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Announcement :: Environment |
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Failing ocean current raises fears of mini ice age |
Current rating: 0 |
by Mike Rhodes
(No verified email address) |
13 May 2006
|
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no such thing as global warming |
Failing ocean current raises fears of mini ice age
The ocean current that gives western Europe its relatively balmy climate is stuttering, raising fears that it might fail entirely and plunge the continent into a mini ice age.
The dramatic finding comes from a study of ocean circulation in the North Atlantic, which found a 30% reduction in the warm currents that carry water north from the Gulf Stream.
The slow-down, which has long been predicted as a possible consequence of global warming, will give renewed urgency to intergovernmental talks in Montreal, Canada, this week on a successor to the Kyoto Protocol.
Harry Bryden at the National Oceanography Centre in Southampton, UK, whose group carried out the analysis, says he is not yet sure if the change is temporary or signals a long-term trend. "We don’t want to say the circulation will shut down," he told New Scientist. "But we are nervous about our findings. They have come as quite a surprise."
No one-off
The North Atlantic is dominated by the Gulf Stream – currents that bring warm water north from the tropics. At around 40° north – the latitude of Portugal and New York – the current divides. Some water heads southwards in a surface current known as the subtropical gyre, while the rest continues north, leading to warming winds that raise European temperatures by 5°C to 10°C.
But when Bryden’s team measured north-south heat flow last year, using a set of instruments strung across the Atlantic from the Canary Islands to the Bahamas, they found that the division of the waters appeared to have changed since previous surveys in 1957, 1981 and 1992. From the amount of water in the subtropical gyre and the flow southwards at depth, they calculate that the quantity of warm water flowing north had fallen by around 30%.
When Bryden added previously unanalysed data – collected in the same region by the US government’s National Oceanic and Atmospheric Administration – he found a similar pattern. This suggests that his 2004 measurements are not a one-off, and that most of the slow-down happened between 1992 and 1998.
The changes are too big to be explained by chance, co-author Stuart Cunningham told New Scientist from a research ship off the Canary Islands, where he is collecting more data. "We think the findings are robust."
Hot and cold
But Richard Wood, chief oceanographer at the UK Met Office’s Hadley Centre for climate research in Exeter, says the Southampton team's findings leave a lot unexplained. The changes are so big they should have cut oceanic heating of Europe by about one-fifth – enough to cool the British Isles by 1°C and Scandinavia by 2°C. "We haven’t seen it yet," he points out.
Though unseasonably cold weather last month briefly blanketed parts of the UK in snow, average European temperatures have been rising, Wood says. Measurements of surface temperatures in the North Atlantic indicate a strong warming trend during the 1990s, which seems now to have halted.
Bryden speculates that the warming may have been part of a global temperature increase brought about by man-made greenhouse warming, and that this is now being counteracted by a decrease in the northward flow of warm water.
After warming Europe, this flow comes to a halt in the waters off Greenland, sinks to the ocean floor and returns south. The water arriving from the south is already more saline and so more dense than Arctic seas, and is made more so as ice forms.
Predicted shutdown
But Bryden’s study has revealed that while one area of sinking water, on the Canadian side of Greenland, still seems to be functioning as normal, a second area on the European side has partially shut down and is sending only half as much deep water south as before. The two southward flows can be distinguished because they travel at different depths.
Nobody is clear on what has gone wrong. Suggestions for blame include the melting of sea ice or increased flow from Siberian rivers into the Arctic. Both would load fresh water into the surface ocean, making it less dense and so preventing it from sinking, which in turn would slow the flow of tropical water from the south. And either could be triggered by man-made climate change. Some climate models predict that global warming could lead to such a shutdown later this century.
The last shutdown, which prompted a temperature drop of 5°C to 10°C in western Europe, was probably at the end of the last ice age, 12,000 years ago. There may also have been a slowing of Atlantic circulation during the Little Ice Age, which lasted sporadically from 1300 to about 1850 and created temperatures low enough to freeze the River Thames in London.
Journal reference: Nature (vol 438, p 655). |
This work is in the public domain |
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Will global warming trigger a new ice age? |
by Bill McGuire
(No verified email address) |
Current rating: 0
13 May 2006
|
What's worrying is that for some years now, global climate models have been predicting a future weakening of the Gulf Stream as a consequence of global warming.
