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Antarctic warming is robust

Filed under: — gavin @ 4 February 2009

The difference between a single calculation and a solid paper in the technical literature is vast. A good paper examines a question from multiple angles and find ways to assess the robustness of its conclusions to all sorts of possible sources of error — in input data, in assumptions, and even occasionally in programming. If a conclusion is robust over as much of this as can be tested (and the good peer reviewers generally insist that this be shown), then the paper is likely to last the test of time. Although science proceeds by making use of the work that others have done before, it is not based on the assumption that everything that went before is correct. It is precisely because that there is always the possibility of errors that so much is based on ‘balance of evidence’ arguments’ that are mutually reinforcing.

So it is with the Steig et al paper published last week. Their conclusions that West Antarctica is warming quite strongly and that even Antarctica as a whole is warming since 1957 (the start of systematic measurements) were based on extending the long term manned weather station data (42 stations) using two different methodologies (RegEM and PCA) to interpolate to undersampled regions using correlations from two independent data sources (satellite AVHRR and the Automated Weather Stations (AWS) ), and validations based on subsets of the stations (15 vs 42 of them) etc. The answers in each of these cases are pretty much the same; thus the issues that undoubtedly exist (and that were raised in the paper) — with satellite data only being valid on clear days, with the spottiness of the AWS data, with the fundamental limits of the long term manned weather station data itself – aren’t that important to the basic conclusion.

One quick point about the reconstruction methodology. These methods are designed to fill in missing data points using as much information as possible concerning how the existing data at that point connects to the data that exists elsewhere. To give a simple example, if one station gave readings that were always the average of two other stations when it was working, then a good estimate of the value at that station when it wasn’t working, would simply be the average of the two other stations. Thus it is always the missing data points that are reconstructed; the process doesn’t affect the original input data.

This paper clearly increased the scrutiny of the various Antarctic data sources, and indeed the week, errors were found in the record from the AWS sites ‘Harry’ (West Antarctica) and ‘Racer Rock’ (Antarctic Peninsula) stored at the SCAR READER database. (There was a coincidental typo in the listing of Harry’s location in Table S2 in the supplemental information to the paper, but a trivial examination of the online resources — or the paper itself, in which Harry is shown in the correct location (Fig. S4b) — would have indicated that this was indeed only a typo). Those errors have now been fixed by the database managers at the British Antarctic Survey.

Naturally, people are interested on what affect these corrections will have on the analysis of the Steig et al paper. But before we get to that, we can think about some ‘Bayesian priors‘. Specifically, given that the results using the satellite data (the main reconstruction and source of the Nature cover image) were very similar to that using the AWS data, it is highly unlikely that a single station revision will have much of an effect on the conclusions (and clearly none at all on the main reconstruction which didn’t use AWS data). Additionally, the quality of the AWS data, particularly any trends, has been frequently questioned. The main issue is that since they are automatic and not manned, individual stations can be buried in snow, drift with the ice, fall over etc. and not be immediately fixed. Thus one of the tests Steig et al. did was a variation of the AWS reconstruction that detrended the AWS data before using them – any trend in the reconstruction would then come solely from the higher quality manned weather stations. The nature of the error in the Harry data record gave an erroneous positive trend, but this wouldn’t have affected the trend in the AWS-detrended based reconstruction.

Given all of the above, the Bayesian prior would therefore lean towards the expectation that the data corrections will not have much effect.

The trends in the AWS reconstruction in the paper are shown above. This is for the full period 1957-2006 and the dots are scaled a little smaller than they were in the paper for clarity. The biggest dot (on the Peninsula) represents about 0.5ºC/dec. The difference that you get if you use detrended data is shown next.

As we anticipated, the detrending the Harry data affects the reconstruction at Harry itself (the big blue dot in West Antarctica) reducing the trend there to about 0.2°C/dec, but there is no other significant effect (a couple of stations on the Antarctica Peninsula show small differences). (Note the scale change from the preceding figure — the blue dot represents a change of 0.2ºC/dec).

Now that we know that the trend (and much of the data) at Harry was in fact erroneous, it’s useful to see what happens when you don’t use Harry at all. The differences with the original results (at each of the other points) are almost undetectable. (Same scale as immediately above; if the scale in the first figure were used, you couldn’t see the dots at all!).

