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Home » Page 1507

Top US scientists warn Congress on the dangers of climate change

Climate change is occurring, is caused largely by human activities, and poses significant risks for a broad range of human and natural systems. These are among the key messages of the US National Research Council – the operating arm of the National Academy of Sciences and the National Academy of Engineering – in a series of three reports that were released yesterday and had been requested by Barack Obama’s administration.

One of the reports, Advancing the Science of Climate Change, reviews the current scientific evidence regarding climate change and examines the state of scientific research efforts in the US. While noting that the scientific process is never “closed”, the report concludes that the core scientific questions have been examined thoroughly but have stood firm in the face of serious debate and strong scepticism. It recommends that future research should be developed around seven interdisciplinary themes covering the fundamental science and human wellbeing issues.

No specific targets

Another report, Limiting the Magnitude of Future Climate Change, recommends that the US should establish a greenhouse gas emissions budget that sets a limit on total domestic emissions over a set period of time. It falls short, however, of setting a specific target. Instead it recommends a goal of 170–200 gigatons of carbon dioxide (CO2) equivalent for the period 2012 through 2050, which is roughly in line with the targets proposed recently by the Obama administration. To achieve this, a cap-and-trade system is put forward as the most cost-effective way to cut emissions, although the NRC does not formally endorse this idea.

The final report, Adapting to the Impacts of Climate Change, insists that the US cannot afford to delay important policy-making despite the uncertainties in the specific impacts and timings of climate change. It says that any response needs to be co-ordinated across a number of levels of organization from central government and the private sector to local community organizations. It also urges that the federal government should provide scientific resources and incentives to enable local and regional authorities to begin adaptation.

“These reports show that the state of climate change science is strong,” says Ralph J Cicerone, president of the National Academy of Sciences. “But the nation also needs the scientific community to expand upon its understanding of why climate change is happening, and focus also on when and where the most severe impacts will occur and what we can do to respond.”

5-paper-suite

The reports are part of a series of five studies called America’s Climate Choices, which was requested by the US Congress. The final two reports will be published later in the year. One will examine how to best provide decision makers information on climate change, while the other will be an over-arching study offering a scientific framework for informing climate change policy.

The project builds on previous reports by the National Research Council as well as incorporating new information collected at a number of public events and workshops. The five reports have been assembled by a team of more than 90 volunteers from a range of communities including academia, government and industry.

Party politics crush US science spending bill

A bill that would have significantly increased the research budgets of several key US government science agencies has become a victim of Washington’s partisan politics. Yesterday, the House of Representatives rejected the $85bn America COMPETES Reauthorization Act of 2010, with advocates claiming they are “dismayed” the bill has become engulfed in party politics.

The original COMPETES act was passed by the House with a large bipartisan majority in 2007 and promised to roughly double R&D spending for the National Science Foundation (NSF), the Department of Energy’s Office of Science, and the National Institute of Standards and Technology. The reauthorization bill, which sought to renew the COMPETES act before it runs out in October this year, was drawn up by Bart Gordon, a Tennessee Democrat, and Michigan Republican (and physicist) Vern Ehlers who both sit on the House Committee on Science and Technology.

However, when the bill reached the full House of Representatives on 22 April, Ralph Hall of Texas, who heads the committee’s Republican minority, proposed a “motion to recommit” (MTR). This sought significant reductions in funding for any government agencies that had employees who were found to be watching pornography on government computers. As the NSF had disciplined some employees for doing just that late last year, it meant the foundation could receive less funding.

To then approve the initial bill, Democrats would have had to vote against the MTR and hence appear to support pornography. On 13 May the majority of the House voted therefore to return the bill to committee, effectively killing it. “This is a political action as opposed to a reflection on the actual passage of science funding,” says Patrick Clemins, who analyses Congressional budgets at the American Association for the Advancement of Science.

A statement by the American Physical Society on 14 May says that it is “dismayed” at the party politics being displayed. “The stakes are too high to put science on hold as our nation grapples with an extraordinary set of challenges that demand investments in research,” it says. “Gutting the essence of the COMPETES reauthorization bill, as the MTR would do, puts our nation on the wrong path at the wrong time.”

