Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling
25 September 2019

A Hierarchical Collection of Political/Economic Regions for Analysis of Climate Extremes

Generation of sets of approximately equal-area land regions specifically designed for policy-relevant analysis of extreme weather.


We examine available collections of regional definitions spanning the global land mass currently used in climate research and find them unsuitable for systematic policy-relevant analysis of extreme weather, because of scale-mismatch, global incompleteness, lack of alignment with policy interest, or lack of rich-world/poor-world consistency.  We develop five new collections of regions based on political/economic divisions, each of a different representative scale, and test their applicability against various broad criteria including the challenges listed above.  We find these regions superior against these criteria than currently available collections.  We also demonstrate their usefulness in highlighting systematic differences in the representation of trends in extreme weather under anthropogenic forcing between two versions of a single climate model:  one with a dynamical ocean and one forced with observed ocean conditions.


These collections of regions will permit global systematic analysis of extreme weather that aligns with policy interests and does not suffer for issues such as a mismatch of spatial scale between rich and poor countries.


This paper describes five sets of regions intended for use in summarizing extreme weather over Earth’s land areas from a climate perspective. The sets differ in terms of their target size: ∼10 Mm2, ∼5 Mm2, ∼2 Mm2, ∼0.5 Mm2, and ∼0.1 Mm2 (where 1 Mm2= 1 million km2). The regions are based on political/economic divisions, and hence are intended to be primarily aligned with geographical domains of decision-making and disaster response rather than other factors such as climatological homogeneity. This paper describes the method for defining these sets of regions; provides the final definitions of the regions; and performs some comparisons across the five sets and other available regional definitions with global land coverage, according to climatological and non-climatological properties.

William D. Collins
Lawrence Berkeley National Laboratory