Turns out climate skeptics' favorite report (the Wegman Report) might not be as scientific as Congressman Joe Barton claims.

Smokey Joe Strikes Out Again?

Turns out climate skeptics' favorite report might not be as scientific as Congressman Joe Barton claims.

— James Berglie/Zumapress.com

by Kate Sheppard, Mother Jones, November 23, 2010

Back in 2005, Joe Barton (R-Texas), then the chair of the House Energy and Commerce Committee, made it his personal mission to investigate both climate science and climate scientists. Nicknamed "Smokey Joe" for his efforts to appease polluters, Barton has long made it clear he thinks the science on climate change is "pretty weak stuff."

To prove that climate scientists have been wrong about their predictions, Barton and Rep. Ed Whitfield (R-Ky.) enlisted Edward Wegman, a statistician at George Mason University, to write a report evaluating studies of man-made global warming. The Wegman Report, released in 2006, has been much-touted by climate skeptics in the years since. But it now looks like large parts of the report used information that was plagiarized, pulled from Wikipedia, or taken out of context—and it appears that Barton's office may have been feeding Wegman's team the information to include in the report.

Wegman's report primarily attacked the "hockey stick chart," first published in a 1998 report co-authored by climate scientists Michael Mann (now of Pennsylvania State University), Raymond Bradley of the University of Massachusetts, and Malcolm K. Hughes of the Laboratory for Tree-Ring Research at the University of Arizona. The chart grew much more notable after it was included in the 2001 report from the Intergovernmental Panel on Climate Change, and a version of it was featured in the movie An Inconvenient Truth several years later. But, now, in a searing piece in USA Today, reporter Dan Vergano reveals numerous problems with the Wegman report which purported to debunk the hockey stick. Studies of the 91-page text "found repeated instances of passages lifted word for word and what appear to be thinly disguised paraphrases," the piece notes.

Much of the reportedly plagiarized text came from a book written by Bradley, who has asked George Mason University to investigate the matter. Analyses of the text show that some phrases were largely reproduced, and at some points tweaked in order to change the meaning. This was revealed in a lengthy report from retired computer scientist John Mashey of California, who concluded that 35 of the report's 91 pages "are mostly plagiarized text, but often injected with errors, bias and changes of meaning."

Mashey's takedown of the Wegman report also points to evidence that Barton's staff was feeding Wegman’s supposedly unbiased team of scientists material to use in the report. Mashey found a presentation (PDF) online from Wegman report co-author Yasmin Said of Johns Hopkins University chronicling the team's "Experiences with Congressional Testimony." The presentation notes that Wegman's group met with Barton staffer Peter Spencer, who delivered a "daunting amount of material" to use in compiling the report, and that Wegman and his team were charged with evaluating whether criticism of the Mann-Bradley chart was "meritorious." The presentation also notes that Barton's staff saw themselves as "'referees' in the Hockey Game"—even though none of those involved had "any real expertise in paleoclimate reconstruction."

Wegman has denied that his team was being primed by Barton's staff.

"Although Dr. Said's presentation seemed to imply that we were being coached by the Republicans being given only their selected materials to look at, this was not true," Wegman told USA Today in response to a Freedom of Information Act request. Barton's office did not respond to Mother Jones' request for comment about the charge that they were feeding information to Wegman's team.

Mashey, though, says all signs point to Barton's office having "manipulated, manufactured" information for the Wegman report. He notes that the report relied heavily on a paper criticizing the hockey stick graph written by two Canadians with no background in climate science, mining consultant Stephen McIntyre and economist Ross McKitrick. McIntyre confirmed in an interview that the Wegman team contacted him for information for their report. However, Mann—the scientist whose work they questioned—was never asked to provide information to the team.

Subsequent studies have found while there was some valid criticism of the statistical methods in the original graph, the McIntyre-McKitrick paper introduced some of its own errors and reached a flawed conclusion. The paper does not, in fact, invalidate the hockey stick—particularly since numerous other studies have reinforced the Mann-Bradley findings. Moreover, Mann and his colleagues acknowledged in the original paper that there are uncertainties and that further study was needed on the subject, and they later issued updates to their findings in response to some valid criticism—but that's all part of the scientific process.

