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Author: Neville

  • Hidden Movements of Greenland Ice Sheet, Runoff Revealed

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    Hidden Movements of Greenland Ice Sheet, Runoff Revealed
    December 15, 2014
    photo of Greenland ice
    Scientists using NASA data released new insights into the hidden plumbing of melt water flowing through the Greenland Ice Sheet as well as the most detailed picture ever of how the ice sheet moves toward the sea.
    Image Credit:
    NASA/Michael Studinger

    For years NASA has tracked changes in the massive Greenland Ice Sheet. This week scientists using NASA data released the most detailed picture ever of how the ice sheet moves toward the sea and new insights into the hidden plumbing of melt water flowing under the snowy surface.The results of these studies are expected to improve predictions of the future of the entire Greenland ice sheet and its contribution to sea level rise as researchers revamp their computer models of how the ice sheet reacts to a warming climate.

    “With the help of NASA satellite and airborne remote sensing instruments, the Greenland Ice Sheet is finally yielding its secrets,” said Tom Wagner, program scientist for NASA’s cryosphere program in Washington. “These studies represent new leaps in our knowledge of how the ice sheet is losing ice. It turns out the ice sheet is a lot more complex than we ever thought.”

    This animation (from March 2014) portrays the changes occurring in the surface elevation of the Greenland Ice Sheet since 2003 in three drainage areas: the southeast, the northeast and the Jakobshavn regions. In each region, the time advances to show the accumulated change in elevation, 2003-2012.
    Image Credit:
    NASA’s Goddard Space Flight Center
    Download video in HD formats from NASA Goddard’s Scientific Visualization Studio

    University at Buffalo geophysicist Beata Csatho led an international team that produced the first comprehensive study of how the ice sheet is losing mass based on NASA satellite and airborne data at nearly 100,000 locations across Greenland. The study found that the ice sheet shed about 243 gigatons of ice per year from 2003-09, which agrees with other studies using different techniques. The study was published today in the Proceedings of the National Academy of Sciences.

    The study suggests that current ice sheet modeling is too simplistic to accurately predict the future contribution of the Greenland ice sheet to sea level rise, and that current models may underestimate ice loss in the near future.

    conceptual image of Greenland with ICESat and IceBridge mapping paths indicated
    Surface elevation changes over the entire Greenland Ice Sheet have been mapped in detail by NASA’s ICESat satellite (gray path lines) and Operation IceBridge airborne campaigns (purple path lines).
    Image Credit:
    NASA

    The project was a massive undertaking, using satellite and aerial data from NASA’s ICESat spacecraft, which measured the elevation of the ice sheet starting in 2003, and the Operation IceBridge field campaign that has flown annually since 2009. Additional airborne data from 1993-2008, collected by NASA’s Program for Arctic Regional Climate Assessment, were also included to extend the timeline of the study.Current computer simulations of the Greenland Ice Sheet use the activity of four well-studied glaciers — Jakobshavn, Helheim, Kangerlussuaq and Petermann — to forecast how the entire ice sheet will dump ice into the oceans. The new research shows that activity at these four locations may not be representative of what is happening with glaciers across the ice sheet. In fact, glaciers undergo patterns of thinning and thickening that current climate change simulations fail to address, Csatho says.

    As a step toward building better models of sea level rise, the research team divided Greenland’s 242 glaciers into 7 major groups based on their behavior from 2003-09.

    “Understanding the groupings will help us pick out examples of glaciers that are representative of the whole,” Csatho says. “We can then use data from these representative glaciers in models to provide a more complete picture of what is happening.”

    The team also identified areas of rapid shrinkage in southeast Greenland that today’s models don’t acknowledge. This leads Csatho to believe that the ice sheet could lose ice faster in the future than today’s simulations would suggest.

    In separate studies presented today at the American Geophysical Union annual meeting in San Francisco, scientists using data from Operation IceBridge found permanent bodies of liquid water in the porous, partially compacted firn layer just below the surface of the ice sheet. Lora Koenig at the National Snow and Ice Data Center in Boulder, Colorado, and Rick Forster at the University of Utah in Salt Lake City, found signatures of near-surface liquid water using ice-penetrating radar.

