17/4/2014 - 11h39
OMM alerta para possível elevação “dramática” das temperaturas neste ano devido à combinação El Niño e aquecimento global
por Fabiano Ávila, do CarbonoBrasil
Em seu mais recente boletim, a Organização Meteorológica Mundial (OMM)
destacou que há sinais de que teremos a formação do fenômeno conhecido como El
Niño em 2014, e que isso poderá resultar em altas temperaturas em todo o
planeta, agravando os efeitos do aquecimento global.
“O El Niño possui um importante efeito de
aquecimento nas temperaturas globais, como vimos durante o forte El Niño de
1998. Porém, somente dois dos últimos 15 anos apresentaram o fenômeno, e mesmo
assim foram mais quentes do que a média. Assim, a combinação entre o
aquecimento natural do El Niño com o aquecimento provocado pelos gases do
efeito estufa resultantes das atividades humanas podem causar uma alta
dramática nas temperaturas globais”, explicou Michel Jarraud, secretário-geral
da OMM.
Segundo
a entidade, a maioria dos modelos indica o desenvolvimento de um El Niño em
meados de 2014, apesar de ainda ser muito cedo para confirmar a força do
evento.
“Para
junho e agosto, cerca de dois terços dos modelos predizem que as condições para
o El Niño serão atingidas. Uma quantidade menor de modelos indica que isso pode
acontecer ainda antes, em maio. Nenhum modelo prevê a ocorrência da La Niña em
2014”, afirma o boletim.
O El Niño é o aquecimento acima da média da
temperatura da superfície do Oceano Pacífico na região equatorial, enquanto o
La Niña é o resfriamento. Os dois fenômenos formam o chamado ciclo ENSO.
Para o Brasil, além da elevação das temperaturas,
as consequências comuns do El Niño costumam ser a seca no Norte e o excesso de
umidade no Sul.
A expressão El Niño é derivada do espanhol, e
refere-se à presença de águas quentes na costa norte do Peru que costuma
ocorrer na época de Natal. Os pescadores da região chamaram esse fenômeno de
‘Corriente de El Niño’ em referência ao Niño Jesus ou Menino Jesus.
* Publicado originalmente no site CarbonoBrasil.
(CarbonoBrasil)
Press Release No. 990
For use of the information media
Not an official record
Not an official record
WMO Update Indicates Possible onset of
El Nino Around Middle of Year
|
Geneva, 15 April 2014 (WMO) - Sub-surface
water temperatures in the tropical Pacific have warmed to levels similar to the
onset of an El Nino event, and climate models surveyed by WMO experts predict a
steady warming of the tropical Pacific during the months ahead, according to
the latest Update
from the World Meteorological Organization.
A majority of models indicate that an El Niño may develop around the middle of
the year, but it is still too early to assess the strength of any such event.
El Niño is characterized by unusually warm
ocean surface temperatures in the central and eastern tropical Pacific. It has
a significant impact on climate in many parts of the world and has a warming
influence on global temperatures. It is the opposite of the La Niña phenomenon,
which is associated with cooling.
Since the second quarter of 2012, El
Niño-Southern Oscillation (ENSO) indicators (e.g., tropical Pacific sea surface
temperatures, sea level pressure, cloudiness and trade winds) have generally
remained at neutral levels. This is expected to continue into the earlier part
of the second quarter of 2014, according to the WMO Update.
However, since February there have been
two strong westerly wind events, and a general weakening of the trade winds in
the tropical Pacific. This has led to a significant warming of the waters below
the surface of the central Pacific, which historically has been one of the
precursors to El Niño development. While there is no guarantee this situation
will lead to an El Niño event, the longer the trade winds remain weakened, and
subsurface temperatures stay significantly warmer than average, the higher the
likelihood of the emergence of an El Niño.
