Jul. 17, 2009
At the Department of Energy's Oak Ridge National Laboratory (ORNL), the world's fastest supercomputer for unclassified research is simulating abruptclimate change and shedding light on an enigmatic period of natural global warming in Earth's relatively recent history. The work, led by scientists at the University of Wisconsin and the National Center for Atmospheric Research (NCAR), is featured in the July 17 issue of the journal Science and provides valuable new data about the causes and effects of global climate change.
This research is funded by the Office of Biological and Environmental Research within DOE's Office of Science and by the National Science Foundation through its paleoclimate program and support of NCAR.
In Earth's 4.5-billion-year history, its climate has oscillated between hot and cold. Today our world is relatively cool, resting between ice ages. Variations in planetary orbit, solar output, and volcanic eruptions all change Earth's temperature. Since the Industrial Revolution, however, humans have probably warmed the world faster than nature has. The greenhouse gases we generate by burning fossil fuels and forests will raise the average global temperature 2 to 12 degrees Fahrenheit (1 to 6 degrees Celsius) this century, the Intergovernmental Panel on Climate Change (IPCC) estimates.
Most natural climate change has taken place over thousands or even millions of years. But an episode of abrupt climate change occurred over centuries—possibly decades—during Earth's most recent period of natural global warming, called the Bolling-Allerod warming. Approximately 19,000 years ago, ice sheets started melting in North America and Eurasia. By 17,000 years ago, the melting glaciers had dumped so much freshwater into the North Atlantic that it stopped the overturning ocean circulation, which is driven by density gradients caused by influxes of freshwater and surface heat. This occurrence led to a cooling in Greenland called the Heinrich event 1. The freshwater flux continued on and off until about 14,500 years ago, when it virtually stopped. Greenland's temperature then rose by 27 degrees Fahrenheit (15 degrees Celsius) in several centuries, and the sea level rose about 16 feet (5 meters). The cause of this dramatic Bolling-Allerod warming has remained a mystery and source of intense debate.
'Now we are able to simulate these transient events for the first time,' says Zhengyu Liu, a University of Wisconsin professor of atmospheric and oceanic sciences and environmental studies whose team simulated the abrupt climate changes using DOE supercomputers at ORNL. The Oak Ridge Leadership Computing Facility allocated supercomputing time through DOE's Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. 'It represents so far the most serious validation test of our model capability for simulating large, abrupt climate changes, and this validation is critical for us to assess the model's projection of abrupt changes in the future,' according to Liu.
The Oak Ridge Leadership Computing Facility is funded by the Office of Advanced Scientific Computing Research in DOE's Office of Science.
Liu, director of the University of Wisconsin's Center for Climatic Research, and his collaborator Bette Otto-Bliesner, an atmospheric scientist and climate modeler at NCAR, lead an interdisciplinary, multi-institution research group attempting the world's first continuous simulation of 21,000 years of Earth's climate history, from the last glacial maximum to the present, in a state-of-the-art climate model. The group will also extend the simulation 200 years into the future to forecast climate. The findings could provide great insight into the fate of ocean circulation in light of continued glacial melting in Greenland and Antarctica.
Three parts to abrupt change
Most climate simulations in comprehensive climate models so far are discontinuous, amounting to snapshots of century-sized time slices taken every 1,000 years or so. Such simulations are incapable of simulating abrupt transitions occurring on centennial or millennial timescales. Liu and Otto-Bliesner employ petascale supercomputers, capable of a quadrillion calculations each second, to stitch together a continuous stream of global climate snapshots and recover the virtual history of global climate in a motion picture. They use the Community Climate System Model (CCSM), a global climate model that includes coupled interactions between atmosphere, oceans, lands, and sea ice developed with primary funding from the National Science Foundation (NSF) and DOE.
Based on insights gleaned from their continuous simulation, Liu and his colleagues propose a novel mechanism to explain the Bolling-Allerod warming observed in Greenland ice cores. The three-part mechanism they suggest matches the climate record.
First, one-third of the warming, or 9 degrees Fahrenheit (5 degrees Celsius), resulted from a 45 parts-per-million increase in the atmospheric concentration of carbon dioxide, the scientists posit. The cause of the carbon dioxide increase, however, is still a topic of active research, Liu says.
Second, another one-third of the warming was due to recovery of oceanic heat transport. When fresh meltwater flowed off the ice sheet, it stopped the overturning ocean current and in turn the warm surface current from low latitudes, leading to a cooling in the North Atlantic and nearby region. When the melting ice sheet was no longer dumping freshwater into the North Atlantic, the region began to heat up.
The last one-third of the temperature rise resulted from an overshoot of the overturning circulation. 'Once the glacial melt stopped, the enormous subsurface heat that had accumulated for 3,000 years erupted like a volcano and popped out over decades,' Liu hypothesizes. 'This huge heat flux melted the sea ice and warmed up Greenland.'
