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March 20th, 2010
In a recent post here at RealClimate, Simon Lewis wrote regarding a 2010 paper by Samanta et al. on the effect of single-year drought conditions on the Amazon. Samanta et al. claimed to have contradicted a 2007 paper by Scott Saleska et al., and to have thereby overturned some IPCC conclusions.
Lewis showed why Samanta’s paper did not contradict the IPCC, even if it may have correctly identified an error in Saleska et al. Now Saleska has written to say that, actually, Samanta et al.’s results do not identify any error in their work: the results agree completely. With our apologies for the journalistic whiplash, Simon Lewis and I are convinced he’s right. The more general point though, is that the the balance of evidence shows that the Amazon is sensitive to drought, and the IPCC’s statements about it remain valid.
Here is Saleska’s commentary in full
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March 15th, 2010
In the alternate universe of Fox News, Anthony Watts, and many others, up is down. Now, it appears, brown is green. Following the total confusion over the retraction of a paper on sea level, claims of another “mistake” by the IPCC are making the rounds of the blogosphere. This time, the issue is the impact of rainfall changes on the Amazon rainforest.
A study in 2007 showed that the forest gets greener when it rains less. A new study, by Samanta et al. in Geophysical Research Letters shows that the earlier work was flawed. Aided by an apparently rather careless press release, this is being used as evidence that the Amazon is less sensitive to rainfall changes than the IPCC claimed. But the Samanta et al. paper actually does not address the central questions at all. It only addresses whether a single anomalous rainfall year had an impact that is measureable and interpretable from a satellite sensor. The conclusion is that they could not detect a change. As noted in a commentary from Simon Lewis, University of Leeds, “the critical question is how these forests respond to repeated droughts, not merely single-year droughts.”
Lewis – a broadly published expert on tropical forests – makes a number of additional important points in his commentary below. Bottom line: IPCC gets it right as usual.
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March 16th, 2010
Those who can’t bear to believe that the laws of physics govern global temperature, still want to maintain that it’s a random walk. They base this on the fact that the ADF (Augmented Dickey-Fuller test) doesn’t reject the presence of a unit root, if you refuse to use the BIC (Bayesian Information Criterion) for model selection and you’re willing to ignore the Phillips-Perron unit root test.
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March 6th, 2010
The Institute of Physics (IoP) recently made a splash in the media through a statement about the implications of the e-mails stolen in the CRU hack. A couple of articles in the Guardian report how this statement was submitted to an inquiry into the CRU hack and provide some background.
The statement calls for increased transparency, and expresses concerns about the public confidence in science if the transparency is absent. The IoP statement, however, fails to note that the issue of transparency is far more general applicable than just to mainstream climate science. It should also involve the critics of climate change, as noted by New Scientist.
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March 6th, 2010
Methane is like the radical wing of the carbon cycle, in today’s atmosphere a stronger greenhouse gas per molecule than CO2, and an atmospheric concentration that can change more quickly than CO2 can. There has been a lot of press coverage of a new paper in Science this week called “Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf”, which comes on the heels of a handful of interrelated methane papers in the last year or so. Is now the time to get frightened?
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March 5th, 2010
Anthony:
It has now been independenly confirmed, by multiple persons, that my results regarding the impact of station dropout on global temperature are correct. Your claims, in your document with Joe D’Aleo for the SPPI, are just plain wrong.
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March 5th, 2010
I’ve finished processing the southern hemisphere GHCN data, and computed the temperature according to the simple procedure for the entire globe.
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March 3rd, 2010
There is an interesting letter in Nature Geoscience this month on what climate changes we have actually already committed ourselves to. The letter, by Mathews and Weaver (sub. reqd.), makes the valid point that there are both climatic and societal inertias to consider.
Their figure neatly demonstrates the different issues:
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March 1st, 2010
By now it’s clear to many readers that others have replicated my results. There’s even one at the blackboard.
Perhaps some industrious reader would consider it worthwhile to scour the net and find out just how often the results have now been confirmed. Then, of course, visit WUWT and ask Anthony Watts whether he’s willing to admit that the false claims in his document with Joe D’Aleo are wrong.
In the meantime, I’ll continue preparing for publication.
