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Science is self-correcting: Lessons from the arsenic controversy

Filed under: — group @ 29 December 2010

Recent attention to NASA’s announcement of ‘arsenic-based life’ has provided a very public window into how science and scientists operate. Debate surrounds the announcement of any controversial scientific finding. In the case of arseno-DNA, the discussion that is playing out on the blogs is very similar to the process that usually plays out in conferences and seminars. This discussion is a core process by which science works.
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Post-holiday round-up

Filed under: — group @ 28 December 2010

What with holiday travel, and various other commitments, we’ve missed a few interesting stories over the last week or so.

First off, AGU has posted highlights from this year’s meeting – mainly the keynote lectures, and there are a few interesting presentations for instance from Tim Palmer on how to move climate modelling forward, Ellen Mosley-Thompson on the ice records, and David Hodell on abrupt climate change during the last deglaciation. (We should really have a ‘videos’ page where we can post these links more permanently – all suggestions for other videos to be placed there can be made in the comments).

More relevant for scientist readers might be Michael Oppenheimer’s talk on the science/policy interface and what scientists can usefully do, in the first Stephen Schneider Lecture. There was a wealth of coverage on AGU in general, and for those with patience, looking through the twitter feeds with #agu10 shows up a lot of interesting commentary from both scientists and journalists. Skeptical Science and Steve Easterbrook also have good round ups. [edited]

Second, there was a great front page piece in the New York Times by Justin Gillis on the Keeling curve – and the role that Dave Keeling’s son, Ralph, is playing in continuing his father’s groundbreaking work. Gillis had a few follow-up blogs that are also worth reading. We spend a lot of time criticising media descriptions on climate change, so it’s quite pleasing to be praising a high profile story instead.

Finally, something new. Miloslav Nic has put together a beta version of an interactive guide to IPCC AR4, with clickable references, cited author (for instance, all the Schneiders) and journal searches. This should be a very useful resource and hopefully something IPCC can adopt for themselves in the next report.

Back to normal posting soon….

Cold winter in a world of warming?

Filed under: — rasmus @ 14 December 2010

Last June, during the International Polar Year conference, James Overland suggested that there are more cold and snowy winters to come. He argued that the exceptionally cold snowy 2009-2010 winter in Europe had a connection with the loss of sea-ice in the Arctic. The cold winters were associated with a persistent ‘blocking event’, bringing in cold air over Europe from the north and the east.

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Responses to McShane and Wyner

Filed under: — group @ 13 December 2010

Gavin Schmidt and Michael Mann

Readers may recall a flurry of excitement in the blogosphere concerning the McShane and Wyner paper in August. Well, the discussions on the McShane and Wyner paper in AOAS have now been put online. There are a stunning 13 different discussion pieces, an editorial and a rebuttal. The invited discussions and rebuttal were basically published ‘as is’, with simple editorial review, rather than proper external peer review. This is a relatively unusual way of doing things in our experience, but it does seem to have been effective at getting rapid responses with a wide variety of perspectives, though without peer review, a large number of unjustified, unsupportable and irrelevant statements have also got through.

A few of these discussions were already online, i.e. from Martin Tingley, Schmidt, Mann and Rutherford (SMR), and one from Smerdon. Others, including contributions from Nychka & Li, Wahl & Ammann, McIntyre & McKitrick, Smith, Berliner and Rougier are newly available on the AOAS site and we have not yet read these as carefully yet.

Inevitably, focus in the discussions is on problems with MW, but it is worth stating upfront here (as is also stated in a number of the papers) that MW made positive contributions to the discussion as well – they introduced a number of new methods (and provided code that allows everyone to try them out), and their use of the Monte Carlo/Markov Chain (MCMC) Bayesian approach to assess uncertainties in the reconstructions is certainly interesting. This does not excuse their rather poor framing of the issues, and the multiple errors they made in describing previous work, but it does make the discussions somewhat more interesting than a simple error correcting exercise might have been. MW are also to be commended on actually following through on publishing a reconstruction and its uncertainties, rather than simply pointing to potential issues and never working through the implications.