Liu and Otto-Bliesner's collaborators include Feng He, a doctoral student at the University of Wisconsin-Madison who is mainly responsible for the deglaciation modeling, as well as ocean modeler Esther Brady (NCAR), atmospheric scientist Robert Tomas (NCAR), glaciologists Peter Clark (Oregon State University) and Anders Carlson (University of Wisconsin-Madison), paleoceanographers Jean Lynch-Stieglitz (Georgia Institute of Technology) and William Curry (Woods Hole Oceanographic Institution), geochemist Edward Brook (Oregon State University), atmospheric modeler David Erickson (ORNL), computing expert Robert Jacob (Argonne National Laboratory), and climate modelers John Kutzbach (University of Wisconsin-Madison) and Jun Cheng (Nanjing University of Information Science and Technology). 'This interdisciplinary team, each member contributing to a different aspect of the project, ranging from a proxy data interpretation to supercomputing coding, has been essential for the success of this project,' says Liu.
The 2008 simulations ran on a Cray X1E supercomputer named Phoenix and an even faster Cray XT system called Jaguar. The scientists used nearly a million processor hours in 2008 to run one-third of their simulation, from 21,000 years ago—the most recent glacial maximum—to 14,000 years ago—the planet's most recent major period of natural global warming. With 4 million INCITE processor hours allocated on Jaguar for 2009, 2010, and 2011, they will complete the simulation, capturing climate from 14,000 years ago to the present and projecting it 200 years into the future. 'This has been a dream run of both of ours for a long time,' says Otto-Bliesner. 'This was an opportunity to take advantage of the CCSM, the computing facility at Oak Ridge, and the INCITE call for proposals.' No other research group has successfully simulated such a long period in a comprehensive climate model.
Science-based forecasts
More accurately depicting the past means clearer insights into climate's outlook. 'The current forecast predicts the ocean overturning current is likely to weaken but not stop over the next century,' Liu says. 'However, it remains highly uncertain whether abrupt changes will occur in the next century because of our lack of confidence in the model's capability in simulating abrupt changes. Our simulation is an important step in assessing the likelihood of predicted abrupt climate changes in the future because it provides a rigorous test of our model against the major abrupt changes observed in the recent past.'
In 2004 and 2005, climate simulations on DOE supercomputers contributed data to a repository that scientists worldwide accessed to write approximately 300 journal articles. The published articles were cited in the Fourth Assessment Report of the IPCC, which concluded that global warming is unequivocal and humans have had a substantial role since the mid-20th century.
Liu and Otto-Bliesner's simulations may soon find their way into IPCC's data repository and reports as other groups succeed in continuous simulation of past abrupt climate changes and demonstrate the results are reproducible. The simulations would thus be a resource for the paleo community at large. Meanwhile, Earth's climate continues to prove that change is an eternal constant. Understanding how we affect the rate of change is a grand challenge of our generation. Petascale computing may accelerate answers that in turn inform our policies and guide our actions.
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20/9/12
Oak Ridge supercomputers provide first simulation of abrupt Climate Change
19/9/12
El deshielo ártico destroza su récord
La superficie helada cae un 18% respecto al anterior mínimo, de septiembre de 2007
La pérdida equivale a 1,5 veces la superficie de España
EL PAIS RAFAEL MÉNDEZ Madrid 19 SEP 2012 - 21:34 CET
El Ártico alcanzó el pasado 16 de septiembre la mínima extensión helada desde que en 1979 los satélites comenzaron a realizar mediciones. Ese día contaba con 3,41 millones de kilómetros cuadrados helados, lo que supone un 18% menos que en el anterior récord, del 18 de septiembre de 2007, según ha anunciado este miércoles el NSIDC, el organismo de EE UU que realiza las mediciones. Respecto al mínimo de hace cinco años, la diferencia es de 760.000 kilómetros cuadrados, lo que supone 1,5 veces el tamaño de España. Los científicos relacionan el deshielo del Ártico con el calentamiento global y prevén que en solo unas décadas quede libre de hielo en verano. Los seis mínimos de extensión han ocurrido los últimos seis años.
El Ártico alcanzó el pasado 16 de septiembre la mínima extensión helada desde que en 1979 los satélites comenzaron a realizar mediciones. Ese día contaba con 3,41 millones de kilómetros cuadrados helados, lo que supone un 18% menos que en el anterior récord, del 18 de septiembre de 2007, según ha anunciado este miércoles el NSIDC, el organismo de EE UU que realiza las mediciones. Respecto al mínimo de hace cinco años, la diferencia es de 760.000 kilómetros cuadrados, lo que supone 1,5 veces el tamaño de España. Los científicos relacionan el deshielo del Ártico con el calentamiento global y prevén que en solo unas décadas quede libre de hielo en verano. Los seis mínimos de extensión han ocurrido los últimos seis años.
alt Meier, científico del NSIDC en la Universidad de Colorado, explica por teléfono la relevancia del dato: “Es muy sorprendente porque el récord de 2007 ya estaba un 22% por debajo del anterior récord. Ahora tenemos la mitad de la superficie helada que hace solo unas décadas”.
Además, cada vez hay menos hielo plurianual, el grueso que ha sobrevivido varios veranos y que acumula varias capas. “Hay pocos datos, pero creemos que el hielo es de media un 50% más fino que hace unas décadas”, señala Meier. La cifra es además notable porque en 2007 la zona tuvo unas condiciones meteorológicas, “vientos, nubes y temperatura del aire, que favorecieron la pérdida de hielo, pero este año las condiciones no han sido tan extremas”, según el comunicado del NSIDC.