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February 25th, 2010
There’s a most interesting comment on Anthony Watts’ blog:
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February 25th, 2010
Two of the most prominent claims of global warming denialists have been proven wrong.
This raises two very serious issues. First, it’s certainly possible to “run the numbers” in order to check the truth or falsehood of their claims, but they didn’t bother to do so. I have. For them to make the claims they’ve made, without even doing the work require to find out, is fundamentally dishonest.
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February 25th, 2010
Two of the most prominent claims of global warming denialists have proven to be utterly false.
I’ve completed processing the GHCN data for the northern hemisphere. This project was undertaken to investigate two denialist claims: 1st, that the dramatic reduction in the number of reporting stations around 1990 introduced a false warming trend; 2nd, that the adjustments applied to station data also introduce a false warming trend.
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February 22nd, 2010
Steven Goddard doesn’t know when to quit. Sad.
But far more interesting than showing him the error of his ways, is to take a look at northern hemisphere snow cover. Here’s the weekly snow cover since satellite observations began:
and here’s the weekly snow cover anomaly:
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February 18th, 2010
Anthony Watts has a new post by Steven Goddard about northern hemisphere snow cover. There’s plenty of snow in the northern hemisphere right now — an exceptional amount. This last week saw the 2nd-highest weekly average ever recorded in the data available from the Rutgers University Global Snow Lab. As we’re well aware, an exceptional event doesn’t mean there’s a trend. But Steven Goddard thinks there is. He even shows this graph:
and tells us that wintertime snow cover is increasing at 100,000 km^2 per year.
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February 24th, 2010
A recent story by Fred Pearce in the February 9th online edition of the Guardian (“Victory for openness as IPCC climate scientist opens up lab doors”) covers some of the more publicized aspects of the last 14 years of my scientific career. I am glad that Mr. Pearce’s account illuminates some of the non-scientific difficulties I have faced. However, his account also repeats unfounded allegations that I engaged in dubious professional conduct. In a number of instances, Mr Pearce provides links to these allegations, but does not provide a balanced account of the rebuttals to them. Nor does he give links to locations where these rebuttals can be found. I am taking this opportunity to correct Mr. Pearce’s omissions, to reply to the key allegations, and to supply links to more detailed responses.
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February 23rd, 2010
Over the last few weeks or so the UK Guardian (who occasionally reprint our posts) has published a 12-part series about the stolen CRU emails by Fred Pearce that are well below the normal Guardian standards of reporting. We delineate some of the errors and misrepresentations below. While this has to be seen on a backdrop of an almost complete collapse in reporting standards across the UK media on the issue of climate change, it can’t be excused on the basis that the Mail or the Times is just as bad. As a long-time Guardian reader and avid Guardian crossword puzzle solver, I’m extremely unhappy writing this post, but the pathologies of media reporting on this issue have become too big to ignore.
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February 19th, 2010
Who says that the climate debate is not evolving? According to the daily newspaper the Guardian, a new application (‘app‘) has been written for iPhones that provides a list of climate dissidents’ arguments, and counter arguments based on more legitimate scientific substance. The app is developed by John Cook from ‘Skeptical Science‘. It’s apparently enough to have the climate dissidents up in arms – meaning that it’s likely to have some effect? Some dissidents are now thinking of writing their own app.
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February 16th, 2010
Suppose you have a child, a son — he’s 10. You want to know whether or not he’s growing normally, so every day you measure his height with a tape measure. You’ve done so since he was 5. You even plot the data on a graph, and notice two things about it. First: the measurements show a fair amount of jitter, sometimes they’re a wee bit higher, sometimes a wee bit lower, there’s noise in the data. Second: there’s also a trend. Your kid is a lot taller at 10 than he was at 5, in fact the trend over the observed time span is upward and reasonably steady. You even do a statistical analysis, estimate the growth rate, and determine that it’s definitely statistically significant — so it’s not a false trend due to noise in the data, it’s real. Your son is growing normally.
