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El calentamiento global como amenaza global

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El calentamiento global como amenaza global

Mensaje por ivan_077 el Febrero 3rd 2017, 23:25


A 1,000-foot-thick ice block about the size of Delaware is snapping off of Antarctica

Dave Mosher

Jan. 6, 2017, 10:22 AM 230,305

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antarctica larsen c ice shelf rift nov 2016 john sonntag nasa gsfc A 300-foot-wide rift in Antarctica's Larsen C ice shelf, as seen in November 2016. John Sonntag/IceBridge/NASA Goddard Space Flight Center

A slab of ice nearly twice the size of Rhode Island is cracking off of an Antarctic glacier, and one scientist says rapid growth in the giant rift between it and the southern continent means its break-off is inevitable in a few months' time.

The giant ice block is part of the Larsen C ice shelf, which is the leading edge of one of the world's largest glacier systems.

It's called an ice shelf because it's floating on the ocean. It's normal for ice shelves to calve big icebergs, since snow accumulation gradually pushes old glacier ice out to sea.

But this piece of floating ice off of Antarctica's prominent peninsula is colossal — more than 1,100 feet (335 meters) thick and roughly 2,000 square miles (5,180 square kilometers) in area — and it's destabilizing quickly, likely accelerated by rapid human-caused global warming.

larsen c ice shelf diagram antarctica Diti Torterat/Wikipedia (CC BY 2.0)

Satellite images suggest the crack began opening up around 2010 and lengthened more than 18 miles (29 kilometers) by 2015. By March 2016, it had grown nearly 14 miles longer.

In November, a team of scientists in NASA's Operation IceBridge survey flew over the rift to confirm it's at least 70 miles long, 300 feet wide, and one-third of a mile deep.

Now another group of researchers — this time at Swansea University in the UK — say the entire block of ice is hanging on by 12 miles of unfractured ice.

How long until it snaps off?

"If it doesn't go in the next few months, I'll be amazed," Adrian Luckman, a glaciologist at Swansea University, said in a January 6 press release. "It's so close to calving that I think it's inevitable."

Here's how the crack has progressed:

Larsen C ice shelf crack rift iceberg swansea university Courtesy MIDAS Project/A. Luckman, Swansea University

Right now, researchers have limited satellite coverage of the area; NASA's Ice, Cloud, and Land Elevation Satellite, or ICESat, mission ended in 2009, and the next similar satellite, ICESat-2, isn't scheduled for launch until 2018. (President-elect Donald Trump's team has said it plans to strip NASA of funding for such earth science missions, which date back to the formation of the space agency 59 years ago.)

That's why estimates of the crack vary somewhat, forcing researchers to fly over the region for confirmation.

antarctica larsen c ice shelf rift crack nov 2016 john sonntag nasa gsfc.JPG The Larsen C ice shelf rift snaking into the distance, as seen from an IceBridge flight. John Sonntag/IceBridge/NASA Goddard Space Flight Center

NASA's program for this, which is funded through 2019, is (poetically) called IceBridge.

"Rifting of this magnitude doesn't happen so often, [so] we don't often get a chance to study it up close," Joe MacGregor, a glaciologist and geophysicist at NASA's Goddard Space Flight Center, previously told Business Insider in an email.

MacGregor was more hesitant in December with his estimate for when Larsen C's iceberg would calve.

"Maybe a month, maybe a year," he said. "The more we study these rifts, the better we'll be able to predict their evolution and influence upon the ice sheets and oceans at large."

But scientists agree the iceberg will calve at some point — and sooner rather than later.

When the block does break off, it will be the third-largest in recorded history. MacGregor said it'd "drift out into the Weddell Sea and then the Southern Ocean and be caught up in the broader clockwise ... ocean circulation and then melt, which will take at least several months, given its size."

Computer modeling by some researchers suggests the calving of Larsen C's big ice block might destabilize the entire ice shelf, which is about 19,300 square miles — roughly two times as large as Massachusetts — via a kind of ripple effect.

MacGregor downplayed this possibility, saying that other "computer models predict that the eventual calving of this iceberg won't affect the overall stability of the ice shelf."

Luckman backed this up.

"We would expect in the ensuing months to years further calving events, and maybe an eventual collapse, but it's a very hard thing to predict, and our models say it will be less stable," Luckman said in the release, adding that it won't "immediately collapse or anything like that."

However, a rapid ice shelf collapse would not be unprecedented.

In 2002, a large piece of the nearby Larsen B ice shelf snapped off, but within a month — and quite unexpectedly — an even larger swath of the 10,000-year-old feature behind it rapidly disintegrated. The rest of Larsen B may splinter off by 2020.

If there's any good news about the rift in Larsen C, it's that the ice shelf "is already floating in the ocean, so it has already displaced an equivalent water mass and minutely raised sea level as a result," MacGregor said. "Melting of the resulting iceberg won't change that contribution."

The bad news is that if Larsen C collapses, all the ice it holds back might add another 4 inches to sea levels over the years and decades — and that it's just one of many major ice systems around the world affected by climate change.
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__________________________________________________________________________________________________
"No hay mas diferencia entre los hombres que el vicio o la virtud" Jose Maria Morelos y Pavon.

