Category Archives: Paleoclimate

Matt Ridley and the Wall Street Journal misrepresent paper cited in Ridley column

Equilibrium climate sensitivity (ECS) evaluated from paleoclimatic data (PALAEOSENS group, Rohling et al., 2012).

There’s more to say about the latest attempt to deny the mainstream estimate of equilibrium climate sensitivity (e.g. NRC, 1979; Annan and Hargreaves, 2006; Knutti and Hegerl, 2008; Rohling et al., 2012) by Matt Ridley (remember him?) at the Wall Street Journal later. But I just wanted to point out something rather troubling about one of Ridley’s and Nic Lewis’s (the source of Ridley’s claims) citations.

Ridley claimed:

Some of the best recent observationally based research also points to climate sensitivity being about 1.6°C for a doubling of CO2. An impressive study published this year by Magne Aldrin of the Norwegian Computing Center and colleagues gives a most-likely estimate of 1.6°C.

I recalled the Aldrin et al. paper from the last time it made the rounds in the “skeptic” blogosphere, when Chip Knappenberger cited it as finding a “low” climate sensitivity.

The funny thing about the Aldrin et al. paper is that it really doesn’t find a “low” ECS at all. Their main result is an ECS of 2.0°C, which is completely consistent with the IPCC AR4 range. Moreover, they caution that their main result is incomplete, because it explicitly does not account for the effect of clouds:

When cloud behavior is included as another term, the ECS increases significantly, from ~2.5°C to 3.3°C depending on the values used:

Surely this wasn’t the Aldrin et al. paper Riddley and Lewis were citing as finding an ECS of 1.6°C.

The 1.6°C value literally never appears in the text of the paper.

Of course, it was entirely possible that Aldrin had published another paper on ECS this year finding 1.6°C that I was simply unable to find. I reached out to Bishop Hill and Matt Ridley for some clarification:

  1. thingsbreak
    @aDissentient Which Aldrin 2012 paper was Lewis citing on your blog?
  2. thingsbreak
    @mattwridley Can you provide either the title or the DOI for the Aldrin paper you cited in your WSJ piece? Thanks!
  3. aDissentient
    @thingsbreak Environmetrics 2012; 23: 253–271 Panel A of Fig 6.
  4. thingsbreak
    @aDissentient The one that finds an ECS of 2.5-3.3K when it bothers to account for clouds (4.8)? LOL.
  5. mattwridley
    @thingsbreak wattsupwiththat.com/2012/12… Aldrin, M., et al., 2012. Bayesian estimation of climate sensitiv… Environmetrics, doi:10.1002/env.2140.
  6. thingsbreak
    @mattwridley Did you personally read the paper? Where does the 1.6 number come from? Did you read section 4.8?
  7. aDissentient
    @thingsbreak Most likely values still only 2 ish. If we are to include cloud lifetime effect shld we include other highly uncertain effects?
  8. thingsbreak
    @aDissentient If you’re making a comparison to IPCC values, should use most apples-to-apples comparison, which Aldrin et al. discuss in 4.8.
  9. thingsbreak
    @aDissentient Where does the 1.6 value come from anyway? Literally doesn’t exist in paper.
  10. aDissentient
    @thingsbreak He got it by measuring the graph (It’s actually slightly lower I believe).
  11. mattwridley
    @thingsbreak lewis calculated it from aldrin’s paper’s data/charts and aldrin agreed it is correct
  12. thingsbreak
    @mattwridley Aldrin agreed that apples to apples comparison with IPCC ECS estimates is 1.6K? Doubtful. Directly contradicts paper itself.

I posted the following to Nic Lewis at Bishop Hill’s blog:

I think that some readers, and probably the authors of a paper themselves, might find it at least slightly misleading for you to claim findings on their behalf that the paper itself does not actually state.

The main result from Aldrin et al., as reported by Aldrin et al., is an ECS of 2.0°C. The authors caution that this result probably isn’t an apples to apples comparison to other ECS estimates due to the unaccounted for cloud term, and find that the value increases to ~2.5-3.3°C with clouds.

Rather than report either of these values, you simply claim Aldrin et al. “an impressively thorough study, gives a most likely estimate for ECS of 1.6°C…”.