That nuance, of course, was lost in the Wegman report. It's also worth noting that Barton's enlisting of Wegman to conduct the report is also outside of typical protocol for committees looking for an independent read on scientific disputes. Congress will generally request a report from the National Research Council, a branch of the National Academies, when there is disagreement on an issue like multiple climate studies. Ralph Cicerone, president of the National Academy of Sciences, wrote to Barton in July 2005 offering the Academies' services. But rather than asking the NRC to review the science, Barton asked Wegman to write the report.

The chairman of the Committee on Science and Technology at the time, Sherwood Boehlert (R-N.Y.), criticized his colleague's multiple attempts to undermine the science as "misguided and illegitimate." Boehlert wrote in a July 2005 letter to Barton, "[Y]ou have taken a decidedly different approach—one that breaks with precedent and raises the specter of politicians opening investigations of any scientist who reaches a conclusion that makes the political elite uncomfortable."

So Boehlert requested an NRC study on the reconstruction of surface temperature records. The NRC report largely supported the work of Mann and Bradley, noting that while there may have been some justifiable questions about statistical methods and that some uncertainties "have been underestimated," there was nevertheless "an array of evidence" supporting the main conclusion of their work. (Boehlert, now retired, penned an op-ed in the Washington Post last week criticizing his party for willfully ignoring the science on climate change.)

Aaron Huertas, press secretary for the Union of Concerned Scientists, also questioned the role Barton and his staff played in shaping the report and called it "an abuse of the power of Congress" to put out a shoddy report for the sole purpose of lobbing baseless attacks at climate scientists. "If something that doesn't meet basic academic scrutiny is being put out there with the congressional seal on it, then that's a problem," said Huertas.

Despite his repeated attacks on the very premise of global warming, Barton has tried to claim that all he wants is an independent evaluation of the science. At a stop at the international climate negotiations in Copenhagen last year, Barton claimed that "the premise that mankind, through the emissions of CO2, is causing the planet to warm...has never been independently analyzed or tested by any scientific group." He asserted that "credible" scientists should look at the evidence, and, in response to a question about who that might include, suggested the National Academy of Sciences—failing to note of course that the NAS had done as much, despite the fact that he has rejected their research on the subject.

Barton and other Republicans have frequently cited the Wegman report as proof that scientists are cooking the books on global warming. The report is also cited heavily in the court filings of crusading Virginia Attorney General Ken Cuccinelli, who has repeatedly tried to force the University of Virginia, Mann's former employer, to hand over documents that he believes will demonstrate that the scientist committed "fraud" in his research. Cuccinelli mentions the Wegman report five times in one subpoena of Mann's documents and email.

The report is now four years old, but Barton might be getting another turn to fire at climate scientists from the bully pulpit as chairman of one of the top committees with jurisdiction on climate and energy policy. While caucus rules typically limit Republicans to three terms, Barton is seeking a waiver so he can again serve as chairman of the Energy and Commerce Committee. Several other incoming leaders of key committees have already indicated they would like to replicate the kind of investigation into climate science next year.

Meanwhile, Barton continues to tout his "investigations" into Mann and other scientists. He wrote a letter to the editor of the Washington Post last month in response to a column from Mann that criticized Barton and others for politicizing the science, and again went after Mann: "I think Mr. Mann is entitled to make up his own mind, but not his own truth." All the evidence coming in about the Wegman report indicates that someone was bent on making up the truth, and it wasn't Mann.

Kate Sheppard covers energy and environmental politics in Mother Jones' Washington bureau. For more of her stories, click here. She Tweets here. Get Kate Sheppard's RSS feed.

Link:  http://motherjones.com/environment/2010/11/joe-barton-wegman-report

Phil Jones cleared and reinstated. Rigor and honesty of CRU climatologists not in doubt

British panel clears climate scientists

By JUSTIN GILLIS, New York Times, July 7, 2010

A British panel issued a sweeping exoneration on Wednesday of scientists caught up in the controversy known as Climategate, saying it found no evidence that they had manipulated their research to support preconceived ideas about global warming.

