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The Connector - Fall 2023 Issue

Inspiring Climate Change Action with Stella®

Cecilie Mauritzen

The world has been effectively ignoring climate change for decades. Since the 1950s, scientists have worried and warned about the buildup of human-produced carbon dioxide (CO2) in the atmosphere, its warming effect, and the devastating consequences of a rise in average global temperature. Despite those warnings, individuals and governments have been slow to react.

Now, with frequent, severe climate events topping the news, scientific warnings have become hard to ignore. The summer of 2023 was the hottest on record, including the four hottest days on record – June 3 through 6 For the past eight years, the Atlantic Ocean hurricane season has begun before its historic June 1 start date. Heavy rainfalls flooded cities and regions in North America, Europe, northern Africa, and southeast Asia, while droughts have crippled other areas on the same continents.

The World Health Organization (WHO) predicts that between 2030 and 2050, climate change will cause 250,000 deaths through drought, disease, and heat stress. Additional deaths will be attributed to flooding and wildfire. In addition, WHO warns that climate change will increase health costs by $2-4 billion by 2030.

“Now we can see that climate change is not just an abstract idea,” says Cecilie Mauritzen, Senior Scientist, Norwegian Meteorological Institute. “But everything people want to do – build, travel, ship things – is bad for the planet, our common good. I wanted to find new and novel ways to use models to gain traction and engagement for curbing climate change."

Mauritzen decided that the answer might be found with the use of a system dynamics model. “I did my PhD in oceanography at Massachusetts Institute of Technology in the 1990s and had seen the work that my peers at the Sloan School of Management were doing using Stella,” says Mauritzen. “It occurred to me that a system dynamics model, with its focus on interactions and feedback, might be a good counterpart to the more complex and process-oriented models typically used in climate change research. Simpler models are much more transparent and easier to understand. They can, for instance, be used to build up intuition and insights much faster than is possible with complex models.”

An oceanographer and natural scientist, Mauritzen appreciated system dynamics’ agnostic approach due to its ability to consider both physical and social science data. “Systems dynamics models are able to document what is happening throughout a complex system that includes both physical laws and empirical insights into human behavior,” says Mauritzen.

Mauritzen has been a lead author for two of the Assessment Reports of the United Nations Intergovernmental Panel on Climate (IPCC) and has seen firsthand the need for a common tool to join the research of all three working groups of the IPCC (Physical Sciences Basis and Impacts, Adaptation and Vulnerability, and Mitigation of Climate Change). With colleagues from the working group on physical science, she proposed the idea to a European project called “WorldTrans – Transparent Assessments for Real People.”

“The World Trans project is attempting to simplify the complex system in which the natural climate and human systems are changing together. It is investigating how physical scientific processes like CO2 accumulation and ocean warming and human systems including agriculture, housing, health care, business, and technological or economic solutions impact one another. We wanted the model to show the interaction between climate and human systems and identify leverage points where CO2 emission mitigation can make a difference,” says Mauritzen.

To create their model, the group needed an experienced system dynamicist. Mauritzen thought of Billy Schoenberg, Lead Software Engineer at isee systems and researcher and lecturer at University of Bergen. “I had read a paper he co-authored called Understanding model behavior using Loops that Matter,” says Mauritzen. “It talked about quantifying the strength of feedback loops over time to identify those that are most responsible for a modeled system’s behavior. When studying climate change, we talk about many feedback loops, the main one concerning CO2. CO2 emissions accumulate in the atmosphere, the atmosphere warms, the warm air causes water to evaporate, water vapor accumulates in the atmosphere increasing warming four times over. The idea of Loops that Matter™ was really appealing and I thought, ‘This is the guy we need.”

Schoenberg is now responsible for the construction, testing, and analysis of the World Trans project model, as well as its interactive learning environment, building a Stella model that will be used by every World Trans Project working group. He is being assisted by development teams that come from system dynamics and specific discipline areas, including energy, economics, land use, and climate.

Basic map of the World Trans Project’s FRIDA model Basic map of the World Trans Project’s FRIDA model that illustrates the interactions between scientific and human systems

Schoenberg and his team have already completed a preliminary version of the model, named FRIDA (short for Feedback-based knowledge Repository for Integrated Assessments, but in reality named after Mauritzen’s grandmother). In November 2023, Mauritzen will introduce FRIDA at the Integrated Assessment Modeling Consortium (IAMC) in Venice, Italy. When FRIDA v1.0 is ready next year, it will be introduced to scientific audiences through published papers.