To give the bill a chance of passing, Gordon, who heads the House’s science and technology committee, reintroduced the bill on 18 May in a slightly different form, reducing the period of the bill from five years to three, and agreeing to include Hall’s wish that any agency found to be employing pornography-watching staff would have to give up grants to cover their salaries — in effect sacking them. However, that action required that the House pass the bill by a two-thirds majority. Although legislators voted 261 to 148 in favor of it yesterday, the bill failed to pass by 12 votes.

Gordon insisted that he would not give up efforts to reauthorize COMPETES. “This bill is too important to let fall by the wayside,” he says. Committee minority spokesman Zachary Kurz told Physics World that Hall does want to see the bill pass. “Mr Hall is very happy to work with the majority on some the concerns outlined in his motion to recommit,” says Kurz.” [But] he still has concerns on spending, first and foremost.”

A failure to authorize the COMPETES act would not mean that these government agencies get no funding. “It is a kind of guidance as to how Congress sees where the funding is going,” says Clemins. “It is not a nail in the coffin, but if will definitely make funding the science agencies more difficult.”

Records reveal robust ocean warming

A re-analysis of conflicting ocean-temperature records covering the past 15 years shows that the seas are getting warmer, according to an international team of scientists. The group compared a number of different published records and found that the discrepancies arise mostly from how different scientists corrected for the variable performance of early temperature probes.

Armed with this knowledge, the researchers were able to combine the data to obtain a more definitive record. Although the calculated warming of 0.64 ± 0.11 W/m2 is in line with other climate observations and global-warming predictions, the study does not explain why the records suggest that ocean warming has stalled since 2004.

Scientists have long known that the Earth’s oceans can absorb and release tremendous amounts of heat and therefore have a large effect on climate. However we know little about how ocean temperatures change on a decadal basis, which makes it hard to understand how oceans respond to climate change.

Expendable bathythermographs

Until about five years ago, most ocean temperature measurements were collected by expendable bathythermographs (XBTs) – devices that have been dropped from ships since the 1960s. XBTs are designed to sink at a known rate while measuring and transmitting the water temperature back to the ship via two wires.

However, there are two problems with XBT data. First, the probes were normally launched from ships on routine passages – and therefore missed out on much of the Southern Ocean and other less-travelled waters. Second, the design of the XBT has changed over the years, and researchers have discovered that some probes do not actually fall as expected. This means that temperature versus depth data could be flawed.

The situation improved in the early 2000s, when researchers began to deploy about 3000 “Argo floats”, which constantly gather temperature data at depths of up to 2000 m. Scattered throughout the oceans, the network of sensors was fully installed by 2007 thanks to a massive international effort.

Networked findings

An important challenge facing scientists is how to put all these data together to get a better picture of how the heat content of the entire ocean changes on decadal time scales. A number of different research groups have used different methods to create “upper-ocean heat content anomaly” (OHCA) curves, but these are not consistent with each other. For example, the curves do not seem to display the same year-to-year patterns. Indeed, during the 1997-98 el Niño climate oscillation in the Pacific Ocean, some curves show cooling, some warming and others no change.

Now, however, a team led by John Lyman of the National Oceanic and Atmospheric Administration (NOAA) in Seattle has taken a close look at these curves and has gained a better understating of why they differ from one another.

The team examined five different methods used to correct the XBT data, one of which is supposed to take into account slight changes in the shape of XBTs that could affect the OHCA curve. However, this correction is particularly difficult to make because the XBT type and manufacturer were not always recorded by users. Other studies tried to correct XBT data by comparing it with more reliable measurements such as Argo floats and conductivity, temperature and depth (CTD) probes.

‘Consistent’ with global warming

After gaining an understanding of the sources of uncertainty in each OHCA curve, the team was able to combine the data to obtain a curve that is more representative of global ocean temperature than its constituents. It reveals that the oceans have warmed at a rate of about 0.64 ± 0.11 W/m2 over the past 16 years. According to Kevin Trenberth of the National Center for Atmospheric Research in Colorado, this is “reasonably consistent with expectations from other indications of global warming”.

However, the re-analysis sheds little light on why ocean temperatures appear to have remained steady since about 2004. This is at odds with satellite measurements, which suggest the Earth has continued to heat up over the past six years, leading to questions over where the “missing heat” has gone.

