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A Treeline Story

Filed under: — Ray Bradley @ 17 November 2009

Some of the highest growing trees in the world are also the oldest—bristlecone pines (Pinus longaeva) from the Great Basin in the western United States (eastern California, Nevada and Utah). The oldest example is more than 4800 years old. Because of their longevity and growth at high elevations (where the growth of trees is generally known to be limited by temperature) bristlecone pines have been of particular interest to dendroclimatologists (paleoclimatologists who study tree rings to reconstruct past climate). Numerous ecological studies carried out at treeline sites all over the world show that temperature imposes a critical limitation on the ability of trees to produce new tissue; mean daily temperatures of 8-9°C are required, so recent warming will have particular benefits for those trees that have managed to eke out an existence for so long, living “on the edge”.

An interesting characteristic of the western bristlecone pines is that their recent growth has markedly increased—ring widths have been higher than in previous decades. Previous studies have debated to what extent this “fact” is real, or just an artifact of the way tree-ring data are analyzed. Because the growth of trees is radial, as trees get older and the diameter of a tree increases, annual ring widths decline in thickness. This is the normal “growth function” that is commonly removed from measurements before further analysis is carried out. The trick is to do this carefully so that as much climate information is retained while the growth function is discarded, and dendroclimatologists know how to do this quite well. However, sometimes the “standardization” procedure can introduce spurious results. This led some to regard the apparent growth increase in bristlecone pines to be a meaningless result of the data processing. In a new article in the Proceedings of the U.S. National Academy of Sciences (PNAS) Matthew Salzer (Laboratory of Tree Ring Research, University of Arizona) and colleagues examine this issue head on. They studied hundreds of trees from treeline sites in the Great Basin, aligned all the samples according to date, and simply averaged the results (Figure 1). Given that these trees are all long-lived, the complicating factor of growth function (which is strongest for the early growth of a tree) was not significant for assessing the most recent growth. Their results show that mean ring width in the last 50 years has been greater than in any previous 50 year period over the last 3700 years. You have to go all the way back to ~1900-1300 B.C. to find mean ring widths approaching recent values. Furthermore, the recent increase in ring widths is seen in trees at the upper forest border at sites hundreds of km away (even when the treelines there were at lower elevations)—but not in trees below the upper forest border. Below the zone closest to treeline, wide rings are formed in cool, wet years, and narrow rings in warm, dry years, and trees from this lower zone do not show the 20th century growth surge.

It is thus clear that the bristlecone pines from the highest regions, close to their growth limit, are showing a very strong response to recent warming, and indicating just how unusual it has been in the context of the last few millennia. Previous explanations have focused on possible CO2 fertilization effects (increasing water use efficiency) but there is no obvious reason why such factors would have affected only trees within approximately 150m of local treeline in different locations. Rather, the high elevation trees, close to the limit of growth, have responded positively to the recent increase in temperature just as ecological studies would have predicted.

One final note: bristlecone pines often have an unusual growth form known as “strip bark morphology” in which annual growth layers are restricted to only parts of a tree’s circumference. Some studies have suggested that such trees be avoided for paleoclimatic purposes, a point repeated in a recent National Academy of Sciences report (Surface temperature reconstructions for the last 2,000 years. NRC, 2006). However Salzer et al’s study shows that there is no significant difference in their results when the data are divided into two classes—strip bark and non-strip-bark cases –when the raw unstandardized data are compared. So that particular issue has apparently had people barking up the wrong tree…

Figure 1: Median ring-widths (non-overlapping 50-year means) of upper forest border Pinus longaeva from 3 sites in western North America, plotted on first year of interval (from Salzer et al, PNAS, 2009)

144 Responses to “A Treeline Story”

  1. 51
    Ike Solem says:

    Gosh, if you want to understand the relationship between global forest cover, human activity and global warming than the best place to look is indeed the Bristlecone Pine forest in the White Mountains…

    Or maybe – just maybe – a more complete survey of the Amazon, the Canadian pine forests, the Siberian forests would be appropriate?

    The only reason this particular story gained traction in the press is that is provides fodder for the “global warming is good for the planet” PR line. If trees are growing under global warming, than the fossil fuel lobby wants that publicized, so they lean on their PR people, who call the newspapers and cable networks, and there you go – propanganda 101. Amazon rainforest or Canadian pine forests just could not substitute in this headline:

    “Ancient bristlecone pines enjoying global warming”
    By Associated Press
    Monday, November 16, 2009 at 12:29 p.m.