In summary, speculation that the erroneous trend at Harry was the basis of the Antarctic temperature trends reported by Steig et al. is completely specious, and could have been dismissed by even a cursory reading of the paper.

However, we are not yet done. There was erroneous input data used in the AWS reconstruction part of the study, and so it’s important to know what impact the corrections will have. Eric managed to do some of the preliminary tests on his way to the airport for his Antarctic sojourn and the trend results are as follows:

There is a big difference at Harry of course – a reduction of the trend by about half, and an increase of the trend at Racer Rock (the error there had given an erroneous cooling), but the other points are pretty much unaffected. The differences in the mean trends for Antarctica, or WAIS are very small (around 0.01ºC/decade), and the resulting new reconstruction is actually in slightly better agreement with the satellite-based reconstruction than before (which is pleasing of course).

Bayes wins again! Or should that be Laplace? ;)

Update (6/Feb/09):The corrected AWS-based reconstruction is now available. Note that the main satellite-based reconstruction is unaffected by any issues with the AWS stations since it did not use them.

375 Responses to “Antarctic warming is robust”

  1. 251
    Rod B says:

    Ray, “solid theory” and incontravertible evidence” are of course subjective phrases that can be determined by whatever a person’s thinks of any particular aspect.

  2. 252
    Hank Roberts says:

    Well, Rod, your task of filling up the Antarctic Warming thread with tempting off topic posts, and encouraging others to reply to you, is going along well. Past 250 responses now, and the substantive ones have about tapered off to zero.

    What was it you were here to accomplish?

  3. 253
    Ray Ladbury says:

    Rod B., No, actually, solid theory is quite well defined in science (e.g. based on principles accepted by the vast majority of experts), as is incontrovertible evidence (e.g. >90% CL). Once again, you are in denial about this one subject–but that is a subject for psychology, not physics.
    I am disappointed that you seem to have given up all pretense of trying to understand the science, Rod. Your emphasis now seems to be to divert conversation away from the hard subjects and onto semantic controversies that you find less taxing. A pity.

  4. 254
    Jim Galasyn says:

    Rod, thermodynamics is not Derrida. Before humans burned the coal and petroleum, Earth was in radiative equilibrium with space.

    Humans abruptly added 500 gigatons of carbon to the atmosphere in the form of “heat-trapping” gases. Earth is now is radiative disequilibrium with space. For Earth to return to equilibrium, the atmosphere must warm. There is ample evidence that abrupt warming is very bad for the biosphere.

    Do you disagree?

  5. 255

    It’s also listed in my Webster’s of 1956 — don’t know what’s wrong with yours. “Denialist” is in none.

    Is ‘absolutist’ in there?

  6. 256
    Rod B says:

    Hank, just trying to toss a little reality out there. Most of the subthreads I participated in were more or less on topic, and, as you say, those have about tapered off to zero. I started none of the subthreads, though depending on your interpretation it might be said I began the OT “denialist” arguement. That one probably didn’t deserve anything beyond my initial post #219 — not much more than a simple observation, but its reality seemingly made everyone mad.

  7. 257
    Sekerob says:

    Okay, following Hank’s lament, a semi try to get back to the south pole region… Yesterday opposed to what I wrote a few days ago, the Antarctic Summer Sea Ice Area was 1.2-1.3 million below same time last year. Minimum calculated from the NCDC data occurs on average Feb-21-26, normally, so another week or more of melt is to be expected and from the NSIDC chart not out with reasonable expectation.

    Last big minimum occurred in 1993 and wonder what drove the growth / recovery since. Was it increased precipitation, snow, thus more incoming water vapor on land and sea ice? Has the Antarctic now reached a tipping point too where the additional precipitation is overwhelmed by further (air) temperature rise? The SST maps indicate a mix of warmer and cooler bordering ocean regions

    So, taking the Antarctic temperature history of recent decades, is sea ice acreage and volume (if there is such data) a good supporter of the Antarctic Temperature trend analysis’ robustness?

  8. 258
    Vernon says:


    I have read some work done by Ryan O about this study and he raised some questions that seem relevant to me. In that light, I have some questions so that I can better understand the paper.