The researcher at the center of the controversy, a leading climatologist named Phil Jones, was immediately reinstated to a job resembling his old one, at the Climatic Research Unit of the University of East Anglia. That unit, often referred to by its initials, has played a leading role in efforts to understand the earth’s past climate.

Embarrassing e-mail messages sent by Dr. Jones and other scientists were stolen in November and posted to the Internet, leading to a deluge of accusations from climate change skeptics as well as admissions from some of the scientists that they had been guilty of poor behavior.

But were they, as the skeptics charged, guilty of scientific misconduct?

“On the specific allegations made against the behavior of C.R.U. scientists, we find that their rigor and honesty as scientists are not in doubt,” said the new review, led by Muir Russell, a leading British civil servant and educator.

The Russell panel also found little reason to question the advice the scientists had given to the Intergovernmental Panel on Climate Change, the United Nations body that produces a major review of the science of global warming every few years. The new report said that “we did not find any evidence of behavior that might undermine the conclusions of the I.P.C.C. assessments.”

The review was the fifth to come to essentially the same conclusion about the e-mail messages sent by Dr. Jones and other scientists, though it was the most comprehensive and eagerly awaited of the investigations. Last week the second of two reviews at Pennsylvania State University exonerated Michael Mann, a scientist there who had also been a focus of the controversy.

The latest report was not a complete vindication for scientists or for the University of East Anglia, which commissioned it. Echoing the findings of an earlier report by a parliamentary committee in London, the reviewers criticized “a consistent pattern of failing to display the proper degree of openness” in responding to demands for backup data and other information under Britain’s law governing public records.

Climate change skeptics criticized the four previous reviews of the issue as whitewashes that failed to delve deeply enough into the scientific uncertainties about climate change.

For their part, the reviewers took the position that conclusions on science get sorted out in academic interchanges and scientific publications and that their role in the inquiry was to focus on a narrower set of questions raised by the private e-mail messages.

Link:  http://www.nytimes.com/2010/07/08/science/earth/08climate.html

Michael Le Page: Climate myths -- Global warming stopped in 1998

Climate myths: Global warming stopped in 1998

by Michael Le Page, New Scientist, August 15, 2008

UK Met Office Hadley Centre dataset Enlarge

NASA's global temperature land-ocean index Enlarge

Satellite imagery of sea surface temperatures taken during January 1998 shows the strong El Nino that helped make it one of the hottest years on record. (Image: NOAA) Enlarge

Even if the atmospheric temperature near the earth's surface has become cooler recently, that doesn't mean the planet as a whole isn't heating up

Imagine two people standing at the South Pole, one dressed in full Antarctic gear and the other wearing not much at all. Now imagine that you're looking through one of those infrared thermal imagers that show how hot things are. Which person will look warmest -- and which will be frozen solid after a few hours?

The answer, of course, is that the near-naked person will appear hotter: but because they are losing heat fast, they will freeze long before the person dressed more appropriately for the weather.

The point is that you have to look beyond the surface to understand how a body's temperature will change over time - and that's as true of planets as it is of warm-blooded bipeds.

Now take a look at the two main compilations (see figures, right) of global surface temperatures, based on monthly records from weather stations around the world.

According to the dataset of the UK Met Office Hadley Centre (see figure), 1998 was the warmest year by far since records began, but since 2003 there has been slight cooling.

But according to the dataset of NASA's Goddard Institute for Space Studies (see figure), 2005 was the warmest since records began, with 1998 and 2007 tied in second place.

Tracking the heat

Why the difference? The main reason is that there are no permanent weather stations in the Arctic Ocean, the place on Earth that has been warming fastest. The Hadley record simply excludes this area, whereas the NASA version assumes its surface temperature is the same as that of the nearest land-based stations.

It is possible that the NASA approach underestimates the rate of warming in the Arctic Ocean, but for the sake of argument let's assume that the Hadley record is the most accurate reflection of changes in global surface temperatures. Doesn't it show that the world has cooled since the record warmth of 1998, as many claim?