The discussions raise some serious general issues with MW’s work – with respect to how they use the data, the methodologies they introduce (specifically the ‘Lasso’ method), the conclusions they draw, whether there are objective methods to decide whether one method of reconstruction is better than another and whether the Bayesian approach outlined in the last part of the paper is really what it is claimed. But there are also a couple of very specific issues to the MW analysis; for instance, the claim that MW used the same data as Mann et al, 2008 (henceforth M08).

On that specific issue, presumably just an oversight, MW apparently used the “Start Year” column in the M08 spreadsheet instead of the “Start Year (for recon)” column. The difference between the two is related to the fact that many tree ring reconstructions only have a small number of trees in their earliest periods and that greatly inflates their uncertainty (and therefore reduces their utility). To reduce the impact of this problem, M08 only used tree ring records when they had at least 8 individual trees, which left 59 series in the 1000 AD frozen network. The fact that there were only 59 series in the AD 1000 network of M08 was stated clearly in the paper, and the criterion regarding the minimal number of trees (8) was described in the Supplementary Information. The difference in results between the correct M08 network and spurious 95 record network MW actually used is unfortunately quite significant. Using the correct data substantially reduces the estimates of peak medieval warmth shown by MW (as well as reducing the apparent spread among the reconstructions). This is even more true when the frequently challenged “Tiljander” series are removed, leaving a network of 55 series. In their rebuttal, MW claim that M08 quality control is simply an ‘ad hoc’ filtering and deny that they made a mistake at all. This is not really credible, and it would have done them much credit to simply accept this criticism.

With just this correction, applying MW’s own procedures yields strong conclusions regarding how anomalous recent warmth is the longer-term context. MW found recent warmth to be unusual in a long-term context: they estimated an 80% likelihood that the decade 1997-2006 was warmer than any other for at least the past 1000 years. Using the more appropriate 55-proxy dataset with the same estimation procedure (which involved retaining K=10 PCs of the proxy data), yields a higher probability of 84% that recent decadal warmth is unprecedented for the past millennium.

However K=10 principal components is almost certainly too large, and the resulting reconstruction likely suffers from statistical over-fitting. Objective selection criteria applied to the M08 AD 1000 proxy network as well as independent “pseudoproxy” analyses (discussed below) favor retaining only K=4 PCs. (Note that MW correctly point out that SMR made an error in calculating this, but correct application of the Wilks (2006) method fortunately does not change the result, 4 PCs should be retained in each case). Nonetheless, this choice yields a very close match with the relevant M08 reconstruction. It also yields considerably higher probabilities up to 99% that recent decadal warmth is unprecedented for at least the past millennium. These posterior probabilities imply substantially higher confidence than the “likely” assessment by M08 and IPCC (2007) (a 67% level of confidence). Indeed, a probability of 99% not only exceeds the IPCC “very likely” threshold (90%), but reaches the “virtually certain” (99%) threshold. In this sense, the MW analysis, using the proper proxy data and proper methodological choices, yields inferences regarding the unusual nature of recent warmth that are even more confident than expressed in past work.

An important real issue is whether proxy data provides more information than naive models (such as the mean of the calibrating data for instance) or outperform random noise of various types. This is something that has been addressed in many previous studies which have come to very different different conclusions than MW, and so the reasons why MW came to their conclusion is worth investigating. Two factors appear to be important – their use of the “Lasso” method exclusively to assess this, and the use of short holdout periods (30 years) for both extrapolated and interpolated validation periods.

So how do you assess how good a method is? This is addressed in almost half of the discussion papers – Tingley in particular gives strong evidence that Lasso is not in fact a very suitable method, and is outperformed by his Composite Regression method in test cases, Kaplan points out that using noise with significant long term trends will also perform well in interpolation. Both Smith and the paper by Craigmile and Rajaratnam also address this point.

In our submission, we tested all of the MW methods in “pseudoproxy” experiments based on long climate simulations (a standard benchmark used by practitioners in the field). Again, Lasso was outperformed by almost every other method, especially the EIV method used in M08, but even in comparison with the other methods MW introduced. The only support for ‘Lasso’ comes from McIntyre and McKitrick who curiously claim that the main criteria in choosing a method should be how long it has been used in other contexts, regardless of how poorly it performs in practice for a specific new application. A very odd criteria indeed, which if followed would lead to the complete cessation of any innovation in statistical approaches.