    Similarly, we’ve headed off a new ice age and also recharged the planet with CO2 for photosynthesis – geoengineering in action. It’s actually a big success story…

    However, if you go with that line, you also have to admit that the phenomenon and the physics are real… and if you admit that, you have to consider the associated processes of water vapor feedback and shifts in ocean-atmosphere circulation and terrestrial soil moisture and the vulnerability of modern human civilization to water scarcity…

    What are the largest North and South American forests? Canadian pines and Amazon rainforest. What is global warming doing to those forests? Pine beetle invasions in the north due to warming conditions, and dieoff in the Amazon:

    Do we see extensive media coverage of these two gigantic regions – no – but we see the bristlecone pine story developing traction. Do we see any mention of long-term forecasts of the conditions in the White Mountains, however? No – instead, we see a cherrypicked trend that has been spun to meet the needs of the fossil fuel lobby – that’s what our press system has become. The Associated Press is particularly bad, as is the company MediaNewsGroup, run by one Dean Singleton, the chair of AP and a noted global warming / fossil fuel spin artist for the billionaire class. MediaNewsGroup owns the SanDiegoTribune, and about 1500 papers across the western U.S., such as the SanJoseMercury – and they all run the same climate & energy disinformation stories.

    If there was ever a good reason to pursue anti-trust legislation targeting the corporate media holding companies, this is it. The media distortion and spin is breaking all records on this, all over the world, as media ownership becomes consolidated in fewer and fewer hands, most of them with a few fingers in fossil fuels as well.

    As another example, take the worst drought in a century in Mexico, such a common phrase these days:

    Farmers reeling from Mexico drought – 17 Nov 09

    Wait – not to worry – the Middle East-based Al Jazeera network is covering the story, and they say it’s just El Nino drying out Mexico. That makes perfect sense. In an El Nino, warm water from the equator piles up along the western coast of North and South America, usually resulting in giant storms due to the increased evaporation, a function of the surface temperature of the oceans (and other factors)… and that dries out the local region, right, yup. Warm wet conditions lead to drought. What could be wrong with that claim?

    Here is the typical view on El Nino effects in Mexico, a wiki blurb:

    In North America, El Niño creates warmer-than-average winters in the upper Midwest states and the Northeast. Meanwhile, central and southern California, northwest Mexico and the southwestern U.S. become significantly wetter while the northern Gulf of Mexico states and northeast Mexico are wetter and cooler than average during the El Niño phase of the oscillation.

    What is the current situation in Mexico?,0,6988447.story

    A months-long drought has affected broad swaths of the country, from the U.S. border to the Yucatan Peninsula, leaving crop fields parched and many reservoirs low. The need for rain is so dire that water officials have been rooting openly for a hurricane or two to provide a good drenching.

    And yes, they then repeat the El Nino claim – strange, because they were previously claiming the drought was due to La Nina:

    2009: LA Times

    This is supposed to be Mexico’s wet season, when daily rains bathe farmland and top off rivers and reservoirs. But rainfall has been sporadic and unusually light — the result, officials say, of an El Niño effect this summer that has warmed Pacific Ocean waters and influenced distant weather patterns.

    2007: San Diego Tribune

    But if La Niña reprises its 2008 performance in the Sierra, California’s water resources will become even scarcer. Deliveries to Southern California farmers were slashed in the past year because of court-ordered pumping restrictions to protect the endangered Sacramento delta smelt.

    Wow – both La Nina AND El Nino cause drought! This new scientific learning amazes me, Sir Belvedere..

    Back in the real world, if atmospheric circulation patterns are shifting along projected lines – Hadley cell expansion northwards – this would explain the ever-more-persistent drought conditions, wouldn’t it? If so, much of Southern California across to Texas might end up looking like Baja and the Sonoran Desert in 100 years.

    No cause for alarm! Global warming is good for you – think about the, um, new desert tortoise habitat?

    There will be winners and losers, but I don’t see too many human winners here – pine beetles & toxic jellyfish are thrilled, however.

  2. 52
    Paul Klemencic says:

    I would like to second dhogaza’s response to Pat’s question, and his plan to study the science by reading RealClimate and some skeptical websites. The denialist sites make a habit of repeating a fabricated piece of evidence or repeating a particular lie that they believe they can sell over and over. It helped me a lot to know about the most common lies in advance, so that I could assess the credibility of the site. For the unvarnished current information on climate science, RealClimate is the best site, but it takes quite a bit of background information to understand the discussion here. In the meantime, the denier sites package a bunch of misleading information or outright lies, and sell the information to people who are gullible enough to believe the fabricated ‘science’.

    I found that the site Skeptical Science really helpful in debunking the most common denier lies. If you go to the site, on the home page you will find a list of the “Hottest Skeptic Arguments, and what the science really says”. Before reading any skeptical information, you should peruse this list, so that you will be able to spot the lies.

    On a lighter vein, and in a more humorous way, the Peter Sinclair videos on YouTube hit the most common ‘Climate Denial Crocks’ which I recommend as a quick briefing that you will need before venturing into the den of deniers. Here is the Denial Crock video covering the original ‘hockey stick’ controversy:

    A word of warning; be especially careful of Anthony Watts. His site is the most heavily censored of the denial sites, and Watts will go after you personally, using information from your sign-in profile, if he doesn’t like what you are saying. You may prefer to simply identify yourself as ‘Pat’, but Watts will happily publish your full name and attack you personally. He did that to me. He snipped my comment, then mis-quoted it, then used my full name from my profile in the inline response to the comment.

