New research monitoring cloud cover over the world's land areas
for the last four decades agrees with previous studies indicating
that the planet's tropical climate zones are expanding, and that
consequently the atmospheric jet streams are shifting towards the
poles, altering patterns of cloud cover. But skeptic blogger
Anthony Watts claims the research provides evidence for the
unconventional suggestion that clouds are responsible for global
warming. We asked the researchers if they agree with his
paper, currently in press at the Journal of Climate, also finds
that cloud cover over land has decreased by around 0.4 per cent per
decade, due to a decline in middle and high atmosphere clouds in
the mid-latitudes - roughly between 30 and 60 degrees latitude.
The paper's authors write that their "dataset offers few
surprises": it shows similar trends to the existing record of cloud
observations that it updates. The researchers explain that the
decrease in mid-latitude cloudiness over the last four decades is
consistent with expanding tropical climate zones, adding further
weight to the evidence that the planet is warming.
But climate skeptic blogger Anthony Watts interprets the new
research differently. Watts
suggests the research bolsters a hypothesis proposed by
skeptic scientist Dr
Roy Spencerthat runs counter to mainstream scientific thinking.
claims that clouds, not greenhouse gases, are causing the
planet to warm.
We asked the paper's author Ryan Eastman,
research scientist at the University of Washington, whether he
agrees with Watts's interpretation of his research. Eastman, who
seems surprised by the attention his research has generated, says
that Watts' conclusions are "misleading".