    Across wide areas of Greenland, water can remain liquid, hiding in layers of snow just below the surface, even through cold, harsh winters, researchers are finding. The discoveries by the teams led by Koenig and Forster mean that scientists seeking to understand the future of the Greenland ice sheet need to account for relatively warm liquid water retained in the ice.

    Although the total volume of water is small compared to overall melting in Greenland, the presence of liquid water throughout the year could help kick off melt in the spring and summer. “More year-round water means more heat is available to warm the ice,” Koenig said.

    Koenig and her colleagues found that sub-surface liquid water are common on the western edges of the Greenland Ice Sheet. At roughly the same time, Forster used similar ground-based radars to find a large aquifer in southeastern Greenland. These studies show that liquid water can persist near the surface around the perimeter of the ice sheet year round.

    Another researcher participating in the briefing found that near-surface layers can also contain masses of solid ice that can lead to flooding events. Michael MacFerrin, a scientist at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, and colleagues studying radar data from IceBridge and surface based instruments found near surface patches of ice known as ice lenses more than 25 miles farther inland than previously recorded.

    Ice lenses form when firn collects surface meltwater like a sponge. When this shallow ice melts, as was seen during July 2012, they can release large amounts of water that can lead to flooding. Warm summers and resulting increased surface melt in recent years have likely caused ice lenses to grow thicker and spread farther inland. “This represents a rapid feedback mechanism. If current trends continue, the flooding will get worse,” MacFerrin said.

    Related Links

    George Hale
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland

  • I’ve got bad news about Abbot Point and the Great Barrier Reef.

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    Louise Matthiesson, WWF-Australia noreply@act.wwf.org.au via server8839.e-activist.com 
    5:17 PM (33 minutes ago)
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    Under water coral, Great Barrier Reef © Troy Mayne

    Hi NEVILLE,

    I’ve got bad news about Abbot Point and the Great Barrier Reef.

    The Queensland Government is still pushing ahead with plans to dredge 3 million tonnes of seabed in the Reef World Heritage Area at Abbot Point, only now instead of dumping the waste at sea, they intend to dump it in the majestic Caley Valley wetlands.

    Last week, the government invited feedback on the plans, but gave us just ten days to respond! We have to ensure the government reject these plans and protect the critical wetlands.

    We need your help. Can you please click here now and let Minister for State Development, Jeff Seeney, know this proposal can’t go ahead.

    The dredging itself will destroy 97 hectares of seagrass habitat that turtles and dugong rely on for food.

    And the dredge waste ponds will be built on top of the wetlands, metres from the coastline. Over 100 hectares of threatened bird habitat will be destroyed and the tailwater from the ponds will be pumped straight back into the Reef World Heritage Area.

    We’ve got a team working on putting together an urgent detailed submission showing just how wrong this is, but we all need to demand Mr Seeney reject this proposal right now for the sake of the wetlands and the Reef.

    We’ll also send your submission to Australian Environment Minister Greg Hunt – he’ll have a final say in this matter so it’s important he sees all these submissions too.

    Please help protect the Reef by lodging a submission of your own.  Click here to send a submission now.

    Thanks for being with us on this – it’s critical we do everything we can right now.

    Louise Matthiesson
    Great Barrier Reef Campaigner
    WWF-Australia

  • A hidden agenda, a questionable deal

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    A hidden agenda, a questionable deal

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    The Australia Institute

    Dear Neville —

      The budget’s hidden gender agenda

    In our workplaces men and women are treated differently and the situation is getting worse, not better. According to the latest figures, the pay gap between male and female workers has blown out to 20 per cent in Australia, and issues of gender inequality continue to be largely ignored in public policy thinking. The government appears happy to do nothing and let things drift.

    But ignoring inequality means policies continue to be enacted which can further entrench the problem. The budget’s hidden gender agenda, a new report from the Australia Institute, finds that – in good times and in bad – women are getting a rougher deal than men from budget and income tax cuts.