Building the model is just part of the project’s effort. Considering how it will be used to inspire action is another essential area of work. The group is experimenting with ways to explain system complexity and evaluate and compare solutions. “Our target audiences are students of interdisciplinary climate science, climate policy makers and shakers, and finally, general EU citizens, including Citizen Assemblies.”

“The change that is needed to combat climate change isn’t happening fast enough,” says Mauritzen. “We can no longer avoid ‘dangerous climate change’ as defined by the U.N, but the faster we act, the less the consequences. We need to find novel ways to explain climate change to people who don’t yet understand and convince leaders to take action.”

Protecting the Apalachicola-Chattahoochee-Flint River Basin with Stella® and Stella® Architect

Steve Leitman

The Apalachicola-Chattahoochee-Flint River Basin (Apalachicola Basin or ACF) flows through Georgia and Alabama before crossing the Florida panhandle into the Gulf of Mexico. It’s a complex ecosystem that supplies water to over four million people in 736,000 acres, supporting commerce, recreation, and agriculture, and serving as a vital environmental resource.

Steve Leitman, PhD, environmental hydrologist, has made a career of addressing ACF Basin water management issues and ecological challenges using Stella. He has been working in the watershed for nearly 50 years and using Stella for over 30 of them.

Creating a water management model

Since three states share the Apalachicola Basin, it’s no wonder that it was the subject of the “Tri-state water dispute,” an intrastate debate that raged for decades. These states, each with their own priorities, needed to cooperatively develop management practices that would keep waterways navigable for commercial shipping and recreational boating without wasting drinking water or damaging the environment.

Rick Palmer from the University of Washington and Bill Werick from Army Corps of Engineers championed the development of a water management model using Stella as part of a basin-wide water resources study. Leitman was a member of the model development team that developed the first Stella model for the basin.

“The project was my introduction to Stella and I saw it as a really good tool for asking and answering questions,” says Leitman. “It was during that comprehensive study of the ACF and the process of model building that I started thinking about the importance of defining metrics to test the solutions. What indicates that a solution is ‘good’ or ‘better’? Defining metrics is more difficult than creating a model.”

“Stella helps with metric definition,” says Leitman. “First, it allows you to make changes as you learn about the system you’re modeling. Second, Stella has a much faster run time than other modeling and simulation programs so you can learn and make changes in less time. With a fast model, you can devote more time and energy to defining metrics.”

Portion of the Apalachicola Basin system model depicting water flow through management points Portion of the Apalachicola Basin system model depicting water flow through management points

Expanding the model’s ecological capabilities

More recently, Leitman has been working as an independent contractor with the U.S. Fish and Wildlife Service (FWS). “The FWS is charged with protecting endangered species,” says Leitman. “To address those concerns, ACF models have to include the impact of changes in water flow variables – frequency, timing, and magnitude – on ecological conditions.”

Currently, the FWS is concerned about the sturgeon and three types of mussels that live in the ACF. The reproductive cycle of the mussel illustrates why a model that includes ecological conditions throughout the entire Basin – the rivers and floodplains in the inland waterways and the bay in the intercoastal waterway – is essential to species protection.

“A male mussel can fertilize a female from 10 miles away,” says Leitman. “The female deposits her eggs in the gills of a fish where they begin to develop. They eventually drop into the water for final development and hatching. So, protecting the mussel population requires protecting the basin ecology for them and for the fish that support their reproduction.”

“Ecology is greatly impacted by extreme events like droughts or floods,” says Leitman. “The initial Stella model used monthly averages of basin inflow. The model was converted to a daily model by the Northwest Florida Water Management District and one of Rick Palmer’s graduate students for two reasons. First, it was important to capture extreme weather events. Second, it needed to support basin management decisions that are made on a daily, not monthly, basis. With a daily model, governmental and non-governmental environmental interests could model their own water management alternatives and share them with the Corps instead of only reacting to proposals brought forth by the Corps.”

