[One-Minute World News] from [BBC NEWS]
[Science , Environment & Technology]
Page last updated at 20:29 GMT, Thursday, 3 September 2009 21:29 UK
Arctic 'warmest in 2,000 years'
Arctic temperatures are now higher than at any time in the last 2,000 years, research reveals.
By Richard Black
Environment correspondent, BBC News website
Arctic temperatures are now higher than at any time in the last 2,000 years, research reveals.
Changes to the Earth's orbit drove centuries of cooling, but temperatures rose fast in the last 100 years as human greenhouse gas emissions rose.
Scientists took evidence from ice cores, tree rings and lake sediments.
Writing in the journal Science, they say this confirms that the Arctic is very sensitive both to changes in solar heating and to greenhouse warming.
The 23 sites sampled were good enough to provide a decade-by-decade picture of temperatures across the region.
How much energy we're getting from the Sun is no longer the most important thing governing the temperature of the Arctic
Nicholas McKay, University of Arizona, Tucson
The result is a "hockey stick"-like curve in which the last decade - 1998-2008 - stands out as the warmest in the entire series.
"The most pervasive signal in the reconstruction, the most prominent trend, is the overall cooling that took place for the first 1,900 years [of the record]," said study leader Darrell Kaufman from Northern Arizona University in Flagstaff, US.
"The 20th Century stands out in strong contrast to the cooling that should have continued. The last half-century was the warmest of the 2,000-year temperature record, and the last 10 years have been especially dramatic," he told BBC News.
On average, the region cooled at a rate of 0.2C per millennium until about 1900. Since then, it has warmed by about 1.2C.
Much debate on climate change has centred on the Mediaeval Warm Period, or Mediaeval Climate Anomaly - a period about 1,000 years ago when, historical records suggest, Vikings colonised Greenland and may have grown grapes in Newfoundland.
The new analysis shows that temperatures were indeed warmer in this region 1,000 years ago than they were 100 years ago - but not as warm as they are now, or 1,000 years previously.
"It shows that the Mediaeval Warm Period is real, and is... an exception from the general trend of cooling," commented Eystein Jansen from Bergen University in Norway, who was not involved in the research.
"It also shows there's lots of variability on the 100-year timescale, and that's probably more so in the Arctic than elsewhere."
Professor Jansen was a co-ordinating lead author on the palaeoclimate (ancient climate) chapter of the last Intergovernmental Panel on Climate Change (IPCC) assessment.
Arctic wobbles
The root cause of the slow cooling was the orbital "wobble" that slowly varies, over thousands of years, the month in which the Earth approaches closest to the Sun.
This wobble slowly decreased the total amount of solar energy arriving in the Arctic region in summertime, and the temperature responded - until greenhouse warming took over.
"The 20th Century is the first century for which how much energy we're getting from the Sun is no longer the most important thing governing the temperature of the Arctic," said another of the study team, Nicholas McKay from the University of Arizona.
The recent warming of the Arctic has manifested itself most clearly in the drastic shrinkage in summer sea-ice extent, with the smallest area in the satellite era documented in 2007.
As the Science study emerged, UN Secretary-General Ban Ki-moon was telling the World Climate Conference in Geneva that many of the "more distant scenarios" forecast by climate scientists were "happening now".
Earlier this week, Mr Ban visited the Arctic in an attempt to gain first-hand experience of how the region is changing.
"Scientists have been accused for years of scaremongering. But the real scaremongers are those who say we cannot afford climate action," he said in his Geneva speech, calling for world leaders to make bigger pledges of action in the run-up to December's UN climate summit in Copenhagen.
[Science , Environment & Technology]
Page last updated at 11:12 GMT, Friday, 4 September 2009 12:12 UK
Quantum computer slips onto chips
Researchers have devised a penny-sized silicon chip that uses photons to run Shor's algorithm - a well-known quantum approach - to solve a maths problem.
