The world’s climate scientists are charged with a difficult task assignment to develop a crystal ball with which to sky a future that promises to be hotter than today.
To be precise how much hotter depends on innumerable factors, both natural and human. Creating the crystal ball is thus a two-stage process.
For starters, you have to build a simulacrum of how Earth’s climate works. Then, you make an effort to perturb this simulacrum with plausible future human actions, to see what picture appears.
Advanced and modern 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 neighbors, both sideways and, if appropriate, above and below.