"The dry seemed to be particularly dry, and the wet seemed to be particularly wet," she said.
La Niña and other events make climate influence unclear
But the unusually wet December in southern California and heavy snowpack in the northern United States are also signs of Arctic air that dipped south as another weather pattern, the North Atlantic Oscillation, hit a negative phase, experts said. That sent cold air and winter storms farther south than normal until the weather pattern started fading away in mid-January.
"The effects of La Niña were sort of muddled together with the effects of the North Atlantic Oscillation," said Ed O'Lenic, chief of the operations branch at NOAA's Climate Prediction Center. "It's very difficult to separate the two."
Further muddling the picture, some research suggests that the unusual behavior of the North Atlantic Oscillation this year and during the winter of 2009-2010 may be a consequence of declining sea ice in the Arctic.
But it's not clear whether climate change has affected or will affect the behavior of La Niña and her counterpart, El Niño. "It's possible that [the El Niño cycle] impacts could be aided and abetted by climate," L'Heureux said, who said the ambiguity can be just as frustrating for climate scientists as it is for the public trying to make sense of unusual weather.
"At this point, it's too difficult to make that real-time attribution," she said. "That's really what our field struggles at -- people want this information on demand. They want to know now what's causing this extreme rainfall event."
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500