    For Table S1, why was 40% complete calibration information picked for the cutoff?
    Why are stations that do not meet the 40% data cut off: Enigma Lake, LGB20, LGB35, Larsen Ice Shelf, and Nico included?

    Why are stations that exceed the 40% data cut off: Byrd, Mt. Siple, pre-correction Harry excluded? If it was because they did not show enough verification skill then how could they be used to show a correlation in Table S2?

    While AWS recon and AVHRR have trends seem similar 1957-2007, this is not the complete picture. AVHRR shows warming from 1980 – 2006 and AWS shows no warming (basically flat) from 1980 – 2006. The trend prior to 1980 was created by RegEM using manned data so is the same for both AWS and AVHRR. It appears that AWS benchmark does not provide the needed certainty.

    Thanks for your time.

    I now have some additional questions. Dr. Steig says that he used the original Schneider code while the article says that he used the modified Rutherford-Mann adapted code. Which is it and if it is the Rutherford-Mann adapted code, where can that be found?


    [Response: You are probably going to have to wait until Eric gets back for most of these kinds of questions. But the code used is the code on Tapio Schneider’s website (using the TTLS options as described). Any decisions on what cut-offs get applied in a Table are always a balance between including enough data to be meaningful while avoiding adding noise. The caption says that the included stations have > 40% data in the calibration period (pre 1995) and verification scores greater than the cut off. The logic would imply that those not included didn’t make one or other of the criteria. – gavin]

  9. 259
    Chris says:

    David (249) – thanks for the link. I knew that it had to be wrong, but I thought Will must have misinterpreted something. I couldn’t believe that he would just make it up–he’s conservative but not really of the Limbaugh/Hannity/Savage type. But as far as I can tell, that is exactly what he did.

    Of course, he did say in his previous column (“How Congress Trumps Darwin”) that the Endangered Species Act is an attempt by Congress to fix evolution: apparently he thinks that species extinctions from dam building, deforestation, and so forth are examples of natural selection. So I suppose that not too much is to be expected.

  10. 260
    William says:

    #215 dhogaza
    Regarding the discussion about bird/animal/plant ranges. To the extent that climate varies in cycles ice age to ice age, can someone define here what the “normal” ranges should be for the species you are discussing for this period of time mid way between ice ages? For simplification perhaps you can start with one species and compare where they range today and where they are supposed to be if there were 100ppm less of CO2 in the air.

  11. 261
    Rod B says:

    Ray (253), no, I fully agree that “solid theory”, etc. is properly defined. I said that deciding if this or that is actually solid evidence is a subjective process.

    I post contrary/skeptic comments on the science if 1) I actually have an opposing view on this or that aspect (a minority of the science posts — I do not disagree with any and all of the science as many here stupidly claim that skeptics do), and 2) if I have at least some basic level of understanding in that aspect. Occasionally I simply ask clarifications. I do occasionally, as you aver, comment tangentially on posts because they are exaggerated, hyperbolic or outrageous, sometimes directly related to the science (your “best known science” comment on another thread being directly related and exaggerated, IMO), sometimes not. The latter I try to limit but find it difficult to pass up sometimes. Ironically, the latter seems to generate vociferous and voluminous responses — much more than I would deem necessary — and can take an undue share of a thread. I do need to even better limit myself here.

  12. 262
    Chris S says:

    #260 William

    Perhaps a more immediate (and economically “interesting”) examination of range change can be found by looking at the recent spread of outbreaks of bluetongue virus (see here: ). (For further commentary see the Institute of Animal Health website here: ). I’d be interested in your thoughts.

  13. 263
    Hank Roberts says:

    William, your question has many assumptions, not useful ones.

    A animals aren’t “supposed” to be anywhere in particular.

    A “species” isn’t a rigid definition over geological time.

    Population genetics is the place to start looking for adaptation over time; the current problem is the rate of change being far greater than anything in the past, and the impediments to adaptation also being enormous.

    You’re asking about ecological change, and ecology doesn’t work with “one species” at a time either — changes occur in the frequency of genes in populations, in the mix of populations in an area, in the timing of their interactions.

