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4/6/17

Crippled Atlantic currents triggered ice age climate change

Melting icebergs may have triggered or exacerbated ice age slowdowns to Atlantic Ocean currents.

SCIENCE

By Eric HandJun. 30, 2016 , 2:00 PM

The last ice age wasn’t one long big chill. Dozens of times temperatures abruptly rose or fell, causing all manner of ecological change. Mysteriously, ice cores from Greenland and Antarctica show that these sudden shifts—which occurred every 1500 years or so—were out of sync in the two hemispheres: When it got cold in the north, it grew warm in the south, and vice versa. Now, scientists have implicated the culprit behind those seesaws—changes to a conveyor belt of ocean currents known as the Atlantic Meridional Overturning Circulation (AMOC).

These currents, which today drive the Gulf Stream, bring warm surface waters north and send cold, deeper waters south. But they weakened suddenly and drastically, nearly to the point of stopping, just before several periods of abrupt climate change, researchers report today in Science. In a matter of decades, temperatures plummeted in the north, as the currents brought less warmth in that direction. Meanwhile, the backlog of warm, southern waters allowed the Southern Hemisphere to heat up.

AMOC slowdowns have long been suspected as the cause of the climate swings during the last ice age, which lasted from 110,000 to 15,000 years ago, but never definitively shown. The new study “is the best demonstration that this indeed happened,” says Jerry McManus, a paleo-oceanographer at Columbia University’s Lamont-Doherty Earth Observatory, and a study author. “It is very convincing evidence,” adds Andreas Schmittner, a climate scientist at Oregon State University, Corvallis. “We did not know that the circulation changed during these shorter intervals.”

To assess the strength of ancient ocean currents over the course of 35,000 years in the middle of the ice age, McManus and his colleagues examined a 10-meter section of a 38-meter sediment core drilled from the bottom of the Atlantic Ocean. The core came from an elevated patch of sea floor known as the Bermuda Rise, where sediments accumulate abnormally fast. The thick layer allows for a more detailed reading of chemical changes within the sediments when they were buried.

Circulation slowdown

Ice Age climate swings may have come from the weakening of powerful Atlantic currents, in which shallow, warm waters move north (red), and deep, cold waters move south (blue).

The researchers measured the ratio of two products of radioactive decay: protactinium-231 and thorium-230. These daughter isotopes come from trace amounts of uranium that are dissolved everywhere in seawater. If the ocean were as still as a bathtub, the two daughter isotopes would bind to sediment particles, settle downward, and become buried at a constant ratio. But thorium gloms on to particles more readily than protactinium. It is therefore buried more readily, whereas protactinium tends to be carried away by ocean currents for burial elsewhere. At places like the Bermuda Rise, where the Atlantic conveyor belt is typically strong, little protactinium ends up in the sediments—except for four instances when the ratio to thorium rose sharply in a matter of decades to centuries, indicating the AMOC’s sudden weakening.

A 2014 study of the AMOC, based on a core from a nearby spot on the Bermuda Rise, found that the currents maintained much of their strength throughout the last glacial period. But because that team took fewer samples from the core and missed the sharp swings in strength. “Now these [new] guys have increased incredibly the data resolution,” says Jörg Lippold, a paleo-oceanographer at the University of Heidelberg in Germany and the leader of the 2014 study. “They found the peaks we missed.”

Still unclear is what triggered the AMOC’s sudden slowdowns. Many of the drops correspond to so-called Heinrich events: rapid releases of icebergs from Canada’s ice sheet. These iceberg armadas often chugged through the Hudson Strait of Canada and may have discharged more ice into the Atlantic Ocean than contained in the entire ice cap of Greenland, raising ancient sea levels by 10 meters. The meltwater brought incredible amounts of freshwater to the North Atlantic, precisely where ocean currents cool off and sink. Because freshwater is less dense than saltwater, it can plug up the AMOC, preventing the overturning and deep water formation the fuels the circulation’s engine. The slowdowns persisted for 1500 years or so, then the AMOC would suddenly regain strength as freshwater melt dissipated and the currents reached a certain threshold, McManus says.

But weak AMOCs are not always accompanied by a Heinrich event, and the timing is fuzzy—some Heinrich events seem to occur after the AMOC already began to weaken. “The Heinrich events may be a response to the change in the overturning circulation rather than a cause,” Schmittner says.

Another question is whether the AMOC—currently known to be in decline—could drop off suddenly today, as depicted in the 2004 movie The Day After Tomorrow, causing temperatures to plummet across northwestern Europe. Schmittner says the past provides an eye-opener. “It’s evidence that this really did happen in the past, on short time scales.” But McManus says that studies looking deeper into the ice ages have found that the 1500-year climate oscillations tend not to be nearly as strong during interglacial periods. “It would suggest that this kind of thing isn’t so likely to happen today,” he says. On the other hand, he adds, “In most interglacials, Greenland didn’t melt … and Greenland is currently melting.”

Gulf Stream Slowing Down Faster Than Ever, Scientists Say

Home › Climate Science
Posted on April 12, 2016 by Kevin Hester

‘The Gulf Stream that helps to keep Britain from freezing over in winter is slowing down faster now than at any time in the past millennium according to a study suggesting that major changes are taking place to the ocean currents of the North Atlantic.

Scientists believe that the huge volumes of freshwater flowing into the North Atlantic from the rapidly melting ice cap of Greenland have slowed down the ocean “engine” that drives the Gulf Stream from the Caribbean towards north-west Europe, bringing heat equivalent to the output of a million power stations.’

———- ———-

And similarly: ‘While you were distracted, this climate change warning arrived‘: ‘With dire warnings of catastrophic sea level rise and superstorms capable of pitching 1,000 tonne mega-boulders onto shorelines, scientist James Hansen sounded an alarm over continued global warming.

In a video, coinciding with a release of a revised version of paper Hansen wrote with 18 other authors, Hansen warned of “feedbacks” between the oceans and ice sheets.’

[dk: like him or not, he does have gravitas here. He seems more urgent than a year ago…]

Is the Gulf Stream broken? NOAA satellite data sounds alarm

Natural News
Friday, January 29, 2016 by: Jennifer Lea Reynolds
Tags: global warming, gulf stream, NOAA

(NaturalNews) It's no secret that the weather is becoming more severe as time goes on. From places like Buffalo, New York, which recently got hit with a hefty 5 feet of snow during one storm, to other areas that experience extreme temperature fluctuations from one day to the next, it's obvious that the climate is changing.

National Oceanic and Atmospheric Administration(NOAA) satellite data and details from an animated map called the Earth Wind Map, show that it's not only changing, but that it's changing fast.