The MW rebuttal focuses a lot on SMR and we will take the time to look into the specifics more closely, but some of their criticism is simply bogus. They claim our supplemental code was not usable, but in fact we provided a turnkey R script for every single figure in our submission – something not true of their code, so that is a little cheeky of them [as is declaring that one of us to be a mere blogger, rather than a climate scientist ;-) ]. They make a great deal of the fact that we only plotted the ~50 year smoothed data rather than the annual means. But this seems to be more a function of their misconstruing what these reconstructions are for (or are capable of) rather than a real issue. Not least of which, the smoothing allows the curves and methods to be more easily distinguished – it is not a ‘correction’ to plot noisy annual data in order to obscure the differences in results!

Additionally, MW make an egregiously wrong claim about centering in our calculations. All the PC calculations use prcomp(proxy, center=TRUE, scale=TRUE) to specifically deal with that, while the plots use a constant baseline of 1900-1980 for consistency. They confuse plotting convention with a calculation.

There is a great deal to digest in these discussions, and so we would like to open the discussion here to all of the authors to give their thoughts on how it all stacks up, what can be taken forward, and how such interactions might be better managed in future. For instance, we are somewhat hesitant to support non-peer reviewed contributions (even our own) in the literature, but perhaps others can make a case for it.

In summary, there is much sense in these contributions, and Berliner’s last paragraph sums this up nicely:

The problem of anthropogenic climate change cannot be settled by a purely statistical argument. We can have no controlled experiment with a series of exchangeable Earths randomly assigned to various forcing levels to enable traditional statistical studies of causation. (The use of large-scale climate system models can be viewed as a surrogate, though we need to better assess this.) Rather, the issue involves the combination of statistical analyses and, rather than versus, climate science.

Hear, hear.

Feedback on Cloud Feedback

Filed under: — group @ 9 December 2010

Guest article by Andrew Dessler

I have a paper in this week’s issue of Science on the cloud feedback that may be of interest to realclimate readers. As you may know, clouds are important regulators of the amount of energy in and out of the climate system. Clouds both reflect sunlight back to space and trap infrared radiation and keep it from escaping to space. Changes in clouds can therefore have profound impacts on our climate.

A positive cloud feedback loop posits a scenario whereby an initial warming of the planet, caused, for example, by increases in greenhouse gases, causes clouds to trap more energy and lead to further warming. Such a process amplifies the direct heating by greenhouse gases. Models have been long predicted this, but testing the models has proved difficult.

Making the issue even more contentious, some of the more credible skeptics out there (e.g., Lindzen, Spencer) have been arguing that clouds behave quite differently from that predicted by models. In fact, they argue, clouds will stabilize the climate and prevent climate change from occurring (i.e., clouds will provide a negative feedback).

In my new paper, I calculate the energy trapped by clouds and observe how it varies as the climate warms and cools during El Nino-Southern Oscillation (ENSO) cycles. I find that, as the climate warms, clouds trap an additional 0.54±0.74W/m2 for every degree of warming. Thus, the cloud feedback is likely positive, but I cannot rule out a slight negative feedback.
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A brief history of knowledge about Antarctic temperatures

Filed under: — eric @ 9 December 2010

Sources in italics.

Early 20th Century:

Scott: It’s cold here.
The media: Scott is a hero!
Scott: It’s really really cold here.
The media: Scott is a hero!
Amundsen: It’s not that cold.
The media: Scott is a hero. Oh, and Amundsen.
Public: Shackleton is a hero, but please shut up, there’s a war on.

Mid 20th Century:

Geophizzicists: Let’s find out just how cold it is.
Media: Scott is a hero!
Public: yawn…

Late 20th Century:

Scientists: It’s colder in some place than others.
Media: Antarctica is cooling.
Scientists: It’s cooling at the South Pole, but warming very fast on the Peninsula.
Media: Antarctica is cooling, but warming faster than anywhere else on earth.
Public: Huh…?

2000
Thompson and Solomon: Most of Antarctica is cooling in summer, but it is warming on the Peninsula. We think it has to do with the ozone hole.
Media: Because of ozone, Antarctica is warming faster than anywhere else on earth and we are all going to die.
Public: Huh…?

Early 21st Century:

2006
Scientists: The troposphere over Antarctica is warming significantly in winter.
Media: Even though that paper was published in Science, our readers don’t know what the troposphere is. Neither do we. Next?

