"Little Ice Age" is on the way.

The so-called Arctic Express, the frigid northern wind that brought record low temperatures to the central United States in December, 1996, could be the harbinger of a "little ice age," predicts Ernest Kung, chairman of the Atmospheric Sciences Department, University of Missouri, Columbia. His research indicates North America can expect a natural cold period for the next 20 or so years as the jet stream from Alaska and western Canada turns its persistent fury on the lower 48 states.

Kung emphasizes the long-range nature of his data. "This is not the daily weather. About every 15 to 25 years, you can recognize a change in the patterns of the global circulation of the atmosphere." During the 1970s, which many people describe as a little ice age, temperatures tended to be below normal, the winters colder and with heavier precipitation, culminating in the bitter winters of the late 1970s. Three consecutive winter seasons from 1976 to 1979 were among the coldest on record for the central and eastern U.S. There were unprecedented occurences such as snow in Miami, and record low temperatures and snowfalls were common from Kansas City, Mo., to Boston. Many of those records still stand today.

Since then, there has been a warm period. North America has enjoyed a temperate interval marked by mild winters with moderate precipitation. Kung's research indicates oceanic surface temperatures play a crucial role in the world's weather patterns. The surface temperature of the tropical and northern regions of the Pacific Ocean "is the key to the weather we get here. If the ocean is unusually warm, it tends to create high pressure." A huge mass of high pressure, like the one now in the central Pacific, forces the jet stream to move around it, to the north. From there, the high pressure front curls around Alaska and flows southward, bringing arctic temperatures with it.

For the past 10 or 15 years, weather patterns have been dominated by El Nino, a distinct mass of warm water and high pressure off the coast of Peru. The northern Pacific, during this time, has remained relatively cool, with insufficient pressure to deflect the jet stream into the arctic regions. "It became reversed [in the spring of 1996]. Now, it is the northern Pacific where most of the places are very warm. It creates pressure that is persistent and powerful." Under these circumstances, western Alaska, which the jet stream encounters just as it is moving off the high pressure mass in the ocean, will be warmer than usual, while the continental U.S. will be cooler.

A number of atmospheric scientists still do not realize the importance of ocean surface temperatures in the evolution of weather patterns, Kung says. "Many meteorologists fail to recognize this. They mostly care about a system when it enters the United States. However, how it enters is important for long-range weather patterns."

He is skeptical about the widely held view that carbon-dioxide global warming was the cause of mild winters in the past decade. "The ocean absorbs most of the excess carbon dioxide. If this trend is occurring, it would be more evident after the year 2000, but probably as a mitigating factor for the natural cold cycle."

Despite the prediction of rough winters ahead, Kung has encouraging words for those who are discouraged by the news: "Even when there's bad weather, good weather eventually comes back. You just don't know when."