Global warming


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Global warming

  2. 2. 1.0 INTRODUCTION Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner. Globally, sea levels rose four to ten inches in the last century. Researchers expect sea levels to continue rising. Climate change can increase or decrease rainfall, influence agricultural crop yields, affect human health, cause changes to forests and other ecosystems, or even impact our energy supply. Climate-related impacts are occurring across regions of the country and across many sectors of our economy. Many state and local governments are already preparing for the impacts of climate change through "adaptation," which is planning for the changes that are expected to occur. A continuous flow of energy from the sun heats the Earth. Naturally occurring gases in the atmosphere, known as greenhouse gases. The gases is includes carbon dioxide (CO2) then trap this heat like a blanket, keeping the Earth at an average of 15 degrees Celsius to warm enough to sustain life. The overuse of fossil fuels is increasing CO2 in the atmosphere, trapping more and more heat and warming the Earth. 2.0 PROBLEM THAT OCCUR IN THE CITY The city administrator has noticed that the mean sea level has been rising for the past 50 years. The raising is small but over a long period of time it may cause problems in the city centre as the level of that part of the city is quite low. Our weather is always changing and now scientists are discovering that our climate does not stay the same either. Climate, the average weather over a period of many years, differs in regions of the world that receive different amounts of sunlight and have different geographic factors, such as proximity to oceans and altitude. The causes of climate change can be divided into two categories that are due to natural causes and those that are created by man. a. Natural cause
  3. 3. There are a number of natural factors responsible for climate change. Some of the more prominent ones are continental drift, volcanoes, ocean currents, the earth's tilt, and comets and meteorites. One of the detail causes are volcanoes. When a volcano erupts it throws out large volumes of sulphur dioxide (SO2), water vapor, dust, and ash into the atmosphere. Although the volcanic activity may last only a few days, yet the large volumes of gases and ash can influence climatic patterns for years. Millions of tonnes of sulphur dioxide gas can reach the upper levels of the atmosphere (called the stratosphere) from a major eruption. The gases and dust particles partially block the incoming rays of the sun, leading to cooling. Sulphur dioxide combines with water to form tiny droplets of sulphuric acid. These droplets are so small that many of them can stay aloft for several years. They are efficient reflectors of sunlight, and screen the ground from some of the energy that it would ordinarily receive from the sun. Winds in the upper levels of the atmosphere, called the stratosphere, carry the aerosols rapidly around the globe in either an easterly or westerly direction. Movement of aerosols north and south is always much slower. This should give you some idea of the ways by which cooling can be brought about for a few years after a major volcanic eruption b. Human cause The overwhelming body of scientific evidence demonstrates unequivocally that the earth is warming. Climate change is happening, it is caused in large part by human activity, its impacts are beginning to be experienced and these damaging effects will only increase in the decades ahead. Green house gas emissions come from cars, power plants, and other human activities rather than natural variations in climate that are the primary cause of contemporary global warming. Due largely to the combustion of fossil fuels, atmospheric concentrations of carbon dioxide (CO2), the principal human-produced greenhouse gas, are at a level unequaled for at least 800,000 years. The greenhouse gases (GHGs) from human activities are trapping more of the sun‟s heat in the earth‟s atmosphere, resulting in warming. Carbon dioxide and other GHGs always have been present in the atmosphere, keeping the earth hospitable to life by trapping heat and warming our atmosphere. Yet, since the industrial revolution, emissions of these gases from human activity have
  4. 4. increased steadily, trapping more heat and amplifying the greenhouse effect. Since pre- industrial times, atmospheric CO2 concentrations have increased by 40 percent, and concentrations of other GHGs have grown significantly as well. As a result, global average temperatures have risen both on land and in the oceans, with observable impacts already occurring that presage increasingly severe changes in the future. Polar ice is melt- ing at record rates. The pressure for new housing and current policies that prioritise the regeneration of brown field land, much of which is already at risk of flooding, may well mean more new development within the floodplain. Increasing urbanisation and higher densities of development have reduced the amount of natural soak-away available and strained existing drainage infrastructure. People and properties that are not within currently recognized and defined floodplains are increasingly at risk of flooding, usually from surface water. The sources of flooding: 1. Tidal Flooding Both sea and river defences may be overtopped or breached by a combination of low pressure weather systems and peak high tides. Storms with high wind speeds cause tall and powerful waves and low pressure fronts cause sea levels to rise above normal levels. High tide levels vary through the lunar and solar cycle and when superimposed upon other tidal variations exceptionally high tides result. 2. Fluvial Flooding Flooding occurs in the floodplains of rivers when the capacity of water courses ismexceeded as a result of rainfall or snow and ice melts within catchment areas further upstream. Blockages of water courses and flood channels or tide locking may also lead to ponding and rising water levels. River defences may then be overtopped due to increased water levels, or breached by large objects. 3. Ground Water
