El Nino literally means ''the boy", but this year the mother of all
El
Ninos seems to be turning the world's weather patterns
upside down.
Climatologists are predicting that the El Nino taking shape in 1997
could well be the biggest such event this century. The
unseasonable droughts and floods which follow in its wake will
probably inflict tremendous carnage: the last major El Nino in
1982-83 caused an estimated 2,000 deaths and US$13 billion worth of
damage.
El Nino is already being blamed for a number of bizarre incidents this
year: Southeast Asia is being blanketed by haze while
the usually smog-ridden city of Los Angeles is expecting the cleanest
air on record; frost has appeared in the highlands of
Papua New Guinea, but tropical fish have been caught in the Pacific
Ocean just south of Canada.
El Nino is not solely responsible for all these events. The forest
fires burning in Indonesia, for instance, were set by
plantation companies and farmers clearing land; El Nino has simply
exacerbated the situation by delaying the rains that
usually put them out. But the impact of this global climatic
phenomenon is being felt all around the Pacific Rim.
Along with Indonesia, El Nino-inspired droughts are also causing
famine in Papua New Guinea and North Korea, and
damaging harvests in Northern Australia and the Philippines. In
Thailand, it has led to a paucity of rain in the North, which
may in turn lead to water shortages for Bangkok and the Central Plains
next year as the Sirikit and Bhumibol dam reservoirs
are only half full.
Meanwhile, across the Pacific, the normally arid coasts of the
Americas are expecting a wet winter. California was almost hit
by a hurricane for the first time ever last month, while unusually
warm ocean waters recently sent Hurricane Nora barrelling
across Mexico's Baja peninsula and into the deserts of Arizona.
Droughts in Africa, mild winters in eastern North America, a dearth
of
hurricanes in the Gulf of Mexico, whale beachings in
the Falklands, fishery declines in South America, higher crop prices
around the world the list of effects seems to go on and
on. But what exactly is El Nino, and how does it cause so much mayhem?
For an answer, it is first necessary to understand how normal weather
conditions come about through the interplay between
the atmosphere and the oceans.
One of the first things meteorologists look at when studying weather
patterns is the atmospheric pressure. When the
weatherman says there is a high-pressure zone on the way, that usually
means there will be clear and sunny skies. A
low-pressure zone makes for rain and cloudy skies (and when weathermen
warn about a depression, or very low pressure,
that generally means a storm is coming).
In equatorial regions, the western Pacific is often dominated by a low
pressure zone, while the eastern Pacific is usually
influenced by higher atmospheric pressure. The trade winds, which blow
almost continually from east to west across the
Pacific, are created as air from the high-pressure zone rushes toward
the area of lower pressure.
These winds also continually blow warm surface water westward until
it
piles up against the Asian land mass. In Micronesia,
for instance, the sea level is typically 90 centimetres higher and
the
water temperature roughly three degrees warmer than in
Peru, where the seas are kept relatively cold because the warm surface
water that has blown away is ''replaced" by
Antarctic currents and an upwelling of cold water from the ocean
depths.
However, every five years or so, for reasons no one really
understands, this circulating pattern is brought to a halt or even
reversed. The trade winds go limp, or change direction. The warm
surface waters of the Pacific flow back toward the east,
forming a huge pool of tepid water off South America.
Peruvian fishermen noted this phenomenon long ago and dubbed it El
Nino after the Christ child because it usually
seemed to occur around Christmas time. For them, the warm seas not
only lead to heavy winter rains and floods, but also
drive away plankton tiny sea creatures that enjoy the cold water
and thus decimate the normally-rich population of
anchovy, a species of fish that feeds on the plankton.
The loss of the Peruvian anchovy harvest hurts everyone, in fact,
because (along with being a popular pizza topping) it is
used to make fishmeal, a vital component of animal feeds. As a result
with crops worldwide also damaged by droughts and
floods food prices in general tend to rise in the wake of El
Nino.
This year, a bulge of warm water the size of Canada has already
migrated from the central Pacific to the coast of South
America, where it has raised sea levels by 25 centimetres and
increased water temperatures by five degrees one sign that
this El Nino is likely to be a big one.
Perhaps more importantly for Asia, however, is a related phenomenon
known as the ''Southern Oscillation" (the full scientific
name for El Nino is actually El Nino-Southern Oscillation, or Enso).
This refers to the atmospheric pressure over the eastern
and western Pacific regions, which flip-flops during Enso years: the
American coast is dominated by a low pressure zone,
while equatorial Asia falls under the sway of a high pressure ridge.
Air pressure measurements on each side of the Pacific carried out
earlier this year revealed that a very dramatic Southern
Oscillation another sign that a serious Enso event has been brewing.
But 1997 is also the first year that a prediction was
made early enough to help prevent some of the damage.
For instance, a drought in northeastern Australia is expected to cause
a roughly US$1 billion shortfall in grain harvests this
year, but the situation would have been much worse if farmers hadn't
sold off much of their cattle and changed their planting
schedules after being warned of a strong El Nino.
Indonesian officials, however, were apparently not as alert. Their
failure to prevent forest fires this year has resulted in the
worst haze crisis ever for Southeast Asia. In years past, Mother
Nature has doused the flames with monsoon rains, but in
1997 ''the boy" has stoked them with drought.
Some experts have suggested that El Nino events and their opposite,
La Nina events, which also occur be considered a
kind of season, taking place every few years and lasting 12-18 months,
rather than within a year like the annual seasons
with which we are more familiar.
But the cause of Enso events remains a mystery. Some have speculated
that they are triggered by earthquakes on the
bottom of the Pacific Ocean, but no one knows for sure.
What's more, El Nino seems to be occurring more frequently, and may
be
getting stronger, perhaps as a result of the
greenhouse effect. Scientists are pretty certain that global warming
is affecting Enso events, but again no one seems to
know quite how.
The one thing we do know is that there is a lot more to learn about
our planet's chaotic climate. In the meantime, look out for
a mighty temper tantrum in the coming months from an extremely naughty
and not-so-little ''boy".