The change in the North Atlantic oscillation may tell them.

North Atlantic oscillation - an atmospheric climate mode.

The North Atlantic oscillation is an atmospheric phenomenon which affects the weather in Western Europe.

It forms one pole of the North Atlantic oscillation, the other being the Icelandic Low.

If this so-called North Atlantic oscillation is in one mode, typified by low atmospheric pressure over the ocean, the East tends to be warm.

A general climatic change resulting in more frequent positive North Atlantic oscillation events has led to earlier spring migration of these short-distance migrants since the 1980s.

However, they are easily overridden, in winter, by the Arctic oscillation and North Atlantic oscillations, which can only be predicted about two weeks in advance.

The North Atlantic oscillation is a climatic phenomenon in the North Atlantic Ocean.

A scientist from the National Weather Service, Bill Goodman, said by telephone that this all had to do with something called the North Atlantic oscillation.

But Dr. McCartney believes, based on observations at sea, that it is linked with the atmosphere to produce the North Atlantic oscillation's interdecadal rhythm.

This modeling may be complicated by the fact that the North Atlantic Oscillation in switching state (see graph) as the effects of global warming are becoming more prominent.

The drought was set in motion when strongly positive Arctic oscillation and North Atlantic oscillation conditions removed winter storms from the US.

A recent study has found that the abundance of one such animal, a copepod called Calanus finmarchicus, rises and falls in close concert with the North Atlantic oscillation.

Whether the North Atlantic oscillation could operate over time scales of a century or more, where even larger climate swings have taken place in the last few thousand years, is unclear.

Known climate oscillations resulting from these interactions, include the Pacific decadal oscillation, North Atlantic oscillation, and Arctic oscillation.

Famous atmospheric anomaly time series are for instance the Southern Oscillation index (SOI) and the North Atlantic oscillation index.

The unusual warmth was due largely to an unseasonal area of high pressure over Greenland, and very negative values of the Arctic oscillation and North Atlantic oscillation.

There is a large variability in dust transport to the Caribbean and Florida from year to year; however, the flux is greater during positive phases of the North Atlantic Oscillation.

In what meteorologists call the North Atlantic oscillation, there is a tendency for the temperature difference between the Arctic and subtropics to narrow abruptly in the spring, usually in April or May.

This millennial-scale variability has been attributed to long-term shifts in the position of the Azores High, which may also be linked to changes in the strength of the North Atlantic Oscillation.

Since the 1970's, scientists say, the North Atlantic oscillation and a similar oscillation in the Pacific have made the continents of the Northern Hemisphere unusually warm, on the average, in winter and spring.

The North Atlantic oscillation's effect "never makes itself felt till the end of December or early January," Mr. Kousky said, adding that forecasters at this point cannot predict its behavior this winter.

Some scientists, like Dr. John Michael Wallace, an atmospheric scientist at the University of Washington, think that the Arctic and North Atlantic oscillations are so closely tied together as to be the same thing.

New evidence is also emerging that implicates the North Atlantic oscillation as the cause of a long drought that archeologists believe caused the collapse, starting about 4,200 years ago, of the ancient Akkadian civilization of Mesopotamia.

The researchers made use of United Nations data on annual food production in various countries over more than 40 years, coupled with climate data involving both El Niño and a weaker atmospheric phenomenon, the North Atlantic oscillation.