Video image by Andy Robinson
For the past six years we have been reading about or experiencing the above average summer rainfall in northern Europe. The rainfall has wrecked havoc on farming, tourism and transportation. During those same six years the summer Arctic sea-ice cover has averaged about 40 percent below its typical summer extent, setting a new precedent. Now Exeter University, UK, scientist Dr. James Screen has a new study published in Environmental Research Letters where he shows the connection between the Arctic melt and the extreme rains experienced in northern Europe.
The study connects shifts in the jet stream which would account for the increased precipitation.
Jet streams are currents of strong winds high in the atmosphere – around the height at which aeroplanes fly. These winds steer weather systems and their rain. Normally in summer the jet stream lies between Scotland and Iceland and weather systems pass north of Britain. When the jet stream shifts south in summer, it brings unseasonable wet weather to Britain and northwest Europe causing havoc for tourism and farming.
The model suggests that while summer rainfall increases in northwest Europe, Mediterranean regions will receive less rain.
Here is Dr. Screen describing his study:
More on Dr. Screen's model below the fold.
Dr. Screen's model suggests that while summer rainfall increases in northwest Europe, Mediterranean regions will receive less rain—and that has proven to be the case.
"The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone," said Martin Hoerling, Ph.D. of NOAA’s Earth System Research Laboratory in Boulder, Colo., lead author of a paper published online in the Journal of Climate this month. "This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region's climate to normal."
The Mediterranean region accumulates most of its precipitation during the winter, and Hoerling's team uncovered a pattern of increasing wintertime dryness that stretched from Gibraltar to the Middle East.
"Human-caused climate change a major factor in more frequent Mediterranean droughts" (NOAA)
Al Gore: It takes time to connect the dots, I know that. But I also know that there can be a day of reckoning when you wish you had connected the dots more quickly.