If you can remember back to the bitter winters of the late 1970s and early 80s you might also recall that there was much discussion in scientific circles at the time about whether or not the freezing winter conditions were a portent of a new ice age.
Over the past couple of decades such warnings have been drowned out by the great global warming debate and by consideration of how society might cope in future with a sweltering planet rather than an icebound one. Seemingly, the fact that we are still within an interglacial period, during which the ice has largely retreated to its polar fastnesses, has been forgotten - and replaced with the commonly-held view that one good thing you can say about global warming is that it will at least stave off the return of the glaciers.
Article continues
Is this really true, or could the rapidly accelerating warming that we are experiencing actually hasten the onset of a new ice age? A growing body of evidence suggests that, at least for the UK and western Europe, there is a serious risk of this happening - and soon.
The problem lies with the ocean current known as the Gulf Stream, which bathes the UK and north-west Europe in warm water carried northwards from the Caribbean. It is the Gulf Stream, and associated currents, that allow strawberries to thrive along the Norwegian coast, while at comparable latitudes in Greenland glaciers wind their way right down to sea level. The same currents permit palms to flourish in Cornwall and the Hebrides, whereas across the ocean in Labrador, even temperate vegetation struggles to survive. Without the Gulf Stream, temperatures in the UK and north-west Europe would be five degrees centigrade or so cooler, with bitter winters at least as fierce as those of the so-called Little Ice Age in the 17th to 19th centuries.
The Gulf Stream is part of a more complex system of currents known by a number of different names, of which the rather cumbersome North Atlantic Meridional Overturning Circulation (Namoc) is probably the most apt. This incorporates not only the Gulf Stream but also the cold return currents that convey water southwards again. As it approaches the Arctic, the Gulf Stream loses heat and part of it heads back to warmer climes along the coast of Greenland and eastern Canada in the form of the cold, iceberg-laden current responsible for the loss of the Titanic. Much, however, overturns - cooling and sinking beneath the Nordic seas between Norway and Greenland, before heading south again deep below the surface.
In the past, the slowing of the Gulf Stream has been intimately linked with dramatic regional cooling. Just 10,000 years ago, during a climatic cold snap known as the Younger Dryas, the current was severely weakened, causing northern European temperatures to fall by as much as 10 degrees. Ten thousand years before that, at the height of the last ice age, when most of the UK was reduced to a frozen wasteland, the Gulf Stream had just two-thirds of the strength it has now.
What's worrying is that for some years now, global climate models have been predicting a future weakening of the Gulf Stream as a consequence of global warming. Such models visualise the disruption of the Namoc, including the Gulf Stream, as a result of large-scale melting of Arctic ice and the consequent pouring of huge volumes of fresh water into the North Atlantic, in a century or two. New data suggest, however, that we may not have to wait centuries, and in fact the whole process may be happening already.
So that the warm, saline surface waters of the Gulf Stream can continue to push northwards, there must be a comparable, deep return current of cold, dense water from the Nordic seas. Disturbingly, this return current seems to have been slowing since the middle of the last century. Bogi Hansen at the Faroese fisheries laboratory, and colleagues in Scotland and Norway, have been monitoring the deep outflow of cold water from the Nordic seas as it passes over the submarine Greenland-Scotland ridge that straddles the North Atlantic at this point. Their results show that the outflow has fallen by 20% since 1950, which suggests a comparable reduced inflow from the Gulf Stream.
Although there is as yet no direct substantiation of this, and his colleagues point to reports of the cooling and freshening of the Norwegian Sea and to temperatures that are already falling in parts of the region as possible evidence of contemporary Gulf Stream weakening.
It also seems that it is not only the intensity of the outflow of cold water that is changing. Bob Dickson of the Centre for Environment, Fisheries, and Aquaculture Science at Lowestoft, and colleagues, have reported a sustained and widespread freshening of returning deep waters south of the Greenland-Scotland ridge, which appears to have been going on for the past three or four decades.
Already the freshening is extending along the North American eastern seaboard towards the equator, in the so-called Deep Western Boundary current.