Not necessarily. The Hadley record is based only on surface temperatures, so it reflects only what's happening to the very thin layer where air meets the land and sea.

In the long term, what matters is how much heat is gained or lost by the entire planet -- what climate scientists call the "top of the atmosphere" radiation budget -- and falling surface temperatures do not prove that the entire planet is losing heat.

Swaddling gases

Think again about that scantily clad person at the South Pole. If they put on some clothing, they'll appear cooler to a thermal imager, but what's really happening is that they are losing less heat.

Similarly, if you could look at Earth through a thermal imager, it would appear slightly cooler than it did a few decades ago. The reason is that the outer atmosphere, the stratosphere, is cooler because we've added more "clothing" to the lower atmosphere in the form of greenhouse gases like carbon dioxide.

As a result, the planet is gaining as much heat from the sun as usual but losing less heat every year as greenhouse gas levels rise (apart from the exceptional periods after major volcanic eruptions, such as El Chichon in 1982 and Pinatubo in 1991).

How do we know? Because the oceans are getting warmer.

Tricky oceans

Water stores an immense amount of heat compared with air. It takes more than 1000 times as much energy to heat a cubic metre of water by 1 degree Centigrade as it does the same volume of air. Since the 1960s, over 90% of the excess heat due to higher greenhouse gas levels has gone into the oceans, and just 3% into warming the atmosphere (see figure 5.4 in the IPCC report (PDF)).

Globally, this means that if the oceans soak up a bit more heat energy than normal, surface air temperatures can fall even though the total heat content of the planet is rising. Conversely, if the oceans soak up less heat than usual, surface temperatures will rise rapidly.

This is why surface temperatures do not necessarily rise steadily year after year, even though the planet as a whole is heating up a bit more every year. Most of the year-to-year variability in surface temperatures is due to heat sloshing back and forth between the oceans and atmosphere, rather than to the planet as a whole gaining or losing heat.

The record warmth of 1998 was not due to a sudden spurt in global warming but to a very strong El Nino (see figure, right). In normal years, trade winds keep hot water piled up on the western side of the tropical Pacific.

During an El Nino, the winds weaken and the hot water spreads out across the Pacific in a shallow layer. Its heat is transferred to the atmosphere. (During a La Nina, by contrast, as occurred during the early part of 2008, the process is reversed and upwelling cold water in the eastern Pacific soaks up heat from the atmosphere.)

A temporary fall in the heat content of the oceans at this time may have been due to the extra strong El Nino.

What next?

Since 1999, however, the heat content of the oceans has steadily increased again (despite claims to the contrary). Global warming has certainly not stopped, even if average surface temperatures really have fallen slightly as the Hadley figures suggest.

In the long term, some of the heat being soaked up by the oceans will inevitably spill back into the atmosphere, raising surface temperatures. Warmer oceans also mean rising sea levels, due to both thermal expansion and the melting of the floating ice shelves that slow down glaciers sliding off land into the sea. The West Antarctic Ice Sheet, which rests on the seabed rather than on land, is also highly vulnerable to rising sea temperatures.

Some climate scientists are predicting that surface temperatures will remain static or even fall slightly over the next few years, before warming resumes. Their predictions are based largely on the idea that changes in long-term fluctuation in ocean surface temperatures known as the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation will bring cooler sea surface temperatures.

If these predictions are right -- and not all climate scientists think they are -- you can expect to hear more claims from climate-change deniers about how global warming has stopped. But unless we see a simultaneous fall in both surface temperatures and ocean-heat content, claims that the "entire planet" is cooling are nonsense.

And while a big volcanic eruption could indeed trigger genuine cooling for a few years, global warming will resume again once the dust has settled.

Link to article:

http://environment.newscientist.com/channel/earth/climate-change/dn14527-climate-myths-global-warming-stopped-in-1998.html

Climate change: The next ten years, by Fred Pearce and Michael Le Page

New Scientist, August 13, 2008

WHAT's going to happen to the climate over the next 10 years or so? Is it time to buy that air conditioner you considered during the last heatwave? Should you rip up your garden and replant it with drought-resistant plants, or can you expect more rain -- perhaps even floods -- in your part of world? The other possibility, of course, is that your local climate will change little in the near future.

