本文是留学生入学coursework代写范例，题目是“Modelling the Earth's Climate System（模拟地球气候系统）”，一个关于地球气候系统能量流动和储存的模型被创建来探索如何实现可持续性。“可持续性是指在不损害后代满足自身需求的前提下满足当前需求的能力。”它允许气候系统维持生态平衡，从而避免了自然资源的枯竭。(Grant and Kenton 2019，第1段)通过使用系统模型，可以对地球气候的未来预测，关于二氧化碳排放和温度变化。作为防止气候变化的一种需要，可以设计出一种解决方案来减少影响最大的变量。
A model of the energy flows and storage of the Earth's climate system was created to explore how sustainability is achieved. "Sustainability is the ability to meet present needs without compromising the ability of future generations to meet their own needs." It allows the climate system to maintain an ecological balance, so depletion of natural resources are avoided. (Grant and Kenton 2019, para.1) By using systems models future predictions of the Earth's climate, regarding CO2 emissions and temperature changes, can be made. As a need to prevent climate change, a solution can be engineered to reduce the variable which has the largest effect.
The model shown in Figure.1 was created using Insight maker, which models energy reservoirs as stocks and energy transfers as flows. The rate of energy flow is measured in units, in which 100 units of energy represents 5.56 x 1024 J/Year. (Bice no date, model of climate system, para.3)
图1所示的模型是使用Insight maker创建的，它将储层建模为库存，将能量转移建模为流动。能量流动率是以单位来计量的，其中100个能量单位代表5.56 x 1024 J/年。(Bice no date，气候系统模式，第3段)
The model takes into account different variables, which can be changed and simulated to show their effects on the Earth's climate system. Variables which emit CO2 have an impact on the rate of change of greenhouse effect. Currently the CO2 emission is 414.7 ppm (parts per million), and is estimated to increase by 2.5 ppm. (Stein 2019, para 9) This results in a 0.6% Yearly increase of CO2 emissions, therefore the rate of change of greenhouse effect is set at a constant of 1.006. Surface albedo is the fraction of incident radiation that the surface reflects. A lower albedo means the surface will absorb more radiation. (Coackley 2003, p. 1)
该模型考虑了不同的变量，这些变量可以被改变和模拟，以显示它们对地球气候系统的影响。排放二氧化碳的变量对温室效应的变化速率有影响。目前二氧化碳的排放量为百万分之414.7，估计还会增加百万分之2.5。(Stein 2019，第9段)这导致二氧化碳排放每年增加0.6%，因此温室效应的变化速率被设定为1.006的常数。地表反照率是地表反射入射辐射的比例。反照率低意味着地表会吸收更多的辐射。(Coackley, 2003，第1页)
Furthermore, ozone depletion is another variable to consider. A constant build up of chlorofluorocarbons will reduces the ozone concentration and this results in an increase of UV rays reaching the Earth surface, which will cause heating in the atmosphere and the surface. (Roy, Gies, Elliot 1990, ozone depletion, p.235)
Initially the simulation shows that radiative equilibrium is sustained. Figure 2.1 shows that the graph consists of two parallel lines which suggests that there is no net energy transfer between the reservoirs. This is the ideal condition of the climate system as CO2 emission rates are constant and sustainability is obtained.
However this isn't realistic as CO2 levels are unlikely to be constant over time, due to a growing population, so the rate of change of greenhouse gases is adjusted to have a yearly increase of 0.6%. Figure 2.2 portrays that the surface energy will exponentially increase, whilst the energy in the atmosphere will exponentially decrease. The exponential pattern shown is caused by positive feedback, in which the greater the CO2 concentration, the greater the accumulation of water vapour and more heat is radiated back to the surface. (Coackley 2003, p. 1) A temperature rise could lead to the melting of glaciers which results in a rise in sea level. This will also have an effect on climate, such as an increase in rainfall or faster wind speeds. Because there is a higher rate of energy flow from the atmosphere to the surface, the energy stored in the atmosphere appears to be depleting over time.
The model has assumed that sunlight is equally distributed across the Earth. However in reality the amount of radiation varies at different latitudes. The equatorial region receives a higher concentration, whereas polar regions receives less. (Ces.fau.edu 2019) So the pattern in figure 2.2 is not evident in some parts of the world.
"The atmosphere is the most unstable and rapidly changing part of the system." (Ahlonsou, Ding and Schimel, n.d.) Therefore this model may not be accurate in the future, as the composition of the atmosphere is unlikely to be the same. Data on the model will have to be continuously updated in order for it to give a reliable representation of the Earth's climate system in the future.
A solution to reduce emissions of greenhouse gases could be to engineer a more sustainable and durable cement. During cement manufacture high temperatures are needed in order for chemical reactions to occur, so CO2 is released from the combustion of fossil fuels, which contributes to global warming. Cement production contributes 7% to global emissions; annual emissions will need to fall by 16% by 2030 in order to meet the Paris Agreement requirements on climate change. (Rodgers 2019) Using the cradle-to-cradle approach, in order to make a sustainable cement mixture, waste products need to be up-cycled. Steel Fibre Reinforced Concrete (SFRC) is a type of concrete in which waste, fly ash and slag, are used as cementitious replacements. This emits 70% less CO2 compared to current cements. (Group 2019)
With less CO2 being emitted the rate of change of greenhouse effect is reduced to 1.004. Also, more heat will be lost to space because less greenhouse gases are present, so the flow rate is increased to 8.4. Figure 3 shows that over one century the surface energy has decreased by 34%, which suggests there is a reduced global warming effect and a smaller change in temperature. However, global warming is still evident over time.
This is not an immediate solution as it is very unlikely that SFRC will replace all cements. Even though it is increasingly being used, its effect in reducing global warming will only be seen over a long period of time, at least 30 Years according to figure 3. In order to have a huge impact, other variables need to be changed simultaneously, such as using more renewable sources of energy and reducing the use of aerosols so there is more ozone in the atmosphere. But most importantly, the actions of humans and their behaviour to climate change is vital in reducing the effects of global warming to achieve a more sustainable future.