    The belt-tightening strategies set out in the 2014 Federal Budget impact women more severely than men. As women are more likely to assume care roles than men, they tend to rely more on services provided by government. Cuts to these services have meant that 55 per cent of the budget savings have fallen on women.

    This situation is far worse when you consider where the ‘budget emergency’, that the government’s budget is supposed to fix, came from.

    In the mid-2000s during the mining boom the Howard government and the first Rudd budget gave away billions in permanent tax cuts. These tax cuts were paid for by the temporary increase in revenues brought on by the mining boom. When the mining boom faded and the budget drifted back to more normal circumstances, the hole left by the income tax cuts was revealed.

    So who benefited from these tax cuts? Overwhelmingly it was high income earners, predominately men. The tax cuts cost the budget $169 billion from 2005 to 2012, of which $115 billion (68 per cent) went to men. Women, on the other hand, received $54 billion (32 per cent) of the windfall.

    So the benefit that caused the hole in the budget was paid to men and the repair job is costing women. This represents a double blow to women at a time when the gap between men’s wages and women’s wages is widening.

    It’s time that the government started to take the issue of gender equality seriously. When the government fails to do so, it can inadvertently create policies that leave women worse off.

    Chairman, the commission and the questionable contract

    “If you want independent advice, don’t ask a barber whether you need a haircut” – Warren Buffett.

    Recently the Abbott Government has been ruthless in chasing former Labor ministers for any dirt they may uncover and which can be used for political advantage. So when the Abbott Government decides not to chase the former government over allegations of irregularities in an immigration contract, it makes you wonder what might be going on.

    At the heart of the story is a 2012 contract between the Department of Immigration and Transfield Services, worth $24.5 million for the management of the Nauru detention centre.

    The contract has attracted strong criticism from former New South Wales Auditor-General Tony Harris. Speaking on the ABC’s Lateline program, Mr Harris said that the contract awarded to Transfield did not include a brief outlining the scope of the work and the services expected by the Department of Immigration. The brief is a critical element of a financial agreement, the absence of which enabled Transfield to dictate the terms of the deal, Mr Harris said.

    “If you haven’t written the script, Transfield will write the script. Transfield will tell you what you need; Transfield will tell you how much it’s going to cost you,” he said.

    And Transfield have indeed made a fortune from government contracts.  And Transfield have indeed made a fortune from government contracts.  Earlier this year the Abbott Government extended the Transfield contract to cover both Nauru and Manus Island until October 2015 at a total cost of $1.2 billion. So why is this not a scandal?

    When all this happened the head of Transfield was Tony Shepherd, former CEO of the Business Council of Australia and current government-appointed Chair of the National Commission of Audit. It is reported there were a series of bad acquisitions, appointments, asset write downs, mismatched debt and covenant currencies made on Mr Shepard’s watch in his time as head of Transfield.

    But Mr Shepard would have to know a thing of two about about business, right? Well, it would be interesting to ask Transfield’s shareholders. Having started as Director of Transfield in 2001, Mr Shepard also went on to become the company’s Chairman in August 2005. At that time Transfield’s share price stood at $5.35.  By the time he stepped down from both positions in 2013, the company’s share price was less than a dollar.

    In 2013 Mr Shepard was appointed Chair of the National Commission of Audit. Interestingly, in their report to government earlier this year, the Commission made the interesting suggestion to do away with the Procurement Connected Policies – the 24 documents that set out the guidelines for government procurement. The Commission made a key recommendation that the government “base procurement decisions on value for money at all times by abolishing Procurement Connected Policies.”

    At a time when a deal worth millions can be struck with key documents missing, it should go without saying that slackening the rules for government officials to pursue ‘value for money’ – without proper probity, legal and other guidelines – is surely a recipe for disaster.

    The (actual) facts about higher education

    When the government launched its “Higher Education” online advertising campaign, reactions came thick and fast. Within hours a student had put up a spoof website calling out the government’s claims and by the next day GetUp had a spoof video.

    The senate cross-benchers have not been impressed and Labor has registered a formal complaint that the campaign breaches the government advertising guidelines.