“Model forecasts indicate a fairly large
potential for an El Niño, most likely by the end of the second quarter of
2014,” said the Update, which is compiled from inputs from climate experts and
prediction models around the world. “For the June to August period,
approximately two-thirds of the models surveyed predict that El Niño thresholds
will be reached, while the remaining models predict a continuation of neutral
conditions. A few models predict an earlier El Niño onset, such as in May. No
model suggests a La Niña in 2014.”
However, the strength of the possible El
Niño cannot be reliably estimated at the current time.
“El Niño and La Niña are major drivers of
the natural variability of our climate. If an El Niño event develops – and it
is still too early to be certain – it will influence temperatures and
precipitation and contribute to droughts or heavy rainfall in different regions
of the world,” said WMO Secretary-General Michel Jarraud. “The major advances
in our forecasting capabilities mean that we will be better prepared to manage
the impact of these events especially if extreme on agriculture, water, health
and many other climate-sensitive socio-economic sectors.”
“El Niño has an important warming effect
on global average temperatures, as we saw during the strong El Niño in 1998”
said Mr Jarraud. “Only two out of the past 15 years were categorized as El Niño
years, and yet all were warmer than average. “The combination of natural
warming from any El Niño event and human-induced warming from greenhouse gases
has the potential to cause dramatic rise in global mean temperature,” he said.
It is important to stress that no two El
Niño events are the same, and that other drivers also influence climate
patterns. At the regional level, seasonal outlooks are needed to assess the
relative impacts of both the ElNiño/La Niña state and other locally relevant
climate drivers. For example, the state of the Indian Ocean Dipole, or the
Tropical Atlantic SST Dipole, may impact the climate in adjacent land areas.
Locally applicable information will be
available via regional/national seasonal climate outlooks, such as those
produced by WMO Regional Climate Centres (RCCs), Regional Climate Outlook
Forums (RCOFs) and National Meteorological and Hydrological Services (NMHSs).
Background:
ENSO stands for El Niño/ Southern
Oscillation. The ENSO cycle refers to the year-to-year variations in sea-
surface temperatures, convective rainfall, surface air pressure, and
atmospheric circulation that occur across the equatorial Pacific Ocean.
El Niño – Spanish for boy child because it
often develops in December and is identified with the Christ Child - and La
Niña represents opposite extremes in the ENSO cycle.
El Niño refers to the above-average
sea-surface temperatures that periodically develop across the east-central
equatorial Pacific. It represents the warm phase of the ENSO cycle. La Niña
refers to the periodic cooling of sea-surface temperatures across the
east-central equatorial Pacific. It represents the cold phase of the ENSO
cycle.
The fluctuations in ocean temperatures
during El Niño and La Niña are accompanied by even larger-scale fluctuations in
air pressure between the western and eastern tropical Pacific known as the
Southern Oscillation.
During El Niño events, the eastward shift
of thunderstorm activity from Indonesia into the central Pacific can result in
abnormally dry conditions over northern Australia, Indonesia and the
Philippines. Drier than normal conditions are also often observed over
southeastern Africa and northern Brazil, during the northern winter season.
During the northern summer season, Indian monsoon rainfall tends to be less
than normal, especially in northwest India where crops are adversely affected.
Wetter than normal conditions are observed along the west coast of tropical
South America, and at subtropical latitudes of North America (Gulf Coast) and
South America (southern Brazil to central Argentina).
During an El Niño event in winter,
mid-latitude low pressure systems tend to be more vigorous than normal in the
region of the eastern North Pacific. These systems pump abnormally warm air
into western Canada, Alaska and the extreme northern portion of the contiguous
United States. Storms also tend to be more vigorous in the Gulf of Mexico and
along the southeast coast of the United States resulting in wetter than normal
conditions in that region. (source)
(Source NOAA NCEP)
Weather, Climate and Water
For more information, please contact Clare
Nullis at +41 22 730 8478 (fixed), +41 79 709 1397 or cnullis(at)wmo.int
No comments:
Post a Comment