Las mediciones por satélite comenzaron en 1979, pero, según Meier, se puede decir con seguridad que esta situación no se ha dado en mucho más tiempo: “Por registros paleoclimáticos, sedimentos y restos fósiles parece que no ha habido una situación igual en los últimos 8.000 o 10.000 años”.
Desde el pasado domingo, el hielo ártico crece —como cada otoño—, aunque el NSIDC advierte de que las condiciones meteorológicas pueden aún reducir algo la extensión y que dará un informe completo en octubre. El deshielo ártico no contribuye a la subida del nivel del mar, ya que es el agua del océano la que se congela en invierno y se deshiela —cada vez más— en verano.
La rapidez del deshielo en el Polo Norte ha superado todas las previsiones. “Vemos que el deshielo en verano va más rápido que lo que preveían los modelos climáticos”, señala Meier, que añade que esto no implica que el año que viene vaya a empeorar: “Puede haber algo de variabilidad natural. Puede que se estabilice unos años”.
Meier enfatiza que la variabilidad natural puede tener alguna responsabilidad, pero no toda, en el deshielo. El resto lo atribuye, como la mayoría de los científicos, al cambio climático producido por la emisión de combustibles fósiles. El uso de estos, principalmente carbón y petróleo desde la Revolución Industrial, emite CO2, que se acumula en la atmósfera, retiene parte del calor que emite la Tierra y calienta el planeta. Meier asegura que “es muy probable que en los próximos 20 o 30 años el Ártico quede en verano libre de hielo”. En solo unos años, los científicos han ido adelantando su previsión sobre cuándo ocurriría eso: de 2070 bajaron a 2040 y ahora no descartan que ocurra en dos décadas.
“Estamos en un territorio inexplorado”, señala en una nota Mark Serreze, director del NSIDC: “Sabemos desde hace tiempo que al calentarse el planeta los cambios se verían primero y serían más pronunciados en el Ártico, pero pocos estábamos preparados para lo rápido que iban a ocurrir”.
Carlos Duarte, del Consejo Superior de Investigaciones Científicas y que ha dirigido expediciones al Ártico, señala que la extensión del hielo no es lo más importante, sino el aumento observado en la varianza, algo que vale para el hielo en el polo y para la Bolsa: “Los datos indican que el Ártico ha llegado a un cambio de régimen y puede haber cambios abruptos”.
Duarte es rotundo: “Esto no es la variabilidad natural del clima. Esto es cambio climático verde y con asas, es lo que la Convención de Naciones Unidas define como ‘cambio climático peligroso’. Mientras, estamos enfrascados en discusiones semánticas”. Duarte tiene un símil para la inacción: “Estamos tocando la lira mientras arde Roma”.
El deshielo del Ártico ha generado enormes expectativas en compañías petrolíferas, de gas y mineras que esperan poder acceder a un territorio rico e inexplorado.
2/9/12
After a glorious autumn... Britain prepares for Siberian freeze in just weeks
·
Forecasters
warning temperatures could drop to -15C by December
UPDATED:
Britain faces an abrupt end to a
remarkably warm autumn with temperatures plummeting towards Siberian levels,
forecasters are warning. The
unusually mild weather is about to give way to a freezing winter, as
thermometers dip well below zero within a fortnight. And
the country will be coping with -15C cold by December, according to experts,
who have warned that the weather could be as brutal as last year.
Big freeze: Last year's snowy weather plunged
the country into chaos
Snow could hit the country even earlier
than it did then, when the big freeze at the end of November sent Britain into
chaos, blocking roads, causing accidents and burying houses.
Some
forecasters fear that temperatures could plunge as low as the -20C recorded a
year ago, or even lower, according to the Daily Express.
More...
Jonathan
Powell of Positive Weather Solutions said: 'It will not be as sustained as last
year, but these episodes are expected to be severe, with Siberian
temperatures.'
The
warnings came as the Government announced the Met Office will send out extreme
weather alerts this year to the NHS, social services and other agencies in a
bid to cut the 25,000 extra deaths caused by winter in the UK.
Forecaster
Brian Gaze of The Weather Outlook, told the newspaper: 'There are signs of a
significant change in the mild weather in mid-November.
The Government has
vowed to be more prepared for extreme conditions this year
'The current mild
weather is caused by a high-pressure block to our east, keeping us under a
south-westerly flow of Atlantic air.
'But it looks as though high pressure
could move further north west, allowing much colder air to filter across the UK
from the north or east, with the risk of snow increasing.'
James Madden, of Exacta Weather, warned
that this winter would be 'very cold and snowy across many parts of the UK'.
He said there would be 'frequent and
widespread heavy snowfalls during November to January across many parts of the
UK and Ireland, with below-average temperatures'.
The Government is bringing in new winter
alerts will come in the form of four possible warnings, depending on the
severity of the conditions predicted by the Met Office.
Level One will initiate long-term planning, Level Two will indicate a 60 per cent risk of extreme cold for 48 hours, Level Three means severe weather is expected to impact on health and Level Four is a 'major cold weather incident'.