  5. 5. Low lying areas sitting over aquifers may periodically flood as ground water levels rise. This type of flooding is often seasonal and therefore can be forecasted with good accuracy. It is often slow in its onset. 4. Pluvial Flooding Surface water flooding is caused by rainwater run-off from urban and rural land with low absorbency. Increased intensity of development in urban areas has given rise to land with a larger proportion of non-permeable surfaces, a problem often exacerbated by overloaded and out-dated drainage infrastructure. These circumstances, combined with intense rainfall, can give rise to localised flooding. This sort of flooding often occurs outside of recognised floodplains and because it is caused by quite localised weather conditions it is very difficult to forecast. Its onset can also be very rapid, and the level of flooding very severe. 5. Flooding from Sewers Flooding from sewers can occur where there are combined storm and foul sewers and their capacity is exceeded due to large amounts of surface water run-off in a short time. Poor cleaning and maintenance can lead to blockages that can also cause local flooding. This type of flooding is hard to predict, has significant sanitary consequences for those affected, and can occur very rapidly. 6. Flooding from Man-made Infrastructure Canals, reservoirs and other man-made structures can fail causing flooding to areas downstream. Industrial activities, water mains and pumping stations can also give rise to flooding due to failure. 3.0 IMPACT OF THE CLIMATE CHANGE EFFECT THE SEA LEVEL While there are obviously many challenges to projecting future sea level rise, even a seemingly small increase in sea level can have a dramatic impact on many coastal environments. Climate change will affect the coastal environments through sea-level rise and its associated impacts, including more frequent storms and flooding, higher rates of beach erosion, submergence of coastal wetlands, and saltwater intrusion. These stressors will put some coastal developments at increasing risk of damage.
  6. 6. Coastal climate change effects include: a. Coastal community flooding Melting glaciers, ice fields and polar ice caps, plus warming ocean waters all contribute to rising sea levels. Climate change is predicted to bring stronger storms with heavier precipitation and higher wave conditions. This will increase the frequency and extent of flooding. b. Coastal erosion and landslides Climate change is predicted to increase storm intensities and wave height in the Pacific Ocean. More frequent, intense storms combined with higher overall sea levels will result in higher coastal erosion rates and more storm damage. Coastal communities will face increased property damage to infrastructure (such as roads and water treatment systems). c. Seawater well intrusion A higher sea level means saltwater may penetrate wells in low-lying communities. This will reduce the availability of freshwater for coastal communities. Islands pose unique challenges for ground water management. Island County‟s ground water aquifers are recharged only by rainfall. Some aquifers (such as those at or below sea level near shorelines) are connected to saltwater. Portions of these aquifers may contain saltwater. Seawater intrusion, the movement of marine saltwater into freshwater aquifers, could become a serious problem. d. Lost wetlands and estuaries. Wetlands often occur in low-lying areas and rising sea levels may convert these valuable habitats to deep water. Wetlands and estuaries: Protect against flooding by absorbing excess water Filter out pollutants Stabilize shorelines, and
  7. 7. Provide important habitat for wildlife such as salmon and waterfowl (in freshwater wetlands) or shrimp, crabs, salmon, terns and herons (in salt water estuaries). e. Beach erosion Beaches are continually changing as sand is shifted by waves, tides, and currents. Sea- level rise and land subsidence contribute to beach erosion and the narrowing or movement of barrier islands. With climate change, rates of beach erosion would double or triple by the 2020s, increasing three to six times by the 2050s, and four to ten times by the 2080s, relative to the first decade of the twenty-first century. Climate models project an increase in storms, which would further contribute to beach erosion. To compensate for losses from erosion, additional sand would have to be placed on the beaches. Sand replacement, also called beach nourishment, may remain a viable option through mid-century, but could become significantly more costly, particularly for the high-end warming scenarios, by the end of the century. The effects of flooding: The effects of flooding from the sources outlined above are felt by various „receptors‟. These include, people, buildings, infrastructure, agriculture, open recreational space and the natural world. In extreme cases flooding may cause a loss of life. However, the social and emotional costs from flooding can also be significant and are often widespread and indiscriminate in flooded areas. These costs include: displacement from homes, the loss of personal valuables and the ongoing fear and insecurity caused by the experience. Potable water supplies may be lost or contaminated in a flood and this can have immediate health effects upon people and animals. The built environment may be damaged or destroyed as a result of flooding with high repair costs and long periods required for reinstatement. The public realm is often badly affected through damage and the deposit of potentially large quantities of debris. Land contamination may also be transported and spread during flooding.
