Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
Non ho nessuna intenzione di prenderti in giro, anzi il contario! Il confronto è sempre necessario, il grafico a cui io mi riferisco non ha i dati strumentali e finisce a un livello inferiore rispetto al picco medievale, ed è quello che mi hai presentato dicendo che l'andamento delle temperature non è cambiato rispetto a MannOriginariamente Scritto da steph
No. Moberg dice esattamente il contrario.
Credo che tu o parli un'altra lingua o vivi su Nettuno.
Visto che non sai l'inglese te lo ritraduco:
"The peaks in medieval times are at the same level as much of the twentieth century, although the post-1990 warmth seen in the instrumental data (green curve in Fig. 2b) appears to be unprecedented."
I picchi medievali sono dello stesso livello (= simili) di quelli di gran parte del XX secolo, sebbene il caldo osservato nei dati strumentali post-1990 sembra essere unico (= negli ultimi 2000 anni). = è il più caldo.
Visto che non sai leggere i grafici te lo riposto spiegandotelo:
Non mi pare di dire fesserie affermando che la fine del grafico (= a destra = anni recenti) superi (= sia più alta) tutta la serie temporale (= controlla in basso: ci sono le date). Anche della prima campanina (= il picco relativo attorno al 1100).
Poi, per carità: si può dire di tutto e il contrario di tutto. Però io non sopporto proprio chi mi prende per i fondelli, mettendomi in bocca cose non dette o rigirando continuamente la frittata.
Clayco, ti avviso: non ho intenzione proseguire con questi atteggiamenti da fanciullo.
Quello che mi hai mostrato dopo ha i dati strumentali diretti ( che non si dovrebbero confrontare) ed è a questi dati diretti, strumentali, precisi, che si riferisce Moberg quando dice sebbene il caldo osservato nei dati strumenali è senza precedenti. (quindi più caldo ...ma con i dati diretti)
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
Già.
Cook ER, Esper J, D’Arrigo R (2004) Extra-tropical Northern Hemisphere temperature variability over the past 1000 years. Quaternary Science Reviews 23, 2063-2074
“[…] Persistently above-average temperatures in the AD 960–1050 interval also suggest the largescale occurrence of a ‘‘Medieval Warm Period’’ in the NH extra-tropics. However, declining site availability and low withinchronology tree-ring replication prior to AD 1200 weakens this interpretation considerably. […]
After recalibration to take this property into account, annual temperatures up to AD 2000 over extra-tropical NH land areas have probably exceeded by about 0.3 °C the warmest previous interval over the past 1162 years.”
(image hosted from Cook, Esper, D'Arrigo, 2004)
~~~ Always looking at the sky~~~
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
ma dice anche che "I picchi medievali sono dello stesso livello (= simili) di quelli di gran parte del XX secolo"
Cmq non fa una grinza; appurato che l'attuale fase di riscaldamento globale è la più calda da almeno 1000 anni (se non oltre), direi che si può anche andare oltre, no? Altrimenti si rischia di entrare in un loop paranoico
~~~ Always looking at the sky~~~
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
ma dice anche che "I picchi medievali sono dello stesso livello (= simili) di quelli di gran parte del XX secolo"
Cmq non fa una grinza; appurato che l'attuale fase di riscaldamento globale è la più calda da almeno 1000 anni (se non oltre), direi che si può anche andare oltre, no? Altrimenti si rischia di entrare in un loop paranoico
Mi piace la regola di non entrare in un loop:
Quindi la chiudo qui!
Vale per Esper quello che ho detto per Moberg.
Entrambi i loro grafici finiscono con valori più bassi dei picchi medievali, poi entrano i valori strumentali ma quelli sono un altra cosa!
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
[quote=steph;1668766]Perfettamente inutile, grazie.
Abbiamo già appurato che quelle cifre sono false.
Eh NO! Questa è una tua opinione!
Altrimenti dovresti mandarmi i link di reply o rebuttal scientifici però cioè in peer review, dove si contestano i suddetti scienziati, che dicono che il valore è 92- 98%
Altrimenti mi dovresti spiegare come salta fuori il valore di vapore + nuvole uguale a 70%, con la CO2 allo 0,04% di presenza in atmosfera.
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
Perché mai? Qui sei tu a inventare di sana pianta.
Ribadisco: i loro lavori (come quelli della gran parte di chi si occupa di ricostruzioni) dicono esattamente il contrario.
Sulle Alpi centro-occidentali, poi, siamo ai massimi dall'Optimum Climatico Olocenico.
Ultima modifica di steph; 26/04/2008 alle 23:58
~~~ Always looking at the sky~~~
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
[quote=clayco;1676043]Ammazza, ma sei proprio duro, eh
Vatti a rileggere quel che avevano scritto questi "sprovveduti"in anni in cui l'IPCC ancora non era neanche stato concepito
Manabe, S., 1968: The dependence of atmospheric temperature on the concentration of carbon dioxide. In Global Effects of Environmental Pollution, D. Reidel Publishing Company, 25-29.