Indeed, Stefan Rahmstorf, a climate scientist at Potsdam University near Berlin, says that the new study does solve this problem. “The accuracy of measurements is still not sufficient to close the energy budget particularly for short-term variations, in other words, over a few years, as associated with El Niño”.

Team member Doug Smith of the Hadley Centre in the UK points out that this stalling seems to occur just when the Argo floats became the primary data source. This could mean that further work is needed on how to interpret Argo results and how to integrate them into temperature records.

Argo data could also help scientists build a better picture of past ocean temperatures by revealing relationships between temperatures in regions where there is good historical data and parts of the oceans where there is not. Smith told physicsworld.com that he plans to exploit such relationships to fill gaps in the data back to 1950 and perhaps even earlier.

The work is reported in Nature 465 334.

Producing novel semiconductors en masse

Compound semiconductors like gallium arsenide (GaAs) could bring a revolution in optics and electronics, with the promise of highly efficient solar cells and a new generation of components. The trouble is that devices made from these materials are difficult to produce and their delicate nature leaves them prone to damage. But now a group of researchers based in the US and South Korea has designed a new assembly technique, which they say could produce these materials en masse and integrate them into devices with relative ease. They demonstrate their technique by producing a number of rudimentary electronic components.

While silicon is still the dominant material in many hi-tech industries, compound semiconductors could hold big advantages for certain applications. This is on account of the high mobility of electrons within the materials and their direct band gaps, which make them particularly effective at manipulating light. But the problem facing the compound-semiconductor industry is that they are competing with a market dominated by silicon with its established manufacturing base that is incompatible with compound semiconductors.

Printing technique

Now, John Rogers, working with colleagues at the University of Illinois at Urbana-Champaign and a related company, offer a production method by adapting a transfer-printing technique that they have been developing for the past few years. They begin by growing stacks consisting of multiple layers of gallium arsenide and aluminium gallium arsenide, which they then “peel” off one-by-one using a silicone-based stamp. The layers detach easily on account of van der Waals forces, which are stronger on the stamp surface than between layers of compound semiconductor. The researchers then stamp these individual flakes to target sites on a silicon wafer.

To demonstrate the precision and robustness of its technique, Rogers’ team creates three well-known components: field-effect transistor with logic gates; near-infrared (NIR) imaging devices and photovoltaic modules. The scientists use the NIR to show the full detail of the devices.

The research group intends to develop its research by developing more complicated component, including detectors for solar cells. The advantage of using direct band-gap materials like this is that incoming photons can easily form liberate electrons, which can then be collected as current. In silicon-based solar cells, the band gap is indirect so electron–hole pairs will only form if a lattice vibration known as a phonon – with the right momentum – is available.

Practical challenges

“Our biggest opportunity is in solar cells, where compound semiconductors haven’t been competitive so far,” says Rogers. He also believes that there is a compelling opportunity in other optoelectronic applications, such as highly efficient switches.

Chris Phillips, a semiconductors researcher at Imperial College London says that he welcomes this kind of practical approach to compound-semiconductor research. However, he warns that there are still major practical challenges to address regarding the “flimsy” nature of these materials. “With conventional semiconductors, the action is deep within the crystal. In these thin flakes, the layers could easily become dislocated leading to electron-hole recombination and severe reductions in efficiency,” he says. Philips feels that the biggest opportunities for compound semiconductors will be with hybrid devices where new materials can be integrated into silicon-based circuitry.

This research is published in Nature.

The great life of Carl Sagan

By Hamish Johnston

As a young lad in the 1970s I remember enjoying Carl Sagan’s television programme Cosmos.

Did it inspire me to become a physicist? Not really, but it was entertaining and there was something very soothing about the way Sagan spoke in an accent best described as “Brooklyn intellectual”.

One physicist (and TV personality) who was inspired by Cosmos is Brian Cox, who was on BBC Radio 4’s Great Lives programme yesterday to sing the praises of Sagan.

“As a young boy of 13, Brian Cox stared at his television screen every Wednesday evening, as Carl Sagan took him on a journey across the Cosmos”, says the BBC’s promotional material.

Sagan, who died in 1996, was somewhat controversial as both a scientist and a promoter of science and the BBC programme asks: “So just how good a scientist was he, and what is his legacy?”

You can listen to the programme here .

The art of science

By Michael Banks

Physicists have come out on top in Princeton University’s fourth “art of science” competition.

