The world’s most-viewed “skeptic” blog, ladies and gentleman.
- Liu, Y., J. R. Key, Z. Liu, X. Wang, and S. J. Vavrus (2012), A cloudier Arctic expected with diminishing sea ice, Geophys. Res. Lett., 39, L05705, doi:10.1029/2012GL051251.
Anthony Watts is desperately trying to spin the initial findings of the BEST re-examination of land-surface temperature data, which has absolutely obliterated his claims to “skeptic” fame (that UHI, station quality, station dropout, etc. are responsible for all or much of the warming in the official instrumental records). His latest misdirection is a regurgitation of an ignorant email blast from David Whitehouse/Benny Peiser, which is little more than creationist-level quote-mining:
The quote cited by Whitehouse/Peiser/Watts comes from the fourth BEST draft paper, “Decadal Variations in the Global Atmospheric Land Temperatures” (Muller et al., 2011).
The context of the paper is that BEST finds a high correlation between land surface temperature variability and the Atlantic Multidecadal Oscillation on interannual (2-15 years). They claim that this result is surprising:
Interannual to decadal variations in Earth global temperature estimates have often been identified with El Nino Southern Oscillation (ENSO) events. However, we show that variability on timescales of 2-‐15 years in mean annual global land surface temperature anomalies, Tavg are more closely correlated with variability in sea surface temperatures in the North Atlantic.
As an aside, I objected yesterday that I thought this was a little bit of a “bait and switch”- BEST is talking about land-only temps, whereas ENSO is the dominant source of interannual variability in global temps (due to its influence on SSTs).
In any event, the quote-mining by GWPF/WUWT comes from the following statement:
Since 1975, the AMO has shown a gradual but steady rise from -‐0.35 C to +0.2 C (see Figure 2), a change of 0.55 C. During this same time, the land-‐average temperature has increased about 0.8 C. Such changes may be independent responses to a common forcing (e.g. greenhouse gases); however, it is also possible that some of the land warming is a direct response to changes in the AMO region. If the long-‐term AMO changes have been driven by greenhouse gases then the AMO region may serve as a positive feedback that amplifies the effect of greenhouse gas forcing over land. On the other hand, some of the long-‐term change in the AMO could be driven by natural variability, e.g. fluctuations in thermohaline flow. In that case the human component of global warming may be somewhat overestimated.
Let’s make some things clear up front. The BEST paper does not actually look at the issue discussed in this paragraph. Rather, it looks at how AMO variance on 2-15 year timescales correlates to the land-only temperature record. In the BEST analysis, both are “cleaned” of any long-term signal, such as the anthropogenic warming trend.
To emphasize the decadal-‐scale variations, the long-‐term changes in the temperature records and oceanic indices were “pre-‐whitened.” This is a process to remove a large signal that is not being studied in order to reduce bias in the remainder. To do this, we fit each record (yearly data sets) separately to 5th order polynomials using a linear least-‐squares regression; we subtracted the respective fits, and normalized the results to unit mean-‐square deviation. This procedure effectively removes slow changes such as global warming and the ~70 year cycle of the AMO, and gives each record zero mean. The 12-‐month smoothing removes high frequency (e.g. monthly) changes. All of the remaining analysis in this paper is based on the pre-‐whitened temperature records and oceanic indices.
So BEST’s actual analysis does not in any way support the claim that”the human component of global warming may be somewhat overestimated”- it cannot by definition.
However, that does not mean that we can’t examine the question they raise. How large is the contribution of actual natural variability in the North Atlantic compared to the contribution of anthropogenic warming?
It’s important to note that the AMO is computed in such a way as to remove linear trends only. As such, the existence of a non-linear external trend like man-made warming of the ocean (including the North Atlantic) is going to show up in the AMO index as though it were internal variability, even though it’s obviously not.
This has led to some “skeptics” attempting to blame anthropogenic ocean warming on the AMO, thinking that the AMO is driving the changes in the global ocean rather than the other way around. Both Tamino and Zeke have had a go at showing why this is exactly backwards.