Manabe, S., and R. T. Wetherald, 1967: Thermal equilibrium of the atmosphere with a given distribution of relative humidity. Journal of the Atmospheric Sciences, 24(3), 241-259
Flohn H. 1961: Man's activity as a factor in climatic change. In: Annals of the New York Academy of Science, Vol. 95, 271-281.
Oeschger, H., U. Siegenthaler, M. Heimann,1980: "The carbon cycle and its perturbation by man", Interactions of Energy and Climate
Oeschger, H., U. Siegenthaler, U. Schotterer, A. Gugelmann, 1975: "A box diffusion model to study the carbon dioxide exchange in nature", Tellus, 27/2, 168-192
In alternativa, ci sono sempre questi bei grafichetti:
~~~ Always looking at the sky~~~
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
NATURE, maggio 2008... commenti piu' che graditi bei bambini
spero pubblichino qualcosa al piu' presto.. pero' e' una bella bomba no?
Sediment cores reveal
Antarctica’s warmer past
VIENNAQuirin Schiermeier
A unique drilling project in the western Ross
Sea has revealed that Antarctica had a much
more eventful climate history than previously
assumed. A new sediment core hints that the
western part of the now-frozen continent went
through prolonged ice-free phases — presumably
offering a glimpse of where our warming
world might be heading.
Researchers reported initial results from
ANDRILL, a US$30-million international drilling
project, on 16 April at the assembly of the
European Geosciences Union in Vienna. During
the past two years, the team has extracted
two cores, each containing some 1,200 metres
of sediment, from the seabed below the vast
Ross Ice Shelf, a floating extension of the West
Antarctic Ice Sheet. Together, the cores provide
an almost uninterrupted 17-million-year
record of Antarctica’s climatic past.
Palaeoclimatological records from ice cores,
although more detailed and easier to interpret,
cover only the past 800,000 years or so. Now,
geologists say, Antarctica’s history is laid out
much more clearly.
“We have every page of the book,” says David
Harwood, an ANDRILL scientist at the University
of Nebraska in Lincoln.
Sediments in the cores, along with microfossils
such as pollen and spores, allow
researchers to reconstruct sea temperatures and
environmental conditions, such as the presence
or absence of ice, over millions of years. The
analytical work has only just begun, but early
results indicate that, during warmer periods,
the West Antarctic Ice Sheet and the Ross Ice
Shelf shrank rapidly and substantially.
During a warm period some 3.5 million years
ago, for instance, the ice sheet may have disappeared
completely for around 200,000 years,
raising sea levels globally by up to 10 metres.
For the first time, the ANDRILL cores show
exactly how ice retreated rapidly and quickly in
Antarctica. “That happened at a time when it
was three to four degrees warmer than today,
owing to atmospheric carbon dioxide concentrations,
which we will very likely reach again
soon,” says Tim Naish, a project leader at the
Institute of Geological and Nuclear Sciences in
Lower Hutt, New Zealand.
In a poster session at the conference, David
Pollard, an ice-sheet modeller at Pennsylvania
State University in University Park, presented
new simulations confirming that western
Antarctica can lose almost all of its ice at temperatures
just three to five degrees higher than
today’s. (During the past 1 million years, Antarctica’s
ice sheets have expanded.)
The first ANDRILL core covered the palaeoclimatic
history of the past 7 million years.
The second core, drilled between October and
December last year, extends the record back
to 17 million years ago. It reveals that during a
period about 16 million years ago, Antarctica
had a climate similar to that found today on the
South Island of New Zealand and in southern
Patagonia.
“It appears there were rivers, rain and trees
in abundance,” says Harwood. “That’s really
the biggest surprise to me so far.”
What is still unclear is exactly how, when
and where Antarctica’s ice sheets started forming
during the greenhouse–icehouse climate
transition 35 million to 40 million years ago. To
find out, the ANDRILL team hopes to resume
drilling in 2012 at a new site on the Ross Ice
Shelf. ■
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
Sempre Nature 27 aprile 2008... l'articolo citato e':
Perlwitz, J., Pawson, S., Fogt, R. L., Nielsen, J. E. & Neff, W. D. Geophys. Res. Lett. 35, L08714 doi:10.1029/2008GL033317
Antarctic ice threatened by ozone-hole recovery
Global winds could accelerate melting.
Amanda Leigh Haag
Recovery of the ozone hole above Antarctica could warm the Antarctic and cause more ice to melt in coming decades, researchers say. As the ozone hole heals, wind patterns that shield the interior of the polar region from warm air may break down, causing warming in the Antarctica as well as warmer and drier conditions in Australia.
Despite global temperatures rising, the interior of Antarctica has experienced a unique cooling trend during its summer and autumn over the last few decades. Scientists attribute this cooling to the hole in the ozone layer, which alters atmospheric circulation patterns and strengthens the westerly winds that swirl around the continent. These winds have isolated the Antarctic interior from the warming patterns seen on the continent’s peninsula and throughout the rest of the world.