  8. 8. Vital infrastructure may also be damaged or disrupted. Electricity and gas supplies can be interrupted to individual properties but also to wider communities if sub stations and transformers themselves are flooded. Road links, railways, canals etc. may be blocked causing disruption to the wider transport network, and accessibility severely disrupted for local inhabitants, especially amongst those considered most vulnerable. 4.0 MITIGATION OF THE PROBLEM Flood generation Woodland offers a number of potential opportunities. Research indicates that those provided by the higher water use by trees and improved infiltration are largely restricted to the hillslope or small catchment scale. There appears to be considerable scope for using woodland to reduce flood risk across a range of scales, although success depends on better integration with other land uses as part of a whole catchment approach to sustainable flood management. 1. Increased evaporation and reduced run-off. Reduced net rainfall under woodland due to interception loss. Reduced transpiration loss from forest but depends on soil available water. Interception loss declines with rainfall intensity. 2. Increased soil infiltration Soil infiltration rate high under well managed woodland due to good soil structure and rooting, reducing direct water runoff. 3. Flow resistance Tress, undergrowth and woody debris increase the hydraulic “roughness” of the floodplain, slowing down the passage of flood flows. Trees and woody debris direct or concentration flows, forming multiple channels and backwater pools, enhancing flood storage. Net effect is to delay and reduce the size of flood peak. 5.0 PLAN ACTION TO REDUCE FLOODING
  9. 9. Classified floods according to three categories that is flash flooding, riverine flooding and sea level rise or storm surge. One mechanism by which increases in the costs of disasters is likely to occur relates to the „sea change‟ phenomenon. Action for future generation: 1. State disaster planning legislation and policy need to be harmonious with state coastal legislation and policy concerning flood disaster events and anticipated sea level rise levels to avoid confusion for individuals, developers, councils and the legal system. 2. A mechanism should be initiated in local government development assessment processes, either at the planning scheme or council decision making end, so that the total land infill impacts are factored into the consideration of the approval of new developments, particularly estates, in flood prone areas. 3. Use a cost-benefit analysis or other economic model to account for the greater costs incurred to the council and subsequently rate paying residents from any disaster impacts on proposed developments. 4. Ensure that new developments incorporate adequate measures so that they are built off the ground but allow for water passage on ground levels. 5. Include a gradient overlay in the local government planning scheme. 6. Undertake research detailing the comprehensive costs from road outages due to flooding including validating historic figures and future estimates, so that future flood mitigation and road maintenance business cases can be presented to decision makers in government at the state and federal levels. 7. Ensure that terminology is more specifically defined under the SPP 1/03 and ensure a greater focus on the intended outcomes of the recommended processes. Use scenarios in the rewriting of the SPP 1/03 to make it understandable to practitioners. 8. To design more resilient communities, create provisions that require flood damaged houses to be rebuilt above the 1/100 ARI flood line and building materials such as plastic cladding rather than timber cladding are used in houses located in floodplains. 9. Commence a campaign that assists individuals and businesses to consider the impacts of climate change into their own risk assessments of property location purchases to transition cost-sharing across individual, business and government sectors.