Ridley likewse claims, “An impressive study published this year by Magne Aldrin of the Norwegian Computing Center and colleagues gives a most-likely estimate of 1.6°C.”

It would be easy for me to lob accusations of bad faith, as we don’t know each other and this is just the internet. Instead, I would encourage you, if your goal is to reach as wide an audience as possible, and try to make an impact beyond the “skeptic” and conservative blogospheres, to be more upfront about the scientific literature about ECS.

Ignoring the two main findings of a paper for values that you’re either estimating from a curve or are creating yourself based on data not used by the paper will be seen by at least some people to be misleading. Claiming that ECS cannot be estimated by paleo data is absurd, especially when so many are aware of efforts like the PALAEOSENS project and various paleoclimatic intercomparison groups.

I won’t attempt to read minds or divine motivations. I will simply suggest that what you have been doing thus far will cause some people to dismiss what you’re trying to say due to perceived dishonesty.

I hope you take this criticism in the constructive context in which it is being offered. There will be plenty of time for name-calling and insults later.

References:

  • Aldrin, M., M. Holden, P. Guttorp, R. B. Skeie, G. Myhre, and T. K. Berntsen (2012), Bayesian estimation of climate sensitivity based on a simple climate model fitted to observations of hemispheric temperatures and global ocean heat content, Environmetrics, 23(3), 253–271, doi:10.1002/env.2140.
  • Annan, J. D., and J. C. Hargreaves (2006), Using multiple observationally-based constraints to estimate climate sensitivity, Geophys. Res. Lett., 33, 4 PP., doi:200610.1029/2005GL025259.
  • Knutti, R., and G. C. Hegerl (2008), The equilibrium sensitivity of the Earth’s temperature to radiation changes, Nature Geoscience, 1(11), 735–743, doi:10.1038/ngeo337.
  • National Research Council (1979),  Carbon Dioxide and Climate: A Scientific Assessment. Washington, DC: The National Academies Press.
  • Rohling, E.J., et al. (2012), Making sense of palaeoclimate sensitivity, Nature, 491(7426), 683–691, doi:10.1038/nature11574.

A new LGM reconstruction, with implications for climate sensitivity

LGM Ice Sheet Extent from Clark et al., 2009

First off, it’s important to note that the paper has only appeared in CPD, it still has to pass review. However, I’m going to comment on the results for two reasons. Mundanely, I have a sliver of free time now, and I don’t know that the same will be true after the paper’s (presumed) eventual publication. More importantly, however, I think it’s safe to say that its results will be misinterpreted to the same or even a greater extent than Schmittner et al., 2011 (hereafter S11) was. The mainstream press largely ignored some potential reasons to be skeptical of that paper’s results (discussed by RealClimate and Skeptical Science among others, as well as by one of the paper’s authors in an interview with me at Planet 3.0). And of course the denialist echo chamber distorted the results ludicrously, going so far as to erase an entire portion demonstrating them to be consistent with the larger body of evidence on climate sensitivity (e.g. Knutti and Hegerl, 2008) and inconvenient to dismissals of the danger posed by unchecked GHG emissions.

With the throat clearing out of the way, here’s how things stand. Fyke and Eby (2012) offered some criticisms of S11. They objected to some of the proxy data used, and more importantly, pointed out that the model used (a version of the UVic model, which is more akin to simplified EMICs than GCMs) simply couldn’t produce realistic behaviors of key atmospheric processes which caused it to underestimate ECS:

[T]o explore the potentially large dependence of Schmittner et al.’s results on the choice of climate model, we carried out a new model simulation with the most recent version of the UVic ESCM in which the atmospheric latitudinal profile of heat diffusion varies in response to the global average atmospheric temperature anomaly (the “Mod” simulation in Fig. 2). This functionality gives a new model with much improved fit to both Antarctic and Arctic LGM temperatures as recorded by ice cores, yet still retains an excellent fit to low-latitude temperatures. Notably, and most importantly, we found that this model ranks very well with respect to the relative RMSE test, but with a much higher ECS (3.6°C) than similarly ranked models in (1). As suggested in (1), the lack of dust forcing in our LGM model may lower the equivalent ECS by ~0.3°C, but this is still well above the median ECS estimate of 2.3°C in (1).

