Did Warming Tropical Waters Give US More Snowstorms?

Was this past winter's polar vortex caused by a rise in tropical temperatures?

Warming waters in the Western Pacific at least partially contributed to the U.S. and the U.K.'s worst winters in a quarter of a century, according to a new study published Friday in the journal Science.

As climate temperatures rise, more heat stays trapped in the ocean, leading to more moisture flowing through the jet stream to North America and Europe, which were smothered with snow and rain last winter.

"The sea temperatures in that crucial region of the west Pacific, which are some of the warmest ocean temperatures anywhere in the world, have reached these all-time record warmings through an additional effect, which is man-made climate change," study author Tim Palmer told Bloomberg Businessweek by phone. "The water's already warm there, and it's just taken it over the brink to create conditions last winter and into this spring that were unprecedented."

Last year's typhoon season was also affected, with warming temperatures in the Western Pacific increasing the effects of storms such as Haiyan as well as Australian heat waves, the professor of climate physics said.

"There are various links in a long chain, and part of my message is that climate is a complex system," Palmer, who has been analyzing climate trends for nearly 30 years, told Businessweek. "Interaction between natural climate variability and man-made climate change are coming together in a perfect storm."

Other experts contend that last winter's storms were exacerbated by other factors, Reuters reported.

According to Martin Hoerling, of the U.S. National Oceanic and Atmospheric Administration's Physical Sciences Division, the unusual winter storms were likely a "freak of nature" and American winters are not linked to Pacific temperatures.

The Pacific Ocean saw a similar pattern of rainfall about two years ago, but the U.S. enjoyed a mild winter, said Jennifer Francis of Rutgers University.

"In both cases the jet stream's path was extremely amplified or wavy, which is exactly the sort of behavior we expect to occur more frequently in association with rapid Arctic warming," she told Reuters, adding that there was little evidence to support the theory that tropical waters are a factor.