Recently, the NAO has made the largest single contribution to the variation of northern hemisphere temperatures outside the tropics. Over the past 30 to 40 years the NAO has increased in amplitude to its highest level this century, and as a result the Atlantic winter storm climate and aspects of the ocean's response have been equally extreme. Seasons to centuries Seasonal monsoons with their associated rainfall are the lifeblood of many countries in Asia and South America. Agriculture depends on the monsoon rains, and to learn how predictable they are is a key to maximising agricultural production. Too much or too little rain can have devastating results.
Similar patterns exist in the Atlantic.
The North Atlantic Oscillation influences Europe's weather but is as yet poorly understood. Longer term Over even longer timescales we know from measurements in the polar ice caps, from tree rings and from ocean sediments that climate has always varied. Evidence suggests that mankind is adding a global warming trend to the natural variability. Not all effects will be harmful but in many parts of the world the impacts of climate change due to the combination of natural variability and warming will be disruptive. New knowledge and understanding of climate variability, predictability and change can only arise by investigating these phenomena in a global context.