    Aside from its general whiff of desperation, the ads repeat a claim Education Minister Christopher Pyne has been making for months now that the government will cover half the cost of university courses. But two months back we checked the facts and found the claim was already clearly false.

    We’ve asked the government about their assumptions, because it seems they’ve just assumed fees will only rise to recover cut funding. Yet, even the Minister expects fee deregulation to boost research rankings, and that’s only possible if fees rise even more. Incidentally, this makes a nonsense of the new proposal to have the ACCC be ‘price monitor’ for fees. Given students already over-pay to fund research – what amount of student ‘co-payment’ will the ACCC decide is fee-gouging, exactly?

    The ads also reassure us that “HECS is here to stay” and, while it’s true the government is keeping the student loan system, increased student debt could make it unsustainable. As University of Canberra VC Stephen Parker put it: “HECS works through the Government advancing all the fees upfront to the university, so if more students default because debts are higher, the taxpayer could end up having paid out more cash.”

    As summed up in the recent UK Higher Education Commission report: “The current funding system represents the worst of both worlds. The Government is funding Higher Education by writing off student debt, as opposed to directly investing in teaching grants.”

    Our experience could be even worse. Without the fee caps of the UK system, we could see the sort of fee inflation of the US system, where fees have increased at ferocious rates – even faster than their notoriously expensive health care!

    It could be that the government wants the system to become unsustainable, or it could be that the government simply hasn’t given it much thought. Either way, It’s clear from the government’s ads that they would rather not have a serious debate about what the sector really needs. Ironically, for such a debate, the ads and the government’s continued intransigence might be the best thing that’s happened.

    TAI in the media

    The Guardian: Solar and wind energy backed by huge majority of Australians
    Canberra Times: Want to break laws and get away with it? Form a company
    The Australian: Murray criticises investor tax breaks
    News.com: Murray Inquiry: Negative gearing in firing line – what will it mean for house prices? 
    Brisbane Times: Generation Less – the young will inherit … budget deficits

    Exciting news – Catalyst and TAI are merging!

    Catalyst Australia, an influential research think tank based in Sydney, is joining forces with the Australia Institute. Together, we’ll provide more first-class research and progressive political analysis.

    If you’re in Sydney, why not join us tomorrow afternoon for some Christmas drinks and nibbles to celebrate the new partnership. We would love to see you there!

    WHERE: Trades Hall Atrium, 4 Goulburn St, Sydney
    WHEN:   4:30pm, Tuesday 16 December
    RSVP via email to: mail@tai.org.au

  • Less Ice or More? What You Need to Know About Antarctica’s Meltdown By John Roach

    Image: Adelie penguins stand atop ice near the French station at Dumont d’Urville in East Antarctica Pauline Askin / Reuters file 14 hours
    Less Ice or More? What You Need to Know About Antarctica’s Meltdown
    By John Roach

    In Antarctica, glaciers are sloshing seaward at an ever faster clip, ocean waters are warming, and, perhaps counterintuitively, sea ice is expanding, according to a batch of recent studies that paint a stark picture of climate change unfolding at the far southern reaches of the globe. For people in North America, the distant events raise the specter of higher seas sooner than climate models suggest.

    Here are answers to key questions about what’s happening on that cold continent.

    Antarctica Ice Sheet Is Disintegrating
    Nightly News

    How can Antarctica be losing ice overall if sea ice is growing?

    About that sea ice, it is indeed expanding at the same time Antarctica is losing nearly the water-weight equivalent of Mount Everest every two years. The expansion fits with the expected natural variability in a warming world, according to a study accepted for publication Dec. 5 in the journal Geophysical Research Letters. In fact, some scientists say, warming may enhance sea ice growth.

    Antarctic sea ice reached its maximum extent of 7.76 million square miles on Sept. 22, another record, according to the National Snow and Ice Data Center in Boulder, Colorado. The sea ice is typically three to six feet thick and most of it melts each summer as it drifts north toward warmer waters.

    While that’s a lot of ice, the continent itself holds even more — about 2,500 times more, according to the Intergovernmental Panel on Climate Change, the world’s climate science body. On average, the Antarctic icecap is 1.3 miles thick and contains a whopping 70 percent of the world’s freshwater. If it all melted, it could raise global sea levels by nearly 200 feet, scientists report.

