Have you ever stopped to wonder how forecasters can predict the weather days in advance, or how scientists figure out how the climate might evolve under different policies?
The Earth system is a vast web of intertwined processes, from microscopic chemical reactions to towering storms. Ocean currents circulating deep in the Atlantic, forests exchanging carbon with the atmosphere, and humans altering the composition of the air all have effects that ripple through the system. These processes are governed by physical laws, such as conservation of mass, energy and momentum.
All of this plays out on such a large scale that no single human mind can truly grasp it in full. And yet, the system is so sensitive that a small perturbation, given enough time, can steer its trajectory in a dramatically different direction. This sensitivity is called “chaos,” also known as the “butterfly effect.” The planet is, at once, immense and delicate.
Despite this complexity and scale, scientists are able to simulate and anticipate how the climate will change.
How is this even possible? Behind the long-term climate projections that affect our lives sits one of the most remarkable scientific achievements of the modern era: climate models that run on supercomputers.
I am a climate data scientist. My colleagues and I try to understand extreme weather and long-term climate risks by using virtual versions of Earth inside these machines.
What a climate model really is
Here is the simplest way to picture a climate model:
Imagine dividing the entire planet into 3D boxes. At the surface, each box might represent an area 50 to 100 kilometers across. Then we stack boxes upward into the atmosphere and downward into the oceans to create a 3D grid wrapping around the globe.
Each box contains numbers: temperature, wind speed, humidity, sea ice thickness, soil moisture and hundreds of other variables. The model contains mathematical expressions that describe how these variables influence one another: how heat moves, how air rises and sinks, how moisture condenses into clouds, how the ocean absorbs and redistributes energy.