The algorithm computes the two numbers that multiply together to form a given figure, and has until now required laboratory-sized optical computers.
This kind of factoring is the basis for a wide variety of encryption schemes.
The work, reported in Science, is rudimentary but could easily be scaled up to handle more complex computing.
Shor's algorithm and the factoring of large numbers has been a particular case used to illustrate the power of quantum computing.
Quantum computers exploit the counterintuitive fact that photons or trapped atoms can exist in multiple states or "superpositions" at the same time.
For certain types of calculations, that "quantum indeterminacy" gives quantum computers a significant edge.
While traditional or "classical" computers find factoring large numbers impracticably time-consuming, for example, quantum computers can in principle crack the problem with ease.
That has important implications for encryption methods based on factoring, such as the "RSA" method that is used to make transactions on the internet more secure.
'Important step'
Optical computing has been touted as a potential future for information processing, by using packets of light instead of electrons as the information carrier.
But these packets, called photons, are also endowed with the indeterminate properties that make them quantum objects - so an optical computer can also be a quantum computer.
In fact just this kind of photon-based quantum factoring has been accomplished before, but the ability to put the heart of the machine on a standard chip is promising for future applications of the idea.
"The way people used to make this kind of circuit consumed square metres of laboratory space and took graduate students many months to align," said Jeremy O'Brien, the University of Bristol researcher who led the work.
"Doubling the complexity of the circuit often times turns it from being a difficult task to a practically impossible one, whereas for us to double the complexity it's really straightforward," he told BBC News.
The Bristol team's approach makes use of waveguides - channels etched into the chips that provide a path for the photons around the chips like the minuscule wires in conventional electronics.
While Professor O'Brien said he is confident that such waveguides are the logical choice for future optical quantum computers, he added that there is still a significant amount of work to do before they make it out of the laboratory.
"To get a useful computer it needs to be probably a million times more complex, so a full-scale useful factoring machine is still at least two decades away," he said.
"But this is one important step in that direction."
[Science , Environment & Technology]
Page last updated at 20:29 GMT, Thursday, 3 September 2009 21:29 UK
Arctic 'warmest in 2,000 years'
Arctic temperatures are now higher than at any time in the last 2,000 years, research reveals.
By Richard Black
Environment correspondent, BBC News website
Arctic temperatures are now higher than at any time in the last 2,000 years, research reveals.
Changes to the Earth's orbit drove centuries of cooling, but temperatures rose fast in the last 100 years as human greenhouse gas emissions rose.
Scientists took evidence from ice cores, tree rings and lake sediments.
Writing in the journal Science, they say this confirms that the Arctic is very sensitive both to changes in solar heating and to greenhouse warming.
The 23 sites sampled were good enough to provide a decade-by-decade picture of temperatures across the region.
How much energy we're getting from the Sun is no longer the most important thing governing the temperature of the Arctic
Nicholas McKay, University of Arizona, Tucson
The result is a "hockey stick"-like curve in which the last decade - 1998-2008 - stands out as the warmest in the entire series.
"The most pervasive signal in the reconstruction, the most prominent trend, is the overall cooling that took place for the first 1,900 years [of the record]," said study leader Darrell Kaufman from Northern Arizona University in Flagstaff, US.
"The 20th Century stands out in strong contrast to the cooling that should have continued. The last half-century was the warmest of the 2,000-year temperature record, and the last 10 years have been especially dramatic," he told BBC News.
On average, the region cooled at a rate of 0.2C per millennium until about 1900. Since then, it has warmed by about 1.2C.
Much debate on climate change has centred on the Mediaeval Warm Period, or Mediaeval Climate Anomaly - a period about 1,000 years ago when, historical records suggest, Vikings colonised Greenland and may have grown grapes in Newfoundland.
The new analysis shows that temperatures were indeed warmer in this region 1,000 years ago than they were 100 years ago - but not as warm as they are now, or 1,000 years previously.
