The simplified example discussed in this study demonstrates that the policy decisions to be made to reduce the adverse effects of climate change on public health of populations from a water quality perspective are not unique. Although eventually all populations will be affected to a certain degree, the degree of urgency and the rate of implementation of public policy decisions to reduce the adverse effects are not the same for all regions and populations of the world. This simple application demonstrates that point. Different regions of the world represented by different initial conditions on the phase diagram will determine the urgency and the relaxed nature of the policy decisions that needs to be implemented. The problem discussed here demonstrates that there are critical points in the system behavior which should be very carefully analyzed. These are identified as "tipping points" in the literature. These tipping points are not fixed and various tipping points may be observed at different times. It is important to recognize that the tipping points of different regions and different populations are also critical to the overall system behavior. In the problem discussed here it is demonstrated that these tipping points can be predicted and certain preventative measures can be implemented to avert the critical points avoiding an undesirable outcome for the population and the state of population in question. What is not modeled and thus could not be demonstrated in this problem, simply because the desire was to keep the analysis simple, is the effect of the failure of some populations on the rest of the system behavior. When this effect is considered we should recognize that although some regions and populations of the world may exhibit more resilient behavior to adverse effects of climate change, at the end the overall effect of the failure of certain populations may also reduce the resiliency condition of more stable parts of the world. This is identified as the "systemic risk." This feedback mechanism may produce a domino effect which may turn the behavior of the overall complex system into a chaotic behavior. In this case it can be said that sum of small failures, which may initially be considered to be unimportant in isolation, may lead to the failure of the overall system. That is, sum of the failure components of the system may become larger yielding a tipping point for the system as a whole. Thus systemic risk is a very important point to recognize and include in the overall analysis. The other important point that is observed from this analysis is that if the climate change is not controlled gradually from the current state the controls that will have to be implemented will be more drastic later on to keep the system within the desired stability domain. In that case the overall control will be achieved over a much longer period and at higher cost rather than implementing controls right away which will reduce the time period to achieve the a stable system at much reduced levels of cost.
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