    Good luck, and come back and report in.

  3. 53
    Lynn Vincentnathan says:

    RE #32, Pat, “Recent talks in my area of carbon taxes and other financial incentives to curb greenhouse gases has peaked my curiosity. Since me and the other citizens of my country will soon have another hand in our pockets, I want to see if I’m getting what I’m about to be paying for.”

    The whole idea of any tax — which would NOT have been necessary had people started doing the right thing 20 years ago — is to inspire them to reduce their fossil fuel consumption through energy/resource efficiency/conservation.

    And once they take their first baby steps in doing so and suddenly realize they can do so without lowering living standards (down to a 1/2 to 3/4 reduction), then they can reap in the great savings (like the $2000 I saved from my $6 low-flow showerhead), help the economy, help their pocketbook (despite any measly taxes the gov might impose), and live happier and healthier lives. My husband and I chose to do so 20 years ago and we’ve been laughing all the way to the bank ever since.

    The climate denialists, on the other hand, are so hell-bent on causing global warming until they rearch 101% confidence that it is happening, that they will insist on paying the higher prices for things and will refuse to implement even one common sense, cost-effective measure to reduce their emissions. I think they’ve booked their Hummers for the next 20 years.

    So, anyway those darned taxes won’t really do much good to inpsire people to reduce, and maybe the government will have to raise them more, and the denialists will just become more obstinate about not reducing, even in the plethora of cost-effective ways that exist, and will insist on emitting all the more (because they just won’t believe in AGW until they die and go that much hotter place). And they’ll get their children to emit even more.

    And that’s history. Er, rather history will be ending sooner than we think….

    Now the scientists are saying 6 degrees C by 2100 — which as Mark Lynas points out in his SIX DEGREES is pretty much doom for the vast majority of us. See

  4. 54
    Lynn Vincentnathan says:

    I had a question about that past warming era about 1900-1300 BC. Were there any great floods in the Mediterranean area at that time. I teach mythology, and one author suggests that the Mediterranean flood myths might be based on some great flooding way back then (but he suggests sometime between 3000 & 2000 BC).

  5. 55
    Theo Hopkins says:

    Just as a matter of interest.

    I am from the UK, but I have been up among the high altitude bristlecone pines of the US.

    I would hate to see them chopped down. Are they investigated in a non-destructive way?

  6. 56
    DrCarbon says:

    #54 – Lynn. I wouldn’t read too much into the 1900 BC period of high growth. This is time period that is difficult to interpret in this study as no detrending was done on the trees and it is possible that that era is represented by young, fast growing trees. Also this is a regional study and by itself it is of very limited utility in inferring paleoclimate of the Mediterranean.

    #51 – Ike. This paper has nothing to do with global forest cover. Rather it investigates growth trends and their possible causes in one species of tremendous importance to paleoclimatology.

  7. 57
    D MacKenzie says:

    @Lynn Vincentnathan, 53.

    Lynn, that’s a pretty big brush you’re tarring ‘denialists’ with. I’m sure there are some that fall into that category, but also there are many that are well educated and have an environmental conscience. Many also take practical steps to be more environmentally friendly. Personally, I’m not as optimistic as some that we understand enough about the various multitude of interactions between the biosphere, atmosphere and beyond to be able to build deterministic computer models of global climate; that’s the main source of my skepticism. I emphatically agree that humans need to do a lot better and treat the environment with much more respect, but don’t agree that global capping and trading of carbon credits is going to give us our best bang for our bucks when there’s a whole host of other options out there that we should seriously be implementing regardless of whether CO2 is the nasty boogieman or not.

    Human’s have a pretty good track record of being proven wrong every time it’s declared the science is settled (earth’s flat, earth is center of the solar system, continents are stationary, etc).

  8. 58

    @ #52 Paul: Speaking of hockey sticks, doesn’t this graph remind you of something. If you look at the last 3,000 years or so.

    (What were those Greeks up to in 1900 BC anyhow?)

  9. 59
    Jim Bouldin says:

    I would hate to see them chopped down. Are they investigated in a non-destructive way?

    Yes, with one pretty unfortunate exception

  10. 60
    anony mouse says:

    Human’s have a pretty good track record of being proven wrong every time it’s declared the science is settled (earth’s flat, earth is center of the solar system, continents are stationary, etc).

    Boilerplate talking-point alert!!

  11. 61
    Glen Raphael says:

    #55 Theo:

    Are the [bristlecones] investigated in a non-destructive way?

    Yes. Researchers drill a long, skinny “core” sample to get their numbers, and you need to get a permit to be allowed to do even this. (Ideally you’d want to core from several angles and average the results, but a lot of these studies involve single-core samples. None of the studies in question involve chopping down a live tree to see rings in detail, helpful though that might be.)

    Whether you do one core or a few, the tree should heal quickly. You can see what a core and a coring tool look like here:

  12. 62
    Hank Roberts says:

    D MacKenzie: counterexamples

    cholera; smallpox; lead; asbestos; tobacco; chlorofluorocarbons; DDT; phthalates …..