Fyke and Eby’s revised LGM-derived ECS was quite similar to other LGM-based studies, such as Holden, et al. (2010). Criticism that the UVic model used had an atmospheric component that was perhaps insufficient to fully capture the climate state at the LGM was echoed in the RealClimate discussion as well as by coauthor Nate Urban in our interview.

Schmittner, et al. (2012) responded to Fyke and Eby by largely disagreeing with their discarding of some proxy records, but conceding that their model choice may well have led to underestimating ECS and uncertainty in their reconstruction:

This tentatively supports the conclusion in (1) that structural model uncertainties (in particular, formulations of atmospheric heat transport) may have led to systematic underestimation of ECS2xC in (2). Further study with new ensemble model experiments, including the modified heat flux formulation and LGM dust forcing, are necessary to quantify the effect of heat flux uncertainties on the best ECS2xC estimate.

Schmittner, et al. go on to suggest that further modeling be done to try to better test the effects of using more realistic models with their approach.

Several groups are doing that, or something very similar. One is Tamsin Edwards, who has teased her experiment but not revealed its results (yet). Another is Jules Hargreaves and James Annan, who discussed S11 and also teased their experiment some months back but likewise did not discuss their results.

Which brings us to today (or, technically, Wednesday). Annan and Hargreaves, 2012 (hereafter AH12) has been submitted to Climate of the Past – Discussion, and their results are now available. They used almost exactly the same proxy data as S11, but used a different model (in fact, an ensemble of the GCMs used in the PMIP2 project) and methodology to constrain the difference in climate between the present and the LGM. Their results share some similarities to S11 but also contain some differences.

AH12 use pseudo-proxy data to validate their reconstruction. Their fit to the proxy data is improved relative to S11 (correlation of 0.73 vs S11’s 0.53).

Figure 5: a) Validation with GCM-Generated Pseudo-Proxy Data and b) Fit to Proxy Data

One of the criticisms of S11 was that it found an LGM globally-averaged surface temperature that seemed awfully warm (areas where proxy data were available averaged a mere~2°C colder than more modern temperatures) relative to other estimates, which show an LGM nearly three times that cold (e.g. von Deimling et al., 2006). This warmer LGM was necessarily responsible for much of the difference in their ECS value vs. the “canonical” estimate of 3°C. The authors attributed much of this difference to the use of warmer MARGO SST data vs. older (and cooler) data, but that explanation might appear somewhat insufficient, as the PMIP2 models that best fit the MARGO data themselves had ECS estimates closer to 3°C (Otto-Bliesner et al., 2009). Another odd result of S11 was the large discrepancy between their land only and ocean only results.

AH12 find an overall cooling at the LGM of ~4°C. Their land only and ocean only data are somewhat different, but are much closer than S11’s and are consistent within their uncertainties:

Figure 1: LGM Surface Air Temperature Reconstruction

Figure 2: LGM SST Reconstruction

In some ways, this represents a validation of S11: it’s certainly warmer than previous estimates, and the warm SSTs do arise from the MARGO data rather than some problem with S11. In other ways, however, it’s a contradiction of S11 and a validation of consensus estimates: the IPCC AR4’s estimate for LGM cooling was 4-7°C, consistent with AH12 but not S11.

AH12’s LGM-derived ECS is where I anticipate the greatest amount of well-meaning misunderstanding as well as outright misrepresentation. Why? Because it’s low: 1.7°C (1.2-2.4°C).

But!

One of the criticisms of S11 I raised with Nate Urban in our interview was the problem of the asymmetry of climate sensitivity during different climatic states- i.e. climate sensitivity itself may be smaller at colder times than it is during warmer times. So hypothetically a perfect estimate of equilibrium sensitivity derived from data from the LGM might be significantly lower than a perfect estimate of ECS in a doubled-CO2 future due to the non-linearity of certain feedacks. While this asymmetry is by no means an unquestionably real phenomenon, there are some very good reasons to suspect it to be true (e.g. Crucifix, 2006; Hargreaves et al., 2007; Yoshimori et al., 2011). In fact, the authors of the MARGO SST data used by S11 themselves go out of their way to warn against mistaking an LGM-derived ECS as being comparable to 2xCO2 ECS for precisely this reason (Waelbroeck et al., 2009).