So how much of the temperature change in the North Atlantic is attributable to the AMO rather than man-made global warming? Ting et al., 2009 take up the question, first reviewing several methods of attempting to isolate the AMO from the global warming signal using observations alone:
Figure 2 shows the application of two of the previously proposed approaches designed to remove the forced signal associated with both anthropogenic and other natural (volcanic and solar) forcing from the total observed NASSTI, with the purpose of uncovering the internal component of the variability. The first commonly used method is to remove the linear trend from the observed North Atlantic SST index, as shown in Fig. 2a (e.g., Enfield et al. 2001; Sutton and Hodson 2005; Knight et al. 2006). This method assumes that the forced trend is linear and uniform over time. The linear detrending method suggests that the positive anomaly in NASSTI at the end of the twentieth century (0.4°C) is equally divided between the externally forced trend and the internal AMO variability (amplitude 0.2°C) and that the latter is currently at a peak state, similar to its state in the middle of the twentieth century. A second method is to use the global mean sea surface temperature as a proxy for the externally forced signal (Trenberth and Shea 2006; Mann and Emanuel 2006). When subtracting the global mean SST anomalies from the tropical North Atlantic SST to remove the forced signal, Trenberth and Shea (2006) concluded a predominant contribution from the anthropogenically forced warming to the total North Atlantic SST anomalies. In this study, we regress the two dimensional SST field on the time series of globally averaged SST (SSTg) and obtain an estimate of the internal component as the local difference between the total field and the regression pattern. The North Atlantic average of both the regressed NASSTI and the residual is shown in Fig. 2b. The regression method used here accounts for the fact that the forced SST is not uniform spatially, which differs from that used in Trenberth and Shea (2006).
Comparing Figs. 2a and 2b, one sees that the two methods imply considerable differences in the amplitude and temporal properties of the forced and internal variability. Unlike linear detrending, regression on the global mean SST implies that the positive NASSTI anomaly at the end of the twentieth century is largely due to the forced signal (~0.34°C) and only a small portion is caused by internal AMO variability (~0.06°C), consistent with Trenberth and Shea (2006). Furthermore, although linear detrending might suggest that theAMOis at its peak amplitude and that the internal variability in the next 2 decades would stay at the same amplitude or decrease, regression on the global mean SST suggests that the internal component of the AMO could cause even warmer north Atlantic SST in the coming years. Another commonly used measure of the anthropogenically forced variability is the global mean surface temperature (Tg), as shown in Fig. 2c. This method suggests an even weaker recent warming due to internal variability than when global mean SST is used, leaving the externally forced signal to explain almost all of the observed change during the late twentieth century. In addition to the difference in relative contribution to forced and internal components of NASSTI, the overall amplitude of the AMO is about 20% weaker using the global mean SST and global mean surface temperature as a proxy for forced trend.
And then using climate models:
To remove the model-based estimate of the forced change from the observed North Atlantic SST record, we averaged the six models’ forced changes…and subtracted it from the observed time series. The uncertainty in this estimate is represented by the spread generated when each model’s forced component is separately removed from the data (see Fig. 5b). The amplitude of the oscillation, to which we hereafter refer to as AMO, is between -0.3° and +0.2°C, which is comparable to the detrended NASSTI in Fig. 2a but larger than those in Figs. 2c and 2e. In terms of the phase of the oscillation, Fig. 5b indicates that theAMOso defined is similar to that using the global mean surface temperature or global mean sea surface temperature as the forced signal (and shown in Fig. 2).
[In other words, the black, dashed line in the second plot is the modeled AMO version of the computed AMO (blue and red) curve in the upper group of plots.]
Ting et al. demonstrate that while there is a range of methods available to examine the issue of how much AMO variability plays a role in addition to the anthropogenically forced (i.e. global warming) component of North Atlantic warming, there does appear to be a genuine AMO contribution- though of arguable size. However, Ting et al. are also clear that the AMO contribution is to variability, rather than to any long term trend:
The results presented here do not lead to dramatically different conclusions from the earlier studies dealing with the same issue. We believe, however, that our rigorous statistical analysis puts the claim that the North Atlantic displayed in the twentieth century an internal ‘‘oscillation’’ of considerable magnitude (compared to overall externally forced trend) on a more robust footing. We were also able to show that this internal variation led to sharp decadal changes in temperature, but due to its oscillatory nature these transitions led to an overall compensation on a century time scale.
In other words, the AMO is not driving long term North Atlantic ocean warming.
While the BEST analysis is interesting, it says nothing about the issue WUWT and GWPF claim it is supporting, and there is no evidence to support the hypothesis that the anthropogenic component of global warming is overstated, based on AMO data.
[First, congratulations to Robert Rohde, and the rest of the team that actually worked on the science end of the project. There are some outstanding issues that need to be resolved prior to calling the work a finished product, and I hope the BEST team addresses them.]
