A fingerprint of human influence has been identified on both global changes in temperature (T) and precipitation (P). It is unclear however whether a human fingerprint can be identified in global changes in vegetation distributions or in global changes in aridity, two examples of quantities that strongly depend on both changes in T and P. It is equally unclear how much changes in past, historical and future vegetation distribution or aridity may be attributable to changes in T and P. This is due to the fact that the mechanisms driving the changes in T and P are complex (including, for P, the “wet get wetter” and the “warmer get wetter” mechanisms, the poleward displacements of current zonal-mean wet and dry patterns, or the shift in the Intertropical Tropical Convergence Zone), and that their relative contributions depend on the time-varying influences of anthropogenic and natural forcings. In this study, we will explore these different questions with the help of formal or derived detection and attribution techniques.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.