WASHINGTON – Lately, the jet stream isnt playing by the rules. Scientists say that big river of air high above Earth that dictates much of the weather for the Northern Hemisphere has been unusually erratic the past few years.
They blame it for everything from snowstorms in May to the path of Superstorm Sandy.
And last week, it was responsible for downpours that led to historic floods in Alberta, Canada, as well as record-breaking heat in parts of Alaska, experts say. The town of McGrath, Alaska, hit 94 degrees. Just a few weeks earlier, the same spot was 15 degrees.
The current heat wave in the Northeast is also linked. While its not unusual to have a heat wave in the east in June, it is part of the anomalous jet stream pattern that was responsible for the flooding in Alberta, Rutgers University climate scientist Jennifer Francis said Tuesday.
The jet stream usually rushes rapidly from west to east in a mostly straight direction. But lately its been wobbling and weaving like a drunken driver, wreaking havoc as it goes. The more the jet stream undulates north and south, the more changeable and extreme the weather.
Its a relatively new phenomenon that scientists are still trying to understand. Some say its related to global warming; others argue its not.
In May, there was upside-down weather: Early California wildfires fueled by heat contrasted with more than a foot of snow in Minnesota. Seattle was the hottest spot in the nation one day, and Maine and Edmonton, Canada, were warmer than Miami and Phoenix.
Consider these unusual occurrences over the past few years:
The winter of 2011-12 seemed to disappear, with little snow and record warmth in March. That was followed by the winter of 2012-13 when noreasters seemed to queue up to strike the same coastal areas repeatedly.
Superstorm Sandy took an odd left turn in October from the Atlantic straight into New Jersey, something that happens once every 700 years.
One 12-month period had a record number of tornadoes. That was followed by 12 months that set a record for lack of tornadoes.
And here is what federal weather officials call a spring paradox: The U.S. had both an unusually large area of snow cover in March and April and a near-record low area of snow cover in May.
Ive been doing meteorology for 30 years and the jet stream the last three years has done stuff Ive never seen, said Jeff Masters, meteorology director at the private service Weather Underground. The fact that the jet stream is unusual could be an indicator of something. Im not saying we know what it is.
Francis is in the camp that thinks climate change is probably playing a role in this.
Its been just a crazy fall and winter and spring all along, following a very abnormal sea ice condition in the Arctic, Francis said, noting that last year set a record low for summer sea ice in the Arctic. Its possible what were seeing in this unusual weather is all connected.
Other scientists dont make the sea ice and global warming connections that Francis does. They see random weather or long-term cycles at work.
Even more scientists are taking a wait-and-see approach with this latest theory. Its far from a scientific consensus, but it is something that is being studied more often and getting a lot of scientific buzz.
There are some viable hypotheses, Stanford University climate scientist Noah Diffenbaugh said. Were going to need more evidence to fully test those hypotheses.
NOAA research meteorologist Martin Hoerling said, Everyone would agree that we are in a pattern of extremes. We dont know how long it will stay in this pattern.