here it comes another one..on el nino...read it!

El Niño grows up?

Australia, country of immigrants, kangaroos and variable and extremes climates. The past year will stay on the books and in Australian people’s minds as one of the worst drought-hit in recent times; it destroyed entire crops, with a severe impact on the agriculture and the economy of the country. (Major crops such as wheat are down more then 50% on an average year)

Let’s have a look at a report dated 1791 from the Australian governor Arthur Phillip: “From June until the present time so little rain has fallen that most of the runs of water in different parts of the harbour have been dried up for several months…”

And again 1814 after another severe drought that forced the Australian government to import big quantities of food, another report stated that was necessary to avoid “…the heavy calamity of very great scarcity, both of animal feed and of grain, if not in actual famine…”

This year event has been not so unique for Australia; is possible to find similar situations in the most recent 1997, 1982, and more and more backwards in time.

As others drought and floods of the past, especially in certain world areas, we have several records. In 1877 famines in various parts of the world, determined by more then unusual meteorological patterns, caused the death of nine million man and women in China and a close amount in India.

Since this catastrophic year, started the first attempts to understand the phenomenon behind those dramatic weather events; in fact was empirically evident how Australia and India experienced droughts at the same time and the particular atmospheric pressure difference before the event occurred, but they were still far to have a scientific theory.

From time to time torrential rains and floods hit the normally arid north-western coasts of Peru; there are written records of the same kind of storms dated 1525, and researchers have found evidence of heavy floods during the Inca period going back in time more then 10.000 years ago.

Peru’s fishermen enjoy (along the usually cold and rich deep sea coasts), flourishing fish populations. They had noticed how around the Christmas period in certain periodic years (every three to seven) the ocean would heat up for few weeks, drastically diminishing the fish populations: they called this recurrent period El Niño for the Christ child.

Also if this anomalous and recurrent extreme weather conditions has been recorded hundreds years ago in different parts of the globe, just recently has been linked as part of a singular big phenomenon now known as El Niño.

In fact it was not until 25 years ago that the scientific world intensified his efforts to deeply understand how El Niño works globally.

I’ll try to make it as simple as possible without being involved in difficult (for me as well) technical theories.

The main energy that drives world climate is the sun. More of this energy is received in the equatorial regions than at the poles. This “imbalance” is redistributed by the oceans and the atmosphere, transporting the excess of energy from the equator to higher latitudes.

The earth rotations cause the air moving away from the equator to turn eastward; the cool air that returns from the high latitudes instead creates a westward movement.

These movements leads to the so called “trade winds”, that have effect again on the oceans; in fact the Pacific ocean is warmer in the west(and this causes heavy rains in this tropical areas such as Indonesia and New Guinea) then in the east( around the Indian Ocean and the west Pacific where is much drier).

During El Niño periods this situations reverse and the trade winds nearly disappear.

El Niño is caused by a sort of cyclic chain effect: a small change in temperature on the sea surface can produce a change of winds along the equator. This affects the currents which changes the sea surface temperature even more. And so on. After a certain period of time (not determinable), the usual air-pressure pattern reverses itself and is higher in Australia than they are in the central Pacific; this atmospheric variations is called ENSO (El Niño/Southern Oscillation).Often El Niño is followed by La Niña (also called El Viejo) that has diametrical opposite effects characterized by unusually cold ocean temperatures in the equatorial Pacific, flooding in Australia, India, Indonesia, Brazil, and dry conditions on the Pacific coast of South America; this changes associated with El Niño, last for around a year.

The clearest sign of the ENSO is the inverse relationship between the air pressure of two sites; Darwin in Australia and in Tahiti.

The main atmospheric consequences consist in a shifting of jet stream, storms and monsoons, causing severe weather changes (droughts and floods) over many regions of the world.

T

he economic impact is relevant as well. Peru’s fishing industry is heavily hit (in favour

of Chile), as well is hit the agriculture of countries were the drought bites harder as in Australia or for the coffee crops of Brazil and Indonesia.

On the other side it can have some positive effects: it generally reduces tornados that usually strike the U.S. by half; on lands in Northern Peru, usually too dry for any cultivation, is possible to grow rice or beans. During 1997-98 El Niño, Northern USA States saved an estimated five billions dollars in heating costs.

The 1997 El Niño will be remembered for his strength: it carried more energy than a million atomic bombs; it killed an estimated 2100 people and caused damages for 33 billion dollars. Where there was a sand desert, created the second largest lake in Peru, 145 km long 30 km wide and 3 meters deep. Forest fires burned in Sumatra, Borneo, and Malaysia.

Kenya’s rainfall was 100 centimetres above normal, Madagascar experienced heavy monsoons and cyclones, violent floods stroked central Europe killing 55 in Poland and 60 in the Czech Republic.

El Niño is a natural event, an ordinary part of life on the planet of which there is evidence for many thousand years. But its consequences can be devastating.

Predicting this event is hard: researchers are using, together with the statistical approach, helped by ships, aircraft and buoys collecting data, computer models in the attempt to reproduce interactions between ocean and atmosphere.

Is not easy to understand how the global warming of the last century (which amounts to one twentieth of degree Celsius) influenced El Niño and La Niña. But the models indicate that the rainfall anomalies become stronger with the Greenhouse effects, and conditions could get more unpredictable with further climate change caused by humans.

Still researchers have to work hard to fully understand the mechanisms and cycle of El Niño and especially to find reliable methods to forecast its impact and evolution, for the great benefit in planning for drought, flood and to limit to the minimum extent the loss for property and human lives.

THE TRUMAN