On the one hand we have weather predictions for the next few days. On the other we have climate forecasts for the very distant future. But what happens in the middle? Why don't we have forecasts for, say, 2010 or 2018? Knowing how temperature and rainfall will change over the next few years would be invaluable to many people, from farmers to the tourism industry to those in charge of our water supplies. Yet while you might think predicting how the climate will change over the next few years would be a lot easier than saying what it will be like in 2030 or 2050, it's actually harder.

Nevertheless, some meteorologists and climate scientists are now trying to make just these kinds of forecasts. It is a new and controversial field, but over the past year some groups have published the first short-term forecasts. So what are they predicting -- and can we trust their conclusions?

Underlying trends

For long-term forecasting, what matters is underlying trends, and at the moment the key trend is warming due to rising levels of greenhouse gases. Predictions made two decades ago are pretty close to the mark. In the short term, though, natural variability matters more than the underlying trend -- global warming does not mean that each year will be warmer than the preceding one.

The problem is a bit like trying to predict how the weather in New York will change over January compared with how the weather will change from January to July. It's hard to say whether the last week of January will be colder than the first, but you can confidently predict that it will be colder during January than in July.

So making forecasts is all about figuring what dominates the state of the atmosphere on various timescales. Some things, like accumulating greenhouse gases, matter over many decades while other things, like warm and cold fronts, dominate over days and months. Over periods of a few years, there's growing evidence that the oceans are the key -- and this is encouraging researchers to attempt short-term forecasts.

Ocean oscillations

"It takes the oceans a long time to heat up and cool down," says Doug Smith, who runs 10-year forecasting trials at the Met Office Hadley Centre in Exeter, Devon, the UK's official centre for climate change research. "That makes it a lot easier to predict than the atmosphere. We now think we can predict the key ocean fluctuations 10 to 20 years ahead."

The oceans are crucial because they store so much heat. It takes more than 1000 times as much energy to heat a cubic metre of water by 1 °C as it does the same volume of air. Globally, this means that if the oceans transfer just a tiny fraction of their heat energy to the lower atmosphere, there can be a big rise in surface air temperatures. Conversely, if the oceans soak up more heat from the atmosphere, there can be surface cooling.

Most of the natural variability in surface air temperature from year to year is due to heat sloshing back and forth between the oceans and atmosphere, rather than any overall loss or gain of heat by the entire planet. The state of the sea surface determines what happens, and it affects both temperature and rainfall. For instance, in recent years, climate scientists have successfully forecast droughts in west Africa and northeast Brazil several months ahead by measuring sea surface temperatures in the tropical Atlantic.

Huge influence

The long-standing droughts in Australia could be due to persistently low sea surface temperatures to the north of country, relative to warmer water in the Indian Ocean, say Wenju Cai and Tim Cowan of the CSIRO marine and atmospheric research centre in Aspendale, Victoria. Rainfall over southern and eastern Australia has been declining for half a century now, causing major problems in river systems like the Murray-Darling basin, which produces much of the country's crops.

The huge influence of sea surface temperatures has led many researchers to try to understand how they fluctuate over years and decades. Predict this, and you should be able to predict all sorts of other things as well.

The best known of these fluctuations is the El Niño-Southern Oscillation. In the tropical Pacific, cold water normally wells up near South America, while hot water piles up on the other side of the Pacific. Sometimes, for reasons poorly understood, the hot water spreads right across the surface of the Pacific in a shallow layer.

This increase in the area of warm water boosts the transfer of heat and moisture to the atmosphere, changing air circulation patterns and producing widespread consequences -- from droughts in Indonesia to floods in the Americas. An especially intense El Niño in 1998 made it one of the warmest years on record.

El Niño

Yet contrary to what you might expect, if El Niño has any long-term effect on global warming it may be to slow it down. Models suggest that by increasing heat radiation into space, it may reduce the net gain of heat by the entire planet as a result of increasing greenhouse gases. Actual measurements are not yet accurate enough to confirm this, however.

