Earth and Space Science

Variability and trends in global drought
Earth and Space Science

Monthly precipitation (P) and potential evapotranspiration (PET) from the CRUTS3.1 data set are used to compute monthly P minus PET (PMPE) for the land areas of the globe. The percent of the global land area with annual sums of PMPE less than zero are used as an index of global drought (%drought) for 1901 through 2009. Results indicate that for the past century %drought has not changed, even though global PET and temperature (T) have increased. Although annual global PET and T have increased, annual global P also has increased and has mitigated the effects of increased PET on %drought.

The objectives of this paper are to answer two basic questions regarding global drought occurrence: (1) are interannual changes in drought occurrence controlled mostly by changes in PET, P, or both equally? and (2) given global warming and associated increases in PET, has the occurrence of drought increased during the past century?

Analysis of the global land area with annual PMPE less than zero for the 1901 through 2009 period indicates that %drought has not changed, even though global T and PET have increased during this period. On a global basis the variability in annual %drought is related to variability in P, and increases in annual global P have mitigated the effects of increases in PET (and T) on %drought.

Pour ceux qui se sont perdus dans le jargon scientifique, cette étude montre que le réchauffement climatique n’a pas été associé à une augmentation du nombre de sécheresses. Bref, la prochaine fois vous dira qu’il y a plus de sécheresses à cause du réchauffement, vous pourrez lui répondre que c’est faux.