he world’s climate scientists are charged with a difficult task: to create a crystal ball with which to skry a future that promises to be hotter than today. But exactly how much hotter depends on innumerable factors, both natural and human. Creating the crystal ball is thus a two-stage process. First, you have to build a simulacrum of how Earth’s climate works. Then, you try to perturb this simulacrum with plausible future human actions, to see what picture appears. Modern magic being what it is, the crystal balls are actually supercomputers running programs with 1m or more lines of code. These programs are models that divide the planet’s atmosphere, ocean and land surface into grids of cells—many millions of them. Land cells are flat. Atmosphere and ocean cells are three-dimensional and are stacked in columns to account for the effects of altitude and depth. A model calculates what is going on, physically and chemically, inside each cell, and how this will affect that cell’s neighbours, both sideways and, if appropriate, above and below. Then it does it again. And again. And again. To view the full article visit the Economist.
