One of the most fundamental discoveries that has come out of the study ofcomplex adaptive systems is a rather appalling one: These systems sometimes
behave in ways that cannot be predicted – no matter how good the science is or
how powerful our computers are. That means that on a practical level, even the
wisest and most well-informed policymaker can make decisions that have
unintended consequences. One lesson of the science of complexity, then, is that
humility and caution are essential in the face of this irremediable uncertainty. The
uncertainty applies to all complex adaptive systems, including cities, fisheries,
forests, ocean-atmosphere systems, water supplies, financial markets – really,
any interaction between humans and a natural system.
Nevertheless, the study of complex adaptive systems can guide decisions,even if it can’t guarantee particular outcomes. Mathematical scientists can
describe the range of behaviors a system might have, find critical thresholds
where the behavior might suddenly change, understand how different parts of the
system interact, and give decision makers a good sense of the most likely
outcomes.
Climate models are an example where this kind of information could behugely helpful, but so far, few mathematical scientists have been deeply involved
in developing these models. These models are extremely complex computer
programs that draw in expertise from mathematics, physics, chemistry and other
sciences, thus forming the collaborative brainchildren of hundreds of scientists
working in parallel. Chemists model how reactions among airborne molecules
affect the transparency of the air; oceanographers model how the currents stir
the oceans; atmospheric scientists model how clouds reflect sunlight. Each of
these parts and many more are then assembled into a giant model that gives us
the clearest view we can get of what our climate future is likely to hold. Analyzing
such models requires months of time to run on our fastest supercomputers. Yet,
when all is said and done, these models are only crude and imprecise
representations of the true processes affecting climate.
Since climate is a complex adaptive system, mathematicians know thatthe interactions of all these different parts deeply matter. And climate scientists
know it too: The El Niño effect, a climate pattern that occurs about every five
years and changes the weather throughout the tropical Pacific ocean area, is
created by the interaction of the ocean and the atmosphere. Until climate models