In addition, the Corps model was using a 1939-2012 basin inflow data set to decide how to manage the watershed and update the Army Corps of Engineers Water Control Manual. The Corps’ Water Control Manual lists regulation schedules for water storage and releases from each reservoir in the Apalachicola River Basin. It also includes the policies and data protocols used to manage flood risk and drought conditions. “In using old data to update the Water Control Manual, the Corps was analyzing how the basin should have been managed in the past, not in the future,” says Leitman. “As the climatic extremes of the past year have shown us, stationarity – consistent conditions over time – is dead.”

Leitman has recently integrated synthetic hydrology data that describes extreme climate events beyond what has been experienced in the historic record. That data integration allows the model to determine the efficacy of the Water Control Manual with more extreme climatic conditions using the ACF Stella model.

“With daily data that included extreme climate events, we saw that it’s possible, for example, that Lake Lanier, Atlanta’s main water resource, could be drained,” says Leitman. “It’s important that we’re able to investigate and find solutions to those potential problems.”

The modeling continues

Leitman is now applying his decades of experience studying the Apalachicola River Basin and expertise in system dynamics modeling to a more specific ecosystem analysis. Working with the Apalachicola Bay Systems Initiative (ABSI), a Florida State University program, he’s building a Stella model that will help gain insight into the root causes of oyster reef deterioration in the bay. Leitman’s model is being used in conjunction with a 3D estuarine model and other ecological models to evaluate how to manage the river system in a way that will restore the reef and oyster population.

The Sixth Annual South African Chapter of System Dynamics Competition

The sixth annual South African Chapter of System Dynamics competition wrapped up with the second and third sessions during the summer. The second session focused on providing individual support for the participants to address their questions and struggles, enabling them to get a deep understanding of how to apply dynamic modeling concepts. The winner for the second session was Tesfaye Gashaw from Addis Adaba. Participants were challenged to build a predator-prey model simulation for Zebra and Cheetah interactions and explore new insights into understanding the dynamics. Tesfaye created an excellent stability analysis on the simulation, showing that the system on its own is not very stable and illustrating the importance of biodiversity.

The third and final session allowed the participants to share their work as well as any insights learned during the competition. Participants were challenged to build a hydrological dam model with the consideration of pollution. The winner for this session was Denver Moodley from South Africa. His model seamlessly bridged the gap between model structure and real-world application, ensuring every iteration held relevance and depth with exceptional sensitivity graphs.

Software Update

This fall's Stella 3.5 release saw the addition of yet more exciting new features. Mappings allow users to map specific numbers to words for both input and output—for example, 0/1 can become Off/On. We've also allowed users to create import templates for only selected variables, made it possible to select different rows and columns in tables to copy to the clipboard, and added a variety of other features and improvements, which can be viewed in the feature updates.

Update to Our Model Showcase

We have recently updated our Showcase page with new simulations for you to explore. Our showcase page is a curated page of simulations we think illustrate a great interface and have a strong model behind them. These simulations range through a variety of areas from economics and urban dynamics to healthcare and environmental. Several simulations include a small interview with the author to get their take on what drew them to dynamic modeling for their solution and what the key takeaway they hope their audience receives. We hope these models engage and perhaps inspire you!

Our Three-Part Special Podcast Series is Complete!

We recently released the final episode of our three-part special podcast series. We interviewed three educators that have dedicated much of their careers to incorporate System Dynamics into the K-12 curriculum. Learn how each was introduced to the field and how they have introduced dynamic modeling to the next generation. Our final podcast featured Jon Darkow. You can listen to all three episodes on our Webinars page.

2023 Barry Richmond Scholarship Award Winner

2023 Barry Richmond Scholarship Award winner Junlai Zhang with isee systems co-president Karim Chichakly

Established in 2007 to honor and continue the legacy of isee systems’ founder, this award is presented to a deserving Systems Thinking practitioner whose work demonstrates a desire to expand the field or apply Systems Thinking to current social issues. This year’s winner is Junlai Zhang for his Work In Progress paper, "Using System Dynamics modeling to forecast China’s population until 2060 to visualize the aging and shrinking population trends." He is modeling the demographic and economic challenges facing China over the next 50 years. The award was presented to Junlai at the International System Dynamics Conference in Chicago. If you are interested in submitting your work for the Barry Richmond Award, you can learn more about the requirements here.

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