    And we know how fast ecology changes while holding complex relations together — about as fast as the ice moved, in the areas where glaciation happened, most of the time, but look at the mammoths found frozen with stomachs full of green plants. They turned the wrong way during one blizzard, probably, and crossed a line, and died.

    Rate of change is what matters for life on the planet, and we’ve pushed the rate of change beyond what has happened in the past except in the previous great extinctions. We’re in the middle of a great extinction now.

    Ther is no ‘normal’ or ‘should’ about how life works.

  14. 264
    Hank Roberts says:

    Sekerob, thanks for the pointer to the Arctic ice.
    Do we have a topic for that currently? It’s time, again.

  15. 265
    James says:

    William Says (16 February 2009 at 11:53 AM)

    “…can someone define here what the “normal” ranges should be for the species you are discussing for this period of time…”

    You’re missing the point. “Should be” doesn’t enter into the discussion at any point. The operative words are “were” and “are”. The study examines historic ranges of numerous species. Those ranges WERE such & such, and now ARE some distance further north. Observational evidence, from which it’s possible to draw the fairly obvious conclusion that the northward shift is due to warming.

  16. 266
    William says:

    Interesting indeed. The studies you cited had a very limited time span and made no conclusions as to whether the movement of this virus was un-natural based on the climate we are experiencing at this stage in time between the previous glacial period and another that may begin thousands of years from now. Neither describes whether the virus made similar incursions in the recent past of 1-2000 years ago when there may have been similar warmings. It may be that the huge changes in European land use humans have made over the last 1000 years may also be a factor.

  17. 267
    Mark says:

    William #260, what about at the tail end of an ice age?

    We ain’t in the middle.

  18. 268
  19. 269
    Rod B says:

    Jim G.(254), Excessive temperature increase will affect the biosphere, but “abrupt” is dicey. I might be missing your point.

  20. 270
    Hank Roberts says:

    Rod, make a minimal effort, would you, to look this stuff up?
    There are whole topics here discussing that question.
    You’ll miss every point if you regularly question every word..
    And you’ll divert every thread by doing so. Consider your goals.

  21. 271
    Chris says:

    For anyone who might be curious about the source of the (off-topic) George Will quote (247), it appears to be this BBC News article; see the section headed “Rises ‘stalled'”.

    Will is taking out of context a sentence that was poorly written to begin with. All the WMO said was that 2008 (a La Nina year) would probably be cooler than 1998 (the big El Nino year, of course); but the BBC’s author misleadingly writes, “This would mean that temperatures have not risen globally since 1998 when El Nino warmed the world.”

    The author follows with some more sensible quotes from the WMO’s Michel Jarraud, but the damage is done.

  22. 272
    Jim Galasyn says:

    Rod, if I read you correctly, your only quibble with my statement is the use of “abrupt” to describe the climate response; you accept the basic thermodynamics.

    “Abrupt” changes in climate have occurred with large excursions in the planet’s carbon budget, typically from flood basalts, and on a time scale of millenia. Mass extinctions were the result.

    What’s happening today is on the time scale of decades, so maybe I should have said “ultra-abrupt.”

  23. 273
    William says:

    #254 Jim
    Hansen at Giss on Sept 2003 stated the following: ( “The enhanced GCM showed the world’s oceans were storing heat at a rate of about 0.2 W/m2 in 1951, and in the past 50 years, as atmospheric temperatures warmed, the rate of heat storage increased to about 0.75 W/m2, capturing more heat from the atmosphere. “This increase in ocean heat storage shows that the planet is out of energy balance,” Hansen said. “This energy imbalance implies that the atmosphere and ocean will continue to warm over time, so we will see continuing climate change.”

    However, if you look at ocean temperatures over the last 5-1/2 years since that statement there has been no significant heating of the oceans. Link here:

    It looks like at least for the last 5 years there has not been any “excess” heat to store. Perhaps we are back in equilibrium. Within another 10-200 years we should find out for sure.