Data suggests rapid changes occurring in Gulf Stream temperature

November 2014 data suggests that the stream is exhibiting colder than normal conditions. On top of that, it's taking place in not just one area, but two, further demonstrating that climate changes are underway. For example, both sites showed that the North Atlantic was colder than average, but also that the Gulf itself is colder than normal, which was not the case just one month prior, in October 2014.

The information has many wondering if the Gulf Stream may be broken, something that surely is cause for concern as bizarre weather patterns continue to occur. Unfortunately, it would appear that it is indeed broken and that climate changes will become the norm.

In fact, according to 1000 climate experts who gathered at the World Meteorological Organization (WMO) conference earlier this year, people should prepare to brace themselves for weather changes of apocalyptic proportions in the coming years. Their observations and words of warning are nothing short of alarming, indicatingthat the atmosphere may bebeyond repair. Instead, it's now a matter of dealing with the consequences, much of which has occurred at the hands of humans.

Changing weather conditions "irreversible"

"It's irreversible and the world's population continues to increase, so we must adapt," says Jennifer Vanos, a professor of atmospheric sciences at Texas Tech University.

Experts are adamant that by 2050, airplane passengers will experience about twice as much in-flight air turbulence, ships will encounter gigantic ocean waves well over 130-feet (40 meters)-high and a two percent rise in average global temperature is expected.

What does this mean? It isn't good.

Simon Wang, assistant director of the Utah Climate Center, says "We'll see clouds forming faster and more easily, and more downpours" which he notes will create an influx of flash flooding.

The changes occurring in the Gulf Stream and the climate overall are attributed to many factors, and experts are not ruling our human disruption.

Natural processes as well as human activity responsible for severe climate changes

Experts from NOAA, for example, say that natural factors such as volcanic activity and changes in solar luminosity are behind climate changes. However, they aren't hesitant to suggest that the changes are also brought on by human actions, mainly regarding greenhouse gas emissions.

The Intergovernmental Panel on Climate Change (IPCC) agrees, stating in a recent news release that "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century."

Thomas Stocker, the IPCC co-chair says, "Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions." Stocker explains that heat waves will become more common and last longer, while dry areas will receive less rainfall and wet regions will likely experience more.

The IPCC notes that "Warming in the climate system is unequivocal" expressing that "Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850, and since 1950 many changes have been observed throughout the climate system that are unprecedented over decades to millennia."

While the changes noted in the Gulf Stream and the overall weather are disturbing, can we really say that they are surprising?

Sources for this article include:

(1) http://www.thebigwobble.org

(2) http://www.skynews.com.au

(3) http://www.ncdc.noaa.gov/paleo/globalwarming/end.html

[PDF] http://www.ipcc.ch

2/4/17

Gulf Stream slowdown tied to changes in Southern Hemisphere

SCIENCE DAILY

Date:

October 5, 2016

Source:

University of Washington

Summary:

The ocean circulation that is responsible for England's mild climate appears to be slowing down. The shift is not sudden or dramatic, as in the 2004 sci-fi movie "The Day After Tomorrow," but it is a real effect that has consequences for the climates of eastern North America and Western Europe. Also unlike in that movie, and in theories of long-term climate change, these recent trends are not connected with the melting of the Arctic sea ice and buildup of freshwater near the North Pole. Instead, they seem to be connected to shifts at the southern end of the planet, according to a recent University of Washington study in the journal Geophysical Research Letters.

"It doesn't work like in the movie, of course," said Kathryn Kelly, an oceanographer at the UW's Applied Physics Laboratory. "The slowdown is actually happening very gradually, but it seems to be happening like predicted: It does seem to be spinning down."

The study looked at data from satellites and ocean sensors off Miami that have tracked what's known as the Atlantic overturning circulation for more than a decade. Together they show a definite slowdown since 2004, confirming a trend suspected before then from spottier data.

Looking at other observations to determine the cause, the researchers ruled out what had been the prime suspect until now: that massive melting and freshening in the North Atlantic could stop water from sinking and put the brakes on the overturning circulation, which moves warmer water north along the ocean's surface and sends cold water southward at depths.

"It appears that this 10-year slowdown is not related to salinity," Kelly said. In fact, despite more ice melt, surface water in the Arctic is getting saltier and therefore denser, she said, because of less precipitation. "That means the slowdown could not possibly be due to salinity -- it's just backwards. The North Atlantic has actually been getting saltier."

Instead, the authors saw a surprising connection with a current around the southern tip of South Africa. In what's known as the Agulhas Current, warm Indian Ocean water flows south along the African coast and around the continent's tip toward the Atlantic, but then makes a sharp turn back to join the stormy southern circumpolar current. Warm water that escapes into the Atlantic around the cape of South Africa is known as the Agulhas Leakage. The new research shows the amount of leakage changes with the quantity of heat transported northward by the overturning circulation.

"We've found that the two are connected, but I don't think we've found that one causes the other," Kelly said. "It's more likely that whatever changed the Agulhas changed the whole system."

She believes atmospheric changes may be affecting both currents simultaneously.

"Most people have thought this current should be driven by a salinity change, but maybe it's the [Southern Ocean] winds," Kelly said.

The finding could have implications for northern European and eastern U.S. climates, and for understanding how the world's oceans carry heat from the tropics toward the poles.

"I think it changes how we think about the whole Atlantic overturning circulation, of which the Gulf Stream is a part," said co-author LuAnne Thompson, a UW professor of oceanography. "It brings back the role of the atmosphere into what's controlling the climate in the high latitudes, that it's not all driven by what's happening in the oceans."

And while a slowdown of the Gulf Stream and broader overturning circulation, for whatever reason, would bring less warm water to eastern North America and Western Europe, any effects are overwhelmed by the overall warming due to global climate change.

"So that whole concept in the movie of New York harbor freezing doesn't make any sense," Kelly said. "If the Gulf Stream doesn't carry as much heat from the tropics, it just means that the North Atlantic is not going to warm up as fast as the rest of the ocean -- it's not going to cool down."

Story Source:

Materials provided by University of Washington. Note: Content may be edited for style and length.

Journal Reference:

Kathryn A. Kelly, Kyla Drushka, LuAnne Thompson, Dewi Le Bars, Elaine L. McDonagh. Impact of slowdown of Atlantic overturning circulation on heat and freshwater transports. Geophysical Research Letters, 2016; 43 (14): 7625 DOI: 10.1002/2016GL069789

Cite This Page:

University of Washington. "Gulf Stream slowdown tied to changes in Southern Hemisphere." ScienceDaily. ScienceDaily, 5 October 2016. .

Danish Scientist Targets Claim that Gulf Stream Is Slowing

REUTERS British Antartic Survey/Handout

A Danish climatologist is pouring cold water over another misleading global warming claim.