No hay raza inferior; solo hay sujetos inferiores
Bendita se la muerte, porque a nadie le concede lo que no les da a todos los demas;alabada sea la muerte que se yergue piadosa ante el hombre que ha cumplido su deber.
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ivan_077
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Re: El calentamiento global como amenaza global

Mensaje por ivan_077 el Febrero 3rd 2017, 23:34


Devastating global warming is inevitable due to inaction of international community, says leading economist

Professor William Nordhaus warns even extreme action on a global scale will still see a rise of 2.5C, but a leading climate scientist says an effort on the scale needed to win World War II could still save the day

Ian Johnston Environment Correspondent
Wednesday 11 January 2017 11:30 BST

The world can no longer avoid dangerous global warming because countries have done little to tackle the problem apart from spout “rhetoric”, a leading economist has warned.

Professor William Nordhaus, of Yale University in the US, said it was no longer practicably feasible to keep the level of warming to within two degrees Celsius above pre-industrial levels, the point at which climatologists believe the world will start to experience particularly dangerous climate change.

This would see devastating storms, droughts, deadly heat waves and floods all become significantly more common, making some areas of the planet increasingly difficult for humans to inhabit.

The US military, among others, has expressed concern about the security implications of the mass movements of people that such scenarios would likely bring about.
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Professor Nordhaus, a noted expert on the economics of climate change, wrote in a paper called Projections and Uncertainties About Climate Change in an Era of Minimal Climate Policies: “The international target for climate change with a limit of 2C appears to be infeasible with reasonably accessible technologies.

“And this is the case even with very stringent and unrealistically ambitious abatement strategies.

“This is so because of the inertia of the climate system, of rapid projected economic growth in the near term, and of revisions in several elements of the model.

“A target of 2.5C is technically feasible but would require extreme virtually universal global policy measures.”

Read more

Climate change 'game over'? Scientists say global warming could hit 7C

He said in all the world only the European Union had introduced major policies designed to reduce global warming – but was scathing about what those would actually achieve.

“Notwithstanding what may be called ‘The Rhetoric of Nations’, there has been little progress in taking strong policy measures,” Professor Nordhaus wrote.

“For example, of the six largest countries or regions, only the EU has implemented national climate policies, and the policies of the EU today are very modest.

“Moreover, from the perspective of political economy in different countries as of December 2016, the prospects of strong policy measures appear to be dimming rather than brightening.”
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__________________________________________________________________________________________________
"No hay mas diferencia entre los hombres que el vicio o la virtud" Jose Maria Morelos y Pavon.

No hay raza inferior; solo hay sujetos inferiores
Bendita se la muerte, porque a nadie le concede lo que no les da a todos los demas;alabada sea la muerte que se yergue piadosa ante el hombre que ha cumplido su deber.
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ivan_077
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Re: El calentamiento global como amenaza global

Mensaje por ivan_077 el Febrero 3rd 2017, 23:49


‘Society could end in less than a decade,’ predicts academic

Professor blames sweeping political turmoil and social unrest for worrying prediction

Lucy Pasha-Robinson
@lucypasha
Saturday 7 January 2017 19:22 BST



Society could come to an end in less than a decade, a “mathematical historian” has predicted.

Professor Peter Turchin said sweeping political turmoil and social unrest could result in the collapse of the world as we know it in the 2020s.

The academic, from University of Connecticut’s department of ecology and evolutionary biology, is a world-leading expert on cliodynamics, a research method that uses mathematics and complexity science to predict historical events, such as the growth and collapse of empires or religions.
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“We should expect many years of political turmoil, peaking in the 2020s,” professor Turchin wrote on Phys.org.

“But this is a science-based forecast, not a ‘prophecy’. It’s based on solid social science.”

He said peaks and troughs in society were inevitable, citing “impersonal social forces”, which bring “us to the top; then comes the inevitable plunge.”

He also blamed the development of “elite overproduction”, which causes wealth gaps in society to widen and the poor to become increasingly alienated.
President Trump protests


“Elite overproduction generally leads to more intra-elite competition that gradually undermines the spirit of cooperation, which is followed by ideological polarisation and fragmentation of the political class,” he wrote.

“This happens because the more contenders there are, the more of them end up on the losing side. A large class of disgruntled elite-wannabes.”

Read more

From Brexit to Trump, 2017 will be dominated by 2016’s decisions

The academic also claimed a stagnation in living standards and declining economic health could cause a fatal collapse in societal structures.

However, professor Turchin denied that his theory was a “prophecy”, or in any way “inevitable.”

“Ours is the first society that can perceive how those forces operate, even if dimly. The descent is not inevitable,” he wrote.

“This means that we can avoid the worst — perhaps by switching to a less harrowing track, perhaps by redesigning the rollercoaster altogether."

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__________________________________________________________________________________________________
"No hay mas diferencia entre los hombres que el vicio o la virtud" Jose Maria Morelos y Pavon.

No hay raza inferior; solo hay sujetos inferiores
Bendita se la muerte, porque a nadie le concede lo que no les da a todos los demas;alabada sea la muerte que se yergue piadosa ante el hombre que ha cumplido su deber.
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ivan_077
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