  24. 274
    William says:

    I appreciate your comments. You may have supplied my answer in that “animals aren’t supposed to be anywhere in particular.” Animals seem to do fairly well surviving differences in 100 degrees between seasons by a variety of adaptations. I think that it is arguable that a half of a degree one way or another is the cause of a “great extinction”.
    I’d suggest that chopping down trees, draining swamps, rerouting rivers, paving over prarie, clearcutting or burning forests and hunting to extinction is a much clearer way of contributing to ecological change rather than trying to link that to 385ppm of CO2.

  25. 275
    Jim Galasyn says:

    William, if Earth were in radiative equilibrium with space, there would be no observed trend in atmospheric mean temperature.

    Because there is a robust upward trend, we can infer that Earth is not in equilibrium.

  26. 276
    Hank Roberts says:

    Sorry, William, picking a few words out of a pointer isn’t solving your problem. You really need to look this stuff up if you want to learn it. If you just want to play ‘arguable’ then you’re not doing science.
    Rate of change, rate of adaptation, ecological community, complexity.
    Migration, food availability, seasonality, warmth, day length.

  27. 277
    William says:

    Thanks for your comments and I acknowledge that I am not trying to do science within the short span of these comments. My argument is that species extinction is continuing unabated as a result of human activities completely unrelated to CO2 production. I cannot recall a species having been declared extinct from an increase in 100ppm of CO2 nor a .5C increase in temperature over the last 160 years. Zoologists can point to hundreds of extinct species and many more endangered species that are directly a result of the negative impact of humans on their environment. I’ve read the same warnings that say IF CO2 doubles, or IF we burn all coal, or IF the icecaps melt, but for the silverback gorilla’s being eaten for meat their problems are a bit more immediate than worrying about it being a bit hotter a hundred years from now.

  28. 278
    Hank Roberts says:

    William, you understand strawman argument, you’ve set out some there.
    Why bother? What are you here to learn? CO2 is going to double and the ice caps are going to melt. Ocean pH is well along to an excursion.
    Sure, idiots with guns are more of a risk to the particular gorillas.

    What’s your reason for contributing to RC?

  29. 279
    Hank Roberts says:

    > look at ocean temperatures over the last 5-1/2 years

    William, good grief. You’re pulling stuff out of the dustbins, proclaiming you’ve found something brand new.

    The amount of debunking already done isn’t worth retyping into this thread where it’s off topic. You can look this stuff up.

    Think about what you know about trend detection.

  30. 280
    Dave Andrews says:


    The paid pros have time and staff to locate them and copypaste their talking points.”

    How does Gavin fit into this scenario then?

    [Response: Ummm….. not at all? – gavin]

  31. 281
    Jim Galasyn says:

    William, for an example of how changing climate can precipitate large-scale disasters, check out the well-timed new post, Bushfires and Extreme Heat in SE Australia.

  32. 282
    Ray Ladbury says:

    William, Google Golden tree frog or Harlequin tree frog.

  33. 283
    William says:

    I did a search on tree frogs as you suggested. And in about 15 minutes I did learn something. Climate change is not what is killing amphibians. Suggested causations for extinctions include: fungus carried by invasive species, hydroelectric projects, toxic chemicals and pesticides. Although climate is mentioned it’s the fungus brought in by invasive species that is killing the amphibians, not a half degree of temperature.

    “No evidence for precipitous declines of harlequin frogs (Atelopus) in the Guyanas”

    “The chytrid fungus is found throughout the world, possibly carried by invasive species such as bull frogs.”

    Lethal amphibian fungus ‘in UK’
    The American bullfrog (Rana catesbeiana) is native to the central and eastern US and parts of Canada. The UK colony was probably derived from animals kept as pets that escaped or were released.
    “If it does get into British species, it’s going to be very difficult to get rid of,” Dr Cunningham told the BBC News website. at:

    The Kihansi spray toad, a small toad that is virtually extinct in the wild after its habitat was destroyed by a hydroelectric project in Tanzania, only exists today, thanks to efforts by the Bronx Zoo, the Detroit Zoo in Michigan and the Toledo Zoo in Ohio, which are planning to reintroduce the species it to its native habitat.
    While climate change, habitat destruction and pollution are factors in their rapid disappearance, Pramuk says the main suspect is the onset of a deadly disease – the chytrid fungus – now found in frog populations around the world.
    So what can we do to help? “Live green,” says Pramuk. “Recycle, avoid using toxic chemicals and pesticides, and don’t purchase frogs caught in the wild.” at:
    Thanks for the suggestions.