Thermographic images released by the National Oceanic and Atmospheric Administration (NOAA) last year showed a mysterious blue blob of cold seawater off the coast of southern Greenland and Iceland. At the time, researchers said the cold blob was likely the result of melting from Greenland’s vast ice sheet, with cold water flowing into the nearby Labrador Sea.

This meltwater was presumed to have slowed the Atlantic Meridional Overturning Circulation (AMOC), or Gulf Stream, that sustains temperate weather in much of western Europe, our East Coast, and the UK.

One of the first researchers at the trough of misinformation was Prof. Michael Mann of Pennsylvania State (and “Hockey Stick” fame), who told the Washington Post that this North Atlantic cold blob happened to fit with his just-published study. Mann also suggested that a “dramatic melting” of Greenland’s ice sheet would slow or stop the AMOC, sending the world into an abrupt climate shift as seen in the climatastrophe flick The Day After Tomorrow.

But Tor Eldevik, a Norwegian climate researcher and professor, subsequently told the newspaper Aftenposten in March 2016 that he was “not convinced that the blue blob was caused by melting Greenlandic ice.” Or that it was slowing the Gulf Stream.

Eldevik said that affecting the AMOC would require vast amounts of freshwater coming into contact with more saline ocean water, which would dramatically change salinity levels and possibly slow the current down. That theory might make sense, Eldevik said, except the currents around Greenland simply aren’t strong enough, or large enough, to slow or stop the Gulf Stream.

Another climate researcher, Peter Langen, showed that this melting Greenlandic ice claim has nothing to do with global warming but rather the result of a particularly cold winter. Dr. Langen, a climatologist at the Danish Meteorological Institute (DMI), said that while Greenland’s coastal areas are melting a little, there simply hasn’t been enough freshwater released to affect the ocean’s circulation in any significant way.

In fact, a year-long study of Greenland’s interior ice sheet showed how very little precipitation is lost via evaporation or melting due to the island’s unique “thermal lid.”

The study, published in Science Advances, illustrates how this unique thermal lid prevents snow and ice from escaping the island, allowing the ice sheet to continuously accumulate in mass. And despite computer climate models claiming Greenland’s ice sheet would be one of the first fatalities in a warming world, this first-of-its-kind study offers convincing evidence that Greenland’s ice sheet remains robust and stable.

Langen also noted that ocean modeling from various studies shows that there simply isn’t enough freshwater being released to influence the Gulf Stream at any great distance from Greenland. After reviewing two new studies, Langen adds that the cold spot seen on NOAA’s map is most likely the result of a simple weather anomaly: an unusually cold winter.

Langen says if the cause of the cold blob was meltwater, it would get mixed and thinned out. The Labrador Sea, which is southwest of Greenland’s southern tip, helps to mix surface and deep ocean water. The saltier the water, the more mixing occurs. If the salinity decreases, so does the mixing. Put simply, the freshwater becomes diluted in such a large area that it is unable to slow or stop oceanic circulation.

Langen adds that the blue blob showed up on NOAA’s maps during the very cold winter of 2014-2015, and the frigid weather actually resulted in increased mixing of surface water with the cold, deep seawater. Langen also explained that researchers reconstructed the cooling of water in the area through complex energy computations, making the weather theory the strongest, and most likely, explanation for the North Atlantic cold blob.

It appears that the cold water observed in the North Atlantic was simply due to a cold winter. And yet, climate alarmists readily attempted to spin it into further proof of global warming. But an analysis of the data shows that, once again, such dramatic claims were overstated.

Thomas Richard is a freelance writer living outside of Boston, MA.

Gulf stream slowdown to spare Europe from worst of climate change

PHYS.ORG

11 de julio de, 2016 James Hakner

The Thermohaline Circulation is a vast system of ocean currents that operates like a conveyor belt, transporting warm water from the tropics to Europe. Credit: istockphoto.com/aristoo

Read more at: https://phys.org/news/2016-07-gulf-stream-slowdown-europe-worst.html#jCp

Europe will be spared the worst economic impacts of climate change by a slowing down of the Gulf Stream, new research predicts.

Scientists have long suggested that global warming could lead to a slowdown – or even shutdown – of the vast system of ocean currents, including the Gulf Stream, that keeps Europe warm.

Known as the Thermohaline Circulation, this system operates like a conveyor belt, transporting warm water from the tropics to Europe, where evaporation decreases salinity and density so that the water sinks.

As the world warms, melting icecaps and increased rainfall are widely predicted to slow this process down by flooding oceans with cold freshwater.

Some experts even fear that the process could shut down altogether, plunging Europe into a new ice age.

However, a new study by the University of Sussex, Universidad Nacional Autónoma de México and the University of California, Berkeley finds that, rather than cooling Europe, a slowdown of the Thermohaline Circulation would mean the continent still warms, but less quickly than other parts of the world.

This would lead to a rise in welfare standards in Europe, concludes the research, which is published in the leading economics journal the American Economic Review.

Professor Tol, Professor of Economics in the School of Business, Management and Economics at the University of Sussex, said: "Cooling is probably a good bit more harmful than warming, particularly in Europe. People rightly fear that climate change would cause a new ice age.

"Fortunately, our study finds no cooling at all. Instead, we find slower warming: a boon for Europeans."

Of course, as ocean currents redistribute rather than create heat, slower warming for Europe means slightly accelerated warming elsewhere.

The study, therefore, adds to a growing body of evidence predicting a rich/poor divide in the climate change stakes. Developing countries will be less able to cope with rising sea levels, for example, and - as this research suggests - may warm faster than other, more developed parts of the world.

Explore further: Retreating sea ice linked to changes in ocean circulation, could affect European climate

More information: David Anthoff et al. Shutting Down the Thermohaline Circulation, American Economic Review (2016). DOI: 10.1257/aer.p20161102

Gulf Stream is slowing down faster than ever, scientists say

INDEPENDENT

Steve Connor
@SteveAConnor
Monday 23 March 2015 17:28 GMT

The Gulf Stream that helps to keep Britain from freezing over in winter is slowing down faster now than at any time in the past millennium according to a study suggesting that major changes are taking place to the ocean currents of the North Atlantic.

Scientists believe that huge volumes of freshwater flowing into the North Atlantic from the rapidly melting ice cap of Greenland have slowed down the ocean “engine” that drives the Gulf Stream (Getty)

However, the researchers believe that Britain is still likely to become warmer due to climate change providing the Gulf Stream does not come to a complete halt – although they remain unsure how likely this is.

Calculations suggest that over the 20th century the North Atlantic meridional overturning circulation – the northward flow of warm surface water and the southward flow of deep, cold water – has slowed by between 15 and 20 per cent, said Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany.

“There is more than a 99 per cent probability that this slowdown is unique over the period we looked at since 900 AD. We conclude that the slowdown many have described is in fact already underway and it is outside of any natural variation,” Professor Rahmstorf said.