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February 16th, 2010
It won’t have escaped many of our readers’ notice that there has been what can only be described as a media frenzy (mostly in the UK) with regards to climate change in recent weeks. The coverage has contained more bad reporting, misrepresentation and confusion on the subject than we have seen in such a short time anywhere. While the UK newspaper scene is uniquely competitive (especially compared to the US with over half a dozen national dailies selling in the same market), and historically there have been equally frenzied bouts of mis-reporting in the past on topics as diverse as pit bulls, vaccines and child abductions, there is something new in this mess that is worth discussing. And that has been a huge shift in the Overton window for climate change.
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February 15th, 2010
One of the section titles in D’Aleo and Watts’s denialist document is “NO WARMING TREND IN THE 351-YEAR CENTRAL ENGLAND TEMPERATURE RECORD.” It comes from a site calling itself “carbon sense.” Only when you read the section do you discover that it only compares 100-year averages of the 20th century to the 18th century, and only for the summer season. In fact their entire case is just smoke and mirrors.
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February 15th, 2010
We’ve already critiqued the analytical skills of Joe D’Aleo and of course the incomparable Anthony Watts….. Incomparable.
They’ve joined forces to create a document which pretends to ask the question, “SURFACE TEMPERATURE RECORDS: POLICY DRIVEN DECEPTION?” but is really just a bunch of false claims intended to state outright that the surface temperature record is not just mistaken, it’s fraudulent.
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February 15th, 2010
Yesterday, the Daily Mail of the UK published a predictably inaccurate article entitled “Climategate U-turn as scientist at centre of row admits: There has been no global warming since 1995″.
The title itself is a distortion of what Jones actually said in an interview with the BBC. What Jones actually said is that, while the globe has nominally warmed since 1995, it is difficult to establish the statistical significance of that warming given the short nature of the time interval (1995-present) involved. The warming trend consequently doesn’t quite achieve statistical significance. But it is extremely difficult to establish a statistically significant trend over a time interval as short as 15 years–a point we have made countless times at RealClimate. It is also worth noting that the CRU record indicates slightly less warming than other global temperature estimates such as the GISS record.
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February 14th, 2010
Currently, a few errors –and supposed errors– in the last IPCC report (“AR4″) are making the media rounds – together with a lot of distortion and professional spin by parties interested in discrediting climate science. Time for us to sort the wheat from the chaff: which of these putative errors are real, and which not? And what does it all mean, for the IPCC in particular, and for climate science more broadly?
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February 13th, 2010
I’ve decided to average the GHCN station data in gridboxes which are 10 deg. latitude tall, and approximately the same width. That makes them 600 nautical miles tall, which is a bit over 1100 km. Within that range, we can expect that all stations which inhabit the same grid box will show correlation with each other. The exception to the “10 deg. tall” rule will be stations north of 70N latitude — instead of defining separate grid boxes for stations north of 80N latitude, I’ll lump them together with the stations north of 70N latitude.
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February 8th, 2010
On a non-climate note, I congratulate the New Orleans Saints for their victory in Super Bowl XLIV. It was a well-deserved victory for the underdogs, and is a source of pride for a city which still shows massive scars from the ravages of Hurricane Katrina.
We’ve already looked at a way to combine data from different locations to obtain a grid-wide average of station anomalies. In that post, I computed anomalies for each location then combined the anomalies. It’s also possible to combine raw temperature data, then compute anomalies for the grid averages. I also combined station records in a simple way, by starting with a “reference station” then adding one new location at a time, computing an offset to align it with existing data and then incorporating it into the average. But I’ve noted that this is not the “optimal” way, that optimally (in a least-squares sense) one would compute the offsets which give the minimum sum of squared differences between all stations.
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February 6th, 2010
Tomorrow is super bowl Sunday, the day of the championship game for American football. It’s the biggest sports day of the year in the U.S., and possibly the world (I really don’t know). For those outside the U.S., the contestants are the Indiannapolis Colts and the New Orleans Saints. I guess I’m rooting for Indiannapolis, but I won’t mind if the upstart Saints take the prize.
But the “grid” for this post is a geographical grid, the 5×5-degree grid box containing Skikda. We looked at the data from Skikda (in northeast Algeria), and we discussed how different data records from the same station can be combined into a single location record. Since that city is at Lat. 36.93N, Lon. 6.95E, let’s see what else is in the GHCN from 35 to 40 deg. N.Lat, from 5 to 10 deg. E.Lon.