    The panel’s most recent analysis put the current high end estimate of global sea level rise at about three feet by the end of this century; though many scientists — and scientific studies — indicate the number could actually be a “bit” higher, Richard Alley, a glaciologist at Pennsylvania State University, told NBC News.

    “It is very, very clear that in the ‘most likely’ estimate there is still a huge amount of ice sitting in places where it could contribute to sea level rise,” he explained.

    Alley was not involved in the current batch of papers, which, he said, bring “cleaner data, more data, [and] more agreement” to the basic narrative that West Antarctica’s glaciers are shrinking faster today because warmer waters are getting under the ice shelves. If this trend continues, it could commit the world to about 11 feet of sea level rise from West Antarctica alone.
    So how fast is that continental ice melting?

    In West Antarctica, according to one of the studies published Dec. 5 in the journal Geophysical Research Letters, the melt rate of glaciers has nearly tripled during the last decade, “which means that things are happening faster and the contribution to sea level is increasing more and more,” Isabella Velicogna, a coauthor of the paper from the University of California at Irvine, told NBC News.

    The result stems from a 21-year analysis of four different techniques used to measure how much ice mass the glaciers discharge into the sea. “It is a very big signal and not one of those techniques misses it and all of (them) agree on the amount that is lost,” added Velicogna, who is also affiliated with NASA’s Jet Propulsion Laboratory.

    Over the 21 years, the average amount lost was 83 gigatons per year, which translates to a Mount Everest’s-worth of water weight every two years. The rate of loss has accelerated an average of 6.1 gigatons per year since 1992. And from 2003 to 2009, the melt rate has increased an average of 16.3 gigatons per year.

    Antarctic Sea Ice Growth Baffles Scientists
    NBC News

    What’s contributing to that increase?

    The melt rate is accelerating because warmer water is getting into the shallow West Antarctic shelf areas, according to a separate study published Dec. 5 in the journal Science.

    Those warmer waters “melt the glaciers on the bottom and reduce the buttressing,” study lead author Sunke Schmidtko from the Helmholtz Centre for Ocean Research Kiel in Germany told NBC News in an email. “This makes the glaciers flow faster into the ocean, the ice loss is accelerated.”

    Elsewhere in Antarctica, a strong coastal current prevents the warmer water from getting onto the shelf, though Schmidtko has his eyes on the southern Weddell Sea, on the east side of the Antarctic Peninsula. There the water is currently below freezing — 29 degrees Fahrenheit — but deep, warmer offshore waters are getting closer, he noted.

    And what is causing the waters to warm? The answer appears to be tied to a shift in winds along with higher sea surface temperatures farther north. “That temperature rise and wind intensification is usually attributed to climate change,” Schmidtko said.

    Are there other factors for sea ice growth?

    Antarctic sea ice has increased over the past three decades; however climate models tend to show a decrease over the same period. The mismatch has caused head scratching throughout the climate science community and fueled skepticism about human-caused global warming.

    Velicogna said the sea ice and the ice sheets are both sensitive to a changing climate, but “they evolve and respond in different ways; you cannot infer one from the other.”

    The formation of Antarctic sea ice, according to Alley, is largely a wind-driven process beginning with winds that blow cold air from the icy landmass over the seas.

    Recent studies have linked changes in regional wind patterns to the ozone hole, greenhouse warming, and natural variability. “Because Antarctic sea ice depends so much on wind, that right there complicates things because it is not primarily a temperature story,” Alley explained.

    A further complication arises as glaciers dump more freshwater into the sea, which stratifies the ocean and keeps warmer water down low where it can’t melt sea ice.

    “A big amount of melting in Antarctica actually favors growth of sea ice around it by putting extra freshwater near the surface,” Alley explained.

