Modelling the Earth's Climate System

Introduction

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.

Methodology

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)

Figure 1. A model of the Earth's climate system on Insight Maker

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)

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)

Critical Analysis

Figure 2.1. A graph to show the energy stored in the reservoirs when CO2 emissions are constant

Figure 2.2. A graph to show the energy stored in the reservoirs when CO2 emissions are increasing annually by 0.6%

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.

Discussion

Figure 3. A graph to show the energy stored in the reservoirs when production of cement is reduced

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.

References

Ahlonsou, E., Ding, Y. and Schimel, D. (n.d.). The Climate System: an Overview. [ebook] Available at: https://www.ipcc.ch/site/assets/uploads/2018/03/TAR-01.pdf [Accessed 22 Nov. 2019].

Bice, D. (2019). climate modeling 1. [online] Personal.ems.psu.edu. Available at: https://personal.ems.psu.edu/~dmb53/DaveSTELLA/climate/climate_modeling_1.htm#1 [Accessed 22 Nov. 2019].

Ces.fau.edu. (2019). Climate Science Investigations South Florida - Temperature Over Time. [online] Available at: http://www.ces.fau.edu/nasa/module-3/why-does-temperature-vary/angle-ofthe-sun.php [Accessed 22 Nov. 2019].

Coakley, J. (2003). REFLECTANCE AND ALBEDO, SURFACE. [ebook] Oregon: Elsevier Science Ltd, p.1. Available at: http://curry.eas.gatech.edu/Courses/6140/ency/Chapter9/Ency_Atmos/Reflectance_Albedo_Surface .pdf [Accessed 22 Nov. 2019].

Grant, M. and Kenton, W. (2019). Understanding Sustainability. [online] Investopedia. Available at: https://www.investopedia.com/terms/s/sustainability.asp [Accessed 22 Nov. 2019].

Group, A. (2019). Reducing carbon footprint: Aether-cement. [online] Aether-cement.eu. Available at: http://www.aether-cement.eu/reducing-the-carbon-footprint-of-cement.html [Accessed 22 Nov. 2019].

Rodgers, L. (2019). The massive CO2 emitter you may not know about. [online] BBC News. Available at: https://www.bbc.co.uk/news/science-environment-46455844 [Accessed 22 Nov. 2019].

Roy, C., Gies, P. and Elliott, G. (1990). Ozone depletion. [ebook] London, p.1. Available at: https://search.proquest.com/docview/2233938197/fulltextPDF/BDBF043552884133PQ/1?accounti d=13828 [Accessed 22 Nov. 2019].

Stein, T. (2019). Rising emissions drive greenhouse gas index increase - Welcome to NOAA Research. [online] Research.noaa.gov. Available at: https://research.noaa.gov/article/ArtMID/587/ArticleID/2455/RISING-EMISSIONS-DRIVEGREENHOUSE-GAS-INDEX-INCREASER [Accessed 22 Nov. 2019].