Floods in Europe - el nino phenomenon? A. Tausch, 30 July 1997

Wed, 21 Jul 1993 14:58:51 -0700
Austrian Embassy (austria@it.com.pl)

An important question is, whether or not the recurrence of major floods
and hurricanes in our age is coincidental or connected to global warming.
In the summer of 1997, Europe again was hard-hit by extensive floods, just
as in summer 1996. In 1996, the Netherlands were hardest hit, and in 1997,
Poland and the Czech Republic. In all that, the delicate long-standing
oscillations in the velocity and temperature of Oceanic currents
intervenes. Precisely this delicate balance seems, one could tentatively
argue, to have been upset now in a fundamental way: already in 1991 it was
discovered that the velocity of the Gulf stream northeast of Iceland
decreased by 80%, thus affecting the delicate equilibrium between the
salt-content of the Oceanic waters, the velocity of Oceanic circulation,
and the cold winds from the North Pole (Gore, 1994). A huge, powerful
current usually carries warm water from the vicinity of Florida to the
coast of Ireland before turning westward, cooling, sinking, and going back
south near Labrador. Deep-lying parcels of unusually warm water move
continually through that pipeline, alternating with cooler ones. Each
parcel takes about 20 years to travel from the tropics, around the North
Atlantic circuit to Labrador. Sea-surface temperatures rise and fall in
concert with the movement of these parcels (New York Times, March 18th,
1997). Since the 1970s, the North Atlantic oscillation and a similar
oscillation in the Pacific have made the continents of the Northern
hemisphere unusually warm, during winter and spring (New York Times, March
18th, 1997). 'El Nino', that vast pool of unusually warm surface water that
comes and goes every few years in the eastern tropical Pacific, and first
discovered around Christmas by Peruvian fishermen 200 years ago, is a
similar phenomenon (Los Angeles Times, May 16th, 1997), that, in the past,
was followed each time by 'La Nina', the corresponding pool of cold water
in the rhythm of two to seven years (NY Times, June 3rd, 1997):

In their search for convincing evidence of global warming, scientists have
been puzzling over shifting tree lines in the Sierra Nevada, dying coral in
the Caribbean, melting alpine glaciers, and seasonal temperatures so
extreme that the 10 warmest years of the past century have occurred in the
last 15 years.
When malaria-infected mosquitoes recently turned up in New Jersey and
tropical microorganisms were discovered poisoning shellfish as far north as
Monterey, climate experts were quick to wonder whether they had detected
evidence of climate changes.

In each case, pests once confined to the world's hottest regions appeared
to be moving into new territory--evidence, perhaps, of formerly cool zones
warmed by greenhouse gases.

Now some researchers believe that they have detected the distinctive
signature of global warming in the infamous Pacific Ocean current known as
El Nino, a seasonal upwelling of warm seawater that has been implicated in
disastrous droughts, torrential rains, killing heat waves and other
distortions of the daily weather from Southern California to South Africa.

The El Nino current arises from the dance between order and chaos as the
ocean and the atmosphere interact to balance the Earth's thermal energy. It
is the heart of a complex system called the El Nino Southern Oscillation,
which is so delicate that even a subtle alteration in temperatures can
affect its seesaw, annual rhythms.

Global warming should make El Nino effects stronger and more frequent, said
Kevin Trenberth of the National Center for Atmospheric Research in Boulder,
Colo. And, as if to prove his point, the most recent El Nino, which some
scientists say lasted from 1990 through 1995, is the longest in 130 years
of record-keeping (Los Angeles Times, May 16th, 1997)

The emerging pattern seems easy to predict: milder and drier winters in
Alaska, Canada, and the Pacific Northwest, cooler in the Southeastern
United States and wetter in the US Southwest. Powerful west-to-east winds
across the Atlantic brings more oceanic warmth to Northern Europe and Asia,
making for milder winters there. Northern Europe gets more precipitation,
while Southern Europe and the Middle East less. Until now, the oscillations
in Oceanic currents caused ups and downs in world weather cycles, causing a
shift of the westerly winds to the European South, making Northern Europe
much colder and drier and bringing more warmth and precipitation to
Mediterranean Europe, Africa and the Middle East. The Medieval warm period
and the Little Ice Age were all - current opinion goes - a consequence of
these oscillations (New York Times, March 18th, 1997). The question is of
course, whether or not we're in for a more secular change, that seems to be
directing towards more hurricanes in the Southeastern US, more torrential
summer rains in Europe, and Western Latin America, and more droughts in
many other parts of the world, among them Australia and many parts of Asia.
It might also well be that the 'peaks' in the common re-occurence of the
'El Nino' phenomenon get larger, up to five years (Los Angeles Times, May
16th, 1996). Several meteorologists, among them Timothy Barnett at the
Scripps Institution of Oceanography, rule out the connection between 'El
Nino' and global warming, however. Their arguments say that similar
prolonged El Ninos were observed during 1911 to 1915, and that volcanic
eruptions, deep-sea thermal events or the 11 to 22 year sun-spot cycle may
cause the phenomenon. Indeed, they'd argue that up to 50% in global
temperature rise since 1900 must be attributed to a rising sunspot
activity, and not to Carbon Dioxide levels (LA Times, ibidem). Fairly safe
predictions estimate that up to a third of the world's glaciers will melt
away over the next decades, together with a 2-6 degrees Fahrenheit rise in
average surface temperature and a rise in the sea levels up to three feet
during the next 100 years (LA Times, ibidem). However, there seems to be
rising consensus that severe hurricanes will develop in the Atlantic arena
over the next years (New York Times, June 3rd, 1997). Sea surface
temperatures in the tropical Atlantic have risen since 1955 in almost
continuous fashion (NY Times, ibidem). It is not yet certain, of course,
whether or not global warming really contributes to this phenomenon. It
should be recalled, that wet weather and low pressure areas in Africa's
Sahel zone are the at the root of hurricane embryos, kept in check by
high-level westerly winds blowing from the Eastern tropical Pacific, and
caused by El Nino (NY Times, June 3rd, 1997). One plausible hypothesis is
of course:

