urban environment are discussed below.

Transport Sector

Worldwide 23% of greenhouse gas (GHG) emission from fossil fuel combustion comes from the transport sector (Bertaud et al., 2009). The share of transport sector in GHG emission for the developing countries like India is much less but it is increasing rapidly due to ever-increasing standard of life style. Two fundamental approaches to mitigation in the transport sector is either to reduce the personal automobile use by encouraging the use of cycling, walking and public electric transport or to use the low GHG emission vehicle (battery or solar operated for example). The government policy should be framed to promote both of the options. This can be achieved by providing necessary infrastructure within the city o ride the cycle or slow moving electric cars or two-wheelers or offering financial incentives to use the energy efficient transport system. The city and transport system should be designed such a way that the necessity of travelling of the inhabitants is reduced. The public transport system should be developed and cheaper and efficient and fashionable so that young generation is attracted to use public mode of transportation instead of private transport. Another policy option may be Introduction of toll taxes, HOV lanes and increasing parking fees to discourage the use of private vehicles.

Built Environment

The built environment within an urban environment consists of all the public (e.g. schools, hospitals, government offices etc), industrial/ commercial (e.g. factories, offices), and domestic buildings which are the major consumer of electricity and heating fuels. The maintenance and operation of the built environments accounts for the 40% of GHG emissions (Satterthwaite D., 2008). The energy requirement within a built environment depends on the interactions among design and material used to built the building, the way water and energy is supplied to the building and the use and maintenance of the building. The various approaches to reduce the GHG emissions from the building sector are as follows: 1) for construction, energy-efficient materials and process should be used, 2) Water and energy efficient design principles, such as passive cooling and heating is to be employed, 3) for small domestic requirements, use of solar energy through photovoltaic, solar space and water heating is followed, 4) by adopting different energy demand reducing measures such as: increasing the level of insulation by retrofitting industrial, commercial and residential buildings, installing energy efficient appliances, designing windows, and minimization of air leakage.

Energy Sector

The energy sector has a wide range of mitigation options to reduce the emission of GHG. The best option is to develop electricity from eco friendly renewable sources including wind, tides, waves, solar radiation, geothermal and bio-energy or less energy intensive sources such as gas and nuclear power. Another option is to increase the efficiency of supply and distribution of energy and to promote highly efficient large scale cooling and heating systems that directly serve a group of buildings by a network of piping. Also design of energy efficient electrical equipment should be encouraged.

Industrial Sector

The different mitigation options include control of emission of CO2 and other GHGs, more efficient use of electrical equipment, material substitution and recycling, recovery of heat and power, introduction of performance standards, subsidies and tax credits for low carbon technologies.

Municipality Services Sector

The municipality authorities are responsible for managing supply of drinking and general use water, collecting solid and liquid waste and maintaining urban green spaces and lakes. The municipal authorities should use the resources by following the “3Rs” (Reduce, Reuse and Recycle) (Wilbanks et al, 2005) to reduce wastage and saving of energy. Methane can be captured from the dumped waste in a well planned manner which will improve the local air quality. Urban green and blue space should be increased to protect biodiversity, lowering air pollution and temperature, and reducing energy demand and chance of flash flooding and improved ground water recharge.

Direct Carbon Capturing and Sequestration

The carbon capturing and sequestration process involves direct removal of green house gases from the atmosphere. It lowers the concentration of greenhouse gases already present in the atmosphere. It is achieved either through enhancing natural carbon sinks and developing new natural or artificial carbon sinks or through the direct capture and storage of GHGs by different engineering and chemical methods.

Adaptation Options

For the benefits of mitigations options to be felt, some time is requires due to the long residence time of the greenhouse gases. Now the effects of the greenhouse gases already trapped in the atmosphere will be felt within very short time span in future. Hence, adaptation measures are the solutions available to the urban authorities to combat the climate change effects over the next few decades before the positive effects of mitigation actions starts to show up (Wilby, R. L., 2007). The process of development of adaptation policies for an particular urban area is an intricate and challenging task as many stakeholders are to be involved in the decision making process to work independently as well as collaboratively. The selection process of appropriate adaptation strategies should be collaborative, multi-disciplinary and forward-thinking (Matthews, 2011). As suggested by Burton et al (2002, p. 157), An effective climate adaptation strategy cannot be taken on a ‘stand alone’ basis but must instead be integrated and incorporated into other policies. The availability of necessary resources, the available information and knowledge base to guide action in the practical field, the quality the governance systems and urban planning, the condition of the already existing infrastructure, and the available financial and technological resources generally determines the choosing of the appropriate adaptation policies. The Adaptation practices can be classified in many ways (Lancao, 2008). First are proactive and reactive adaptation measures, proactive measures aims at forecasting the imminence of the disaster and warning the likely affected people to reduce the damage and loss, while reactive adaptation measures aim at speedy and early recovery from the disaster already happened by means of giving relief. Secondly, adaptation actions can be either autonomous or at individual level (e.g., reductions in use of water by self motivated individuals) or policy driven taken at international, national or local government. The various adaptation policies and action that can be taken in an urban environment is listed in the Table-3 (World Bank, 2010).