The scientists calculated that some 8,000 cubic kilometres of freshwater has flowed from Greenland into the Atlantic between 1900 and 1970, and this rose significantly to 13,000 cubic kilometres between 1970 and 2000.

Freshwater is lighter than salty water which means that it tends to float on the surface of the ocean and in doing so disturbs the normal sinking of dense, cold saltwater to the ocean floor, which is the main driver of the Atlantic circulation.

Jason Box of the Geological Survey of Denmark and Greenland, who helped to calculate the amount of freshwater flowing into the Atlantic from melting ice caps, said that the slowdown can be linked to man-made climate change.

“Now freshwater coming off the Greenland ice sheet is likely disturbing the circulation. So the human-caused mass loss of the Greenland ice sheet appears to be slowing down the Atlantic overturning, and this effect might increase if temperatures are allowed to rise further,” Dr Box said.

Michael Mann of Pennsylvania State University said: “Common climate models are underestimating the change we’re facing, wither because the Atlantic overturning is too stable in the models or because they don’t properly account for Greenland ice melt, or both.”

15/9/16

“Efecto Ártico” Años muy cálidos, Inviernos muy fríos ¿Hacia una Pequeña Glaciación?

TIEMPO.COM

Inviernos extremos, repotenciados por el Mínimo Solar del 2020 podrían llevar al Hemisferio Norte a una “Pequeña Glaciación”

El "Efecto Ártico” (*) es una hipótesis que sostengo desde el 2 de diciembre de 2002, cuando fue publicada ("Efecto Ártico” ¿Pequeña Glaciación antes del 2020?) por EcoPortal de la Argentina y por la Unidad de Comunicaciones e Información Pública del Programa de las Naciones Unidas para el Medio Ambiente- PNUMA- en México.

El “Efecto Ártico” es la denominación al fenómeno del deshielo ártico como consecuencia del calentamiento global sostenido, que afecta el equilibrio térmico del Ártico, el cual tiende a ser restituido con ciclos de inviernos extremos.

La hipótesis inicialmente citada, sostiene que las llamadas "Pequeñas Glaciaciones” tienen un elemento en común “un calentamiento global sostenido” de 35 a 40 años crea las condiciones mínimas para su inicio”, destacando como característica que entre mas cálidos sean los años del citado calentamiento, mas intensos y extremos serán sus inviernos, por lo cual los inviernos del 2012 al 2017 serán gradualmente extremos.

Según la Organización Meteorológica Mundial (OMM) el actual calentamiento global se inició 1.976 cuando se elevó a un ritmo tres veces mayor de lo previsto y el decenio 1998-2007 fue el más cálido desde 1850.

Según la NASA el Calentamiento Global afecta dos veces más las áreas Occidentales del Océano Ártico, que a otras regiones del planeta.

El año 2014 ha sido confirmado como el más cálido para la Tierra desde 1880, por la NASA y la Administración Nacional Oceánica y Atmosférica (NOAA).

Por lo anteriormente expuesto, el actual invierno 2014-2015 debe de ser el de mayor intensidad y de las temperaturas mas extremas en por lo menos los últimos 30 años, en especial en algunas regiones del Atlántico Norte (Este de Norteamérica y Europa Occidental) por la incidencia del deshielo ártico sobre la referida región.

El “Efecto Ártico” sostiene que los veranos de los años muy cálidos tienden a extenderse hasta el otoño y los extremos inviernos pueden prolongarse hasta la primavera, lo cual será de mayor intensidad a finales del ciclo 2014-2017.

El “Calentamiento Global Sostenido” cumple este año 39 años, el mas largo periodo cálido desde la Edad Media, en que se produjo un ciclo similar de calentamiento conocido como “Optimo Climático”, el cual fue abruptamente interrumpido por un periodo de bajas temperaturas (del siglo XIV hasta 1850) denominado como “La Pequeña Glaciación”.

Un breve ciclo de Calentamiento Global Sostenido (de 40 años) y un Mínimo Solar en el año 2020, estaría creando las condiciones mínimas que podría llevar a una “Pequeña Glaciación”.

El Histórico deshielo ártico en el año 2007-2008 afectó el termostato del planeta.

El Ártico es como el termostato del planeta: activa la circulación de las corrientes oceánicas y contribuye a la distribución del calor entre el Ártico y los trópicos. Un estudio del Centro Nacional de Investigación Atmosférica en Boulder, Colorado demostró que las temperaturas del Ártico, en el verano de las últimas décadas han sido las más altas en dos mil años.

Según el Centro Nacional de Datos sobre el Hielo y Nieve de la Universidad de Colorado en Boulder, el Ártico perdió 2.500.000 Km2 de hielo permanente debido al derretimiento, la mitad 1.200.000 K2, entre febrero de 2007 y febrero de 2008".

El Albedo es parte de la radiación solar reflejada por una superficie: la nieve y el hielo refleja el 90% y el color oscuro absorbe el 90%., el color del océano ártico es oscuro.

Imaginemos un gran espejo de 2.500.000 Km2 del tamaño del Mar Mediterráneo, que reflejaba el 90% del calor en el Ártico se diluyó y ahora absorbe calor en verano 24 horas al día de mayo a julio, aportando una extrema humedad que se convierte en excepcionales lluvias de primavera a otoño y extremas nevadas en invierno.

Al aumentar el caudal de agua dulce sobre el océano Ártico y en la región septentrional del Atlántico como consecuencia del deshielo de los glaciales y de la lluvia extrema (la cual aumenta el caudal de los ríos que desembocan en la región) estos pierden salinidad, lo cual facilita su congelación y crea las condiciones mínimas para el próximo extremo invierno.

Un ciclo de inviernos árticos repotenciados por un Mínimo Solar a partir del 2020 podrían llevar a una “Pequeña Glaciación”.

El 19 de mayo del 2014 en el taller de clima espacial del Space Weather Prediction Center, de la NOAA, en Boulder, Colorado, científicos demostraron que el actual Máximo Solar número 24, el cual se inició el 4/01/2008/es uno de los más débiles de los 23 ciclos solares (de 11 años) documentados desde el año 1755.

Al concluir el actual Máximo Solar se invierte la polaridad del Sol y se inician los ciclos de Mínimos Solares a partir del año 2020.

La baja actividad solar con pocas manchas solares esta asociada con períodos de inviernos extremos que llevan a ciclos de enfriamiento en el hemisferio norte del planeta como el ocurrido entre 1645 y 1715, el cual es conocido como “Mínimo de Maunder” o La Pequeña Edad de Hielo.

De acuerdo a modelos climáticos un Sol menos activo, implica una mayor presencia de rayos cósmicos que provocan la formación de nubes bajas, lo cual disminuye la entrada de la radiación solar, favoreciendo una disminución de la temperatura y posibilitando un enfriamiento del planeta.