The annual exhibition features images created during scientific research and this year’s event was held on 7 May with the theme of “energy”. Jerry Ross, a postdoc at the Princeton Plasma Physics Laboratory won first place for his “xenon plasma accelerator” image. The picture (below) is of a so-called “Hall effect thruster” – a type of ion thruster where electrons, held in a magnetic field, are used to ionize a propellant, which is then used to produce a thrust.

Xenon Plasma Accelerator
Xenon Plasma Accelerator. (Credit: Princeton University Art of Science Competition)

Third place also went to a physicist. Tim Koby, a physics undergraduate at Princeton, produced a picture of the interaction of a neutron star with a black hole in the centre of a galaxy.

Koby was beaten into second place by David Nagib, a chemistry graduate at Princeton who produced an image called “therapeutic illumination”.

Ross bagged $250 for winning best exhibit, with $154.51 awarded to Nagib in second place and $95.49 to Koby in third.

And if you are wondering why those last two figures are not rounded to $150 or $100, it is apparently because they are derived according to the golden ratio – equal to 1.6180339887 – that represents, in this case, the ratio of the higher to the lower number.

You can also watch a video of the exhibits here.

XENON100 is certain about its uncertainty

xenon.jpg
Part of the XENON100 experiment (Courtesy: XENON100 collaboration)

By Hamish Johnston

Is the XENON100 collaboration in the dark about dark matter, or will its critics see the light? The latest installment of this debate has appeared on the arXiv preprint server.

On 6 May Jon Cartwright reported on a furore that has broken out in the dark-matter detection community.

Earlier that week the XENON100 collaboration posted a preprint with an analysis of the first experimental results from its dark-matter detector. It didn’t see any of the dark stuff, which means that the positive sightings reported by two other experiments (DAMA and CoGeNT) could be false.

But then two US-based physicists – Juan Collar and Dan McKinsey — posted a preprint that took XENON100 physicists to task on their analysis of the data. In particular, Collar and McKinsey believe that the XENON100 team is overconfident about how it extrapolated the known response of the detector to high-energy particles to lower energies – where the response is unknown.

This low-energy response is crucial because that is where XENON100, DAMA and CoGeNT have all looked for dark matter.

Now, XENON100 has responded with yet another preprint defending its analysis and claiming that it has “properly taken into account the uncertainty” in the low-energy response.

I can’t wait for the next preprint in this dark-matter “he said, she said”!

Spotting explosives with a puff of air

Transport authorities are about to be presented with a new type of body scanner that could identify explosives on the clothes of passengers with unprecedented resolution and fewer false alarms. The device has been created by academics and their spin-off company based in Austria by adapting a mass spectrometry technique that is common in environmental science.

Foiled terrorist attacks in New York City and Detroit in the past year have raised security levels, which were already on high alert since the attacks on New York in 2001. In response, governments around the world have been seeking more advanced technologies to scan travellers for weapons and explosives in airports. Any new technology deployed, however, must always represent a difficult balance between many factors including quality, cost and intrusiveness. Indeed, some passengers and human rights groups have already protested that full-body scanning is in breach of an individual’s rights. And various scientists have said that existing scanners are not fit for purpose anyway because there are common explosives that could pass through the scan undetected.

Spectrometry, a ubiquitous chemistry technique for determining the quantity or concentration of chemical species, offers a more directed approach to detecting chemical traces. One variety known as ion mobility spectrometry (IMS) is already used in a number of airport scanning systems. It works by taking a sample of dust from each passenger – usually by wiping their shoe with a cloth – and transferring this sample to an ionization chamber. The problem with IMS is that it is prone to false alarms because it is sensitive to interference and cannot distinguish between different types of volatile.

Quick puff of air

Now, however, a research group based at the University of Innsbruck claims to have created a new type of scan, based on an alternative mass spectrometry technique, which is far more sensitive and reliable. It involves a process known as proton-transfer-reaction mass spectrometry (PTR-MS) and the scanning process begins by blasting each passenger with a quick puff of air, which should liberate any residual explosives. This passenger “dust” is then passed into a chamber containing protonated water, which contains water molecules with an extra proton. If the passenger were to have traces of explosives about their person, the extra protons would “jump” to these volatile compounds because they have a higher proton affinity. Finally, the water vapour mix is passed into a high-resolution mass spectrometry device, which can identify protonated explosives in less than a second.

