This area of Lakeport, California was flooded due to extreme weather during the 1998 El Niño event. El Niño causes changes in rainfall patterns around the world. Click on image for full size (24 Kb) Courtesy of FEMA

Sometimes there is a change in the way air moves through parts of the atmosphere. And there are sometimes changes in the way water moves through the ocean too. This disturbs typical weather patterns, or climate, for a few weeks or a few months or a year or more. Weather conditions return to their normal patterns when the atmosphere and ocean return to normal.

These events in the atmosphere and ocean can cause changes in the weather near the disruption and far from it. Changes in the atmosphere in one place that affect weather far away are called teleconnection patterns. Scientists are trying to sort out how this works so that they can better understand and predict weather patterns worldwide.

There are several different events that happen in the atmosphere and oceans. The largest are described below. These events are natural parts of the Earth’s climate. However they might be changing because of global warming.

The El Niño-Southern Oscillation (ENSO) is the strongest natural variation in climate. It is a disruption of the ocean-atmosphere system in the tropical Pacific that causes changes to weather and climate in places around the globe. Both phases of ENSO – El Niño and La Niña – can cause changes in weather including intense rainstorms, drought, and a change in the amount of storms.

Changes in the North Atlantic Oscillation (NAO) cause variability in Northern Hemisphere winter conditions like the amount of snow and cold temperatures. The NAO is closely related to the Arctic Oscillation and is also affected by ENSO.