"It shows that the Mediaeval Warm Period is real, and is... an exception from the general trend of cooling," commented Eystein Jansen from Bergen University in Norway, who was not involved in the research.
"It also shows there's lots of variability on the 100-year timescale, and that's probably more so in the Arctic than elsewhere."
Professor Jansen was a co-ordinating lead author on the palaeoclimate (ancient climate) chapter of the last Intergovernmental Panel on Climate Change (IPCC) assessment.
Arctic wobbles
The root cause of the slow cooling was the orbital "wobble" that slowly varies, over thousands of years, the month in which the Earth approaches closest to the Sun.
This wobble slowly decreased the total amount of solar energy arriving in the Arctic region in summertime, and the temperature responded - until greenhouse warming took over.
"The 20th Century is the first century for which how much energy we're getting from the Sun is no longer the most important thing governing the temperature of the Arctic," said another of the study team, Nicholas McKay from the University of Arizona.
The recent warming of the Arctic has manifested itself most clearly in the drastic shrinkage in summer sea-ice extent, with the smallest area in the satellite era documented in 2007.
As the Science study emerged, UN Secretary-General Ban Ki-moon was telling the World Climate Conference in Geneva that many of the "more distant scenarios" forecast by climate scientists were "happening now".
Earlier this week, Mr Ban visited the Arctic in an attempt to gain first-hand experience of how the region is changing.
"Scientists have been accused for years of scaremongering. But the real scaremongers are those who say we cannot afford climate action," he said in his Geneva speech, calling for world leaders to make bigger pledges of action in the run-up to December's UN climate summit in Copenhagen.
[Science , Environment & Technology]
Page last updated at 11:12 GMT, Friday, 4 September 2009 12:12 UK
Quantum computer slips onto chips
Researchers have devised a penny-sized silicon chip that uses photons to run Shor's algorithm - a well-known quantum approach - to solve a maths problem.
The algorithm computes the two numbers that multiply together to form a given figure, and has until now required laboratory-sized optical computers.
This kind of factoring is the basis for a wide variety of encryption schemes.
The work, reported in Science, is rudimentary but could easily be scaled up to handle more complex computing.
Shor's algorithm and the factoring of large numbers has been a particular case used to illustrate the power of quantum computing.
Quantum computers exploit the counterintuitive fact that photons or trapped atoms can exist in multiple states or "superpositions" at the same time.
For certain types of calculations, that "quantum indeterminacy" gives quantum computers a significant edge.
While traditional or "classical" computers find factoring large numbers impracticably time-consuming, for example, quantum computers can in principle crack the problem with ease.
That has important implications for encryption methods based on factoring, such as the "RSA" method that is used to make transactions on the internet more secure.
'Important step'
Optical computing has been touted as a potential future for information processing, by using packets of light instead of electrons as the information carrier.
But these packets, called photons, are also endowed with the indeterminate properties that make them quantum objects - so an optical computer can also be a quantum computer.
In fact just this kind of photon-based quantum factoring has been accomplished before, but the ability to put the heart of the machine on a standard chip is promising for future applications of the idea.
"The way people used to make this kind of circuit consumed square metres of laboratory space and took graduate students many months to align," said Jeremy O'Brien, the University of Bristol researcher who led the work.
"Doubling the complexity of the circuit often times turns it from being a difficult task to a practically impossible one, whereas for us to double the complexity it's really straightforward," he told BBC News.
The Bristol team's approach makes use of waveguides - channels etched into the chips that provide a path for the photons around the chips like the minuscule wires in conventional electronics.
While Professor O'Brien said he is confident that such waveguides are the logical choice for future optical quantum computers, he added that there is still a significant amount of work to do before they make it out of the laboratory.
"To get a useful computer it needs to be probably a million times more complex, so a full-scale useful factoring machine is still at least two decades away," he said.
"But this is one important step in that direction."
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