    All cases where people were doing something provably stupid, learned that it was stupid, and (after years, or decades, or in the case of lead, a couple thousand years) mostly got organized to see that fools were stopped from continuing to do what everyone knew was doing damage.

  13. 63
    RichardC says:

    55 Theo, they bore into the trees and pull out a tiny core. The wound is sealed and the tree isn’t harmed.

  14. 64
    matt wilkie says:

    @joseph (comment #8): there was an episode of The Nature of Things* a year or two ago which spoke of periodic drought periods evident from tree rings etc. in the prairies, beginning at the eastern edge of the Rockies, which made the Great Depression of the 1930’s look like nothing, lasting from decades to a century.

    Not to say that what you’re seeing is not evidence of global warming, I don’t know, just a possible path for future research.

    unfortunately this particular episode is not one of the ones available online

  15. 65
    Ray Ladbury says:

    D. MacKenzie, Given that science dates from about 1600, perhaps you would care to provide some evidence that the scientific consensus that Earth is flat or a geocentric Universe. Or perhaps you would care to give a concrete example of an uncertainty about the biosphere or “the beyond” that is sufficiently large to negate anthropogenic warming.

    Failing that, perhaps you would care to provide us with some reason why we should not consider you just another denialist reveling in his ignorance.

    No? I thought not.

  16. 66
  17. 67
    Jeffrey Davis says:

    “Personally, I’m not as optimistic as some that we understand enough about the various multitude of interactions between the biosphere, atmosphere and beyond to be able to build deterministic computer models of global climate;”

    I’d like to hear what you think the uses of GCMs are.

  18. 68
    mike roddy says:

    Great Post, Ike, #51.

    Forests are going to broadcast warming sooner and much more consistently than Western droughts or Atlantic hurricanes. Effects on hydrological cycles and regional microclimates are likely to be catastrophic: while logged or dead forests have more albedo, this is more than compensated locally by 10 degree hotter local air temperatures due to less transpiration, according to numerous studies.

    Dead pines in Canada and withering trees in the Amazon are a mild preview. When we see another 2 degrees, it will be hickory barbeque time- with another undervalued feedback.

    You’re also right about the sorry state of media coverage of climate change. It would really make me crazy were it not for the fact that most educated younger people have wised up and gone to blogs for information- such as this one. The New York Times, AP, Newsweek, and the rest of them have cut their own throats by permantly destroying their credibility.

  19. 69
    Thomas says:

    Lynn @53: I have the misfortune to have a number of hardcore denialists around me at work. I think their motivation is the pure free-market stuff, the fear of any sort of government regulation is orders of magnitude greater than any concern about the planet. But I do find they are open to saving energy, both for the impact on their families expenses, and because they know energy insecurity is an issue for the country. It is possible to work with them on some conservation issues (just not on why it is important to do so). I probably have an anomalous sample, as they are high end engineers, and can appreciate system issues -so long as they aren’t too ideologically threatening.

  20. 70
    Dr Dahlstrom says:

    It might be worthwhile to point to tree limit changes in Scandinavia :over the last century the tree limit (limited by cold) has increased 150-190 m, as measured over several sites, and with different tree species …
    Holocene pine tree-line evolution in the Swedish “Scandes: Recent tree-line rise and climate change in a long-term perspective”, by Leif Kullman et al
    And a very old tree:

  21. 71
    D MacKenzie says:

    Whoa! Touchy bunch over here aren’t we.
    @ Ray Ladbury: How about Galileo being placed under house arrest in 1632? His views were contrary to the science (in the general sense of knowledge) of the day. If you must know I work in ecology and have seen plenty of people using models completely inappropriately. Often they fall into the fallacy of believing the model represents truth and not thinking hard about the underlying assumptions and what the consequences are if those assumptions are not meet 100%. Sometimes those assumption violations are relatively minor, sometimes not. It’s particularly important when people try to extrapolate beyond observed data. The fact that there’s no single model that everyone can agree upon immediately indicates that not everything is known. I have no problem working with multiple models either, provided they represent the spectrum of the uncertainties and those uncertainties are suitable acknowledged and incorporated into final conclusions. From what I’ve read, that doesn’t always seem to be the case.

    Some pretty important things are still being discovered in ecology (eg Ca pooping fish), some of which could have big impacts on our understanding of things like the carbon cycle (especially if you consider that a lot of fish have been taken out of the worlds oceans over the same timeframe C02 has been rising, and no I’m not implying a causative link there), it would be great news for ecologists everywhere if the climate scientists have got it all figured out already, though they’d have to start looking for new jobs.

    @ Hank Roberts: most your examples also started as situations where majority of folks said 1 thing, a few tried to buck the trend and got shouted down for it, but it turned out those that went against the grain were right afterall.

    Look, if you disagree with my views, fine, I don’t really care. I was just trying to note that just because you’re a ‘denalist’ that doesn’t mean you want to keep on ransacking the earth until it’s nothing but a burnt ember then move on to the next planet and start again. I lot of us are pro-environment but just disagree with the direction things are going especially with proposed cap and trade schemes. 10 years I whole-heartedly agreed with AGW, now with the more I read, the less I’m convinced.