Previously local areas were left to decide
how to react to cold snaps, but the Government has now introduced a Cold
Weather Plan.
It also contains advice for individuals
and carers, such as making sure at-risk groups get vaccinated against flu and
keep their homes heated.
A minimum of 21C is being recommended during the day
and 16C at night.
It will not be as sustained as last year, but these episodes are
expected to be severe, with Siberian temperatures.
- JONATHAN POWELL POSITIVE WEATHER SOLUTIONS
Below that, the risk of heart
problems, strokes and respiratory illness increases.
Health Secretary
Andrew Lansley said: 'Older people and those with long-term illnesses are
particularly vulnerable to the cold and we need to be aware – within families,
in communities and across the NHS – of how we can help others.'
'Every year,
there is a 20 per cent increase in deaths in the winter in England. By working
together, this coordinated plan will help protect those most in need. We are
determined to do all we can to achieve this.'
Michelle
Mitchell, charity director at Age UK said: 'The coalition Government has set a
new emphasis on public health as one of its key objectives, and this Cold
Weather Plan is a very important step in the right direction.
'Age UK will be
building on this with its own winter campaign to help vulnerable older people
live well through the cold months of the year.'
The Met Office
said: 'Our excess winter mortality, of an average 25,000 extra deaths in winter
compared to other months of the year – 80 per cent thought to be due to the
cold – is very poor compared to other countries in Europe.
'The aim of the
cold weather alerts is to reduce winter mortality by allowing action to be
taken, helping people and patients reduce the risks of cold weather.'
29/8/12
El cambio climático incrementa el número y la intensidad de los ciclones
La
supercomputación predice el comportamiento de la tormenta tropical Isaac
PUBLICO
DAVID BOLLERO Londres 29/08/2012 12:08 Actualizado: 29/08/2012 18:01
A pocos kilómetros para alcanzar las
costas de Luisiana, tocando tierra en Nueva Orleans, la tormenta tropical Isaac ya ha dejado tras de sí 24
muertos en Haití y casi 45.000 desplazados entre este país y su vecina
República Dominicana. Hoy se conmemora el séptimo aniversario porla catástrofe del Katrina y Barack Obama no quiere “tentar al
destino”.
Hasta el
punto de que el presidente de EEUU ha hecho un llamamiento a sus ciudadanos
para que “se tomen en serio” las advertencias de las autoridades. Desde el Centro
Nacional de Huracanes se trabaja activamente para anticiparse a los movimientos
de la tormenta tropical.
Sergio
Alonso, catedrático de Meteorología y Cambio Climático en la Universidad de
Illes Balears (UIB), sostiene que “las tormentas tropicales no son precisamente
una de las perturbaciones más sencillas de predecir, debido a sus propios
procesos y a los instrumentos disponibles para realizar pronósticos”. Sin
embargo, aunque resulta complicado anticiparse a su generación, no sucede lo
mismo con su comportamiento una vez formada la perturbación.
Más
ciclones por el cambio climático
Alonso
explica que “este tipo de perturbaciones, que si se forman en el Pacífico se
denominan tifones y si lo hacen en el Atlántico, huracanes, dependen en gran
medida de la temperatura superficial del mar, formándose a partir de los 27
grados centígrados”. Aunque éste no es, ni mucho menos, el único factor que
determina su intensidad –influyen otros como la propia estructura vertical de
la perturbación-, sí que ayuda a delimitar las áreas geográficas más propensas
a sufrir estos fenómenos meteorológicos.
En este
sentido y como experto en cambio climático, el catedrático indica que “el
incremento global de la temperatura puede incrementar no sólo el número de
perturbaciones, sino su severidad, esto es, la intensidad de las mismas”. El
experto puntualiza que “el clima no es una cuestión de año a año, sino de más
largo plazo. Ello, unido a que la subida de las temperaturas no se produce en
todas las regiones de un modo uniforme, deriva en que habrá años que el número
de ciclones decaiga, pero, en el global, podríamos decir que la tendencia es al
alza, tanto en número de perturbaciones como de potencia intrínseca de los
fenómenos”.
Anticipar
su comportamiento
En contra de
la creencia extendida de que el histórico de ciclones ayuda a establecer
patrones de comportamiento de las futuras perturbaciones, el catedrático de la
UIB asegura que “este conocimiento histórico no es crítico para realizar las
predicciones”, hasta el punto de que queda excluido de la modelización
atmosférica con que trabajan los expertos.
Esta
modelización se basa en “un conjunto complejo de ecuaciones matemáticas con
base física que ha de resolverse mediante supercomputación”, indica Alonso. A
través de estas formulaciones se establecen modelos de predicciones, únicamente
basados en las variables medidas del objeto de estudio, determinando estudios
de trayectorias y probabilidades de las mismas.
En cuanto a
los efectos de estas perturbaciones, Alonso señala que, “como sucede con casi
cualquier otro, en este casos dos fenómenos idénticos pueden provocar efectos
absolutamente desiguales según la región, en función de, por ejemplo, el nivel
de desarrollo de los países afectados”.