Table-3: Adaptation Opportunities in Urban Area by Different Sectors

Sector	Adaptation Options	Underlying Policy Framework	Constraints (-) or Opportunities (+) for Implementation
Water	Water conservation and storage measures such as rainwater harvesting at local and community scale. Increase of water use and irrigation efficiency. Recycling of water. Desalination and other purification techniques.	Hazard management, Integrated water resources planning and management. Water policy framework at national and state specific level.	(-) Human, financial, physical and resources barriers (+) Integrated water resources management and planning consulting with other sectors.
Infrastructure	Construction of seawalls and storm surge barriers. Relocation plans. Town planning in a climate resilient manner. Acquisition of land and Wetlands creation to act as a buffer against flooding and rise of sea-level.	Upgrading land use policies. Formulating new standards and regulations to integrate effects of climate change into Building and Design codes. Providing insurance against loss.	(-) Technological and financial barriers (+) Integrated policies and managements keeping an eye on sustainable development goals, availability of space for reallocation.
Health	Improvement in control and surveillance of climate sensitive disease. Action plans to reduce heath damage due to heat stress. Emergency medical services. Improved sanitation and safe water.	International and regional cooperation. Formulating Public health policies to consider climate effects. Improved health services.	(-) Human tolerance limit (-) Limitations of knowledge (-) Financial capacity (+) Health services will be upgraded. (+) Quality of life will be improved
Transport	Planning and design of rail, roads and other mode of transport considering the increased air temperature. Relocation/realignment. Planting of trees and beautification of public transport.	Encouraging new research and innovation through government policies and Integration of climate change considerations into the national transport policy.	(-)Technological and financial barriers (-) Accessibility of less vulnerable routes (+) Improvement of existing technologies (+) Integration with other important sectors (e.g., energy)
Energy	Use of renewable sources of energy. Reducing the demand of energy. Increasing the efficiency of distribution and use of energy. Energy conservation. Strengthening of distribution and transmission infrastructure. Reducing dependence on single energy source.	Formulation of national energy policies and regulations. Providing various financial incentives like cheap loan to promote utilization of alternative energy sources. Incorporation of climate change factors in existing design standards	(+) Knowledge of feasible alternatives (-) Technological and financial barriers (-) Skepticism and inertia about new technologies (+) Encouraging of new technologies (+) Utilization of local resources
Tourism	Modernization of tourist places. Identification of potential nature of attraction. Diversification of tourism revenues. Artificial ice making or shifting to higher altitudes.	Financial subsidies and tax credits to attract tourists. Integrated planning with other sectors. Using media for advertisement.	(+) Marketing of new attractions (-) Logistical and financial challenges (-) Possible negative impacts on other sectors (+) Increase in earnings by creating new attractions and (+) Participation of larger group of people.

Conclusion

Worldwide, climate change and rapid population growth is posing a significant challenge for urban environment. The adverse effect will be felt by the urban inhabitants in near future. If, urgent action at international, national and municipal level is not taken, most of the urban conglomerate will face unprecedented problems and most of cities be abandoned and become extinct like so many cities of the past (Babylon, Harappa etc). To avert that type of emergency situation, long term planning and preparation is required. Hence, in this short concise review paper, the total issue of cause of climate change, its effects on urban environment and various mitigation and adaptation options have been discussed to motivate the concerned people for further study and take this challenging area as a future profession and research area. Mitigation actions are not sufficient alone as the positive effect of mitigation options takes longer time to show up. Hence, adaptation will almost certainly be necessary in order to cope with these effects. Gaining knowledge about climate change effects and preparing and attempting to control climate change impacts by proper planning of various mitigation and adaptation options are becoming an important challenge for the 21st century and beyond.

References

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Editor: Kunal Konar, Consultant (Business Development & Analytic Hydrology)