More Frost-Free Days
27 August, 2004
will become less and less common across much of the world as global
warming accelerates, U.S. researchers reported. The latest of a series
of reports on the real-life effects of climate change shows fewer days
and nights when the air temperature dips below freezing.
The report, from
the National Center for Atmospheric Research in Boulder, Colorado, joins
a study from the same group released earlier this month predicting more
severe and common heat waves in cities such as Paris and Chicago and
another one focusing on California that showed higher temperatures would
threaten the dairy and grape industries.
Also this month,
the European Environment Agency predicted that cold winters could disappear
almost entirely from Europe by 2080 and that heat waves and floods would
become more common.
have already noticed fewer days when there is a frost in some areas,
especially in the Western United States.
Writing in the journal
Climate Dynamics, NCAR researchers Gerald Meehl, Claudia Tebaldi and
Doug Nychka used a Department of Energy climate model to forecast day-to-day
changes in temperature at the end of this century.
The model predicted
a steady loss of days when there will be a frost in 2080 to 2099 compared
there is a gradient from west to east across the continent, with greater
decreases in frost days in the western regions," Meehl said in
Changes in atmospheric
circulation will cause the change, Meehl said.
The model predicts
that in northwestern North America, low-level winds will blow more often
from the Pacific, carrying mild air during the winter.
Eastern North America
will get more cold Canadian air, however. A similar pattern is seen
in Europe and Asia, with Northern Europe getting more warm ocean air
and Asia getting cold continental blasts.
But the researchers
do not find that the change in frost patterns will affect agriculture.
For example, the
average first frost and last frost dates do not change, although the
technical growing season may lengthen because more days, on average,
will see average temperatures of above 41 degrees F.