Diez tormentas
tropicales mortíferas
1900. Huracán en Galveston: El 8 de septiembre de 1900, la isla
Galveston, del estado de Texas, vio cómo una tormenta tropical procedente de
Cuba y el Golfo de México hacía estragos. La Oficina Meteorológica EE.UU. había
evitado hablar de ‘huracán’ o ‘tornado’ con el fin de no alarmar a la
población. Sin embargo, cuando la tormenta tocó tierra, la velocidad del viento
superaba los 215 km/h, transformándose en un huracán de categoría 4. El balance
de víctimas alcanzó las 8.000, destruyendo más de 3.600 casas y provocando
daños por valor de 30 millones de dólares de entonces, uno 500 millones
actuales.
1957. Huracán Audrey: Detectado inicialmente en el suroeste
del Golfo de México, en un solo día (del 24 al 25 de junio) pasó de tormenta
tropical a huracán. Para el día 27 ya era de categoría 4, dirigiéndose hacia
Texas y Luisiana. Ya con menor intensidad en tierra, alcanzaría Mississippi y
algo menos los Grandes Lagos. Las inundaciones en Luisiana causaron casi 400
muertes. Los costes sólo en EEUU superaron los 150 millones de dólares.
1970. Ciclón Bhola: Aunque se desconoce la cifra exacta de
muertos, se estima que ésta se situó en la horquilla de los 300.000 a los
500.000. La peor parte de Bhola se la llevó Bangladesh y el Golfo de
Bengala en India, el 12 de noviembre, cuando alcanzó la categoría 3 de huracán,
provocando inundaciones en el delta del Ganges, engullendo cosechas y pueblos
enteros.
1975. Tifón Nina: Este tifón arrasó con la presa de
Bangiao en China, lo que provocó sucesivos colapsos en el resto de las presas,
multiplicando los efectos de Nina y causando la muerte de más de 100.000
personas.
1992. Hurricane Iniki: En septiembre de 1992 y fruto de lo que
entonces se denominó la fase más calida del fenómeno de El Niño, Iniki asoló la isla de Kaua’i, en pleno
Hawaii. La buena gestión de los acontecimientos redujo las bajas a seis a pesar
de que el aviso tan sólo se dio con 24 horas de antelación. El coste de los
daños superó los 1.800 millones de dólares.
1992. Huracán Andrew: Habiendo partido de la costa occidental
de África, su trayectoria por Bahamas, el sur de Florida y el suroeste de
Luisiana causó la muerte directa de 26 personas e indirecta de otras 39, con
daños superiores a los 34.000 millones de dólares. El viento superó los 280
km/h en algunas regiones, derivando en algunas zonas en tornado, como fue el
caso del sudeste de Luisiana.
1997. Huracán Pauline: Pauline tiene el dudoso honor de no sólo ser el
huracán más destructivo sino, además, el más mortífero de cuantos han asolado
la costa mexicana, incluido Acapulco con lluvias torrenciales. Esta
perturbación se llevó consigo cerca de 400 vidas, dejando tras de sí a 300.000
personas sin hogar y provocando daños por valor de más de 7.500 millones de
dólares.
2005. Huracán Katrina: Se trata de la tormenta tropical más
mortífera de los últimos años, con un balance de más de 1.200 víctimas según el
Centro Nacional de Huracanes de EEUU y más de 700 desaparecidos. Katrina se cebó con el Estado de Luisiana y,
más concretamente, con Nueva Orleans, a la que inundó en más de un 80% debido a
la mala gestión de la Administración Bush, durante su paso y en los días
posteriores durante las labores de rescate. Como consecuencia de ello, a las
negras cifras de muertos se sumaron los daños por valor de 80.000 millones de
dólares. Se llegaron a registrar hasta 33 tornados derivados de Katrina.
2008. Ciclón Nargis: En mayo de 2008, la bahía de Bengala fue
golpeada por esta perturbación, cebándose con Birmania a la que golpeó con
vientos de más de 215 km/h. La ONU estimó que la cifra de afectados superaba
los 2,5 millones de personas y la Cruz Roja habló de casi 130.000 víctimas sólo
en este país.
2008. Huracán Ike: Tras el paso de esta perturbación, que partió de Cabo
Verde, casi 200 personas murieron, desde Haití a Galveston (Texas). Alcanzó la
categoría 3 y los mayores daños se registraron en EEUU, con 24.000 millones de
dólares, seguido de Cuba (7.300 millones) o Bahamas (200 millones), entre
otros, hasta alcanzar un total de pérdidas de 32.000 millones de dólares.
18/8/12
El Ejército alemán podrá intervenir en su país en casos excepcionales El Constitucional autoriza el despliegue militar, prohibido desde el nazismo
EL PAIS
ENRIQUE MÜLLER Berlín 17 AGO 2012 - 16:52 CET
ENRIQUE MÜLLER Berlín 17 AGO 2012 - 16:52 CET
En un acto inédito y de trascendencia histórica, las dos cámaras del Tribunal Constitucional alemán pusieron fin ayer a una sabia medida que tenía como meta evitar que el Ejército actuara contra la población civil, un temor que fue heredado de la época de abusos del régimen nazi. La más alta instancia jurídica del país legalizó el uso de medios militares por parte del Ejército sobre el territorio nacional contra posibles amenazas terroristas.