Was anyone outside of the “skeptic” blogosphere surprised by the findings that UHI, station quality, station drop out, etc. weren’t really affecting the surface record? I don’t think so. But there is a great deal of revisionist history going on, which I’ll get to in a moment. Speaking of revisionist history, though-
That Anthony Watts has done a complete 180 from his earlier pledge to accept the BEST results should surprise no one. His whining that the results have been released prior to review- given his entire “surface stations” project and his years of insinuating if not outright claiming that much of the instrumental warming was spurious- is the height of chutzpah. BEST is being transparent with their data and methodology, something that people (even WUWT regulars and “skeptic” true believers) fought tooth and nail to get Watts to do.
Roger Pielke Sr. was quick to attempt to downplay the BEST results by implying they were not independent of previous analyses. Perhaps Roger should have actually bothered to read the papers he was attacking. I guess it all depends what his goal was- to offer legitimate criticism, or provide Marc Morano with soundbites attacking BEST.
I agree with WMC that this changes basically nothing about my opinion of Muller himself. The charges that Muller grossly distorted the truth about the so-called “hockey stick” controversy, he doesn’t appear to really even understand basic aspects of climate science, etc. stand. My negative opinion of Muller stems not just from his current attempts to portray himself as single-highhandedly saving climate science from the “skeptics”, but go back to earlier encounters with him in paleo/geology literature. Let’s just say the dynamic of Muller trying to claim the mainstream has failed to account for something significant and Muller positioning himself as the tough truth-teller is nothing new. At least in this case Muller has the fortune of actually coming down on the correct side, something that can’t be said for his previous efforts.
Lastly, let’s talk for a moment about the furious backpedaling that’s happening in response to BEST. “Skeptics” over at Curry’s, WUWT, on social media sites like Reddit, etc. are falling all over themselves trying to claim that No True Skeptic actually denies that the Earth is warming. They’re claiming the BEST results are meaningless because they don’t actually address attribution.
To which I reply, “Bullshit.” A staggeringly large number of climate “skeptics” do in fact deny that the Earth is warming. A survey less than a month ago found that less than half (49%) of self-identified Republicans and even fewer (41%) self-identified Tea Partiers agreed that the Earth is actually warming.
No, the BEST papers do not directly address attribution, but neither did the myths that they (along with all the other analyses and data sets) exploded. Are we supposed to believe that “skeptics” weren’t claiming that all or much of the warming in the instrumental record was due to UHI, station siting, station drop out, etc.? Please.
If the “skeptics” want to pretend that they never claimed we weren’t warming as NASA GISS, Hadley-CRU, NOAA, et al. showed, and instead want to focus on the attribution of warming to human causes, so be it. I hope they don’t expect the rest of us to join them in their revisionism.
When the initial furor dies down, I’d like to discuss some of BEST’s interesting (as opposed to merely confirmatory) results.
I have been quiet of late in part because of real world obligations, and in part because I’ve been trying to do a little “communications outreach” at social media sites like Reddit. Over at their anything but skeptical “climate skeptics” sub-message board, a handful of people spam links from the same handful of denialist websites day after day (though some discussions are more productive than others). Today, I noticed a link from WUWT that was terrible even for Watts’s incredibly low standards. So much wrong packed into so few sentences. What follows is a brief fisking I undertook in the Reddit comments, that might be useful to anyone looking for a rebuttal.
It follows that temperatures must have been higher than those of today’s during that first settlement of Greenland which lasted from approximately 900 until the mid-1400s AD, when these settlements died out.
No. It follows that temperatures were probably warmer for longer than the modern period until recently, but it does not follow that the recent warming, which is unearthing the items described, has not exceeded the medieval warming of Greenland. And in fact, we can look at the Greenland ice core record to see that it has:
This plot was from the last time WUWT tried to promulgate BS about warmer than present Greenland temps, showing the GISP2 ice core and GRIP updates scaled to GISP values for the modern warming.
Yet the whole reason for the existence of the Intergovernmental Panel of Climate Change (IPPC)
The IPPC is it?
is to thrust upon the world’s population the idea that industrialisation in the West over the last 100 years and our profligate use of fossil fuels is producing a run-away heating of the planet
This is a strawman on several counts. We’re not worried about a “run-away” warming like that on Venus. We’re worried about changes to climatic norms that will prove more detrimental than the cost of limiting emissions to avoid those changes.
through the emission of greenhouse gases, mainly CO2, which unless checked will lead to [the planet’s] — and humanity’s — death.
I’d like to see the cite for that from any of the ARs. Again, strawman.