AH12 note this explicitly:

However, such a simplistic estimate is far from robust, as it ignores any asymmetry or nonlinearity which is thought to exist in the response to different forcings… The ratio between temperature anomalies obtained under LGM and doubled CO2 conditions found in previous modelling studies varies from 1.3… to over 2…

Therefore, a more apples-to-apples comparison (taking into consideration the asymmetry issue) of their findings to a doubling of CO2 might look more like 2.8°C, with a range of 1.56-4.8°C.

[All I've done is apply the average of asymmetry values (1.3-2) cited by AH12 to their central value of 1.7°C, while applying the low and high end asymmetry values to their lower and upper 95% CI values respectively. This is obviously meant to be illustrative of the difference taking asymmetry into account makes for 2xCO2 vs. LGM values rather than a rigorous quantitative exploration.]

This puts the 2xCO2 ECS inline with consensus estimates such as the IPCC AR4 GCM-only estimate of 3±1.5°C. Interestingly, some of the S11 authors, using the same UVic model but with instrumental rather than LGM paleo data, found broadly similar results for ECS (Olson et al., 2012).

I’m not claiming to show what AH12 “really” says about ECS, but rather making a general point that often gets overlooked in discussions of ECS estimates derived from colder climates. And it’s certainly possible that my not-even-back-of-the-envelope extrapolation of their LGM ECS into a 2xCO2 ECS is horribly misguided for some reason that I am as of yet unaware- but I’ve inquired, and will dutifully revise this post if there is.

More than anything, this is a place-marker in the event that the typical denialist spin cranks up as it has over papers in the past.

References:

  • Annan, J. D., and J. C. Hargreaves (2012), A new global reconstruction of temperature changes at the Last Glacial Maximum, Climate of the Past Discussions, 8(5), 5029–5051, doi:10.5194/cpd-8-5029-2012.
  • Clark, P. U., A. S. Dyke, J. D. Shakun, A. E. Carlson, J. Clark, B. Wohlfarth, J. X. Mitrovica, S. W. Hostetler, and A. M. McCabe (2009), The Last Glacial Maximum, Science, 325(5941), 710–714, doi:10.1126/science.1172873.
  • Crucifix, M. (2006), Does the Last Glacial Maximum constrain climate sensitivity?, Geophys. Res. Lett.33(18), L18701, doi:10.1029/2006GL027137.
  • Fyke, J., and M. Eby (2012), Comment on “Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum,” Science, 337(6100), 1294–1294, doi:10.1126/science.1221371.
  • Hargreaves, J. C., A. Abe-Ouchi, and J. D. Annan (2007), Linking glacial and future climates through an ensemble of GCM simulations, Clim. Past3(1), 77–87, doi:10.5194/cp-3-77-2007.
  • Holden, P., N. Edwards, K. Oliver, T. Lenton, and R. Wilkinson (2010), A probabilistic calibration of climate sensitivity and terrestrial carbon change in GENIE-1, Climate Dynamics, 35(5), 785–806, doi:10.1007/s00382-009-0630-8.
  • Knutti, R., and G. C. Hegerl (2008), The equilibrium sensitivity of the Earth’s temperature to radiation changes, Nature Geoscience, 1(11), 735–743, doi:10.1038/ngeo337.
  • Olson, R., R. Sriver, M. Goes, N. M. Urban, H. D. Matthews, M. Haran, and K. Keller (2012), A climate sensitivity estimate using Bayesian fusion of instrumental observations and an Earth System model, J. Geophys. Res., 117(D4), D04103, doi:10.1029/2011JD016620.
  • Otto-Bliesner, B. et al. (2009), A comparison of PMIP2 model simulations and the MARGO proxy reconstruction for tropical sea surface temperatures at last glacial maximum, Climate Dynamics32(6), 799–815, doi:10.1007/s00382-008-0509-0.
  • Schmittner, A., N. M. Urban, J. D. Shakun, N. M. Mahowald, P. U. Clark, P. J. Bartlein, A. C. Mix, and A. Rosell-Melé (2011), Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum, Science, 334(6061), 1385–1388, doi:10.1126/science.1203513.
  • Schmittner, A., N. M. Urban, J. D. Shakun, N. M. Mahowald, P. U. Clark, P. J. Bartlein, A. C. Mix, and A. Rosell-Melé (2012), Response to Comment on “Climate Sensitivity Estimated from Temperature Reconstructions of the Last Glacial Maximum,” Science337(6100), 1294–1294, doi:10.1126/science.1221634.
  • von Deimling, T. S., A. Ganopolski, H. Held, and S. Rahmstorf (2006), How cold was the Last Glacial Maximum?, Geophys. Res. Lett., 33(14), L14709, doi:10.1029/2006GL026484.
  • Waelbroeck, C. et al. (2009), Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum, Nature Geoscience, 2(2), 127–132, doi:10.1038/ngeo411.
  • Yoshimori, M., J. C. Hargreaves, J. D. Annan, T. Yokohata, and A. Abe-Ouchi (2011), Dependency of Feedbacks on Forcing and Climate State in Physics Parameter Ensembles, Journal of Climate, 24(24), 6440–6455, doi:10.1175/2011JCLI3954.1.