Aunque la sentencia estipula que tales acciones deben ser llevadas a cabo bajo estrictas condiciones, la decisión anunciada por el Tribunal consternó a un amplio sector de la población y provoco ácidos comentarios en la prensa. Hasta ayer el país había vivido con la certeza de que sus soldados solo abandonarían sus cuarteles en Alemania para luchar contra grandes catástrofes naturales o para viajar a países lejanos, como Afganistán.
En las últimas seis décadas, la intervención armada sobre el territorio alemán, en caso de amenazas terroristas, había estado reservada a las fuerzas de la policía con el fin de separar claramente las operaciones de defensa nacional del Ejército y las operaciones de seguridad interior, tal como ocurrió en 1972 durante los Juegos Olímpicos en Múnich, cuando un comando palestino tomó como rehenes a varios deportistas de la delegación de Israel.
Según la decisión del Tribunal Constitucional, que tiene su sede en Karlsruhe, el Ejército podrá utilizar sus medios militares en el país en caso de que exista una “situación excepcional de naturaleza catastrófica”, una decisión que no tiene precedentes en el país desde que el canciller Konrad Adenauer diera vida a la Bundeswehr, el moderno Ejército alemán, en noviembre de 1955.
La sentencia del Tribunal no autoriza al Ejército a actuar para evitar peligros que puedan surgir de una manifestación, ni tampoco permite la actuación de aviones de combate para abatir a un avión que transportara civiles y que hubiese sido secuestrado por terroristas. En un caso así, los pilotos de guerra alemanes solo tendrán permiso para realizar disparos de emergencia y lograr el aterrizaje del avión secuestrado.
Según la sentencia del Tribunal Constitucional, el despliegue de las fuerzas militares solo es posible como último recurso y corresponderá al Gobierno federal en su totalidad evaluar los llamados “casos de extrema urgencia” que justifiquen un despliegue militar en territorio alemán.
La sentencia fue bien recibida por los dos partidos democristianos, CDU y CSU, que comparten el Gobierno junto con los liberales del FDP. La oposición socialdemócrata del SPD y Los Verdes acogieron bien la decisión, si bien algunos portavoces lamentaron que la Corte no haya aclarado lo que entiende por una “situación excepcional de naturaleza catastrófica”.
El partido La Izquierda rechazó la sentencia y comentó que encerraba una reforma de la Constitución llevada a cabo por la puerta trasera y que hacía posible la militarización de la política interna alemana. “Es una decisión catastrófica de Karlsruhe”, advirtió el influyente periodista del Süddeutsche Zeitung Heribert Prantl en un editorial. “Los jueces no han interpretado la Ley Fundamental [Constitución], sino que la han cambiado, y esa no es su tarea”.
13/8/12
Rate of Arctic summer sea ice loss is 50% higher than predicted
The view from a yacht’s mast. Summer pack ice is showing a rate of loss 50% higher than anticipated. Photograph: Mike Powell/Corbis
GUARDIAN
Robin McKie. Science Editor
Sea ice in the Arctic is disappearing at a far greater rate than previously expected, according to data from the first purpose-built satellite launched to study the thickness of the Earth's polar caps.
Preliminary results from the European Space Agency's CryoSat-2 probe indicate that 900 cubic kilometres of summer sea ice has disappeared from the Arctic ocean over the past year.
This rate of loss is 50% higher than most scenarios outlined by polar scientists and suggests that global warming, triggered by rising greenhouse gas emissions, is beginning to have a major impact on the region. In a few years the Arctic ocean could be free of ice in summer, triggering a rush to exploit its fish stocks, oil, minerals and sea routes.
Using instruments on earlier satellites, scientists could see that the area covered by summer sea ice in the Arctic has been dwindling rapidly. But the new measurements indicate that this ice has been thinning dramatically at the same time. For example, in regions north of Canada and Greenland, where ice thickness regularly stayed at around five to six metres in summer a decade ago, levels have dropped to one to three metres.
"Preliminary analysis of our data indicates that the rate of loss of sea ice volume in summer in the Arctic may be far larger than we had previously suspected," said Dr Seymour Laxon, of the Centre for Polar Observation and Modelling at University College London (UCL), where CryoSat-2 data is being analysed. "Very soon we may experience the iconic moment when, one day in the summer, we look at satellite images and see no sea ice coverage in the Arctic, just open water."
The consequences of losing the Arctic's ice coverage, even for only part of the year, could be profound. Without the cap's white brilliance to reflect sunlight back into space, the region will heat up even more than at present. As a result, ocean temperatures will rise and methane deposits on the ocean floor could melt, evaporate and bubble into the atmosphere. Scientists have recently reported evidence that methane plumes are now appearing in many areas. Methane is a particularly powerful greenhouse gas and rising levels of it in the atmosphere are only likely to accelerate global warming. And with the disappearance of sea ice around the shores of Greenland, its glaciers could melt faster and raise sea levels even more rapidly than at present.
Professor Chris Rapley of UCL said: "With the temperature gradient between the Arctic and equator dropping, as is happening now, it is also possible that the jet stream in the upper atmosphere could become more unstable. That could mean increasing volatility in weather in lower latitudes, similar to that experienced this year."