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February 6th, 2010
How much additional carbon dioxide will be released to, or removed from, the atmosphere, by the oceans and the biosphere in response to global warming over the next century? That is an important question, and David Frank and his Swiss coworkers at WSL have just published an interesting new approach to answering it. They empirically estimate the distribution of gamma, the temperature-induced carbon dioxide feedback to the climate system, given the current state of the knowledge of reconstructed temperature, and carbon dioxide concentration, over the last millennium. It is a macro-scale approach to constraining this parameter; it does not attempt to refine our knowledge about carbon dioxide flux pathways, rates or mechanisms. Regardless of general approach or specific results, I like studies like this. They bring together results from actually or potentially disparate data inputs and methods, which can be hard to keep track of, into a systematic framework. By organizing, they help to clarify, and for that there is much to be said.
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February 4th, 2010
First of all, thanks to Scott Mandia for the link to the story of the duck. That sums up what denialists are doing. Plain and simple.
The very first data record in the GHCN (using the raw data, not the adjusted) is for Skikda in northeast Algeria near the Mediterranean Sea.
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January 30th, 2010
I stole the title from the Rabett. He posted an invitation to readers to put up links your mom would warn you away from. Naughty bunny!
Just to keep the blogosphere “fair and balanced” I’d like to invite readers to post links your mom would recommend. If you can hear her, in your mind’s ear, saying “Why are you looking at that? You should be reading (*blank*)!” Fill in the blank.
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January 29th, 2010
A quick post for commentary on the new Solomon et al paper in Science express. We’ll try and get around to discussing this over the weekend, but in the meantime I’ve moved some comments over. There is some commentary on this at DotEarth, and some media reports on the story – some good, some not so good. It seems like a topic that is ripe for confusion, and so here are a few quick clarifications that are worth making.
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January 19th, 2010
Like all human endeavours, the IPCC is not perfect. Despite the enormous efforts devoted to producing its reports with the multiple levels of peer review, some errors will sneak through. Most of these will be minor and inconsequential, but sometimes they might be more substantive. As many people are aware (and as John Nieslen-Gammon outlined in a post last month and Rick Piltz goes over today), there is a statement in the second volume of the IPCC (WG2), concerning the rate at which Himalayan glaciers are receding that is not correct and not properly referenced.
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January 17th, 2010
This is Hansen et al’s end of year summary for 2009 (with a couple of minor edits).
If It’s That Warm, How Come It’s So Damned Cold?
by James Hansen, Reto Ruedy, Makiko Sato, and Ken Lo
The past year, 2009, tied as the second warmest year in the 130 years of global instrumental temperature records, in the surface temperature analysis of the NASA Goddard Institute for Space Studies (GISS). The Southern Hemisphere set a record as the warmest year for that half of the world. Global mean temperature, as shown in Figure 1a, was 0.57°C (1.0°F) warmer than climatology (the 1951-1980 base period). Southern Hemisphere mean temperature, as shown in Figure 1b, was 0.49°C (0.88°F) warmer than in the period of climatology.
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January 19th, 2010
NASA GISS has released the estimated monthly temperature for December 2009, which closes out the year 2009, which closes out the decade of the 2000s. The result: 2005 is still the hottest calendar year, 2009 is the 2nd-hottest year ever, although it’s really in a statistical tie with 1998, 2002, 2003, 2006, and 2007.
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January 13th, 2010
RealClimate is run by a rather loosely organized volunteer consortium of people with day jobs that in and of themselves can be quite consuming of attention. And so it came to pass that the first I learned about Gavin’s interest in the work of Plass was — by reading RealClimate! In fact, David Archer and I have a book due to appear this year from Wiley/Blackwell (The Warming Papers), which is a collection of historic papers on global warming, together with interpretive essays by David and myself. Needless to say, we pay a lot of attention to the seminal work by Plass in this book. His 1956 QJRMS technical paper on radiative transfer, which is largely the basis of his more popular writings on global warming, was one of the papers we chose to reprint in our collection. In reading historic papers, it is easy to fall into the trap of assuming that investigators of the past are working on the basis of the same underlying set of assumptions in common use today. Through a very close reading of the paper, David and I noticed something about the way Plass estimated surface temperature increase, that Gavin and all previous commentators on Plass — including Kaplan himself — seem to have overlooked.