  22. 72
    Ike Solem says:

    Actually Hank, the tobacco smoking rates have increased globally, so if that’s a strange form of success… All the tobacco companies had to do was accept a higher cost per cigarette, with the taxes going to anti-smoking campaigns. Some 21% of adults today have smoked cigarettes within the past week, according to the polls. On a global scale, the numbers are slightly higher, according to the WHO:

    “Worldwide, between 80,000 and 100,000 kids start smoking every day. Approximately one quarter of children alive in the Western Pacific Region* will die from smoking.”

    The latest effort by tobacco involves sugary candy-laced tobacco products, aimed at kids – almost all lifetime smokers begin smoking as children or teens. The actual tax increases are passed on to the addicted consumers, and the tobacco companies make the same profit as before. A few cities have tried to ban the sale of tobacco products except in licensed ‘smoke shops,’ but the grocery stores, corner markets and gas stations don’t like that any more than the cigarette makers do.

    Limiting smoking is “an imposition on basic rights” – but what about secondhand smoke and the right of redress for harm caused to bystanders?

    Arguing that one did not intend to cause harm does not usually work, especially if people have been pointing to the harm caused for decades.

    Fossil fuel emissions? Clearly, there’s been harm associated with this over a prolonged period of time. While there are still a few denialists running around making ever-more ridiculous claims about global cooling, solar cycles, and so on, much of the fossil fuel lobby has settled on a new tactic: rather than denial, they’re going with deception.

    The central deception is a lot like that involved in tobacco: a big public show followed by moves to create “low-tar cigarettes”, which is suspiciously similar to the “low-carbon coal” line. Healthy cigarettes, made with modern technology that removes all the problems – Futuregen cigarettes.

    Or try the patch – made from nicotine extracted from tobacco, and equally addictive, just not as carcinogenic. What is the patch for coal? Coal-to-gasoline programs, which are all based on coal gasification, and syncrude production using natural gas and tar sands.

    The deception is based on creating the appearance of doing something to fix the problem, such as cap-and-trade or carbon sequestration. By appearing to be doing something, one can avoid binding legislation that funnels investment away from fossil fuels and towards renewable energy.

    In that case, a tobacco farmer might suddenly find themselves unable to get credit – and the bank wouldn’t put up money for a new tobacco processing center, because they wouldn’t recoup the investment. All that would have to happen is for the government to remove the subsidies granted tobacco farmers, and banks would walk away.

    The same goes for fossil fuels and renewables. That’s the real problem with failure on Copenhagen – what will investors make of the apparent opposition on the part of world leaders to binding legislation that would step up the replacement of fossil fuels by renewables?

  23. 73
    Hank Roberts says:

    Yep, the marketing to youngsters, the ones who get addicted, proceeds apace; most of the world hasn’t gotten the message yet.

    And there’s still lead turning up freshly painted on kids’ toys too.

    And going to chloramine instead of chlorine in water supplies flushed an awful lot of lead into some cities’ drinking water.

    It’s not that science _makes_ people change. But science, and statistics, gives people information they couldn’t get before the methods were invented.

    Science isn’t enough. Y’all who try to get policy people to pay attention have all my respect — ‘try everything, something’s got to work or else …”

  24. 74
    Hank Roberts says:

    D. MacKenzie, you say you’re an ecologist; you also say
    > regardless of whether CO2 is the nasty boogieman …

    Do you mean you’ve studied ecology, as opposed to being an ‘environmentalist’?
    The CO2 work is physics, but ought to be clear enough to be understood.
    Have you read the history (first link under Science in the right hand sidebar)?

    Touchy? If you’re wondering “whether CO2 is the nasty boogieman” there may be some difficulty here but not entirely on the part of those of us who’ve been reading here for a while and read the science.

    Where are you starting from? How much ecology, for example?

  25. 75
    Hank Roberts says:

    On carbon trading (yes, a lot of us think it’s business as usual)

    Hat tip to the inimitable:

  26. 76
    Deep Climate says:

    I know this is off topic. But with talk of denialists trying to disrupt Copenhagen, maybe not so far off …

    Friends of Science radio ads are playing across Canada. And, as in the case of the Monckton tour and the 2006 election ads, the usual suspects appear to be involved: The Calgary Foundation and oil and gas lobbyist Morten Paulsen (who also happens to be well connected with Stephen Harper’s Conservative Party).

    Meanwhile, Harper and Environment Minister Jim Prentice keep trash talking chances of meaningful agreement and seem to be relieved at the prospect of a weak, political agreement. But some are starting to push back …

    The leader of the federal Green Party and about 1,000 supporters had strong words for Prime Minister Stephen Harper Tuesday night.

    They gathered at the Victoria Conference Centre to call on the government to shape up and get serious about the upcoming UN Conference on the Climate in Copenhagen, Denmark.