WUWT not even going through the motions of fact-checking any more

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.

Mann et al. 1999  was plotted along with other paleoclimatic reconstructions published between the TAR and the AR4:

IPCC AR4 Figure 6.10: Records of NH temperature variation during the last 1.3 kyr.

Etc.

Wegman plagiarism scandal heating up

 

Courtesy of Flickr user TalkMediaNews

 

I’ve been a little unsure how or when to discuss John Mashey’s and Deep Climate’s yeoman’s work on uncovering the depths to which Edward Wegman stooped in attempting to discredit the work of Mike Mann, Ray Bradley, and Malcolm Hughes.

But the ScienceFair blog at USA Today has posted on it, so it’s probably going to reach “mainstream” status soon. Wegman’s university is formally investigating him for plagiarizing (at the very least) Raymond Bradley.

I’m curious to see how far this will go. There’s certainly enough circumstantial evidence to consider investigating the full extent of Reps. Barton and Whitfield’s offices involvement in this farce.

For those of you who don’t have a clue what this is all about, DeSmog Blog has a good backgrounder here.

As an aside- many of the champions of the Wegman Report (e.g Steve McIntyre) took up Wegman’s claim “Method Wrong + Answer Correct = Bad Science” as a sort of incantation, chanting it as though it might somehow dispel the fact that reality appears to have a hockey-stick-shaped bias. I am sure that these same people will maintain their integrity and immediately disavow the Wegman Report and its conclusions.

—-

 

I’ve been an outspoken critic of Keith Kloor, but please give him deserved respect for at least covering this, unlike so many other “climate journalists”.

Videobreak: Rob Dunbar – The threat of ocean acidification

Tom Fuller’s climate misdirection at WattsUpWithThat, Part I

It seems that Anthony Watts has decided to give Tom Fuller the reigns at his denialist propaganda outlet, WUWT. Tom obliges with some retreads of “skeptic” arguments we’ve all seen before.

Yesterday, Fuller treated us to a little “polar bears aren’t threatened by anthropogenic warming” nonsense:

The polar bear has recovered strongly from the 1960s, and there are now about 25,000 of them. They congregate in subgroups geographically, and the status of those subgroups is not uniform–some are growing, some are declining some are staying the same.

But the bears are robust enough that the indigenous tribes of the North say that they have completely recovered, and want hunting restrictions lifted. Indeed, about 1,000 polar bears a year are killed by hunting, according to The Polar Bear Specialist Group. And simple arithmetic showed that polar bears survived warmer periods than today that almost certainly included eras when Arctic ice was completely gone.

So the issue is ultimately an unfortunate distraction. The Arctic is warming. Polar bears are doing okay. And the point is?

I’ve addressed this canard previously in “The Age of Polar Bears”. Fuller’s argument amounts to little more than cherry picking and non sequitur. Polar bear populations have recovered somewhat from overharvesting since the 1960s, but remain threatened by numerous environmental stressors (harvest [hunting], contaminants, oil and gas development, and additional interactions with humans). Anthropogenic warming-induced loss of the sea ice from which these bears hunt- in combination with other stressors- presents a genuine threat. This is not the opinion of cynical environmentalists intent on “selling” the problem of global warming- this is the finding of the relevant scientific and regulatory communities.

Videobreak: Lee Hotz – Inside an Antarctic time machine

Project home at NHU here.

[h/t Ezra Klein]