The opposite of El Niño, La Niña, results in a heat transfer from the lower atmosphere to the ocean. The strong La Niña during the early part of this year could make 2008 one of the coldest years since the early 1990s.

The El Niño cycle lasts anywhere from three to eight years, but its state cannot be predicted more than a year in advance. However, in the Pacific north of the tropics, there seems to be something akin to El Niño that lasts far longer. It is called the Pacific Decadal Oscillation and its influence is extensive, on land as well as at sea (see "Trendsetters").

The PDO was in a negative phase -- with cooler sea surface temperatures -- between the mid-1940s and the mid-1970s, and may have been partly responsible for the cooler global surface temperatures during this time. This does not mean a negative PDO has a cooling effect overall; on the contrary, it's likely that a negative PDO increases the planet's total heat by reducing heat transfer from the oceans to the atmosphere and thence into space. Since 1976, the PDO has been mostly positive again, which may have contributed to the strong warming in Alaska and the prolonged droughts in south-east Australia.

Droughts and monsoons

The other major ocean fluctuation is the Atlantic Multidecadal Oscillation, a semi-periodical change in surface temperatures north of the equator. Most researchers agree that the AMO is largely due to changes in the speed of the deep-ocean current known as the thermohaline circulation.

When the circulation speeds up, more warm water from the tropics moves up into the North Atlantic, transferring huge amounts of heat to the air as it goes -- the positive phase of the AMO. When a slowing circulation pushes the AMO into a negative phase, more warm water stays in the tropics, and surface temperatures fall in Europe and the eastern side of North America.

The AMO was in a negative phase from the late 1960s until the mid-1990s. We're now in the middle of a positive phase again, which may have contributed to the very rapid warming in the Arctic in recent years and the dramatic fall in the extent of its sea ice during the summer. The effect of a positive AMO on the planet's overall heat budget is not clear, but it may speed up global warming since less ice cover means less solar radiation is reflected back into space.

What's more, there is growing evidence linking the AMO to climatic trends on land, even in areas far from the Atlantic. Decades-long fluctuations in the intensity of the Indian monsoon rains, droughts in the region of west Africa called the Sahel and even the numbers of Atlantic hurricanes all seem to depend on the AMO. Droughts in the western US, including the 1930s Dust Bowl and low river levels in the 1990s, all happened during its positive phase.

The big picture

So what does the future hold? If the AMO stays positive in the coming decade, it will increase summer rainfall over India and the Sahel -- and increase Atlantic hurricane activity. However, the AMO may be poised to turn negative, says Rowan Sutton of the Walker Institute at Reading University, UK, who has studied the phenomenon in detail.

The thermohaline circulation is driven by the sinking of cold, salty water near the Arctic. Its strength, and thus the phase of the AMO, seems to depend on what happens in the waters between Greenland and Scandinavia. "There is evidence that we can sometimes predict the changes up to 10 years ahead," Sutton says.

Meanwhile, the PDO has already been negative for the past couple of years. If both ocean fluctuations were to be in a negative phase over the next few years, things will be very different.

For starters, there will be a slowdown in the rapid warming seen around the Arctic and North Atlantic in recent years. The rapid fall in the extent of sea ice in summer -- which has been happening much faster than predicted -- could slow and perhaps even reverse.

A temporary respite

Droughts could return to India and the Sahel, but for the parched American west there could be a desperately needed respite. On current trends, the great reservoirs on the Colorado river that sustain western cities like San Diego and Phoenix could be dry within a decade. "We are stunned at the magnitude of the problem, and how fast it is coming at us," says Tim Barnett of the Scripps Institution of Oceanography in San Diego. If the AMO enters a negative phase, then the river may live on.

Some also predict a decline in hurricane activity in the Atlantic. But Michael Mann of Penn State University says some things attributed to the AMO are more likely a result of global warming. He thinks the AMO has little influence on tropical sea temperatures, so he predicts that Atlantic hurricanes will intensify even if the AMO is negative. We will have to wait and see.