  27. 77
    Andrew Hobbs says:

    #71 D.MacKenzie,

    “10 years I whole-heartedly agreed with AGW, now with the more I read, the less I’m convinced.”

    I am interested in that, your last comment. What exactly have you read over the last few years that has made you less convinced. I would be interested in following some of it up since I too have read lots in that time and I can’t seem to find anything, anything at all, that would make me less convinced.


  28. 78
    Lawrence Coleman says:

    I now believe climate science has got to be the most absorbing and fascinating fields to be invloved in. I used to have a healthy scepticism when it comes to climate modelling but now finally it seems to be getting more predictable and a more reliable tool for forcasting future outcome scenarios. As more variables are being understood and the sheer increase in raw data from almost every source it’s beginning to become quite useful. One new example I read in Science daily… Re: the oceans abiltity to absorb CO2 may be waning but paradoxically the land seems to be taking more of it up than before even with continuing logging and land clearing. Gavin, your colleague Tim Hall has said that the increasing atmospheric CO2 has probabaly caused a faster growth rate in vegetation thus a larger ability to uptake the gas. However, like the oceans this increased uptake cannot last forever since the amount of nitrogen in the soils also determines uptake. So I would suggest this is uccuring more in the equatorial regions is this correct?
    Since the oceans make up over 2/3rds of the earth’s surface and their CO2 uptake is trailing off..for chemical reasons now and probably later down the track (or perhaps even now) because the oceans’s are warming at surface levels and so thermally less able to sequester carbon this will or is compounding the level of atmospheric CO2 (the slight increase in land carbon sequestration is more than offset by the relative area of the oceans) producing a viscious +ve feedback loop exponential in nature. To me this would indicate we need to adopt a reverse log approach to CO2 reduction if we are going to win this battle. Anotherwords immediately adopt a 95%+ global emmissions reduction and then only when CO2 reaches 350ppmv or lower can we afford to take the breaks off a little. Sounds impossible? I think so too! I hope you can see that only having a global concensus of a pathetic 20% reduction by 2020-2030 is like pissng into a raging forest fire..utterly useless!

  29. 79

    Your figure caption says “Median ring-widths (non-overlapping 50-year means)” but the graph in the paper is captioned ” Ring-width medians for non-overlapping 50-year intervals plotted on first year of interval.” Are you sure they took used means in this graph? The supplementary material includes data for means of the bins but as far as I can tell that is not used in the main paper. Or am I missing something?

    In any case, if you take the mean rather than median, it is more influenced by rapid increases (if the last few data points are much higher than the rest, they pull the mean up but the median is not influenced by anything other than whatever was the midpoint in size). As you can see from the earlier peaks, those were not particularly long-lived. But the last 3 data points look like a pretty steep rise. Any bets on what the 2000-2049 data point will look like?

    Hockey, anyone?

  30. 80


    There is good geological evidence for massive flooding around the Mediterranean Basin area in 4000, 2400, and 1600 BC. Probably one of those events influenced the Utnapishtim/Noah/Deucalion story.

  31. 81
  32. 82
    Lynn Vincentnathan says:

    RE #57, D MacKenzie, yes I heartily agree that “cap and trade” is not the way to go. We need a carbon tax that slowly (or quickly) increases each year, and we need all of that money it generates to go back to the people as some sort of divident (equally divided in the U.S., say, among all SS card holders) — they can pay for their higher energy bills, OR better yet become energe/resource efficient/conservative and pocket that money, get a better education or those braces for Suzie.

    That’s what James Hansen proposes, and it makes a lot of sense – see

    I also think a portion of that tax money should go to the poor peoples around the world, esp in Africa and Asia, that are suffering from GW impacts — you know, the people who don’t even have electricity or cars, whose crops are failing due to global warming — those crops they sow and reap by hand bec they don’t have tractors…..

    We break it, we buy it

  33. 83
    Lynn Vincentnathan says:

    #71 & “How about Galileo being placed under house arrest in 1632?”

    Are you suggesting that because most people believe the earth goes around the sun that they might be wrong, and that some flat-earther might be the one who is actually right? And we should accept (or even consider) what he says because he’s a loner?

    And BTW, the Catholic Church is sorry now for that incident, and they’ve decided to support science, and are speaking out about our need to mitigate global warming, such as the pope’s recent address at the World Food Summit.

  34. 84
    Tony Rogers says:

    I really can’t understand the conclusion from your final paragraph. Salzer’s Fig. S4 in his SI clearly shows that strip-bark ring widths have increased massively over the last 300 years (from about 0.2mm to about 1mm) whilst whole-bark trees have varied much less (from about 0.5mm to about 0.6mm with peaks in 1720-ish at about the same level as 1980).

    How is it possible to conclude that “there is no significant difference in their results when the data are divided into two classes—strip bark and non-strip-bark cases –when the raw unstandardized data are compared”?