Expertos en el tema vinculan la similitud del próximo mínimo solar con el “Mínimo de Maunder” en una entrevista publicada por el diario BBC de Londres (¿Se quedó dormido el Sol? Rebecca Morelle /18/01/2014).

Según la doctora Lucie Green, del laboratorio de ciencia espacial de la University College London, de Londres, “Existen indicios muy fuertes de que ahora el Sol está actuando de la misma forma que cuando ocurrió en el mínimo de Maunder".

Y de Mike Lockwood, profesor de física ambiental espacial, de la Universidad de Reading, Reading, (Berkshire, Inglaterra) “el Sol esté cada vez menos activo: Un análisis del núcleo de hielo, que registra un largo periodo de actividad solar, sugiere que esta disminución de la actividad es la más rápida que se ha visto en 10.000 años”.

El deshielo ártico y el Mínimo Solar una vía a la “Pequeña Glaciación”

Un estudio publicado el 6 Mayo del 2012 en la revista Nature Geoscience realizado por un equipo de científicos europeos del Centro Alemán de Investigación en Geociencias (GFZ), demostró que un mínimo solar ocasiono un enfriamiento brusco(menos de una década) en Europa Occidental hace 2.800 años, con afectación de patrones de viento y aumento de la humedad.

Un informe del Instituto Real de los Países Bajos para la Investigación Marina (4/04/2011), demostró que el deshielo ártico había aumentado el contenido de agua dulce del Ártico en un 20% desde la década de 1990, en cerca de 8.400 kms3, equivalente a toda el agua en el lago Michigan y el Lago Huron juntos, o al doble del volumen de agua del lago Victoria, el más grande de África.

Hasta el presente el agua dulce acumulada en el Ártico, no se ha desplazado sobre el Atlántico, debido a que el patrón de viento no ha variado significativamente, de ocurrir la citada variación, el desplazamiento afectaría la deriva de la cálida Corriente del Golfo (corriente del Atlántico Norte) y la densidad de la fría Corriente de Labrador, lo que llevaría a un periodo de inviernos árticos y con ello al inicio de una “Pequeña Glaciación”, en el Hemisferio Norte.

Es probable que el Mínimo Solar, pueda incidir con sus bajas temperaturas y altere el “patrón de viento” en la región ártica y con ello desplazar sobre el Atlántico el agua dulce acumulada.

La termosfera aumenta la temperatura durante los "máximos solares", y la disminuye durante los "mínimos solares".

Según la NASA entre el año 2008–2009, las manchas solares prácticamente desaparecieron y se produjo la contracción más pronunciada de la termosfera, de dos a tres veces mayor que lo que usualmente ocurre con una baja actividad solar, fue causada en parte por el exceso de dióxido de carbono, el cual al llegar a la referida capa, funciona como un refrigerante extrayendo calor a través de la radiación infrarroja.

De acuerdo a Scripps Institution of Oceanography los niveles de dióxido de carbono medidos en la cima del Mauna Loa en Hawái de diciembre de 2014 a principios de enero de 2015, estuvieron sobre los 400 ppm.

El experto Bob Ward, director de comunicaciones del Instituto Grantham de Investigación sobre el Cambio Climático y el Medio Ambiente de la Escuela de Londres de Economía y Ciencias Políticas ,aseguro que a última vez en que los niveles de CO2 se mantuvieron de forma estable por encima de 400 ppm fue hace tres millones de años.

De acuerdo a las evidencias científicas expuestas en un mínimo solar de un año (2008-2009) se redujo de dos a tres veces la termosfera.

¿Con un mínimo solar de 11 años, en cuantas veces se reduciría la termosfera con una Atmosfera cargada con mas 400 ppm de CO2 y como se afectaría la temperatura del planeta?

Erik Quiroga Ambientalista,

Promotor de la creación del Día Internacional de la Preservación de la Capa de Ozono, aprobado por la Asamblea General de las Naciones Unidas (Resolución 49/114 del 23/01/95) promovido el 16 de septiembre.

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TEMPORAL EN EUROPA 2012

1/02/2012. La ola de frío polar continental que afectará a partir de este jueves a España se produce aproximadamente una vez entre siete u ocho años y, de hecho, "esta podría ser de las cuatro más frías desde 1950", según la Agencia Estatal de Meteorología (AEMET).

MADRID, 1 (EUROPA PRESS)

Así, el portavoz de la AEMET, Ángel Rivera, ha explicado a Europa Press que esta situación "no es desconocida en invierno", pero ha añadido que, en este caso, además de las bajas temperaturas, la sensación térmica será de "aún más frío" debido a los vientos del nordeste de entre 30 y 40 kilómetros por hora y de hasta 70 u 80 kilómetros por hora en el cuadrante nordeste y Baleares.

En este contexto, ha precisado que el temporal consiste en un anticiclón que se extiende por el norte de Europa con un eje inclinado nordeste-suroeste y que lleva un borrasca fría al sur en torno al Mediterráneo y sur de Europa. Esto implicará una descarga de viento del nordeste que arrastra masas de aire que proceden de Rusia o el interior de Europa y, a veces, de la propia Siberia.

Según ha indicado, ese es el motivo por el que se conocen como "olas siberianas", aunque ha detallado que su nombre técnico es "aire polar continental", el cual se distingue del aire polar marítimo en que el segundo es menos frío y más húmedo, mientras que este es más frío y de carácter seco. "Esta tipo de masas de aire son las que más frío pueden traer a España", ha apuntado.

En este contexto, el portavoz de la AEMET ha apuntado que el inicio de esta ola viene precedido asimismo de una descarga de aire frío que recorrerá la Península "desde este jueves a mediodía, de nordeste a suroeste" y que, a su paso dejará precipitaciones de lluvia y sobre todo de nieve a partir de 400 o 500 metros de altura, aunque salvo en las cordilleras, las nieves no serán "muy importantes".

MÁS NIEVE EN ÁFRICA QUE EN ESPAÑA

Rivera ha advertido que a lo largo de este jueves esta masa de aire frío cubrirá toda España e incluso rebasará la Península y llegará al norte de África, donde destacará por las temperaturas mínimas en el norte de Argelia, Túnez o Libia que serán "significativas" y donde la nieve hará presencia, "de hecho de forma más destacable que en España".

En cuanto a la duración de la situación, el portavoz de la AEMET, considera que se prolongará el jueves, el viernes y el sábado y que comenzará a disminuir el domingo.

Así, ha adelantado que en España lo que pasará es que una corriente de vientos fuertes de unos 30 a 40 kilómetros por hora y que en la zona de Cataluña, Baleares y Aragón, la tramontana y el cierzo podrían llegar hasta los 70 u 80 kilómetros por hora.