2007
Scientists: The troposphere over Antarctica is warming significantly in winter and spring, especially over West Antarctica.
Media: That paper wasn’t published in Nature, so we’re not very interested.

2009
Scientists: Antarctica is cooling in fall — not summer — in some places, but warming, especially in winter and spring, especially in West Antarctica.
Media: Antarctica stops cooling! Conservative or liberal, we are ALL going to die.
Steve McIntyre: The “team” made up the data again. I don’t know what Antarctica is doing, but I think it is probably cooling.
Media: Antarctica starts cooling again, global warming is a fraud.

2010
Ryan O’Donnell: Our paper in the Journal of Climate shows a somewhat better way to look at the same data. Antarctica is warming a bit more in summer, and a bit less in winter in the Ross Sea region. In fall it is cooling a bit more too, and so the overall trends are smaller. Still, West Antarctica is definitely warming significantly, as Steig et al. found. That’s interesting.
Eric Steig: Nice paper Ryan. Thanks for sending along a pre-print.
Steve McIntyre: Hey, we got published in the Journal of Climate! Another paper showing that the “team” made up the data again! (Sotto voce): Ryan says it it is warming a bit more in summer, and a bit less in winter in the Ross Sea region. In fall it is cooling a bit more. Otherwise we get the same results, though the magnitude of the trends is smaller. But West Antarctica is still warming significantly. But I really don’t care. The peer review process is broken, which is why.. umm…our paper was published in the leading climate journal.
Liberal Media: That paper wasn’t published in Nature, so we’re not very interested.
Conservative Media: Antarctica is cooling. Global warming is a fraud.
Public: zzzZZZzzz
————-
P.S. For those actually interested, yes, I’ll have more to say about O’Donnell et al., but overall, I like it.–eric

Losing time, not buying time

Filed under: — raypierre @ 6 December 2010

Control of methane, soot, and other short-lived climate-forcing agents has often been described as a cheap way to "buy time" to get carbon dioxide emissions under control. But is it really?

Expectations for the outcome of the Cancun climate talks seem to be running low, and the suggestion has emerged that maybe we should forget about controlling CO2 emissions for now, and instead do something with short lived climate forcing agents like methane or soot. This is often described as "buying time" to put CO2 emissions controls into place. For example, in a recent New York Times Op-Ed, Ramanathan and Victor write:

"Reducing soot and the other short-lived pollutants would not stop global warming, but it would buy time, perhaps a few decades, for the world to put in place more costly efforts to regulate carbon dioxide." — Ramanathan and Victor

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The AGU Q & A Service–Open for Business

Filed under: — group @ 6 December 2010

This is just a brief notice for those members of the media who may not be aware of the American Geophysical Union‘s (AGU) re-vamped question and answer service for climate science questions. There are about 700 participating AGU scientists, with several answering questions at any given time. This service should be highly useful for getting relatively quick answers to specific, climate science questions during the United Nations COP-16 negotiations in Cancun, Mexico this week, as well at the AGU annual meeting which runs the following week. The service will continue some time beyond the AGU meetings as well.

Contrary to incorrect media and blog stories last month, this service is for climate science questions only from members of the media–no policy or politically related questions are fielded. Go here for more background and procedural information if interested.

Update: The Service’s coordinator informs us that bloggers are considered part of the media, and so their questions are welcome as well.

Update 2: Jeff Taylor, the service’s coordinator, has addressed, in the comments, a number of the questions and suggestions raised, and provided further links for those with more questions about climate and/or the service’s operation.

Coldest Winter in 1000 Years Cometh. Not.

Filed under: — stefan @ 4 December 2010

This claim circulates in the internet and in many mainstream media as well: Scientists have allegedly predicted the coldest winter in 1,000 years for Europe. What is behind it? Nothing – no scientist has predicted anything like it. A Polish tabloid made up the story. An interesting lesson about today´s media.

By Stefan Rahmstorf and Olivia Serdeczny

We had read about it a few times and last Wednesday even were asked by German TV about the allegedly coldest winter in 1000 years, predicted by (depending on the source) Polish or Russian climatologists or meteorologists. Reason enough for us to take a closer look at the story behind the story.

