The word of the week is parameterization

A big weakness of global climate modeling is the numbers they assign to everything in the world—the parameters. When it comes to carbon dioxide and the whole carbon cycle, for instance, each type of plant community handles carbon differently. This article is about a large set of experiments that raise the CO2 levels in the open air around bits of forest, bog, grassland, whatever. That way all these biomes can get more accurate numbers.