One of the scariest aspects of the current dramatic changes occurring in the system of North Atlantic currents is that the deep, southward-flowing limb of the Namoc can be thought of as representing the headwaters of the worldwide system of ocean currents known as the Global Thermohaline Circulation. The possibility exists, therefore, that a disruption of the Atlantic currents might have implications far beyond a colder UK and north-west Europe, perhaps bringing dramatic climatic changes to the entire planet.
Yet again, this highlights the fact that global warming, for which we have only ourselves to thank, is nothing more nor less than a great planetary experiment, many of the outcomes of which we cannot predict. Wallace Broecker, an ocean circulation researcher at New York's Lamont-Doherty Earth observatory, described the situation perfectly when he pointed out that "climate is an angry beast and we are poking at it with sticks". Let's hope that when it truly turns on us, its teeth don't match its outrage.
· Bill McGuire is Benfield Professor of Geophysical Hazards and director of the Benfield Hazard Research Centre at University College London. He will appear on BBC2 Horizon's The Big Chill tonight
Special report
Climate change
http://www.guardian.co.uk/climatechange/0,,782494,00.html
http://www.guardian.co.uk/climatechange/story/0,12374,1083419,00.html |
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Abrupt Climate Change: Should We Be Worried? |
by Robert B. Gagosian
(No verified email address) |
Current rating: 0
13 May 2006
|
Robert B. Gagosian
President and Director
Woods Hole Oceanographic Institution
Prepared for a panel on abrupt climate change at the
World Economic Forum
Davos, Switzerland, January 27, 2003
Are we overlooking potential abrupt climate shifts?
Most of the studies and debates on potential climate change, along with its ecological and economic impacts, have focused on the ongoing buildup of industrial greenhouse gases in the atmosphere and a gradual increase in global temperatures. This line of thinking, however, fails to consider another potentially disruptive climate scenario. It ignores recent and rapidly advancing evidence that Earth’s climate repeatedly has shifted abruptly and dramatically in the past, and is capable of doing so in the future.
Fossil evidence clearly demonstrates that Earthvs climate can shift gears within a decade, establishing new and different patterns that can persist for decades to centuries. In addition, these climate shifts do not necessarily have universal, global effects. They can generate a counterintuitive scenario: Even as the earth as a whole continues to warm gradually, large regions may experience a precipitous and disruptive shift into colder climates.
This new paradigm of abrupt climate change has been well established over the last decade by research of ocean, earth and atmosphere scientists at many institutions worldwide. But the concept remains little known and scarcely appreciated in the wider community of scientists, economists, policy makers, and world political and business leaders. Thus, world leaders may be planning for climate scenarios of global warming that are opposite to what might actually occur.1
It is important to clarify that we are not contemplating a situation of either abrupt cooling or global warming. Rather, abrupt regional cooling and gradual global warming can unfold simultaneously. Indeed, greenhouse warming is a destabilizing factor that makes abrupt climate change more probable. A 2002 report by the US National Academy of Sciences (NAS) said, “available evidence suggests that abrupt climate changes are not only possible but likely in the future, potentially with large impacts on ecosystems and societies.”2
The timing of any abrupt regional cooling in the future also has critical policy implications. An abrupt cooling that happens within the next two decades would produce different climate effects than one that occurs after another century of continuing greenhouse warming.
Are we ignoring the oceans' role in climate change?
Fossil evidence and computer models demonstrate that Earth’s complex and dynamic climate system has more than one mode of operation. Each mode produces different climate patterns.
The evidence also shows that Earth’s climate system has sensitive thresholds. Pushed past a threshold, the system can jump quickly from one stable operating mode to a completely different one—“just as the slowly increasing pressure of a finger eventually flips a switch and turns on a light,” the NAS report said.
Scientists have so far identified only one viable mechanism to induce large, global, abrupt climate changes: a swift reorganization of the ocean currents circulating around the earth. These currents, collectively known as the Ocean Conveyor, distribute vast quantities of heat around our planet, and thus play a fundamental role in governing Earth’s climate.
The oceans also play a pivotal role in the distribution and availability of life-sustaining water throughout our planet. The oceans are, by far, the planet’s largest reservoir of water. Evaporation from the ocean transfers huge amounts of water vapor to the atmosphere, where it travels aloft until it cools, condenses, and eventually precipitates in the form of rain or snow. Changes in ocean circulation or water properties can disrupt this hydrological cycle on a global scale, causing flooding and long-term droughts in various regions. The El Niño phenomenon is but a hint of how oceanic changes can dramatically affect where and how much precipitation falls throughout the planet.
