Modeling the structural consequences of climate change in the city of Ahvaz using the System Dynamic model

Climate change is the greatest threat to humanity, because it is the main factor in increasing the frequency and severity of atmospheric events such as droughts, floods, heat waves, etc. that are experienced today. Climate change can cause a wide range of environmental problems, including severe drought and water scarcity, crop loss, and increased socioeconomic consequences. One way to identify climate change is to evaluate climate and temperature indicators. Based on statistical tests and time series of occurrence of these parameters in the long run, the status of change and its trend can be identified. Given the importance of the impact of climate change on all sectors, the study of the consequences of these changes requires the study of all sectors and effective factors with a systemic approach. One of the concerns of human society is the changes that have caused climate change due to global warming. In this regard, given the importance of climate change on all sectors, the study of the consequences of these changes requires the study of all sectors and factors with a systemic approach. Considering the importance of climate change and its effects, this study seeks to answer the following questions by considering important climatic parameters and vulnerable urban dimensions (economic, social, political, environmental):1- The trend of climate change changes (Temperature and rainfall, humidity, wind speed) what is it like in Ahvaz?2- What is the causal relationship between the causes of climate change and vulnerable sectors in the city of Ahvaz? 3- What are the effects and consequences of climate change on the city of Ahvaz?

The research methodology is based on statistical tests and qualitative modeling with a systemic approach. The present study analyzes the trend of changes in climatic parameters including temperature, precipitation, relative humidity, and wind speed for a period of 30 years (1991-2020) in Ahvaz using the statistical Mann-Kendall Test was examined. Then, using the science of system dynamics, the causal relationships between variables and structural modeling of the consequences of climate change in Vensim software are investigated. The main stage of using the system dynamics approach is to try to understand and identify the feedback loops of the system under study, for which purpose diagrams of causal loops are drawn. In this study, inputs are the factors that shape climate change are factors that affect the city system. System outputs will be the consequences of climate change.

Based on the results of the analysis of the trend of climatic parameters, the city of Ahvaz in the study period has faced an increase in temperature, increase in relative humidity, decrease in wind speed, and decrease in rainfall. During the 30-year trend (1991-2020), the average rainfall has been (226) mm, each year (1.32) mm, has decreased and followed a downward trend. The average temperature has been (25.38) degrees Celsius, it has increased every year (by 0.051) degrees, which shows an increasing trend over 30 years. Based on the results, the average relative humidity was (41.1), which increased every year (0.007). Also, according to the results, the average wind speed is (2.65 m/s) and has decreased by about (0.018) every year. Therefore, the wind speed shows a decreasing trend over 30 years. Given that climate change refers to the spatial-temporal changes in the long-term average of climatic elements, the results of this study clearly showed that climatic parameters (temperature, relative humidity, precipitation, wind speed) in the study area have undergone fundamental changes. The consequences of climate change on all economic, social, political, and environmental aspects were evaluated. The results of qualitative modeling and causal relationship showed that climate change in Ahwaz has a direct impact on different sectors of water resources, agricultural production, and energy consumption. Variables of (reduction of water reserves upstream, extreme heat waves) are the most important leverage points of the model. Different outcomes have complex interactions with each other in such a way that they affect different economic, social, environmental, and political dimensions and ultimately intensify each other's effects on reducing the quality of life and increasing climate migration.

As a result, climate change has consequences such as increasing unemployment, reducing the quality of life, reducing urban resilience, and ultimately increasing climate migration in the city of Ahvaz, and the urban environment is not equipped to adapt to climate change.