  • Researchers link extreme weather events to global warming in new study

    Researchers link extreme weather events to global warming in new study

    22952 views


    By Scott Sutherland
    Meteorologist, theweathernetwork.com
    @ScottWx_TWN
    Monday, August 18, 2014, 9:20 AM

    Unseasonably cool through central Canada, with downpours and flooding taking their toll on several regions. Warmer and drier weather spreading up into the western prairies, southern B.C. and the mountains, and even up through the northern territories. It seems like summer has foregone the more usual consistent heat, in favour of performing a ‘copy and paste’ routine from this past winter – dropping in the same kind of patterns that gave us January’s polar vortex slip and the subsequent persistent conditions that made early months of this year so unusual. Although the comparatively extreme cold snaps (winter or summer) from these patterns is causing some to question whether global warming is really happening, a new study is showing evidence that these patterns are a direct result of global warming.

    When a weather forecast mentions the ‘jet stream’, it’s referring to the meandering ‘river’ of powerful winds that stretches around the globe, and acts as the southern boundary of the north polar vortex. You can see the patterns this forms in the video animation above. The reason why the jet stream plays such a featured role in forecasts is because it has a big impact on our day-to-day weather. It may be over 9 kilometres above the ground, but the pattern it forms at any time has a big influence on our temperature, wind and precipitation patterns. It can even influence how long a particular kind of weather – frigid and snowy, hot and sticky, stormy, etc – stays over any particular area.

    The pattern of the ‘planetary waves’ that are created in the flow of the jet stream are largely dependent on the difference in temperatures between the equator and the north pole. If the temperature difference is large (hot at the equator and cold at the pole), the polar vortex is relatively strong and the waves are fairly small, as shown below (from early in the animation).

    In this case, the waves tend to move along at a fairly good pace, and thus the weather conditions change fairly quickly as well, and no particular area gets trapped under extreme conditions for long periods of time. However, if the temperature difference between equator and pole is smaller (hot equator and cool or warm polar region), the polar vortex weakens, waves can become quite large, dipping far to the south and stretching far to the north – like in the snapshot below – and the overall movement of the waves slows down at the same time.

    “Behind this, there is a subtle resonance mechanism that traps waves in the mid-latitudes and amplifies them strongly,” said Stefan Rahmstorf, a researcher at the Potsdam Institute for Climate Impact Research who co-authored a new study investigating these waves and how they become trapped in these static patterns. According to the study, one of the key conditions for the patterns to become stuck is the formation of a ‘double-jet’ – seen at times throughout the animation, when a second, weaker band of winds (in blues and greens) appears closer to the pole, while the main jet (greens through reds) is still flowing through the mid-latitudes (over Canada and the U.S.). You can see this double jet in the image above, and it shows up again just at the end of the animation as well.

    The animation also shows the long-lived nature of some of these patterns, as one develops at about 12 seconds in, and lasts until the 19 or 20 second mark. With each second of the animation representing 1 day, that’s at least a week of persistent weather conditions. This could mean a week-long heat wave for anyone living in the central part of North America (in the above image), and an equally-long period of chilly cold or extreme storms for those along the eastern part of Canada and the United States. We saw this sort of situation develop over the winter, with the initial slip of the polar vortex in early January, and then a pattern of persistent dips in the jet stream over the weeks after. We’re also seeing a similar pattern during this summer, which is why it’s been so cool across eastern Canada and so warm and dry through the west.

    Lately, global warming has been implicated in the fact that we’re seeing more of these extreme patterns in the jet stream, largely due to the unprecedented warming that’s been seen in the Arctic in recent years. This is due to a process called Arctic Amplification, where less sea ice in the Arctic Ocean to reflect sunlight back into space means more heat being absorbed into the ocean waters. This not only melts more ice, causing something of a cascade effect, but it also means that it takes longer for the Arctic to cool down in the winter, so there’s even more open ocean for longer. This causes the overall temperature difference between the equator and the pole to be smaller for longer periods of time, and we get these persistent large meanders in the jet stream. While the process of Arctic Amplification is well known, and linking it to the processes of global warming is easy enough, it’s still difficult to point to these events and definitively say in each case ‘That was caused by global warming.’

    Phil Plait, of Slate’s Bad Astronomy blog, uses an excellent analogy in a recent article: “Think of it as playing craps with ever-so-slightly loaded dice. You can’t be sure that snake eyes you threw was due to the dice being weighted, but over time you’ll see a lot more of them than you’d expect, statistically, from fair dice.”