Thus, the oceans and the atmosphere constitute intertwined components of Earth’s climate system. But our present knowledge of ocean dynamics does not match our knowledge of atmospheric processes. The oceans’ essential role is too often neglected in our calculations.
Does Earth's climate system have an 'Achilles' heel'?
Here is a simplified description of some basic ocean-atmosphere dynamics that regulate Earth’s climate:
The equatorial sun warms the ocean surface and enhances evaporation in the tropics. This leaves the tropical ocean saltier. The Gulf Stream, a limb of the Ocean Conveyor, carries an enormous volume of heat-laden, salty water up the East Coast of the United States, and then northeast toward Europe.
This oceanic heat pump is an important mechanism for reducing equator-to-pole temperature differences. It moderates Earth’s climate, particularly in the North Atlantic region. Conveyor circulation increases the northward transport of warmer waters in the Gulf Stream by about 50 percent. At colder northern latitudes, the ocean releases this heat to the atmosphere—especially in winter when the atmosphere is colder than the ocean and ocean-atmosphere temperature gradients increase. The Conveyor warms North Atlantic regions by as much as 5° Celsius and significantly tempers average winter temperatures.
But records of past climates—from a variety of sources such as deep-sea sediments and ice-sheet cores—show that the Conveyor has slowed and shut down several times in the past. This shutdown curtailed heat delivery to the North Atlantic and caused substantial cooling throughout the region. One earth scientist has called the Conveyor “the Achilles’ heel of our climate system.”3
What can disrupt the Ocean Conveyor?
Solving this puzzle requires an understanding of what launches and drives the Conveyor in the first place. The answer, to a large degree, is salt.
For a variety of reasons, North Atlantic waters are relatively salty compared with other parts of the world ocean. Salty water is denser than fresh water. Cold water is denser than warm water. When the warm, salty waters of the North Atlantic release heat to the atmosphere, they become colder and begin to sink.
In the seas that ring the northern fringe of the Atlantic—the Labrador, Irminger, and Greenland Seas—the ocean releases large amounts of heat to the atmosphere and then a great volume of cold, salty water sinks to the abyss. This water flows slowly at great depths into the South Atlantic and eventually throughout the world’s oceans.
Thus, the North Atlantic is the source of the deep limb of the Ocean Conveyor. The plunge of this great mass of cold, salty water propels the global ocean’s conveyor-like circulation system. It also helps draw warm, salty tropical surface waters northward to replace the sinking waters. This process is called “thermohaline circulation,” from the Greek words “thermos” (heat) and “halos” (salt).
If cold, salty North Atlantic waters did not sink, a primary force driving global ocean circulation could slacken and cease. Existing currents could weaken or be redirected. The resulting reorganization of the ocean’s circulation would reconfigure Earth’s climate patterns.
Computer models simulating ocean-atmosphere climate dynamics indicate that the North Atlantic region would cool 3° to 5° Celsius if Conveyor circulation were totally disrupted. It would produce winters twice as cold as the worst winters on record in the eastern United States in the past century. In addition, previous Conveyor shutdowns have been linked with widespread droughts throughout the globe.
It is crucial to remember two points: 1) If thermohaline circulation shuts down and induces a climate transition, severe winters in the North Atlantic region would likely persist for decades to centuries—until conditions reached another threshold at which thermohaline circulation might resume. 2) Abrupt regional cooling may occur even as the earth, on average, continues to warm.
Are worrisome signals developing in the ocean?
If the climate system’s Achilles’ heel is the Conveyor, the Conveyor’s Achilles’ heel is the North Atlantic. An influx of fresh water into the North Atlantic’s surface could create a lid of more buoyant fresh water, lying atop denser, saltier water. This fresh water would effectively cap and insulate the surface of the North Atlantic, curtailing the ocean’s transfer of heat to the atmosphere.
An influx of fresh water would also dilute the North Atlantic’s salinity. At a critical but unknown threshold, when North Atlantic waters are no longer sufficiently salty and dense, they may stop sinking. An important force driving the Conveyor could quickly diminish, with climate impacts resulting within a decade.