De este modo, ha dicho que se espera que las temperaturas máximas sean "muy bajas" y que se queden entre los 0 y los cinco grados centígrados en buena parte de la península. Incluso en muchos sitios de Castilla y León, Navarra y el norte peninsular las máximas rondarán los cero grados.

En cuanto a las mínimas, prevé que los termómetros no suban de los -5 a -10 grados centígrados en la mayor parte de España, que lleguen a -14 grados centígrados en zonas de montaña e incluso hasta -20 grados centígrados en alta montaña. "Sin embargo, la sensación térmica será todavía más fría, debido a las fuertes rachas de viento polar", ha subrayado.

En cuanto a precipitaciones, ha avisado de que donde más nevará será en la costa de Cataluña, en la costa del país Vasco y unos kilómetros hacia el interior y, sobre todo serán más importantes en Baleares donde las precipitaciones serán sobre los 200 metros e incluso podría nevar en la costa.

A partir del domingo, la tendencia es que esta situación comience a disminuir por la mitad occidental peninsular, aunque la tendencia general apunta a que la situación comience a aminorar de virulencia y que las temperaturas empiecen a subir a partir del lunes en la mitad oeste peninsular. En cuanto a la mitad este y Baleares, la situación se prolongará hasta el martes. La estabilización o normalización en todas las zonas no llegará hasta el miércoles.

En general, las zonas más frías serán las situadas al norte de una línea imaginaria desde La Coruña a Almería. Esta entrada pueblos de España

ANTECEDENTES

Esta masa de aire es "bastante más fría que en otras ocasiones", ya que esta situación se afecta a España una vez cada siete u ocho años. En lo que va del siglo XXI se conocen dos situaciones similares, en diciembre de 2001 y en enero de 2005, aunque "esta las podría igualar o incluso superar".

Por otro lado, desde los años 50 del siglo pasado esta situación se ha producido entre siete u ocho ocasiones, la mayoría de ellas en las décadas de los 50, 60 y comienzos de los 70 y menos en los 80 y 90. La de esta ocasión se podría situar entre las cuatro más fuertes desde 1950. Es una situación bastante intensa, de bastante frío y no estamos acostumbrados a este tipo de entradas tan severas que no se estaban produciendo mucho.

La ola de frío "paradigmática" de este tipo se remonta a 1956, cuando España estuvo afectada del 1 al 20 de febrero y provocó graves daños a la agricultura y la industria. "Aquello fue un hito en la historia de España", ha concluido.

TIMING OF ABRUPT CLIMATE CHANGE - YOUNGER DRYAS

TIMING OF ABRUPT CLIMATE CHANGE AT THE END OF THE YOUNGER DRYAS INTERVAL FROM THERMALLY FRACTIONATED GASES IN POLAR ICE

Jeffrey P. Severinghaus*, Todd Sowers†, Edward J. Brook‡, Richard B. Alley† & Michael L. Bender*§

* Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882, USA

† Geosciences Department, Pennsylvania State University, University Park, Pennsylvania 16802, USA

‡ Departments of Geology and Environmental Science, Washington State University, Vancouver, Washington 98686, USA

Rapid temperature change fractionates gas isotopes in unconsolidated snow, producing a signal that is preserved in trapped air bubbles as the snow forms ice. The fractionation of nitrogen and argon isotopes at the end of the younger Dryas cold interval, recorded in Greenland ice, demonstrates that warming at this time was abrupt...

http://homologa.ambiente.sp.gov.br/proclima/artigos_dissertacoes/dissertacoes_ingles/timingofabruptclimatechange.pdf

Climate Change and the Big Arctic Thaw Tweet. Share Email Wed, May 4, 2011 -- 9:00 AM

An alarming new report says climate change is happening in the Arctic at a more rapid pace than previously believed. Melting ice could elevate the global sea level by as much as five feet in this century. We talk with writer, environmentalist and climate change expert Tim Flannery about what this new information says about the future of our planet. Host: Michael Krasny Guests: Tim Flannery, Australia's chief commissioner for climate change, director of the Australian Wildlife Conservancy and author of "The Weather Makers" and the new book, "Here on Earth: A Natural History of the Planet" More info: About the book "Here on Earth: A Natural History of the Planet" : at Amazon.com

Probing a glacier as it thaws

BY LAUREN MORELLO, E&E REPORTER Third in a three-part series. KANGERLUSSUAQ, Greenland -- In her knitted ski hat, parka and hiking boots, Åsa Rennermalm doesn't look like an accountant -- or a plumber. But the Rutgers University hydrologist draws on both disciplines as she works at the southwestern edge of Greenland's vast ice sheet. She's spent the past four years trying to answer a deceptively simple question: When Greenland's ice melts, where does the water go? "Satellites show the surface of the ice is melting and the volume of ice is decreasing," Rennermalm says. "But how much meltwater is leaving and reaching the ocean? That will influence future sea level rise." She and colleagues from the University of California, Los Angeles, are studying the runoff from one chunk of the Greenland ice sheet -- Russell Glacier, which sits 16 miles outside of this small town. Because it rests entirely on land, it isn't vulnerable to the influxes of warming ocean water that cause outlet glaciers to calve. The main way Russell loses ice is surface melting. Some of the resulting water runs off the glacier into nearby lakes and streams. Some drains into cracks and channels in the ice, where it can refreeze or flow to subglacial streams and lakes that feed into the sea. The scientists are trying to track the water that runs off Russell Glacier and trace it back to its source.

INUNDACIONES UK

Inundación - Reino Unido Los equipos de rescate británicos trabajan a pleno rendimiento. Con helicópteros y botes hinchables, han logrado poner a salvo a decenas de personas atrapadas por la inundaciones que asolan el noroeste de Inglaterra y el sur de Escocia. Las fuertes lluvias registradas en las últimas horas han anegado centenares de viviendas, obligando a sus habitantes a refugiarse en centros especiales. La región más afectada es la de Cumbria, donde hay varios desaparecidos. En la localidad de Cockermouth, por ejemplo, el nivel de las aguas supera los dos metros y medio. La calle principal de esta localidad se ha convertido en un auténtico río. Las previsiones para este viernes no son nada halagüeñas. La agencia meteorológica británica habla de abundantes lluvias y fuertes vientos. Copyright © 2011 euronews

Nonnormal Amplification of the Thermohaline Circulation

Laure Zanna

Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts

Eli Tziperman

Division of Engineering and Applied Sciences, and Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts

Abstract

A simple zonally averaged coupled ocean–atmosphere model, with a relatively high resolution in the meridional direction, is used to examine physical mechanisms leading to transient amplification of thermohaline circulation (THC) anomalies. It is found that in a stable regime, in which small perturbations eventually decay, there are optimal initial conditions leading to a dramatic amplification of initial temperature and salinity anomalies in addition to the THC amplification. The maximum amplification occurs after about 40 years, and the eventual decay is on a centennial time scale. The initial temperature and salinity anomalies are considerably amplified by factors of a few hundreds and 20, respectively. The initial conditions leading to this amplification are characterized by mutually canceling initial temperature and salinity anomalies contributions to the THC anomaly, such that the initial THC anomaly vanishes. The mechanism of amplification is analyzed and found to be the result of an interaction between a few damped (oscillatory and nonoscillatory) modes with decay time scales lying in a range of 20–800 years. The amplification mechanism is also found to be distinct from the advective feedback leading to THC instabilities for large freshwater forcing.

