At IIASA in Laxenburg this week, renowned mathematician Don Saari laid out a challenge for the Institute’s scientists:  to better understand complex systems, he said, researchers must find better ways to model the interactions between different factors.

“In a large number of models, we use climate change or other factors as a variable. What we’re doing is throwing in these variables, rather than representing interactions—like how does energy affect population?” said Saari, a longtime IIASA collaborator and council member, and newly elected IIASA Council Chair, a position he will take up in November. “The great challenge of systems analysis is figuring out how to connect all the parts.”

“Whenever you take any type of system and look at parts and how you combine parts, you’re looking at a reductionist philosophy. We all do that in this room,” said Saari. “It is the obvious way to address a complex problem: to break it down into solvable parts.”

The danger of reductionism, Saari said, is that it can turn out completely incorrect solutions—without any indication that they are incorrect.  He said, “The whole may be completely different than the sum of its parts.”

Take a Rubik’s cube as an example: Saari said “If you try to solve it by first doing the red side, then the green, then the blue, you will end up with a mess. What happens on one side is influenced by what’s happening on all the other sides.”

In the same way, the world’s great systems of energy, water, climate all influence each other. During the discussions, IIASA Deputy Director Nebojsa Nakicenovic noted that current work to extend the findings of the Global Energy Assessment to include water resources could narrow the potential number of sustainable scenarios identified for energy futures by more than half.

Saari pointed out that many of the world’s great scientists—including Nobel Prize winner Tom Schelling and Kyoto prize winner Simon Levin, both IIASA alumni—reached their groundbreaking ideas by elucidating the connections between two different fields.

It may sound like a simple solution to a methodological challenge. However, understanding the connections and influences between complex systems is far from simple. As researcher Tatjana Ermoliova pointed out in the discussion, “In physical systems you can hope to observe and discover the linkages.” But between human, economic, and global environmental systems those linkages are elusive and fraught with uncertainty.

At the end of the lecture, IIASA Director & CEO Prof. Dr. Pavel Kabat turned the challenge towards IIASA scientists, and we now extend it also to our readers: How can scientists better model the connections between systems, and what needs to change in our thinking in order to do so?