Nov 29, 2017

Is There a Role for Human-Induced Climate Change in the Precipitation Decline that Drove the California Drought?

by
Richard Seager, Naomi Henderson, Mark A. Cane, Haibo Liu, and Jennifer Nakamura
,
AMS Journal of Climate
  • States that the recent California drought was associated with a persistent ridge at the west coast of North America that has been associated with, in part, forcing from warm SST anomalies in the tropical west Pacific
  • Considers whether there is a role for human-induced climate change in favoring such a west coast ridge
  • Finds that reanalyses show that over the last century there has been a trend toward circulation anomalies over the Pacific–North American domain akin to those during the height of the California drought
  • States that the trend has been associated with a trend toward preferential warming of the Indo–west Pacific, an arrangement of tropical oceans and Pacific–North American circulation similar to that during winter 2013/14, the driest winter of the California drought
  • Finds, however, that these height trends are not reproduced in SST-forced atmosphere model ensembles
  • Finds, in contrast, idealized atmosphere modeling suggests that increased tropical Indo-Pacific zonal SST gradients are optimal for forcing height trends that favor a west coast ridge
  • These results allow a tenuous case for human-driven climate change driving increased gradients and favoring the west coast ridge, but observational data are not sufficiently accurate to confirm or reject this case