That's the broad-brush picture. In Europe, several groups are trying to model exactly what might happen over the next 10 years or so. Smith's team produced the first such forecast last year. It suggests that surface air temperatures will remain steady for the next six years or so as cooler sea surface temperatures keep the lower atmosphere cool despite ever higher greenhouse gas levels.

But this respite won't last. Smith expects surface temperatures will start to rise again by 2014, and that they will go into overdrive with a string of record highs at the end of the next decade if both the major ocean oscillations kick back into positive phases.

Global cooling

Earlier this year another group, headed by Noel Keenlyside of the Leibniz Institute for Marine Sciences in Kiel, Germany, produced an even more striking forecast: "Global surface temperature may not increase over the next decade."

Climate change deniers promptly proclaimed that we could expect "more global cooling ahead". But surface temperature is not the same as the overall heat content of the planet. Since the 1960s, 90% of the excess heat due to higher greenhouse gas levels has gone into the oceans, 7% into land and ice, and just 3% into warming the atmosphere. Even if the lower atmosphere doesn't warm in the next few years, that's no reason for comfort so long as the strong warming trend in the oceans continues. In the long run, warmer oceans inevitably mean a warmer atmosphere.

In any case, many climate researchers don't think the Keenlyside forecast is right. "The way they try to predict the AMO is almost guaranteed to give you the wrong answer," says Gavin Schmidt of NASA's Goddard Center for Space Studies in New York.

"The way they try to predict it is guaranteed to give you the wrong answer"

The issue is where the models start from. If you're trying to forecast natural variability, conditions in the seas in the model must match those in the real world. Thanks to a network of undersea sensors, we are now starting to get good data on both temperature and salinity levels in the crucial upper layers of the Atlantic. However, feeding this information into models is not as easy as it might seem and -- unlike Smith's team -- the Keenlyside team put only sea surface temperatures into their model.

Completely wrong

"If you match the sea surface temperatures but not the salinity values, the water density will be completely wrong," says Schmidt. Yet this density is crucial for determining the state of the thermohaline circulation and hence the AMO.

Some of the scientists who write for the RealClimate blog are so sure that the forecast is wrong that they offered the Keenlyside team a bet of €2500 that the average surface temperatures for 2005 to 2015 will, contrary to the team's forecast, turn out be higher than during 1994 to 2004. The team has not accepted the bet.

Even if the various "model initialization" problems can be solved, is it really possible to predict how the oceans will behave so far in advance? According to David Battisti at the University of Washington in Seattle, who specializes in studying natural variability, there's a growing consensus that the PDO is just the mid-latitude "debris" left by the past two or three El Niños or La Niñas. If this is right, it means the PDO cannot be predicted long in advance.

No predictability

"There is no predictability in the Pacific," he says. "If there's any hope for predicting natural variability, it's in the Atlantic." Even there, Battisti thinks it will only be possible to make accurate decadal forecasts for tropical regions where there is far less variability from year to year than in higher latitudes.

What's more, there is another aspect of natural variability that cannot be predicted years in advance: volcanoes. Major volcanic eruptions like those of El Chichón in 1982 and Pinatubo in 1991 can throw up so much dust and sulphur that they cool the entire planet. The average effect of eruptions can be included in forecasts looking several decades ahead, but not in 10-year ones. "The forecast will be wrong when one occurs," says Smith.

There is no doubt that enormous progress has been made in understanding and predicting some of the factors responsible for the tremendous variability in surface air temperatures and rainfall from year to year. But the field is in its infancy. It is still far from clear to what extent natural variability can be predicted years in advance -- and it's going to take decades to find out for sure.

In the meantime, 10-year forecasts should come with a very clear health warning. "There is a danger that if we make a forecast and it's wrong that people will lose faith," Smith acknowledges. "But I don't agree we shouldn't make them."

Climate Change – Want to know more about global warming: the science, impacts and political debate? Visit our continually updated special report.

From issue 2669 of New Scientist magazine, 13 August 2008, page 26-30.

Link to article:
http://environment.newscientist.com/channel/earth/mg19926691.500-climate-change-the-next-ten-years.html