In an important paper published in 2002 in Nature, oceanographers monitoring and analyzing conditions in the North Atlantic concluded that the North Atlantic has been freshening dramatically—continuously for the past 40 years but especially in the past decade.4 The new data show that since the mid-1960s, the subpolar seas feeding the North Atlantic have steadily and noticeably become less salty to depths of 1,000 to 4,000 meters. This is the largest and most dramatic oceanic change ever measured in the era of modern instruments.
At present the influx of fresher water has been distributed throughout the water column. But at some point, fresh water may begin to pile up at the surface of the North Atlantic. When that occurs, the Conveyor could slow down or cease operating.
Signs of a possible slowdown already exist. A 2001 report in Nature indicates that the flow of cold, dense water from the Norwegian and Greenland Seas into the North Atlantic has diminished by at least 20 percent since 1950.5
At what threshold will the Conveyor cease?
The short answer is: We do not know. Nor have scientists determined the relative contributions of a variety of sources that may be adding fresh water to the North Atlantic. Among the suspects are melting glaciers or Arctic sea ice, or increased precipitation falling directly into the ocean or entering via the great rivers that discharge into the Arctic Ocean.6 Global warming may be an exacerbating factor.
Though we have invested in, and now rely on, a global network of meteorological stations to monitor fast-changing atmospheric conditions, at present we do not have a system in place for monitoring slower-developing, but critical, ocean circulation changes.
The great majority of oceanographic measurements was taken throughout the years by research ships and ships of opportunity—especially during the Cold War era for anti-submarine warfare purposes. Many were taken incidentally by Ocean Weather Stations—a network of ships stationed in the ocean after World War II, whose primary duty was to guide transoceanic airplane flights. Starting in the 1970s, satellite technology superseded these weather ships. The demise of the OWS network and the end of the Cold War have left oceanographers with access to far fewer data in recent years.
Initial efforts to remedy this deficit are under way,7 but these efforts are nascent and time is of the essence. Satellites can measure wind stress and ocean circulation globally, but only at the ocean surface. Also recently launched (but not nearly fully funded) is the Argo program—an international program to seed the global ocean with an armada of some 3,000 free-floating buoys that measure upper ocean temperature and salinity. Measuring deep ocean currents is critical for observing Conveyor behavior, but it is more difficult. Efforts have just begun to measure deep ocean water properties and currents at strategic locations with long-term moored buoy arrays, but vast ocean voids remain unmonitored.
New ocean-based instruments also offer the potential to reveal the ocean’s essential, but poorly understood, role in the hydrological cycle—which establishes global rainfall and snowfall patterns. Global warming affects the hydrological cycle because a warmer atmosphere carries more water. This, in turn, has implications for greenhouse warming, since water vapor itself is the most abundant, and often overlooked, greenhouse gas.
What can the past teach us about the future?
Revealing the past behavior of Earth’s climate system provides powerful insight into what it may do in the future. Geological records confirm the potential for abrupt thermohaline-induced climate transitions that would generate severe winters in the North Atlantic region. A bad winter or two brings inconvenience that societies can adapt to with small, temporary adjustments. But a persistent string of severe winters, lasting decades to a century, can cause glaciers to advance, rivers to freeze, and sea ice to grow and spread. It can render prime agricultural lands unfarmable.
About 12,700 years ago, as Earth emerged from the most recent ice age and began to warm, the Conveyor was disrupted. Within a decade, average temperatures in the North Atlantic region plummeted nearly 5° Celsius.
This cold period, known as the Younger Dryas, lasted 1,300 years. It is named after an Arctic wildflower. Scientists have found substantial evidence that cold-loving dryas plants thrived during this era in European and US regions that today are too warm. Deep-sea sediment cores show that icebergs extended as far south as the coast of Portugal. The Younger Dryas ended as abruptly as it began. Within a decade, North Atlantic waters and the regional climate warmed again to pre-Younger Dryas levels.
A similar cooling occurred 8,200 years ago. It lasted only about a century—a blip in geological time, but a catastrophe if such a cooling occurred today.
Are 'little ice ages' and 'megadroughts' possible?
Scientists are investigating whether changes in ocean circulation may have played a role in causing or amplifying the “Little Ice Age” between 1300 and 1850. This period of abruptly shifting climate regimes and more severe winters had profound agricultural, economic, and political impacts in Europe and North America and changed the course of history.