CryoSat-2 is the world's first satellite to be built specifically to study sea-ice thickness and was launched on a Dniepr rocket from Baikonur cosmodrome, Kazakhstan, on 8 April, 2010. Previous Earth monitoring satellites had mapped the extent of sea-ice coverage in the Arctic. However, the thickness of that ice proved more difficult to measure.
The US probe ICESat made some important measurements of ice thickness but operated intermittently in only a few regions before it stopped working completely in 2009. CryoSat was designed specifically to tackle the issue of ice thickness, both in the Arctic and the Antarctic. It was fitted with radar that can see through clouds. (ICESat's lasers could not penetrate clouds.) CryoSat's orbit was also designed to give better coverage of the Arctic sea.
"Before CryoSat, we could see summer ice coverage was dropping markedly in the Arctic," said Rapley. "But we only had glimpses of what was happening to ice thickness. Obviously if it was dropping as well, the loss of summer ice was even more significant. We needed to know what was happening – and now CryoSat has given us the answer. It has shown that the Arctic sea cap is not only shrinking in area but is also thinning dramatically."
Sea-ice cover in the Arctic varies considerably throughout the year, reaching a maximum in March. By combining earlier results from ICESat and data from other studies, including measurements made by submarines travelling under the polar ice cap, Laxon said preliminary analysis now gave a clear indication of Arctic sea-ice loss over the past eight years, both in winter and in summer.
In winter 2004, the volume of sea ice in the central Arctic was approximately 17,000 cubic kilometres. This winter it was 14,000, according to CryoSat.
However, the summer figures provide the real shock. In 2004 there was about 13,000 cubic kilometres of sea ice in the Arctic. In 2012, there is 7,000 cubic kilometres, almost half the figure eight years ago. If the current annual loss of around 900 cubic kilometres continues, summer ice coverage could disappear in about a decade in the Arctic.
However, Laxon urged caution, saying: "First, this is based on preliminary studies of CryoSat figures, so we should take care before rushing to conclusions. In addition, the current rate of ice volume decline could change." Nevertheless, experts say computer models indicate rates of ice volume decline are only likely to increase over the next decade.
As to the accuracy of the measurements made by CryoSat, these have been calibrated by comparing them to measurements made on the ice surface by scientists including Laxon; by planes flying beneath the satellite's orbit; and by data supplied by underwater sonar stations that have analysed ice thickness at selected places in the Arctic. "We can now say with confidence that CryoSat's maps of ice thickness are correct to within 10cm," Laxon added.
Laxon also pointed out that the rate of ice loss in winter was much slower than that in summer. "That suggests that, as winter starts, ice is growing more rapidly than it did in the past and that this effect is compensating, partially, for the loss of summer ice." Overall, the trend for ice coverage in Arctic is definitely downwards, particularly in summer, however – a point recently backed by Professor Peter Wadham, who this year used aircraft and submarine surveys of ice sheets to make estimates of ice volume loss. These also suggest major reductions in the volume of summer sea ice, around 70% over the past 30 years.
"The Arctic is particularly vulnerable to the impact of global warming," said Rapley. "Temperatures there are rising far faster than they are at the equator. Hence the shrinking of sea-ice coverage we have observed. It is telling us that something highly significant is happening to Earth. The weather systems of the planet are interconnected so what happens in the high latitudes affects us all."
26/7/12
The Prospect of Sudden Climate Change
NASA
By now, many of us have heard the ominous predictions of a possible future global apocalypse, where cataclysmic floods, tornadoes, and blizzards threaten to destroy civilization.
Image Right: Near Dimmitt, Texas on June 2, 1995. Credit: NOAA Photo Library, OAR/ERL/NSSL
As a consequence of climate change, the melting of polar ice supposedly could send vast quantities of fresh water into the North Atlantic's salty oceans. This torrent would work to shut down a major Atlantic Ocean current that stabilizes the Northern Hemisphere's climate system, unleashing abrupt and drastic changes to our climate.
While these forecasts are extreme, most climate experts agree that climate change is occurring now and may accelerate in the future, although not as drastic as some fiction might portray. Scientists agree that a sudden shift in our climate, such as flipping from today's slowly warming planet to an icebox is bogus and does not obey fundamental rules of physics.
Examining Climate: A Complicated Puzzle
There is little doubt that the Earth has been warming, at least since 1850. In the last century alone, temperature has climbed about one degree Fahrenheit on average around the world. Sea levels have also risen by as much as eight inches because as the oceans warm, the waters expand. Larsen B, a floating ice shelf in the Antarctic, collapsed in 2002, and there is evidence that Greenland's ice sheets are melting.
But, these changes are complex and brought on by several factors. Most scientists say higher temperatures are likely the result of an atmospheric increase in greenhouse gases, including carbon dioxide from burning fossil fuels such as coal and petroleum. Other human-caused factors, like changing land cover also appear to be influencing the climate. And, finally, natural phenomena, like swings in the sun's energy and volcanic eruptions, also play a crucial role. It's important to recognize that our climate would fluctuate even without these factors since the atmosphere and oceans contain numerous gases and liquids that are constantly "sloshing" around.