“The warming of the Antarctic may have been delayed because of the ozone hole,” says atmospheric scientist Judith Perlwitz, a climate scientist at the of the University of Colorado at Boulder and the National Oceanic and Atmospheric Administration.
But thanks to the 1987 Montreal Protocol that banned the release of ozone-depleting substances, most scientists agree that the ozone hole has probably reached its largest and that ozone levels will recover by the end of the century.
Model system
Perlwitz and her colleagues simulated the interaction between stratospheric ozone dynamics and atmospheric conditions between 1950 and the end of the twenty-first century. They conclude that as ozone levels recover, the lower part of the stratosphere above Antarctica — some 10-20 kilometres above Earth’s surface — will absorb more ultraviolet radiation, and rise in temperatures by as much as 9ºC, reducing the existing strong north-south temperature gradient.
Along with balmier temperatures in Antarctica, a weakening of the westerly winds could also produce warmer and drier temperatures in Australia and increased precipitation in South America.
ADVERTISEMENT
Climate models, including those used in the Intergovernmental Panel on Climate Change’s (IPCC) fourth assessment, have not accounted for these details of ozone chemistry. Most models do not extend beyond 30 kilometres above the Earth’s surface, and adequate representation of the stratosphere would require modelling up to 60 kilometres. “This paper opens the discussion about how ozone depletion and recovery in the twentieth and twenty-first centuries can be included in climate models,” Perlwitz says.
“If we get the feedbacks and the ice-melt wrong in our climate models, then that means we could be really wrong in terms of what a safe level of carbon dioxode is,” says Theodore Shepherd, an atmospheric scientist at the University of Toronto, Canada, who was not involved in the study. Biological productivity of the oceans is driven largely by ocean and atmospheric circulation patterns, so the next step, he says, is to couple ocean dynamics to ozone chemistry and climate.
Re: L'Antartide si espande sempre di più, e l'artico subisce la corrente del golfo
Grazie hai un link per caso?NATURE, maggio 2008... commenti piu' che graditi bei bambini
spero pubblichino qualcosa al piu' presto.. pero' e' una bella bomba no?
Sediment cores revealAntarctica’s warmer past
VIENNAQuirin Schiermeier
A unique drilling project in the western Ross
Sea has revealed that Antarctica had a much
more eventful climate history than previously
assumed. A new sediment core hints that the
western part of the now-frozen continent went
through prolonged ice-free phases — presumably
offering a glimpse of where our warming
world might be heading.
Researchers reported initial results from
ANDRILL, a US$30-million international drilling
project, on 16 April at the assembly of the
European Geosciences Union in Vienna. During
the past two years, the team has extracted
two cores, each containing some 1,200 metres
of sediment, from the seabed below the vast
Ross Ice Shelf, a floating extension of the West
Antarctic Ice Sheet. Together, the cores provide
an almost uninterrupted 17-million-year
record of Antarctica’s climatic past.
Palaeoclimatological records from ice cores,
although more detailed and easier to interpret,
cover only the past 800,000 years or so. Now,
geologists say, Antarctica’s history is laid out
much more clearly.
“We have every page of the book,” says David
Harwood, an ANDRILL scientist at the University
of Nebraska in Lincoln.
Sediments in the cores, along with microfossils
such as pollen and spores, allow
researchers to reconstruct sea temperatures and
environmental conditions, such as the presence
or absence of ice, over millions of years. The
analytical work has only just begun, but early
results indicate that, during warmer periods,
the West Antarctic Ice Sheet and the Ross Ice
Shelf shrank rapidly and substantially.
During a warm period some 3.5 million years
ago, for instance, the ice sheet may have disappeared
completely for around 200,000 years,
raising sea levels globally by up to 10 metres.
For the first time, the ANDRILL cores show
exactly how ice retreated rapidly and quickly in
Antarctica. “That happened at a time when it
was three to four degrees warmer than today,
owing to atmospheric carbon dioxide concentrations,
which we will very likely reach again
soon,” says Tim Naish, a project leader at the
Institute of Geological and Nuclear Sciences in
Lower Hutt, New Zealand.
In a poster session at the conference, David
Pollard, an ice-sheet modeller at Pennsylvania
State University in University Park, presented
new simulations confirming that western
Antarctica can lose almost all of its ice at temperatures
just three to five degrees higher than
today’s. (During the past 1 million years, Antarctica’s
ice sheets have expanded.)
The first ANDRILL core covered the palaeoclimatic
history of the past 7 million years.
The second core, drilled between October and
December last year, extends the record back
to 17 million years ago. It reveals that during a
period about 16 million years ago, Antarctica
had a climate similar to that found today on the
South Island of New Zealand and in southern
Patagonia.
“It appears there were rivers, rain and trees
in abundance,” says Harwood. “That’s really
the biggest surprise to me so far.”
What is still unclear is exactly how, when
and where Antarctica’s ice sheets started forming
during the greenhouse–icehouse climate
transition 35 million to 40 million years ago. To
find out, the ANDRILL team hopes to resume
drilling in 2012 at a new site on the Ross Ice
Shelf. ■
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