1. A method for creating a space-time surrogate model of a subsurface region, the method comprising: generating an explicit surrogate model of an implicit model of a subsurface region for preselected variables at a first time value; repeating the generating n times for n additional time values that are different than the first time value, wherein n is an integer greater than 1, wherein the first time value and the n additional time values define a range of time values; and creating an explicit space-time surrogate model of the implicit model based on the surrogate models produced by the generating and the repeating, wherein the space-time surrogate model is parametric for at least the preselected variables and also indicates changes in the variables over at least the range of time values.