Received: September 10, 2004; Accepted: March 1, 2005

Corresponding author address: Laure Zanna, Department of Earth and Planetary Sciences and Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138. zanna@fas.harvard.edu

http://journals.ametsoc.org/doi/full/10.1175/JPO2777.1

El papel de polvo en el cambio climático abrupto

El papel de polvo en el cambio climático abrupto: Claves desde las costas de África del Noroeste y de Alborán registros de sedimentos del Mar

Autores : A. Moreno, M. Canales

Contribuciones a la Ciencia, ISSN 1575-6343, Vol . 2 , N º. 4, 2004 , pags . 485-497
Los sedimentos marinos son uno de los mejores archivos de los cambios climáticos del pasado , ya que son esencialmente de carácter permanente y su edad se puede determinar con relativa facilidad. Durante las últimas décadas , muchos estudios paleoclimáticos han centrado en los cambios climáticos bruscos , que puedan ser utilizadas como modelos de los futuros cambios climáticos . Una de las preguntas clave que se plantea es el papel de la atmósfera en el desencadenamiento y la transferencia de los cambios bruscos del clima. En este sentido , la investigación de la influencia de las partículas de polvo eólico sobre el cambio climático merece una atención especial. El estudio de la acumulación de polvo eólico en los sedimentos marinos es crucial no sólo para entender el cambio climático pasado, sino también para explicar los mecanismos del cambio climático en general . En este artículo , las interacciones entre polvo en la atmósfera y el cambio climático rápido se discuten después de una revisión de los registros de sedimentos marinos , en las escalas temporales glaciales e interglaciales y milenario , desde la costa del noroeste de África y el Mar de Alborán .

Cambio de la temperatura del agua del Atlantico Norte 2008-2010

Teniendo en cuenta las condiciones de estabilidad de temperaturas del agua que necesita la corriente del Golfo es de considerar esta información. Hay una tendencia al enfriamiento de la temperatura del agua que rodea a las islas británicas y también en las áreas del Cantábrico. Si se compara la situación térmica entre el 10 de octubre del 2008 con la del 2006, hay lugares del mar de Irlanda en donde la temperatura descendió mas de 6º centigrados.
Se explica en las imágenes de Meteociel:

http://www.meteociel.com/accueil/sst.php

Informe sobre posibilidad de cambio de clíma súbito,del Departamento de Defensa de los EEUU, de 2003

Informe sobre la posibilidad de un cambio de clima súbito, que afectaría a todo el hemisferio Norte ( para una miniglaciación) y al hemisferio sur (calentamiento ecuatorial), para el Departamento de Defensa de los EEUU, de Peter Schwartz and Doug Randall, en octubre de 2003.

Report on the possibility of sudden climate change that would affect the whole northern hemisphere (for a miniglaciación) and the southern hemisphere (warm equatorial) for the Department of Defense U.S., Peter Schwartz and Doug Randall, October 2003.

Enlaces de publicación (posting):

http://www.edf.org/documents/3566_AbruptClimateChange.pdf

http://www.gbn.com/consulting/article_details.php?id=53

Ocean Circulation Shut Down by Melting Glaciers After Last Ice Age

NASA. Top Story

At the end of the last Ice Age 13 to 11.5 thousand years ago, the North Atlantic Deep Water circulation system that drives the Gulf Stream may have shut down because of melting glaciers that added freshwater into the North Atlantic Ocean over several hundred years, NASA and university researchers confirm. Since the Gulf Stream brings warm tropical waters north, Western Europe cooled.

The National Science Foundation (NSF) funded study also finds that if a shutdown persisted for a long enough time, the entire Northern Hemisphere would eventually cool.

The computer model simulations of ocean and atmosphere processes used in this study imply a similar phenomenon has the potential to occur in the future due to freshwater additions from increased rain and snow caused by global climate change.

"For the first time, it is shown that realistic additions of glacial meltwater into the North Atlantic would have shutdown North Atlantic Deep Water production over a period of a few hundred years if the initial ocean circulation was somewhat weaker than that of today," said David Rind, lead author of the study and a senior climate researcher at NASA's Goddard Institute for Space Studies in New York, NY. The study appears in the November 16 issue of Journal of Geophysical Research - Atmospheres.

When Rind and his colleagues entered realistic estimates of freshwater from melting glaciers into their model, they found the North Atlantic circulation stopped completely after some 300 years. When the model was adjusted to make the circulation weaker than it is today, cessation of the Gulf Stream took only 150-200 years, matching current estimates based on paleo-climate records .

Freshwater additions into the ocean through the St. Lawrence River have a profound effect on the ocean circulation.

"The more freshwater you add, and the longer you add it, the greater reduction in the North Atlantic circulation," Rind said. "According to our model, this is a linear response."

When the Gulf Stream moves warm surface water from the equator north through the Atlantic, the water cools, gets saltier due to evaporation and becomes very dense. By the time it approaches the coast of Newfoundland, or further northeast in the Norwegian Sea, it becomes dense enough to sink. This process is called overturning. The dense water then slowly travels through the deep water southward into the Southern Hemisphere, with the return flow to the north occurring at the surface.

But when freshwater gets mixed with the salty water in the North Atlantic, it makes the water less dense and slows the overturning process and the ocean circulation.

While the study finds that freshwater input could slow and stop overturning, this would not stop the Gulf Stream entirely. That's because the stream is partially pushed by winds. As a result, the model shows the reduced Gulf Stream would only transport about half as much heat northward, thereby cooling Western Europe. Were this to occur in a global warming scenario, it would act to partly counter the effects of projected greenhouse warming in parts of Western Europe.

Many scientists suspect more rainfall in parts of the Northern Hemisphere during this century as a result of greenhouse warming. That's because warmer temperatures increase the atmosphere's capacity to carry water. "The North Atlantic circulation may already be weakening due to freshwater rainfall additions associated with global warming," Rind said.

