Abstract
We investigate whether the observed surface specific humidity (q) trends
over the Mediterranean region in the period 1974-2003 are consistent
with climate model (CMIP3, CMIP5) simulations of q in response to
anthropogenic forcing (Greenhouse gas and sulphate aerosols). The
natural (internal) variability is estimated using 6,000-year of
pre-industrial control simulations. With the exception of winter, the
increases in annual and seasonal q over this region are very unlikely
(with less than 1% chance) due to natural (internal) variability or
natural forcing alone. Using several climate models and ensemble means,
we demonstrate that the large-scale component (spatial-mean trend) of
the anthropogenic forcing is detectable (at 1% level) in the annual and
seasonal trends of q (except winter). However, the smaller-scale
component (spatial anomalies about the mean trend) of the anthropogenic
signal is detectable only in warm seasons (spring and summer). We
further show that the spread of projected trends based on the A1B
scenario derived from 13 CMIP3 models encompasses the observed
area-averaged trend in q. This may imply that the observed trends of
surface humidity, which is an important factor in human thermal comfort,
serves as an illustration of plausible future expected change in the
region. Citation: Barkhordarian, A., H. von Storch, and E. Zorita
(2012), Anthropogenic forcing is a plausible explanation for the
observed surface specific humidity trends over the Mediterranean area,
Geophys. Res. Lett., 39, L19706, doi:10.1029/2012GL053026.