By Eric J. Lyman
As El Niño’s storms pounded the Pacific coast of the Americas starting in late
1997, its effect on the Peruvian coastal city of Trujillo reached apocalyptic proportions. Rivers
burst their banks and the sea surged 15 kilometers inland to flood the main plaza of the
desert city of one million, which can go a decade without a drop of rain. The deluge rendered
hundreds of kilometers of roads in Trujillos’s district of La Liberdád useless and destroyed
or disabled 43 of 56 bridges around the city. Flood waters even eroded the earth in the city’s
oldest graveyard, sending cadavers and ancient coffins floating through the streets in a
spectre so horrible that city leaders dedicated one stormy Sunday in March to ask
beleaguered citizens to beg God for relief.
The name El Niño -- Spanish for "the Christ Child" --
comes from Peruvian fisherman, who named it
generations ago for the timing of its peak, which
usually comes around Christmas. Historical
records show the phenomenon has occurred
every two to ten years for at least the last five
centuries. Since the turn of this century, 23 El Niños
have affected the earth, according to the US National
Oceanic and Atmospheric Administration (NOAA).
But the four strongest have all struck since 1980.
El Niño is a fluctuation in the distribution of sea-surface temperatures and of atmospheric
pressure across the tropical Pacific Ocean, leading to worldwide impacts on regional
weather patterns. No one knows exactly why it takes place, but recent computer climate
modeling suggests the frequency and strength of both El Niño and its sister effect La Niña
are increased by global warming -- and 1998 was by far the warmest year since worldwide
records began 150 years ago.
Despite doubts over the precise relationship of climatic cause-and-effect, the mechanisms
are well documented. In normal conditions, trade winds blowing west along the equator
push warmer surface waters towards southeast Asia, where they accumulate, evaporate and
fall as heavy tropical rains. Meanwhile, off the Pacific coast of Latin America, cooler nutrient-
rich waters well up from the ocean depths, causing dryer conditions along the shores of Peru
and Chile, and making their fishing grounds among the most fertile in the world.
- During El Niño, trade winds weaken or reverse, and the
warm surface waters of the western equatorial Pacific
shift east. This generates unseasonal rain and storms
over the Pacific coast of the Americas, while leaving
drought to afflict southeast Asia and the western Pacific.
By January 1998, at the peak of the latest El Niño, a pool
of hot water the size of Canada and up to 400 meters
deep stretched west from Latin America, preventing the
cooler coastal waters from welling up and seriously
disrupting oceanic food chains. Surface water
temperatures in the eastern equatorial Pacific reached
around the world. But the areas hit hardest by El Niño’s effects are usually the western and
eastern rims of the Pacific, between 35 degrees north and south of the equator.
Pioneer meteorologist Sir Gilbert Walker, working in the 1920s, was the first to notice that
when air pressure increases in the west Pacific, it drops in the east, causing the Pacific’s
west-bound trade winds to reverse course. Subsequent statistical analysis in the 1960s
linked this pressure inversion (known as the Southern Oscillation) with El Niño. Lower
pressure in the eastern equatorial Pacific during El Niño events also draws the subtropical
jet stream further south, producing water winter storms and in the south-west US and north-
west Mexico. As the jet stream continues east, it meets little resistance from weak westerly
trade winds and slices off the tops of Atlantic hurricanes, preventing many of them from
reaching the US east coast and Caribbean.
Once El Niño has passed, seawater and air circulation reverse direction again. If the swing
back is dramatic, it creates a condition called La Niña -- less frequent and therefore less
studied than recent El Niños. During La Niña, the warm waters off Latin America head west
and are replaced by unusually cold currents known as the "equatorial cold tongue," chilling
sea-surface temperature by up to seven degrees Celsius below El Niño levels. Westbound
trade winds blow stronger than usual, and cycles of flooding and drought are often inverted.
Heavier rains fall on the western Pacfic, southern and eastern Asia, northern Australia, and
as far west as southern Africa. High atmospheric pressure over the central Pacific weakens
the subtropical jet stream, allowing powerful Atlantic hurricanes to form. On 24 September
1998, for the first time this century, four Atlantic hurricanes -- including the deadly Hurricane
Mitch -- were active at once. "Such enhanced hurricane activity," says the World Meteorogical
Organization, "is consistent with developing La Niña conditions."
El Niño pummels Peru
In Latin America, the unusually long and severe weather fluctuations of 1997-98’s El Niño
were aggravated by changes in population concentration, over-development of in urban
areas and the rapid growth of weather-sensitive industries like fishing and agriculture,
making the fallout among the worst ever recorded.
Across Peru, rain-swollen rivers and mudslides destroyed 300 bridges and swept away
entire villages, leaving up to a half a million homeless. Government estimates put El Niño-
related damage to public infrastructure alone at US$ 2.6 billion -- nearly five percent of the
country’s gross domestic product. Waters offshore became so warm that many fish species
headed north or south in search of cooler, more than nutrient-rich climes. Violent rainfall
churned up coastal seas and fresh water runoff decreased salinity, further affecting fish
stocks. Peru’s merchant fishing fleet -- usually the country’s second largest industry -- saw
output in the first quarter of the 1998 fall a staggering 96 percent compared to the same
period in 1997. Severe weather completely closed the ports of Callao and Chiclayo (Peru’s
first and fourth most important ports) and flooding buried half the major port of Ica (the fifth
largest port) under two meters of mud that kept the port closed more than a year after
weather began to return to normal.
lingering effect of El Niño could be the diseases spread, argued that such diseases and even birth defects may not become apparent
for a generation. Even if this overstates the case, floods increased the chance of contracting diseases transmitted by rodents and
polluted water. Pan-American Health Organization (PAHO) warned that floods and warmer weather produced conditions favoring the
spread of malaria, yellow fever, and dengue fever. In the Piura region alone, three times as many residents as usual contracted
malaria -- 30,000 cases affected one in 50 of the population. And health services were severely handicapped by El Niño-related
flooding, which damaged equipment, supplies, and buildings. Nevertheless, health preparedness throughout the region was far better
than prior to the 1982-83 event.
The economic impact on Peru may be felt for a decade or more. The fishing industry isn’t expected to match 1996 levels (the last full
pre-El Niño year) until 2002-03 and may not resume its growth curve for several years after that, according to the private sector National
Association of Fishing Workers. Mining, Peru’s largest industry, had already been crippled by low commodity prices associated with
Asia’s economic problems, and El Niño prolonged production schedules at several important coastal mines through flooding and
road damage. Tourism-related revenues fell in 1998 for the first time this decade. Consumer spending fell 15 percent compared to the
previous year. And one survey showed the Peruvian’s confidence in the economy and government sliding to 18% at its low point during
El Niño, compared to 72 percent in late 1996. Damage to the agricultural sector, which saw production fall by a quarter in the first half
of 1998, compared to 1997 levels, forced Peru to become a net importer of several key food products, swelling the country’s trade gap
to an estimated US$ 2.7 billion in 1998 from US$ 1.8 billion in 1997. The country’s usually robust economy, which grew an average of
6.9 percent a year from 1993 to 1997, mustered only 0.7 percent year-on-year growth in 1998 -- which amounted to an economic
contraction in per capita terms, as Peru’s population grew 2.2 percent during the same period.
International Federation of Red Cross and Red Crescent Societies
www.ifrc.com
All rights reserved.
1 2 3 Sources