Since inventing the technique, academics at the University of Innsbruck have created a spin-off company, Ionicon Analytic, which has gone on to fine-tune the technology. It now works to a sensitivity of one part per quadrillion (1015), with the scanner being comparable to a standard home refrigerator in size. Kurt Becker, who works for Ionicon but is based at the Polytechnic University of New York, says that his project is seeking contracts with security agencies in the UK, Germany and France. He also revealed that he intends to meet with operators of New York airports to present the technology within the next few weeks.

Negotiations should be aided by the fact that this spectrometry technique is already established in a number of other applications including waste incineration and air quality control. Becker says that his company was inspired to adapt the technique for airport security after recent security alerts, which led to fears that terrorists are getting smarter with their methods and the type of substances they might deploy. “Terrorists may use improvized devices involving a combination of different explosives, including TNT, RDX, HDX and PETN,” he tells physicsworld.com.

Selectivity issues

Paul Monks, a chemist at the University of Leicester in the UK, agrees that the technique does hold benefits over established scanners. “Though ion mobility spectrometry is sensitive, it does suffer from selectivity issues,” he says. “The advantages of PTR-MS and its variants is that only those molecules with proton affinities in excess of that of H2O can accept a proton from H3O+, a criterion that excludes the major components of air such as N2, O2 and CO2, but includes many trace gases, including most volatile organic compounds.”

Ionicon and its various academic partners intend to develop the technology by improving the user interface to make life easier for security guards. “To make this airport-ready we need to create a push-button system,” says Chris Mayhew, one of Ionicon’s affiliates based at the University of Birmingham in the UK. Mayhew says that he will be presenting the technology to the UK government at a meeting in London this week.

Japanese robotics couple married by android

By James Dacey

We all know colleagues who allow their work to stray a little bit too far into their personal lives.

But a pair of robotics researchers in Japan surely took this to whole new levels when they were married yesterday by a 1.5 m android named I-Fairy.

The bride was 36-year-old Satoko Inoue who works for Kokuro, the firm that produced I-Fairy, one of their new generation of androids.

“This was a lot of fun. I think that the Japanese have a strong sense that robots are our friends,” she told the Associated Press.

Her new husband is Tomohiro Shibata, a 42-year-old professor of robotics at the Nara Institute of Science and Technology, was a bit more critical of their plastic priest. “It would be nice if the robot was a bit more clever, but she is very good at expressing herself,” he said.

The service took place at a rooftop restaurant in central Tokyo and you can enjoy the happy couple exchanging vows in this short YouTube clip.

Happy birthday to the laser

By Margaret Harris

Fifty years ago today, a little-known scientist working in an underfunded lab in California set off a scientific and technological revolution. On 16 May 1960, Theodore Maiman and his assistant Irnee d’Haenens succeeded in coaxing a beam of coherent light out of a flashlamp-pumped crystal of pink ruby. The laser had arrived.

Of course, the events of that day were not the whole story. Although Maiman is rightly honoured for inventing the first working laser, many others played a role in the laser’s development, both before and (particularly) after the initial breakthrough. Among the key early figures were Einstein, whose predictions about stimulated emission laid the theoretical groundwork; and Charles Townes, who invented the laser’s microwave predecessor, the maser.

To learn more about the early days of the laser, I’d highly recommend downloading Physics World’s May special issue, which you can do for free via this link. On page 23, you’ll find a great article by Pauline Rigby called “And then there was light”, which describes the events leading up to Maiman’s breakthrough and some of the controversy that followed it.

As for what happened next, I think the thing that surprised me most when I was researching the special issue was just how quickly researchers in various fields found ways of putting Maiman’s new toy to use. Barely a year after its invention, a device that d’Haenens memorably called “a solution looking for a problem” was already being used for human eye surgery.

So what will we be doing with it in 2060? Well, as Niels Bohr supposedly said, “Prediction is difficult, especially about the future” — but if you want to hear some experts’ views , check out “Where next for the laser?” on p53 in the downloadable pdf. You can also watch our laser video series .

Update: Pauline Rigby has written an entry on her own blog about how the article “And then there was light” came into being — including additional material from her interview with Maiman’s wife Kathleen. You can read it here

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