So the possibility that temperatures were higher in the past in any part of the world was a thorn in the sides of those Climatologists who are wedded to the whole idea of Anthopogenic Global Warming (AGW), also known as Climate Change.
Again, this is false. Warmer than present temperatures undeniably took place in Earth’s geologic past, this has no bearing on the reality of anthropogenic warming or its potential to disrupt climatic norms.
Unfortunately for them, an English Climatologist, Hubert H Lamb, first formulated the idea of a Medieval Warming Period (MWP) in 1965 and other surveys have found that this warming did not just occur in the northwestern hemisphere but was global (6).
Lamb’s maximum warming took place hundreds of years after (i.e. 1100-1300) the peak warming of the NH is now recognized to have taken place (prior to 1000).
The IPCC FAR curve, based on Lamb, along with the updated CET instrumental record in blue with the same 50 year smoothing (Jones 2009).
NH paleoclimatic reconstructions from Mann 2008, Moberg 2005, Ljungqvist 2010, and the NCDC instrumental record, courtesy of Zeke Hausfather at The Blackboard
Lamb did not believe that the Medieval Climate Anomaly (or “Medieval Warm Epoch” as he originally called it) was a period of continuous temporally and spatially coherent global warming, but rather that it was more pronounced in the Atlantic Northern Hemisphere. You can see Lamb’s own discussion of the subject here (note, I haven’t read the other contents of that page beyond verifying that the quotes from Lamb’s writings are correct and in context. I’m in a hurry and couldn’t find a publicly accessible version of Lamb’s texts. If the guy starts talking about Lizard people, disregard his comments and stick to what Lamb says).
Much like Lamb, modern paleoclimate scientists believe the MCA was characterized by a warm North Atlantic, giving rise to unusual warmth in Western Europe and Eastern North America. Like Lamb, they believe that the MCA was marked by cooling of much of the North Pacific and Asia.
Unlike Lamb, they have a wealth of paleoclimatic and physics-based modeling data that has only become available in past several decades. The MCA seems to have been dominated by persistent La Niña-like and positive NAO conditions, similar to but differing in origin and some specific consequences than Lamb’s proposed proximate causes.
But Dr David Darning (University of Oklahoma College of Earth and Energy) in his recent testimony to Congress (7) said ‘…I received an astonishing email from a major researcher in the area of climate change. It said “We have to get rid of the Medieval Warm Period”’
Where is this email? Why quote this “Darning” instead of the email itself?
Possibly because it’s an apocryphal quote, based on the innocuous comment by Phil Jones indicating a desire to reconstruct temps far back enough to capture the entirety of any MCA: “it would be nice to try to “contain” the putative “MWP”, even if we don’t yet have a hemispheric mean reconstruction available that far back”.
Note that “Darning” does not actually appear to exist, and this claim should be attributed to David Deming, apparently from back in 2006.
In 1998 a graph was produced by geophysicist Michael Mann, known as the Hock Stick Graph’, which managed to almost air-brush out of existence the Medieval Warming Period .
Mann et al. 1998 only went back ~600 years, and said nothing about the time of the MCA.
This was published in the eminent scientific magazine Nature and also in several places in the IPPC Report of 2001 and created a world-wide sensation. Here was proof positive the world was overheating and it was All Our Fault.
As has been pointed out exhaustively, the millennial NH reconstructions say very little on the issue of attribution, and indeed if you throw out all of our late Holocene reconstructions, that would have virtually no impact on the evidence for attribution of the present warming to human causes.
However, investigation of the graph by historians and climatologists who doubted the existence of global warming, brought criticism centred around the statistical method used and the associated computer programme. It was eventually called the most discredited study in the history of science
The author of this article was eventually called the dumbest person in the history of dummies. I was eventually called the tallest matador in all of Spain. Gee, this is fun!
and quietly dropped by the IPPC from the latest 2007 IPPC report for policy makers.
IPCC AR4 Figure 6.10: Records of NH temperature variation during the last 1.3 kyr.
[NOTE: Please see the update at the bottom of the post for a more detailed explanation]
The denialosphere and the ‘winger echo chamber would like you to believe that a weather station in Darwin, Australia is Undeniable Proof of Something Nefarious regarding the global temperature record. Their evidence is that the GHCN raw station data have been *gasp* adjusted.
Here is the “smoking gun” graph that is currently causing all of the pearl-clutching:
Don’t you see? The GHCN has taken the raw station data and adjusted them to create a false warming trend! In the words of the post’s author [frothing, breathless emphasis in original]:
indisputable evidence that the “homogenized” data has been changed to fit someone’s preconceptions about whether the earth is warming
Got that? Some nefarious individual or group responsible for the GHCN has deliberately and fraudulently inflated the Darwin station temperature record to produce warming, not based on what has actually been occurring but in order to buttress claims of global warming.
