does El Nino occur?
occurs as a warm water current moves eastwards across the
Pacific off of the South American coast. This shifts the
world's pressure and so the climate of regions changes.
does this warm water current move across the Pacific in
the first place?
is exactly sure although our understanding has improved
in the last few years. One of the most commonly accepted
theories is that there is an east-west circulation of
heat between high and low pressures. This is called the
worldwide Walker Circulation. For some reason, every 2-7
years, this circulation breaks down. This means that the
easterly winds decline dramatically and the warm water
pulse is created around Australia.
does this cause unusual weather phenomena?
winds move over the Pacific Islands, particularly Tahiti,
the conditions for tropical cyclones are now present.
Additionally, because the pressure is high, the
temperature of the ocean is up to 6 degrees Celsius
higher than it should be. The warm water means that
rainfall occurs in areas which are norm ally arid and
drought elsewhere. Finally, the American jet stream is
forced south, causing freak weather occurrences in Canada,
the USA and Mexico. For instance, flooding and heavy snow
are common in El Nino years.
is the worst El Nino so far?
the worst yet hit in 1982. It caused some $1000 million
worth of damage worldwide. There were monsoons in the
Pacific Ocean, fires in Borneo, dust storms in Australia,
as well as worldwide droughts. Fish and bird populations
plummeted all over the world.
can be done to predict El Nino?
very little. There have been some small scale programmes
in Zimbabwe and Australia to predict when the Walker
Circulation might break but this has proved unreliable.
is La Nina?
is effectively the opposite of El Nino, where the jet
stream moves due to a well established Walker Circulation.
The last one occurred in 1989, when there were monsoons
in Bangladesh, Thailand, Sudan and Australia, and severe
droughts in Midwest USA.