During this era, the Norse abruptly abandoned their settlements in Greenland. The era is captured in the frozen landscapes of Pieter Bruegel’s 16th-century paintings and in the famous painting of George Washington’s 1776 crossing of an icebound Delaware River, which rarely freezes today. But the era is also marked by persistent crop failures, famine, disease, and mass migrations. “The Little Ice Age,” wrote one historian, “is a chronicle of human vulnerability in the face of sudden climate change.”8
Societies are similarly vulnerable to abrupt climate changes that can turn a year or two of diminished rainfall into prolonged, severe, widespread droughts. A growing body of evidence from joint archaeological and paleoclimatological studies is demonstrating linkages among ocean-related climate shifts, “megadroughts,” and precipitous collapses of civilizations, including the Akkadian empire in Mesopotamia 4,200 years ago, the Mayan empire in central America 1,500 years ago, and the Anasazi in the American Southwest in the late 13th century.9
Rapid changes in ocean circulation associated with the abrupt North Atlantic cooling event 8,200 years ago have been linked with simultaneous, widespread drying in the American West, Africa, and Asia.10 Regional cooling events also have been linked with changes in the Southwest Asian monsoon, whose rains are probably the most critical factor supporting civilizations from Africa to India to China.11
What future climate scenarios should we consider?
The debate on global change has largely failed to factor in the inherently chaotic, sensitively balanced, and threshold-laden nature of Earth’s climate system and the increased likelihood of abrupt climate change. Our current speculations about future climate and its impacts have focused on the Intergovernmental Panel on Climate Change, which has forecast gradual global warming of 1.4° to 5.8° Celsius over the next century.
It is prudent to superimpose on this forecast the potential for abrupt climate change induced by thermohaline shutdown. Such a change could cool down selective areas of the globe by 3° to 5° Celsius, while simultaneously causing drought in many parts of the world. These climate changes would occur quickly, even as other regions continue to warm slowly. It is critical to consider the economic and political ramifications of this geographically selective climate change. Specifically, the region most affected by a shutdown—the countries bordering the North Atlantic—is also one of the world’s most developed.
The key component of this analysis is when a shutdown of the Conveyor occurs. Two scenarios are useful to contemplate:
Scenario 1: Conveyor slows down within next two decades.
Such a scenario could quickly and markedly cool the North Atlantic region, causing disruptions in global economic activity. These disruptions may be exacerbated because the climate changes occur in a direction opposite to what is commonly expected, and they occur at a pace that makes adaptation difficult.
Scenario 2: Conveyor slows down a century from now.
In such a scenario, cooling of the North Atlantic region may partially or totally offset the major effects of global warming in this region. Thus, the climate of the North Atlantic region may rapidly return to one that more resembles today’s—even as other parts of the world, particularly less-developed regions, experience the unmitigated brunt of global warming. If the Conveyor subsequently turns on again, the “deferred” warming may be delivered in a decade.
What can we do to improve our future security?
Ignoring or downplaying the probability of abrupt climate change could prove costly. Ecosystems, economies, and societies can adapt more easily to gradual, anticipated changes. Some current policies and practices may be ill-advised and may prove inadequate in a world of rapid and unforeseen climate change. The challenge to world leaders is to reduce vulnerabilities by enhancing society’s ability to monitor, plan for, and adapt to rapid change.
All human endeavor hinges on the vicissitudes of climate. Thus, the potential for abrupt climate change should prompt us to re-examine possible impacts on many climate-affected sectors. They include: agriculture; water resources; energy resources; forest and timber management; fisheries; coastal land management; transportation; insurance; recreation and tourism; disaster relief; and public health (associated with climate-related, vector-borne diseases such as malaria and cholera).
Developing countries lacking scientific resources and economic infrastructures are especially vulnerable to the social and economic impacts of abrupt climate change. However, with growing globalization of economies, adverse impacts (although likely to vary from region to region) are likely to spill across national boundaries, through human and biotic migration, economic shocks, and political aftershocks, the National Academy of Sciences (NAS) report stated.