One of the most powerful indicators, according to the new study by Dr.
Saunders and Andrew R. Harris, climate scientists at University College
London in Britain, is the Atlantic sea-surface temperature. Their
statistical analysis found that while most of the relevant factors were
indeed favorable for hurricane development in the banner year of 1995, the
dominating influence was the unusually warm ocean. The temperature in the
region where hurricanes develop was 1.2 degrees Fahrenheit above the
1946-1995 average, a record. The development region was 0.36 of a degree
warmer than average last year and is about 0.9 of a degree warmer now.
This, said Dr. Saunders, presages another active season. His study appeared
in the May 15 issue of the journal Geophysical Research Letters.

The researchers suggest that warmer seas cause more water to evaporate from
the surface. With evaporation, latent heat is released in the atmosphere,
and the researchers believe that this is what imparts more energy to the
embryonic storms coming out of Africa, making it more likely that they will
develop into hurricanes. "It seems that this is a stronger effect that any
other mechanism, like El Nino or the monsoon in the western Sahel," Dr.
Saunders said.

The question, he said, is whether the rising sea temperature is a natural
expression of the climate system's variability, independent of any
influence from a warming atmosphere. Dr. Gray, for his part, says he
believes the warmer ocean temperature is "a manifestation of a major change
in North Atlantic ocean circulation." Stately currents in the North
Atlantic undergo periodic shifts on decadal time scales. Dr. Gray said he
believed that a new pattern was in place, and that it was likely to presage
a decade or two of above-average hurricane activity.

"This is the greatest fear we have," he said, "that we're entering a new
era. I believe we are." (New York Times, June 3rd, 1997)

In the northern hemisphere, regions north-east of the warming Ocean regions
receive above than average rainfalls, while in the southern hemisphere,
regions south-east of the 'El Nino' area receive the highest rainfalls. On
the western shores, severe droughts can develop, in regions as far apart as
North Korea, Australia, and Eastern Canada. Severe storms are to be
expected in countries or regions like Western Mexico, Peru, and Chile
(Reuters, North America News Report, July 15th, 1997). World poverty and
environmental degradation in marginal lands are closely inter-linked with
such phenomena. During the last El Nino, which happened in 1982-83,
hundreds died in Peru in flood and landslides, and tens of thousands were
left homeless. Colombia braces itself for a severe drought, starting in
February 1998, in turn, while Brazil and low-lying areas of Argentina
expect heavy rainfalls, and the Argentinean Andes will receive unusual
amounts of snow. More than 500 million poor people live on marginal lands
in the Sahel and in the upper regions of the Andes and the Himalayas. Dry
lands are the home to 1.5 billion people on earth. Conflicts between
farmers and herders are proliferating in Africa and in Asia (UNDP, 1997).
The tragic events in Rwanda and Burundi cannot be separated from two
processes a) these conflicts b) the structure of land intensive raw
material exports, like coffee growing, imposed by the structures of world
tariffs and world trade, on Africa (Amin, 1994). The water supply per
capita in developing countries today is only a third of what it was in
1970. More than 55% of the people in the Arab world suffer from serious
water shortages. Over the past 50 years, 65 million hectares of productive
land have become desert (UNDP, 1997).
World pollution is even a clear statistical function of the ups and downs
of the longer swings in the world economy, most notably the Kuznets cycle
and the Kondratieff cycle. The World Resources Institute has provided
information on the basis of the Carbon Dioxide Information Analysis Center
about CO2 emissions in the world from 1950 onwards. The growth rates of CO2
consumption clearly correspond to the Kondratieff and Kuznets cycle
analysis about economic growth