  10. 10. The Threat to Place-making and Good Design Standard responses to the risk of flooding include flood defenses, barriers to flood pathways and raising accommodation above the potential water level onto columns or stilts. These measures are often not well integrated with the overall architecture and landscape design, resulting in poor quality and badly functioning neighborhoods and streetscapes. Flood barriers limit opportunities for linkage as they are often both physically and visually isolating which can result in poor quality public and private spaces. Also, developments characterized by empty undercrofts or dominated by car parking at ground level tend to lack identity and a sense of neighborhood. 6.0 ADAPTATION TO CLIMATE CHANGES The process of adaptation planning identifies a set of actions to decrease a system's vulnerability, or increase its resilience, to the impacts of climate change. The main tool of adaptation planning is the vulnerability assessment: an evaluation of a system's risk compared to its adaptive capacity or ability to cope with climate change. Vulnerability assessments reveal where and which actions are needed to improve resilience to risk factors. They can be geographic or systemic in nature. For example, a vulnerability assessment for a city could include mapping future sea-level rise and areas at risk of urban heat-island effects alongside demographic information to reveal which populations may be most exposed to flooding or extreme heat. A vulnerability assessment for a wastewater system might model the system's performance under a range of predicted future storm intensities and sea levels to see whether infrastructure needs to be protected or moved and where urban flooding is most likely to occur. Vulnerability assessments can be used to set priorities for early-, medium-, and long-term actions, and to develop "trigger points" for decision making in the future. Adaptation strategies should be implemented according to future conditions, regular assessment, and recalibration. This process, called adaptive management, is necessary because there is great uncertainty about how fast the climate is changing and when the predicted effects may occur. Natural-resource managers have long used adaptive management to plan for uncertainty in the environment. It is an iterative process in which managers and scientists work together to consider
  11. 11. management strategies, predict their outcomes, implement actions, monitor conditions, and adjust future actions accordingly. In the near term, some adaptation strategies have benefits that can be realized today, and may be things we are already working on to achieve other policy goals. Two examples of these "no- regrets" adaptation strategies include energy efficiency and water conservation, both activities that are valuable today and may be even more valuable in the event of future climate change. In a way, agencies and utilities working in these areas are doing climate adaptation planning already. But the severity and trajectory of climate change will require a thorough examination of goals, targets, and programs in these areas to ensure that they are effective in the future under changed conditions. Physical strategies for sea-level rise There is a continuum of strategies we can use to manage changing sea levels, ranging from armoring the shoreline — keeping the sea out — to abandoning low-lying development altogether. Among them: barrier(s) or tidal barrage(s) to manage tidal flows in and out of THE Bay (at the Golden Gate or in smaller, strategic parts of the bay) coastal armoring with linear protection, such as levees and seawalls, to fix the shoreline in its current place elevated development in which the height of land or existing development is raised and protected with coastal armoring floating development on the surface of the water, or that which may be floated occasionally during a flood, making it largely invulnerable to changing tides floodable development designed to withstand flooding or to retain stormwater living shorelines with wetlands that absorb floods, slow erosion, and provide habitat managed retreat that safely removes settlement from encroaching shorelines, allowing the water to advance unimpeded, and bans new development in areas likely to be inundated Governance of sea-level rise Many public agencies have responsibility for managing the challenges of climate change. Water supply and wastewater agencies will have to deal with changes in flow, facilities at risk, and
  12. 12. saltwater intrusion into intake systems. Airports and ports will have to deal with shoreline infrastructure that is not at the right height. Transit and transportation agencies will have to deal with roads, railways, and subways that are vulnerable to flooding. Parks, planning, and redevelopment agencies will have to figure out how to deal with floodwater in residential neighborhoods, especially in those neighborhoods that are least prepared to cope with new risks. Managing infrastructure Infrastructure — the physical fabric of functioning cities — is at risk from climate-change hazards, especially sea-level rise. Roads, mass transit, airports, bridges, ports, energy generation and distribution facilities, sewer systems, and water systems suffer already from underinvestment, making certain assets even more at risk of weather and climate-related events. In the Bay Area, shoreline infrastructure is among the most vulnerable, where it is in the path of sea-level rise and storm surges. Yet the shoreline is also where some of our most significant public assets, including our airports, major highways, railroads, and wastewater treatment facilities, are located. Transportation. Climate change will affect transportation systems at all levels, including planning, design, construction, operation, and maintenance. Potential economic impacts of climate change on transportation include: lost worker productivity from delays; impeded and more expensive movement of goods through ports, airports, and rail systems; and increased costs of repairs and maintenance of transportation systems. Climate change could also impair the safety of travel. Several factors contribute to the susceptibility of transportation infrastructure to climate change impacts, including age, condition, proximity to other infrastructure elements, and current level of service. CONCLUSION Climate change adaptation will need to be dealt with at all levels of government. Yet it is at the local and regional levels where vulnerability can best be understood and addressed. Although there is some uncertainty around when we will experience various climate changes, planners can today anticipate their trajectories and begin thinking ahead about how to prevent catastrophic impacts.