The key is to reduce our uncertainty about future climate change, and to improve our ability to predict what could happen and when. A first step is to establish the oceanic equivalent of our land-based meteorological instrument network. Such a network would begin to reveal climate-influencing oceanic processes that have been beyond our ability to grasp. These instruments, monitoring critical present-day conditions, can be coupled with enhanced computer modeling, which can project how Earth’s climate system may react in the future. Considerably more research is also required to learn more about the complex ocean-air processes that induced rapid climate changes in the past, and thus how our climate system may behave in the future.
The NAS report is titled Abrupt Climate Change: Inevitable Surprises. Climate change may be inevitable. But it is not inevitable for society to be surprised or ill-prepared.
References:
1 “Are We on the Brink of a New Little Ice Age?”—testimony to the US Commission on Ocean Policy, September 25, 2002, by T. Joyce and L. Keigwin (Woods Hole Oceanographic Institution).
2 Abrupt Climate Change: Inevitable Surprises, US National Academy of Sciences, National Research Council Committee on Abrupt Climate Change, National Academy Press, 2002.
3 “Thermohaline Circulation, the Achilles’ Heel of Our Climate System: Will Man-Made CO2 Upset the Current Balance?” in Science, Vol. 278, November 28, 1997, by W. S. Broecker (Lamont-Doherty Earth Observatory, Columbia University).
4 “Rapid Freshening of the Deep North Atlantic Ocean Over the Past Four Decades,” in Nature, Vol. 416, April 25, 2002, by B. Dickson (Centre for Environment, Fisheries, and Aquaculture Science, Lowestoft, UK), I. Yashayaev, J. Meincke, B. Turrell, S. Dye, and J. Hoffort.
5 “Decreasing Overflow from the Nordic Seas into the Atlantic Ocean Through the Faroe Bank Channel Since 1950,” in Nature, Vol. 411, June 21, 2001, by B. Hansen (Faroe Fisheries Laboratory, Faroe Islands), W. Turrell, and S. østerhus.
6 “Increasing River Discharge to the Arctic Ocean,” in Science, Vol. 298, December 13, 2002, by B. J. Peterson (Marine Biological Laboratory), R. M. Holmes, J. W. McClelland, C. J. Vörösmarty, R. B. Lammers, A. I. Shiklomanov, I. A. Shiklomanov, and S. Rahmstorf.
7 “Ocean Observatories,” in Oceanus, Vol. 42, No. 1, 2000, published by the Woods Hole Oceanographic Institution.
8 The Little Ice Age: How Climate Made History 1300-1850, by Brian Fagan (University of California, Santa Barbara), Basic Books, 2000.
9 “Cultural Responses to Climate Change During the Late Holocene,” in Science, Vol. 292, April 27, 2001, by P. B. deMenocal (Lamont-Doherty Earth Observatory, Columbia University).
10 “Holocene Climate Instability: A Prominent, Widespread Event 8,200 Years Ago,” in Geology, Vol. 26, No. 6, 1997, by R. B. Alley and T. Sowers (Pennsylvania State University), P. A. Mayewski, M. Stuiver, K. C. Taylor, and P. U. Clark.
11 “A High-Resolution Absolute-Dated Late Pleistocene Monsoon Record From Hulu Cave, China,” in Science, Vol. 294, December 14, 2001, by Y. J. Wang (Nanjing Normal University, China), H. Cheng, R. L. Edwards, Z. S. An, J. Y. Wu, C. C. Shen, and J. A. Dorale.
ROBERT B. GAGOSIAN is President and Director of Woods Hole Oceanographic Institution in Woods Hole, Massachusetts. He was appointed Director in 1994 and President in 2001, following a distinguished career as a marine geochemist. He has served as Chairman of the Board of Governors for the 52-institution Consortium for Oceanographic Research and Education and as a member of the Ocean Research Advisory Panel of the US National Oceanographic Partnership Program. In 2002, he was appointed to the Science Advisory Panel of the US Commission on Ocean Policy and the US National Oceanic and Atmospheric Administration’s Science Advisory Board, and was elected a Fellow of the American Academy of Arts & Sciences.
More info and extensive graphics at:
http://www.whoi.edu/institutes/occi/viewArticle.do?id=9986 |
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Re: Failing ocean current raises fears of mini ice age |
by Ed
crazyhawk22 (nospam) hotmail.com (unverified) |
Current rating: 0
13 May 2006
|
Fire and Ice
Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.
Robert Frost |
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