After all, if these kinds of adjustments were actually justified, you would see the warming reflected not just in the GHCN-globalwarmspiracy-adjusted data, but in the official station record as well!
What?! This can only mean one thing: BOM is in on it, too! The conspiracy is even bigger than we ever imagined.
Monday, like any other day, was a pretty miserable one to be a climate denialist.
As with Intelligent Design proponents (née Creation Science proponents, née Creationists), 9/11 Truthers, the anti-vax loons, et al., in order to give themselves the appearance of credibility, climate denialists have to simultaneously wrap themselves in the vestments of science while rejecting what the science actually says. It is, as you can imagine, an entirely unconvincing act.
The evidence that man-made processes, notably our emissions of greenhouse gases, are warming the planet and altering the climate has grown astoundingly in the 30 years since the National Academies of Science-commissioned Carbon Dioxide and Climate: A Scientific Assessment. Each week, evidence pours in in the form of primary scientific literature documenting the changes to our climate, their already-significant impacts on plants and animals, and so on. Calls to cut GHG emissions are heard from the science academies of nations around the world. There is, to put it mildly, a stunning lack of scientific evidence suggesting we should keep on as we are and expect no fallout.
Hence you get Serious Thinkers like Jonah Goldberg asserting that, despite a study’s lead author’s clear statement that his paper on sunspots has nothing to do with anthropogenic warming, we should in fact believe it has something to do with- and indeed undermines- our understanding of anthropogenic warming. There are only a few avenues open to denialists who seek to keep up the charade that they care about science: attempt to discredit the actual science and substitute their own bloggy version, champion studies that are tremendously flawed, clumsily misrepresent papers that don’t actually challenge the undeniable reality of anthropogenic warming, or some combination thereof.
Enter Kyle Swanson and Anastasios Tsonis.
Swanson and Tsonis have been exploring an apparent series of climatic regime changes (marked by the synchronization, coupling, and decay on multidecadal scales of naturally variable climate features) superimposed on the long term warming trend of the 20th century (e.g. here and here). They think that the existence of these regimes might better explain some features of the temperature record than the mechanisms usually invoked (e.g. mid-century cooling via sulfate production). Naturally, their hypothesis has been seized upon by a denialosphere desperate for anything that seemingly challenges the mainstream on global warming (e.g. here, here, here, etc.) and touted as evidence that “the science isn’t settled”, “nature not humans controls the climate”, and similar rubbish. Thus Swanson and Tsonis became a sort of fig leaf behind which the denialists sought to conceal their anti-science beliefs.
For its part, the reaction from the larger climate science community has been along the lines of, “interesting, but absent any physical explanation, not entirely convincing at the present” and it was repeatedly pointed out that Swanson and Tsonis’s work wasn’t saying anything like what the denialists imagined it to. In the interests of clarifying some misconceptions, RealClimate recently hosted a guest post by Swanson. There, Swanson points out that those attempting to use any findings of increased influence of natural variability over the 20th century as a rebuttal to concerns over enhanced greenhouse warming couldn’t be more wrong; a climate system more sensitive to natural variability is one also that will respond more strongly to anthropogenic forcing:
A climate that is highly sensitive to radiative forcing (i.e., responds very strongly to increasing greenhouse gas forcing) by definition will be unable to quickly dissipate global mean temperature anomalies arising from either purely natural dynamical processes or stochastic radiative forcing, and hence will have significant internal variability. The opposite also holds.
In a new paper published this week in the early edition of the journal PNAS entitled Long-term natural variability and 20th century climate change (or here), Swanson and Tsonis, along with coauthor George Sugihara (from here on “SGT”), have attempted to address more explicitly the mechanism by which this enhanced natural variability hypothesis might work and its impact on the 20th century temperature record.
In the paper, SGT make a point to highlight the same argument made by themselves and others in response to specious (denialist) claims that their findings mean anthropogenic warming is as a result less of a concern:
Viewed in this light, the lack of modeled compared to observed interdecadal variability may indicate that current models underestimate climate sensitivity.
Reiterating that a climate system highly sensitive to natural variability is one also that will respond more strongly to anthropogenic forcing. A higher climate sensitivity would mean, for example, that the IPCC estimates of ~3°C warming in response to doubled CO2 are too optimistic. Continue reading