It did not take much googling to find the source: various articles on the internet name the Polish scientist Michał Kowalewski, sometimes in the Russian spelling version of Mikhail Kovalevski. A few clicks later we arrive at the original article with Kowalewski´s quotes. Except that Kowalewski does not predict a record winter there – the “millennium winter” merely appears in the headline. A closer reading of the article quickly reveals: the quotes were answers to questions concerning the role of the Gulf Stream for Europe´s climate. The frosty temperatures are hypothetical effects of a breakdown of the Gulf Stream – which, as Kowalewski points out, can be pretty much ruled out.

We asked Kowalewski for his comments on the media coverage and promptly got his answer in an email from Warsaw:

The reports in some media are absolutely unbelievable. A journalist who interviewed me for radio had asked me about the theoretical climatic effects of a breakdown of the Gulf Stream. I answered that this purely hypothetic scenario would lead to much colder winters in Poland. A few days later I found on the internet the article of a journalist who mixed his own words with some of my quotes without their context so well that a completely new meaning came out. An absolutely absurd thesis. My quotes as such are correct, so I was not able to demand a correction.


Winter has Europe in its grip: the Süring-building of the Potsdam Institute.

It’s an interesting and insightful tale how this story spread. Here is a brief chronology:

September, 10. Michał Kowalewski is interviewed by the Polish radio station tok.fm. The same day the website of a Polish tabloid, Gazeta.pl, publishes an article with the headline of a „millennium record winter“ („once-in-a-millennium winter“). A certain Gianluigi Zangari is being quoted at the outset. He has apparently claimed to have found a slow-down of the Gulf Stream in satellite data, which he attributes to the BP oil spill (we did not follow this bizarre claim to the source). Subsequently Kowalewski´s radio interview is brought in – in order to explain the Gulf Stream and its effects on climate in general.

September, 12. „Fakt“, a Polish tabloid, writes „Millennium Winter is Coming!“ Again the BP oil spill is blamed. This time, however, without any reference to Zangari, so readers could easily be left with the impression that this is Kowalewski´s idea.

September, 22. The Voice of Russia reports that the Polish scientist „Mikhail Kovalevski“ is worried about the Gulf Stream breaking down, which Russian scientists counter as being an exaggeration.

Oktober, 4. The Russian RT News Service predicts „The coldest winter in 1.000 years“. Which is explained by the Gulf Stream having slowed down by half. RT refers to Polish scientists: “Polish scientists say that it means the stream will not be able to compensate for the cold from the Arctic winds. According to them, when the stream is completely stopped, a new Ice Age will begin in Europe”. This is where the Russian Vadim Zavotschenkow enters the scene. However, he mentions merely a cold winter: “Although the forecast for the next month is only 70 percent accurate, I find the cold winter scenario quite likely”.

Oktober, 4. The “climate sceptics” website wattsupwiththat, noted for their false reports, takes up the RT piece, presents it together with The Voice of Russia and mentions „Mikhail Kovalevski“. Watts seems to be the bridge for the story´s crossing into the western media. Is it just coincidence that the „record cold winter“ story nicely suits the political agenda of the climate sceptics?

From then on, the story is repeated on many other European media, including serious newspapers and television.

It is staggering how one journalist just copied another, sometimes even embellishing the story, without ever bothering to check the source or ask Kowalewski himself. It took us less than ten minutes of googling to get serious doubts about whether this story was real. The familiar pattern of „Chinese whispers“ emerges here once again – the same that widely spread the false whatevergate-stories.

But the often self-righteous free western press can actually learn a lesson from its Chinese counterpart in this case. The Chinese news agency Xinhua checked the story and issued the following on October, 20.:

A forecast attributed to Polish scientists of the coldest European winter in 1,000 years has drawn plenty of media attention recently but investigations by Xinhua reporters have cast doubts on its veracity.

p.s. There are, by the way, scientifically well-founded attempts to explain the currently cold weather in Europe. The basic check for seriousness: a peer-reviewed journal source is provided, and according to Google Scholar the author has a decent publication record. A millennium-record-winter, however, is not being predicted there.

p.p.s. Should your newspaper have also reported this turkey, feel free to write a polite letter to the to editors asking for a correction. It is only if readers demand published information to be verified (or if needed corrected) that something will change to the better.

This article is adapted from the German original at KlimaLounge.


Olivia Serdeczny is a scientist with the Potsdam Institute for Climate Impact Research in Germany.