    “We’re throwing an awful lot of meteorological snake eyes lately,” he added.

    Incidences of ‘planetary wave resonances’ over time.

    According to Rahmstorf, “Evidence for actual changes in planetary wave activity was so far not clear. But by knowing what patterns to look for, we have now found strong evidence for an increase in these resonance events.”

    The study conducted by Rahmstorf and his colleagues showed the link from weather records. As the graph to the right shows, there has been a fairly consistent 1-2 incidences of these ‘planetary wave resonances’ in the past, even going back to just the early 2000s. Now, in the past decade or so, the number has been increasing – to more than double what it was before.

    “We argue that the changes in the zonal mean temperature profile, associated with rapid warming in the Arctic, have created favorable conditions for double jet formation and hence resonant flow regimes,” the researchers concluded in the study. “This study thus adds to the growing body of evidence that rapid changes in the Arctic affect the large-scale circulation and thereby extreme weather in the midlatitudes.”

    The full study is available online, in the journal Proceedings of the National Academy of Sciences (PNAS) – click here.

    Images and video courtesy of NASA Visualizations, Graph courtesy Potsdam Institute for Climate Impact Research

    Scott Sutherland writes daily on weather, space and science. Check back often for his Insider Insights.

  • Global warming’s influence on extreme weather

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    from universities, journals, and other organizations

    Global warming’s influence on extreme weather

    Date:
    December 12, 2014
    Source:
    Stanford University
    Summary:
    Understanding the cause-and-effect relationship between global warming and record-breaking weather requires asking precisely the right questions. Extreme climate and weather events such as record high temperatures, intense downpours and severe storm surges are becoming more common in many parts of the world. But because high-quality weather records go back only about 100 years, most scientists have been reluctant to say if global warming affected particular extreme events.

    Understanding the cause-and-effect relationship between global warming and record-breaking weather requires asking precisely the right questions.

    Extreme climate and weather events such as record high temperatures, intense downpours and severe storm surges are becoming more common in many parts of the world. But because high-quality weather records go back only about 100 years, most scientists have been reluctant to say if global warming affected particular extreme events.

    On Wednesday, Dec. 17, at the American Geophysical Union’s Fall Meeting in San Francisco, Noah Diffenbaugh, an associate professor of environmental Earth system science at the Stanford School of Earth Sciences, will discuss approaches to this challenge in a talk titled “Quantifying the Influence of Observed Global Warming on the Probability of Unprecedented Extreme Climate Events.” He will focus on weather events that — at the time they occur — are more extreme than any other event in the historical record.

    Diffenbaugh emphasizes that asking precisely the right question is critical for finding the correct answer.

    “The media are often focused on whether global warming caused a particular event,” said Diffenbaugh, who is a senior fellow at the Stanford Woods Institute for the Environment. “The more useful question for real-world decisions is: ‘Is the probability of a particular event statistically different now compared with a climate without human influence?’”

    Diffenbaugh said the research requires three elements: a long record of climate observations; a large collection of climate model experiments that accurately simulate the observed variations in climate; and advanced statistical techniques to analyze both the observations and the climate models.

    One research challenge involves having just a few decades or a century of high-quality weather data with which to make sense of events that might occur once every 1,000 or 10,000 years in a theoretical climate without human influence.

    But decision makers need to appreciate the influence of global warming on extreme climate and weather events.

    “If we look over the last decade in the United States, there have been more than 70 events that have each caused at least $1 billion in damage, and a number of those have been considerably more costly,” said Diffenbaugh. “Understanding whether the probability of those high-impact events has changed can help us to plan for future extreme events, and to value the costs and benefits of avoiding future global warming.”

    Story Source:

    The above story is based on materials provided by Stanford University. Note: Materials may be edited for content and length.

    Cite This Page:

    Stanford University. “Global warming’s influence on extreme weather.” ScienceDaily. ScienceDaily, 12 December 2014. <www.sciencedaily.com/releases/2014/12/141212190237.htm>.