    [Response: Hmmm. You seem to be somewhat confused about what that figure is showing. Fig. S4 of the paper uses data from the previously published work of Graybill and Idso. Figure S4A shows that the growth rates of their strip bark and whole bark trees have been similar over the last 100 yrs. or so. Before that, the whole bark trees have wider rings because the whole bark trees are younger. S4B shows that only when Graybill and Idso standardized the data was a divergence was introduced! -mike]

  35. 85
    Lynn Vincentnathan says:

    I hope the denialists at least are happy. Mission accomplished. They can all now go and take a breather. I understand the U.S. is not going to have anything to take to Copenhagen (see ). Our beloved legislators are bowing out of the issue for now.

    Anyone for a tea party? Organic, sun-cooked tea?

  36. 86
    Dappled Water says:

    “10 years I whole-heartedly agreed with AGW, now with the more I read, the less I’m convinced.” – D MacKenzie.

    Very clearly a typo. Seeing as this is a site run by climate scientists, surely he/she meant “10 years I whole-heartedly disagreed with AGW, now with the less I read, the more I’m convinced”

  37. 87
    Anne van der Bom says:



    I think you are the first commenter on this site to feel insulted by Hank Roberts.

    Questions are rarely just a request for information, they usually convey a lot of information too.

    You wrote “will soon have another hand in our pockets”

    I thought: “here’s another right-wing, tax-hating free market fundamentalist thinking global warming is merely an excuse for raising taxes”

    You wrote: “and it’s CO2 that is solely driving our climate?”

    I thought: “here’s another person that has been tricked into believing the fabrication that climate scientists disregard all other factors because their orders are to prove that CO2 is the culprit”

    My thoughts are a caricature, don’t conclude too much from them. They are not meant to insult you. I know I am almost certainly all wrong about my analysis of your beliefs, I am not a professional profiler, but I can’t help me from reading between the lines.

    You are not the first one to pose a question in this manner. RC regularly gets visitors claiming true skepticism and an open mind. But that skepticism usually breaks down pretty fast as the exchange of comments progresses, and you find out they merely come here for confirmation of their beliefs. Or you never hear from them again after 2 or 3 comments. Forgive us from being skeptic about ‘skeptics’ and ‘open minds’.

  38. 88
    Deech56 says:

    RE D. MacKenzie: “How about Galileo being placed under house arrest in 1632?”

    Maybe my history is a bit fuzzy, but wasn’t that the Church’s doing?

  39. 89
    Dale says:

    Number 60#, I don’t think that has anything to do with “Settled science.” That’s a misrepresentation. You seem to be confusing science with religion. It’s settled science that’s disproved the religious claims that you used.

  40. 90
    Donald Oats says:

    #71 D.MacKenzie,

    “10 years I whole-heartedly agreed with AGW, now with the more I read, the less I’m convinced.”

    Well, it depends upon what you have been reading, and how hard you have been willing to work at the details. For example, if you have been reading from Plimer’s tome, then you have a problem. You see, that book isn’t science, as Ian Plimer himself explains on Lateline earlier this year:

    By contrast to what Barry Brooks says, this book is not a book of science. It’s a book for the public who have felt quite disenfranchised and quite helpless that they have scientists talking down to them and they know there’s a smell, they can’t quite work out where the smell’s from, but they know there’s a smell, and this book is to give the public some information such that they can say, I think we’re being led astray.

    The difficulty here is that Plimer has written a book that has taken a detour past the usual scientific process, which he justifies by saying it isn’t a book of science. Fair enough at this stage. But then, he goes on to make the book a centre-piece in his all out assault upon climate scientists and the like. As far as I’m concerned that is reprehensible behaviour because Plimer, of all people, knows why the scientific process matters. Once a scientist starts misbehaving as badly as this, they are off my Xmas list.

    These sorts of landmines make it more difficult than ever for a newbie to get a starting point on Climate Science that is scientifically honest; this site here isn’t bad (in fact it is very good, excellent even) at doing just that. Have a perusal through the archives and you will find some great articles which help you to find a way into the literature, should you wish to venture that way.

    Good luck.

  41. 91
    Pat says:

    I would like to gauge some opinion on using Geo-engineering as a solution to global warming. The telegraph made this report last week:

    Would this type of activity on a wider scale be a solution to the warming that is occuring? Or possibly this:

    Now that’s two questions there, don’t kill me!! haha j/k, hope you got a sense of humor :)

    Thanks guys

  42. 92
    Ike Solem says:

    Carbon taxes are a bad idea, unless connected to renewable energy feed-in tariffs. Just look at the record around the world – all the countries with the biggest renewable energy programs have instituted significant feed-in tariff programs.

    What this would do is obligate all of the nation’s utilities, public and private, to buy power from renewable energy producers at above market rates. These guaranteed above-market rates give investors the confidence to put money into solar projects that will pay off over 10-20 years if they are guaranteed market access.

    Unlike a carbon tax, feed-in tariffs for renewable energy technology are designed to be phased out once the technology reaches about 20% market penetration. At that point, the technology should be able to compete with old fossil fuels with no assistance, as long as the government subsidies for fossil fuels are removed.