  34. 284
    William says:

    With a little more research, google provides a dozen additional causes besides the chytrid fungus for declining amphibian populations: invasive plant, animal and fish species as predators, weed invasion, erosion, sedimentation of streams, habitat fragmentation, urbanization, dredging, conversion of wetlands, deforestation, pollution, Pet trade, consumption of frog legs as food and an increase in UV-B radiation at 30nm.

    In terms of overall habitat destruction, humans have altered nearly half of the Earth’s land mass over the past 150 years and could rise to 70% within 30 years.

    In addition, the decline in amphibian populations had already been recognized by the early 1980’s. GISS temperature anomolies were at or below zero up until about 1980. Any rise in temps occurred between 1980 and 2000 after many amphibian populations were in decline from one or many other causations.

  35. 285
    herbert stencil says:

    Re #278: “[William] What’s your reason for contributing to RC?”

    What a good question Hank. And what would your response be?? [edit]

  36. 286
    Ray Ladbury says:

    William, I said specifically to look for info on the golden tree frog. The evidence is quite strong there. None of the fungi were contributing factors there. You are either a poor reader or you are being disingenuous.

  37. 287
    Chris S says:

    #266 William
    Thanks for your comment, although I would note that neither link was a study rather they are reports. Unfortunately the second link seems to be dead at the moment but it did state that the virus has previously made only brief, sporadic appearances in Southern Europe. (indeed, according to SchwartzMellor et al in Preventative Vetinary Medicine Vol 87 (2008) pp 4-20 the most recent outbreaks of BT in Europe are further north than this virus has ever previously occurred anywhere in the world.)
    Whilst land-use could be a factor it has been suggested that the real limiting factors of this disease and its vector were winter temperature and the distribution of its primary vector. Purse et al (2005) found that its spread is due to “recent changes in European climate that have allowed increased virus persistence during winter, the northward expansion of Culicoides imicola, the main bluetongue virus vector, and, beyond this vector’s range, transmission by indigenous European Culicoides species” ( )
    For further studies see: , and elsewhere.

    A further question to you – what factors do you think keep tropical diseases in the tropics?

  38. 288
    Sekerob says:

    Chris S., Gee, why’s malaria not prevalent in Europe, where it was common even not far from the place I live and not a century ago?

  39. 289
    Sekerob says:

    With my previous comment… only in 1970 was Italy declared Malaria free and now:

    Climate change brings malaria back to Italy

  40. 290
    Nick Gotts says:

    You say “climate change is not what is killing amphibians”, but one of the source you cite in your support says, specifically:
    “While climate change, habitat destruction and pollution are factors in their rapid disappearance…”
    Multiple causation is common in complex systems. A lot of denialists seem to have problems with it.

  41. 291
    Chris says:

    Not to be a pest about this (247, 271), but I’ve posted a blog entry on the George Will column. Since I’m not a professional (or even a scientist), I’d appreciate any comments or corrections, either here or on my blog.


    [Response: See also – gavin]

  42. 292
    Mark says:

    Nick, #290. Although it’s hard to tell which way it goes, they seem to have a problem with multiple causation all over the shop.

    I.e. when it comes to what’s causing it, there are two sorts of denialist

    Type A: “It’s the SUN!!!!”
    Type B: “Huh, so you don’t think the sun could be the cause???”

    Type A has a problem with multiple causation. They see the sun as the sole source of heating. Multiple causation is impossible or merely invisible. Though they ought to be the sort that Type B are complaining about:

    Type B thinks that the climate science community has never considered that there is ANY OTHER cause for warming than antropogenic global warming, mistaking the number one cause for the ONLY cause. That is what the Type A denialist would say if they were pro-AGW, but this blindness to multiple causation seems to be a denialist thing.

  43. 293
    Chris S says:

    #288 Sekerob
    Malaria was present (though not common) in Europe through both the MWP and the Little Ice Age – at least if the clinical diagnoses of mediaeval reports are correct. Furthermore, there were outbreaks right up until 1880 & beyond (including a minor one just after WWI). Malarial outbreaks tailed off (during a warming phase) mainly due to: continued drainage of wetlands for agriculture – thus destroying the vector’s habitat; an increase in livestock providing altrnative blood sources for the vector; reduction in rural populations & improvement in buildings reducing the availability of human hosts.