Understanding the history of these factors, or "forcings," is essential for future climate predictions. "Knowing about the future means knowing about the past, how things have changed previously and why," said NASA research climatologist Gavin Schmidt.
Drastic Changes in Days?
Once considered inconceivable, recent studies have given credence to the idea that climate can change rapidly, within decades. For example, new research shows that as the world warmed at the end of the last ice age, about 13,000 years ago, melting ice sheets added enormous amounts of fresh water to the North Atlantic.
Image Right: Click the image to see a conceptual animation of the North Atlantic overturning circulation. Credit: NASA
The ocean circulation system relies on the sinking of heavy, dense saltwater in the North Atlantic. But, the rapid infusion of freshwater made the surface of the ocean more buoyant, shown in the animation below. This triggered a sudden halt in the ocean's circulation system, resulting in a return to ice-age-like conditions known as the Younger Dryas. This ocean circulation system has slowed down at least twice in the distant past. Each time, the slow down led to significant, but not disastrous cooling over the span of a few decades in parts of the world.
Although there is some evidence that North Atlantic Ocean currents and patterns of saltiness have shown recent changes consistent with these previous climate disruptions, "the time period is far too short to indicate a change in long-term circulation," says NASA oceanographer David Adamec. It will take another decade of data collection to determine whether the recently observed changes in our ocean-climate system are permanent or merely a short-lived phenomenon.
The physical makeup of the world today is also very different. Areas that once had major ice sheets are now much warmer and the amount of freshwater that could be added to the North Atlantic over the next 50 to 100 years is trivial compared to the influx seen just prior to the Younger Dryas.
Next: An Uncertain Future
By now, many of us have heard the ominous predictions of a possible future global apocalypse, where cataclysmic floods, tornadoes, and blizzards threaten to destroy civilization.
Image Right: Near Dimmitt, Texas on June 2, 1995. Credit: NOAA Photo Library, OAR/ERL/NSSL
As a consequence of climate change, the melting of polar ice supposedly could send vast quantities of fresh water into the North Atlantic's salty oceans. This torrent would work to shut down a major Atlantic Ocean current that stabilizes the Northern Hemisphere's climate system, unleashing abrupt and drastic changes to our climate.
While these forecasts are extreme, most climate experts agree that climate change is occurring now and may accelerate in the future, although not as drastic as some fiction might portray. Scientists agree that a sudden shift in our climate, such as flipping from today's slowly warming planet to an icebox is bogus and does not obey fundamental rules of physics.
Examining Climate: A Complicated Puzzle
There is little doubt that the Earth has been warming, at least since 1850. In the last century alone, temperature has climbed about one degree Fahrenheit on average around the world. Sea levels have also risen by as much as eight inches because as the oceans warm, the waters expand. Larsen B, a floating ice shelf in the Antarctic, collapsed in 2002, and there is evidence that Greenland's ice sheets are melting.
Image Above: This animation (360KB) shows the annual minimum sea ice extent and concentration for 24 years, from 1979 to 2003. The year 2002 showed lowest level of sea ice on record. Credit: NASA
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But, these changes are complex and brought on by several factors. Most scientists say higher temperatures are likely the result of an atmospheric increase in greenhouse gases, including carbon dioxide from burning fossil fuels such as coal and petroleum. Other human-caused factors, like changing land cover also appear to be influencing the climate. And, finally, natural phenomena, like swings in the sun's energy and volcanic eruptions, also play a crucial role. It's important to recognize that our climate would fluctuate even without these factors since the atmosphere and oceans contain numerous gases and liquids that are constantly "sloshing" around.
Understanding the history of these factors, or "forcings," is essential for future climate predictions. "Knowing about the future means knowing about the past, how things have changed previously and why," said NASA research climatologist Gavin Schmidt.
Drastic Changes in Days?
Once considered inconceivable, recent studies have given credence to the idea that climate can change rapidly, within decades. For example, new research shows that as the world warmed at the end of the last ice age, about 13,000 years ago, melting ice sheets added enormous amounts of fresh water to the North Atlantic.
Image Right: Click the image to see a conceptual animation of the North Atlantic overturning circulation. Credit: NASA
The ocean circulation system relies on the sinking of heavy, dense saltwater in the North Atlantic. But, the rapid infusion of freshwater made the surface of the ocean more buoyant, shown in the animation below. This triggered a sudden halt in the ocean's circulation system, resulting in a return to ice-age-like conditions known as the Younger Dryas. This ocean circulation system has slowed down at least twice in the distant past. Each time, the slow down led to significant, but not disastrous cooling over the span of a few decades in parts of the world.
Although there is some evidence that North Atlantic Ocean currents and patterns of saltiness have shown recent changes consistent with these previous climate disruptions, "the time period is far too short to indicate a change in long-term circulation," says NASA oceanographer David Adamec. It will take another decade of data collection to determine whether the recently observed changes in our ocean-climate system are permanent or merely a short-lived phenomenon.
The physical makeup of the world today is also very different. Areas that once had major ice sheets are now much warmer and the amount of freshwater that could be added to the North Atlantic over the next 50 to 100 years is trivial compared to the influx seen just prior to the Younger Dryas.
Next: An Uncertain Future
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