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January 13th, 2010
Chapter 8 of the IPCC AR4 report lists 23 computer models which contributed to the AR4 assessment. The output of those models is available from Climate Explorer, and for most of the models multiple ensemble member runs are available. Downloading the global average temperate data from the 20C3m (20th-century) and SRES-A1B experiments provides data for 118 runs of those 23 models. This enables us to compare the models’ global average surface temperature, as well as the average of all the model runs, to the observed global temperature according to NASA GISS (using anomalies on a 1980-2000 baseline):
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January 10th, 2010
I said on Friday that I didn’t think that Lindzen and Choi (2009) was obviously nonsense. Well, a number of people have disagreed with me, and in doing so, have presented some of the back story on the how the response was handled. I think this deserves to be more widely known in the hope that it will generate some discussion in the community for how such situations might be dealt with in the future.
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January 8th, 2010
The first published response to Lindzen and Choi (2009) (LC09) has just appeared “in press” (subscription) at GRL. LC09 purported to determine climate sensitivity by examining the response of radiative fluxes at the Top-of-the-Atmosphere (TOA) to ocean temperature changes in the tropics. Their conclusion was that sensitivity was very small, in obvious contradiction to the models.
In their commentary, Trenberth, Fasullo, O’Dell and Wong examine some of the assumptions that were used in LC09’s analysis. In their guest commentary, they go over some of the technical details, and conclude, somewhat forcefully, that the LC09 results were not robust and do not provide any insight into the magnitudes of climate feedbacks.
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January 8th, 2010
A recent paper by Lindzen and Choi in GRL (2009) (LC09) purported to demonstrate that climate had a strong negative feedback and that climate models are quite wrong in their relationships between changes in surface temperature and corresponding changes in outgoing radiation escaping to space. This publication has been subject to a considerable amount of hype, for instance apparently “[LC09] has absolutely, convincingly, and irrefutably proven the theory of Anthropogenic Global Warming to be completely false.” and “we now know that the effect of CO2 on temperature is small, we know why it is small, and we know that it is having very little effect on the climate”. Not surprisingly, LC09 has also been highly publicized in various contrarian circles.
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January 4th, 2010
Gilbert Plass was one of the pioneers of the calculation of how solar and infrared radiation affects climate and climate change. In 1956 he published a series of papers on radiative transfer and the role of CO2, including a relatively ‘pop’ piece in American Scientist. This has just been reprinted (as an abridged version) along with commentaries from James Fleming, a historian of science, and me. Some of the intriguing things about this article is that Plass (writing in 1956 remember) estimates that a doubling of CO2 would cause the planet to warm 3.6ºC, that CO2 levels would rise 30% over the 20th Century and it would warm by about 1ºC over the same period. The relevant numbers from the IPCC AR4 are a climate sensitivity of 2 to 4.5ºC, a CO2 rise of 37% since the pre-industrial and a 1900-2000 trend of around 0.7ºC. He makes a lot of other predictions (about the decrease in CO2 during ice ages, the limits of nuclear power and the like), but it’s worth examining his apparent prescience on these three quantitative issues. Was he prophetic, or lucky, or both?
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December 31st, 2009
Continuation of the open thread. Please use these threads to bring up things that are creating ‘buzz’ rather than having news items get buried in comment threads on more specific topics. We’ll promote the best responses to the head post.
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December 31st, 2009
It’s way too easy to look at data and think you see cycles. After all, if it went down, then up, then down, then up — it must be cyclic, right? The amount of analysis that goes into such conclusions is often limited to “Looks pretty cyclical to me.” Such “analysis” is tantamount to seeing a rock formation on Mars that looks vaguely like a face, and concluding that aliens constructed it millions of years ago as a message to future humanity.
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December 31st, 2009
Apparently Lucia thinks that my “estimation of uncertainty intervals without treating the effect of volcanic eruptions like Pinatubo as exogeneous is very misleading.” I’ve come to expect such foolishness from her; whenever she approaches the trend in temperature data, she reeks of desperation.
But if we do model some of the exogenous factors, we might get smaller uncertainties in our trend estimates. Yay! Let’s give that a try.
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