El Nino And La Nina

El Nino is a warm ocean current that appears off the coast of Peru during the winter. On some years it flows much further south than usual, and this has an affect on weather patterns in many areas. This is known as an El Nino event. The areas that are most affected by El Nino are North America, South America Asia and Australia. El Nino can sometimes bring warmer winters to Europe and the UK, and La Nina will usually bring colder winters, but to make it clear, both events can bring extreme weather to many areas. It is just that the effects locally are reversed, depending on location. The average duration of an El Nino event is about eighteen months. These events tend to repeat themselves roughly every five to seven years.

El Nino occurs because of a weakening of the trade winds that blow westward from South America towards Asia. The trade winds keep the surface water of the Eastern Pacific cool, due to evaporation and the upwelling of cooler water. If they weaken it causes a warming of the Pacific over a much larger area than usual. This warming stops the cool waters from upwelling and consequently disrupts sea currents. This has a severe affect on weather patterns locally and sometimes globally, bringing rain and floods to usually dry areas and long periods of dry weather where it would normally be wet. The reach of El Nino’s affects depends on its strength and severity. Freak snowstorms, torrential rain, and many other things are blamed on El Nino.

La Nina, the partner in crime of El Nino, is where the opposite happens and the sea has a marked cooling. La Nina does not follow every El Nino event, as they are much less frequent. La Nina’s effects are often as extreme as that of El Nino. The media usually blames ENSO or El Nino Southern Oscillation (El Nino for short) for every severe weather event that occurs from Scotland to South Africa and China to America. El Nino’s affects are widespread, and although it is felt by most that Europe can be affected by it, Northern Europe is at its furthest (and weakest) reach.

Scientists have a fairly good understanding of how El Nino works, but they still have much to learn about its repetitive cycle. During the 1970’s, oceanographers and meteorologists began to combine their efforts to refine a hypothesis by Jacob Bjerknes, who twenty years earlier had carried out much research into El Nino. He had said that ‘El Nino was just the oceanic expression of a large-scale interaction between the ocean and the atmosphere and that the climate anomalies could be understood as atmospheric "teleconnections" emanating from the warm-water regions along the equator in the mid-Pacific’. The studies carried out during the 1970’s had combined the work of Sir Gilbert Walker from the 1930’s (he coined the phrase ‘Southern Oscillation’) and what was already known about El Nino. Sir Gilbert walker had given this name to worldwide climate anomalies, which he had been studying.

By combining the names El Nino and Southern Oscillation, the term ENSO came about, even though they are actually two separate events. It has been confirmed that this year is an El Nino year, and therefore many parts of the world could experience some severe and extreme weather events. The El Nino of 1997 is one of the strongest in recent years. These are some of the highlights of this event. The sea temperature rose by five degrees in the El Nino region. Hurricane activity in the Pacific increased, while hurricane activity decreased in the Atlantic. Record snow and low temperatures were recorded in Europe. Hotter temperatures affected Australia and Indonesia causing drought and bush fires. Torrential rains in South America were much more frequent, bringing landslides and floods to many areas including California, Texas and Florida. Canada had milder temperatures than normal.

The El Nino event of 1997-98 was a strong one, similar to that of 1982. If this year’s event is a weak affair, the effects on the climate are only likely to be felt in the areas closest to the event itself. This winter's temperatures have been above average in the UK and in other parts of the world. For Instance, the Eastern and Central states of America have had one of the warmest winters on record. Like Britain, the NAO was in neutral for most of the winter, and blocking seemed to be the norm. As previously said, El Nino had not really started in time for winter 2001-2002, so if anything, the winter of 2002-2003 could see some extreme weather events for eastern and central America. The disappointing (for some) winter that the UK and the US have had this year probably cannot be blamed on Global Warming. In fact the Polar Regions are colder than usual this year. The Antarctic has been at its coldest for 20 years and the ice sheets has grown. One of the reasons for the warmer weather this year appears to be Solar Flux.

It is relatively easy to say that El Nino is caused by ‘a disruption of ocean currents in the Pacific...' but I can’t help wondering what exactly causes this disruption. Is it the sun? Is this star of ours the all-controlling dictator it seems to be? From my studies, I have realised that the sun can play a significant role in global warming, El Nino, ice ages and magnetic pole reversal, and as we all know it controls normal weather patterns too.

A few years ago, scientists working at the University of Michigan released some information about El Nino studies that they had been doing. The studies were related to how El Nino may have influenced previous ice ages. While studying sediments at the bottom of Lake Huron, they found evidence of ‘brief, sudden episodes of rapid warming at the end of the last Ice Age which melted glaciers and sent water surging through the Great Lakes to the North Atlantic. Obviously, at this time much of North America was covered in an ice sheet, but it seemed that a strong high-pressure region had developed over the ice, stabilising the jet streams path and pulling heat and moisture along the southern edge of the ice sheet. One of the scientists involved, Ted Moore, wondered whether the younger Dryas which was a 16,000 year freeze that started and finished abruptly, could have come about (or even been halted) as a result of this possible El Nino activity.

There is still much work that needs doing before we get close to understanding the El Nino-La Nina events. Perhaps one day we will be able to see the link between El Nino and its causes. It may be even become possible to predict them accurately, and be more certain about which areas would be affected.

© Brian Taylor 2002.

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