  44. 294
    Mark says:

    Will says: “With a little more research, google provides a dozen additional causes besides the chytrid fungus for declining amphibian populations”

    But you do now admit that climate change has caused another additional plague for the species.

  45. 295
    Sekerob says:

    Great Chris S, so after reading up on what you did not know before you found yourself one answer why tropical diseases are concentrated in the tropics… but now Dengue and West Nile are moving up too and a few more.

  46. 296
    Chris S says:

    #295 Sekerob
    What part of that did I not know?* I’m aware that vector distribution is a major limiting factor in tropical diseases and the recent outbreak of WNV in the US is illustrative of that. In addition it’s worth keeping an eye out for Chikungunya, African Horse Sickness, Usutu virus and Tick-borne encephalitis (louping ill) arriving in Europe soon as their vectors undergo range expansion along the same lines as Culicoides imicola.

    (*I should note that I am an entomologist with interest in Arboviruses and their vectors)

  47. 297
    William says:

    #285 Herb Thanks for your inquiry but I believe the discussion here is restricted to scientific topics not why I am interested in discussing impending frog extinctions.
    #290 Nick I dont understand your point in calling me a denialist. I’m not a scientist. However, Feynman stated in 1969 that “Science is the belief in the ignorance of experts” and other contributors to this site much smarter than I am have already pointed out that “any scientist outside his known specialty is just another commentator”.

    Ray #286 Although you do not say so explicitly you must be referring to the Alan Pounds Study published in Nature in 2006. Other experts in the field do not agree with Pounds conclusions:
    “Most experts agree that the disease-causing chytrid fungus Batrachochytrium dendrobatidis is taking a terrible toll on frogs and toads. One in three species worldwide is threatened with extinction.
    “There seems to be convincing evidence that chytrid fungus is the bullet killing amphibians,” said University of South Florida biologist Jason Rohr, lead author of the study, published in a recent issue of the journal Proceedings of the National Academy of Sciences. “But the evidence that climate change is pulling the trigger is weak at this point.”
    Beer to Blame? Rohr and colleagues don’t completely discount the role of global warming in amphibian declines. But they say decades of data show only that some correlation exists between rising air temperatures and Latin American amphibian extinctions—and that data are well short of proving causation.
    In fact, the researchers found that, in the Latin American countries they studied, beer and banana production were actually better predictors of amphibian extinctions than tropical air temperature.
    While beer and bananas are certainly not to blame, the whimsical comparison makes a point.
    “We can’t jump to conclusions of causality based on a correlation—especially when we’re talking about 60 or 70 species,” Rohr said.”

    Pounds is touting the Gold Tree Frog as the first species extinction linked to global warming but until the frog experts agree we’ll have to agree to disagree.

    After a little further research, the cloud cover mechanism pounds suggests is questionable:
    Ellis et al. (2004) provides a global map of cloud cover trends from 1987-2001, which includes the period of maximum amphibian extinction. If you look at the study area of Pounds et al., Ellis found no change in cloud cover in that region during the period 1987-2001.
    Ellis T.D., et al., 2004. Evaluation of cloud amount trends and connections to large scale dynamics. 15th Symposium of Global Change and Climate Variations, Paper No. 5.7, American Meteorological Society.

    [Response: No more frogs on an Antarctic thread. Please stay focused people. – gavin]

  48. 298
    William says:

    #293 Chris
    Habitat destruction, such as draining swampland for agricultural use has been cited as one of the factors putting pressure on amphibian populations such as frogs.

  49. 299
    Sekerob says:

    Chris S. #296

    So the question “what factors do you think keep tropical diseases in the tropics?” was rhetoric?

    Some of these diseases came along to any country that has a seafaring history doing Africa/Asia, irrespective of LIA or MWP climate state.

  50. 300
    Rod B says:

    Nick Gotts (290), “…are factors in …” is the phrase often used to get someone to infer a cause that otherwise has little correlation.