But the model shows a number of inconsistencies with previous studies on the last ice age. Those studies speculate that once freshwater stopped flowing, the ocean circulation would return within only a few decades, matching a rapid warming seen in the climate record. The model finds that deepwater circulation does not return for at least hundreds of years when the freshwater additions end. Also contrary to observations, the model showed cooling throughout the Northern Hemisphere; during the last ice age, the majority of the United States land mass did not appear to cool.

"It's hard to understand how parts of the Northern Hemisphere might have cooled to the magnitude suggested, but not North America," Rind said. "That seems to imply that either the paleo-records are being misinterpreted, or something else went on, something major that is not being accounted for. This isn't necessarily the end of the story."

UPDATES ON WARM SEAS AND ARCTIC ICE (The New York Times, 20.09.09)

http://dotearth.blogs.nytimes.com/2009/09/16/august-seas-warmest-in-120-years/

The National Climatic Data Center has released its review of worldwide sea surface temperatures for August and for the stretch from June through August and finds that both the month and the “summer” (as looked at from the Northern Hemisphere) were the warmest at least since 1880, when such records were first systematically compiled.

Sea ice in the Arctic appears to be starting the slow late-summer freeze after reaching its minimum extent several days ago, by a couple of estimates ( National Snow and Ice Data Center; International Arctic Research Center / Japan Aerospace Exploration Agency). Here’s the global sea ice trend, combining what’s going on up north and down south. This season’s Arctic ice retreat ranks well behind the extraordinary ice retreat of 2007 and also last year’s but remains below the average ice extent for the stretch since 1979, when satellites started monitoring Arctic conditions with some precision. Here’s a compilation of various groups’ experimental ice forecasts for this year and the results.

The National Oceanic and Atmospheric Administration summarized ocean temperature conditions for August in this description of the video above:

The world’s ocean surface temperature was the warmest for any August on record, and the warmest on record averaged for any June-August summer season, according to N.O.A.A.’s National Climatic Data Center in Asheville, N.C. Worldwide records began in 1880. Shown here is a visualization of the August global temperature anomalies — or in other words, how the average temperature in August differed from the average climate of 1961-1990. Notice that in some areas, such as the western United States, temperatures were much cooler than average. But overall, land and ocean temperatures were several degrees above normal.

Clearly the current El Niño warming in the tropical Pacific Ocean has contributed to the warm sea conditions. (UPDATE, 9/17: I’ve asked N.O.A.A. officials about their choice of temperature data sets, which has been criticized by some.) Variations in polar sea ice on short time scales, up or down, are essentially meaningless, my contacts studying the cryosphere always stress. Keep track of the long-term trends at the links above.

Q&A: Copenhagen climate change summit 2009

THE GUARDIAN
Environment ministers and officials are meeting in at a UN summit Copenhagen in December to thrash out global deal on climate change. What's on the agenda?

Abigail Edge and David Adam
guardian.co.uk, Friday 1 May 2009 15.47 BST
Article history

What is the Copenhagen climate change summit?
From 7 December environment ministers and officials will meet in Copenhagen for the United Nations climate conference to thrash out a successor to the Kyoto protocol. The conference, held at the modern Bella Center, will run for two weeks. The talks are the latest in an annual series of UN meetings that trace their origins to the 1992 Earth Summit in Rio, which aimed at coordinating international action against climate change.

What does COP15 stand for?
COP15 is the official name of the Copenhagen climate change summit — the 15th Conference of the Parties (COP) under the United Nations Framework Convention on Climate Change (UNFCCC). The COP is the highest body of the UNFCCC and consists of environment ministers who meet once a year to discuss developments in the convention.

Which countries are taking part in the climate change summit, and how many people will be there?
One hundred and ninety-two countries have signed the climate change convention. More than 15,000 officials, advisers, diplomats, campaigners and journalists are expected to attend COP15, joined by heads of state and government.

Who are the main players?
Developing countries, including China and India, believe it is the responsibility of wealthy industrialised nations such as the UK and US to set a clear example on cutting carbon emissions. Significantly, the US rejected the 1997 Kyoto protocol, with George Bush arguing that the 5% reductions required by Kyoto would "wreck [the American] economy" while making no demands on emerging economies. COP15's chances of success have been improved by President Barack Obama's stated intention to achieve an 80% reduction of greenhouse gas emissions by 2050.
In April, the secretary of state, Hillary Clinton, acknowledged the role the US had played in past climate emissions at a gathering of officials from the world's 17 largest economies. She said the US was "determined to make up for lost time both at home and abroad". "The US is no longer absent without leave," she said. However, Denmark's minister for climate and energy, Connie Hedegaard, has warned that American leadership on climate change will be undermined if the Obama administration does not pass laws swiftly to reduce carbon pollution.

What does the summit hope to achieve?
Officials will try to agree a new climate treaty as a successor to the Kyoto protocol, the first phase of which expires in 2012. According to Yvo de Boer, executive secretary of the UNFCCC, the four essentials needing an international agreement in Copenhagen are:

1 How much are industrialised countries willing to reduce their emissions of greenhouse gases?
2 How much are major developing countries such as China and India willing to do to limit the growth of their emissions?
3 How is the help needed by developing countries to engage in reducing their emissions and adapting to the impacts of climate change going to be financed?
4 How is that money going to be managed?

What are the sticking points?
The main issue is that of "burden-sharing". Climate scientists say that the world must stop the growth in greenhouse gas emissions and start making them fall from around 2015 to 2020. By 2050 they estimate the world must cut its emissions by 80% compared with 1990 levels to limit global warming to a 2C average rise.Money is also a major issue. The developing countries know they must hand over hundreds of billions of pounds to poorer nations, to help them adapt to the likely consequences. Earlier this year, Gordon Brown said this climate funding needed to reach $100bn a year by 2020. If the recent recession has made rich countries less willing to part with their cash, this could raise tensions in Copenhagen
But which countries must make the cuts and by how large should they be? For example, the rapidly growing Chinese economy has recently overtaken America as the world's largest emitter of carbon dioxide. Yet America has historically emitted far more emissions than China, and on a per capita basis Chinese emissions are around a quarter of those of the US.
The Chinese government argues that it has a moral right to develop and grow its economy — carbon emissions will inevitably grow with it. There is also the issue of industrialised nations effectively outsourcing carbon emissions to developing nations such as China. This is a consequence of huge quantities of carbon-intensive manufacturing taking place in China on behalf of buyers in the west. It wants consumer countries to take responsibility for the carbon emissions generated in the manufacture of goods, not the producer countries that export them.
Problems such as these have cast doubts on whether COP15 can succeed. There are also concerns about whether any action we take now to prevent climate change may be too little too late. A Guardian poll revealed almost nine out of 10 climate scientists do not believe political efforts to restrict global warming to an additional 2C — the level the EU defines as "dangerous" — will succeed.