Let's dispense with the inevitable: - no, no one can say with 100% certainty that global warming is completely responsible for this BUT no one has any more likely cause either.
Global warming is impacting Pacific Ocean ecosystems. From the Sydney Morning Herald:
"Professor Jane Lubchenco, from Oregon State University, said: "Wild fluctuations in the intensity of ocean upwellings are wreaking havoc with the ecosystems of the west coast.
"We're seeing extreme distortions on both sides of the norm. This is a system that is out of kilter. It's fluctuating rapidly."
"Up to five decades of data had shown that the events were "unprecedented in this ecosystem", she said.
"She pointed out that similar ocean current disruption had been seen in other regions of the world, particularly Peru, Chile and parts of Africa.
"Experts at the annual meeting of the American Association for the Advancement of Science in San Francisco described two extraordinary linked events in 2005 and 2006.
"The first occurred when a nutrient-rich ocean current that normally appears off northern California and Oregon in spring was delayed by a month.
"This led to a loss of phytoplankton, the microscopic plant organisms that form the vital base of the ocean ecosystem and upon which larger animals depend for food.
"Salmon, which normally take to the sea at this time, starved. The effects rippled up through the food web as predators, including many sea birds, went hungry and died.
"The following year the west coast current came back with a vengeance, producing an upwelling of nutrient-rich water twice as strong as the average recorded for several previous years.
"Phytoplankton bloomed to levels not seen before, turning the sea to green-brown soup. They then died and sank, causing oxygen levels in the water to plummet virtually to zero.
"The result was a "dead zone" in which nothing could survive. Scientists conducting a submarine survey found dead crabs and marine worms scattered across the ocean floor, and no sign of any fish.
"The knock-on effects were once again disastrous for sea birds which relied on the sea creatures for food. Huge numbers of dead birds were washed up on the shores.
"The 2006 dead zone, which remained for nearly 17 weeks, was three times bigger than any seen in the region before, said Dr Francis Chan, from Oregon State University in Corvallis."