    Using this strategy, it should not be too hard to get 20% wind and 20% solar electricity generation across the U.S. – and with another 20% coming from nuclear, you could, within a decade, end up with a 60% non-carbon energy power system.

    This would mean the end of coal, it is true. But isn’t that the goal?

    Not according to the U.S. government, specifically Assistant Secretary for Land and Minerals Management Wilma Lewis:

    “America’s vast coal resources are a vital component of our energy future and our economy, but we have a responsibility to ensure that development is done in a way that protects public health and safety and the environment.

    How are you going to meet Obama’s campaign promise to “roll back global warming” without getting rid of coal combustion? With cap-and-trade and carbon capture and sequestration? That’s not going to work – both strategies are failures, economically and technicallly. Neither one results in lowered fossil CO2 emissions or renewable replacements for fossil fuels.

    An entirely new strategy is needed, one that doesn’t cater to coal and tar sand operations.

  43. 93
    Ike Solem says:

    P.S. for a good discussion of the issue of whether carbon sinks filling up to the point of exhaustion, see:

    John Timmer did a very good job of discussing two different papers on the subject, as well as pointing out how various other media outlets were distorting the results:

    So, are carbon sinks beginning to reach their limits? Given the two papers, I have to admit I lack the expertise to judge.

    What is clear, however, is that two extremely cautious and technical papers have been handled awkwardly from a media perspective. The GRL paper was heralded with a press release that touted it as “Controversial new climate change data,” even though it didn’t directly address climate change, and actually applies new methods to existing data sets. Two articles removed from the press release, and you end up with an article that claims “new research shows that atmospheric levels of CO2 have effectively remained unchanged since the advent of the industrial revolution.” It’s hard to imagine anyone getting it so badly wrong.

    Press release, GRL paper: “Controversial new climate change data”

    New data show that the balance between the airborne and the absorbed fraction of CO2 has stayed approximately constant since 1850, despite emissions of CO2 having risen from about 2 billion tons a year in 1850 to 35 billion tons a year now

    Press release, Nature Geosciences paper: “Fossil fuel CO2 emissions up by 29 percent since 2000.”

    The strongest evidence yet that the rise in atmospheric CO2 emissions continues to outstrip the ability of the world’s natural ‘sinks’ to absorb carbon is published this week in the journal Nature Geoscience…

    Interestingly, both see an increase in the airborne fraction, but the GRL author claims this is due to land use variables, not to sink limitations – the Nature Geoscience folks disagree.

    There is a third line of research as well that relates here:
    CO2 emissions caused by humans rise 2% despite global financial crisis</a

    …despite the economic effects of the global financial crisis (GFC), carbon dioxide emissions from human activities rose 2% in 2008 to an all-time high of 1.3 tonnes of carbon per capita per year. The research, by scientists from the internationally respected climate research group, the Global Carbon Project (GCP), said that rising emissions from fossil fuels last year were caused mainly by increased use of coal, but there were minor decreases in emissions from oil and deforestation.

    There are clear physical reasons why CO2 uptake by plants and the oceans is set to decrease, and this seems to be going on. Coal remains the #1 problem, as well as the #1 opportunity for reduced emissions. Despite the full-scale propaganda effort, there’s no way to burn it for energy generation without increasing fossil CO2 and hydrocarbon residues in the air and mercury, arsenic, and sulfur pollution in water and soils. Cap-and-trade won’t solve it, sequestration doesn’t work, and that leaves replacement with renewables as the only option, assuming you want to keep the lights on while avoiding terminal climate destabilization and ecological collapse.

  44. 94
    Lynn Vincentnathan says:

    #69, Thomas, you are fortunate to have climate skeptics around you who are into “saving energy, both for the impact on their families expenses, and because they know energy insecurity is an issue for the country.”

    Most denialists I’ve known just don’t care about the plethora of measures they can take to reduce GHGs and save money. Probably because most measures in themselves don’t save a whole lot — it’s mainly when you add them all up that you realize bigger savings; and then many are a “wash” which neither cost nor save.

    So I’ve come to realize that it takes heart (not just an economic mind) to mitigate GW; heart to seek out and find solutions and more heart to implement them. Because most solutions are very very small, and people don’t care about pennies & don’t think that pennies add up to $$ and eventually to big $$. They just can’t be bothered.

    And we are too rich to bother.

    And (skip the carbon taxes) there’s the subsidies to coal and oil (not even counting the military costs & lives involved), so we’re paying the rest of our energy & product* bills April 15th, even if we have electric cars running on 100% wind power and conscientiously reduce, reuse, recycle, & buy recycled, and thus don’t use nearly as much (direct/indirect) oil/coal as our neighbors, but have just as high a living standard and accomplish just as much as they.

    So we’re paying for our neighbors’ oil/coal addiction on April 15th. But more than that, what really hurts me, is we’re paying for their killing of people in Africa thru GW harms.

    Where’s Stupak when you really need him?
    *Note that most products have an energy (most likely fossil fuel) component, and/or involve other GHGs.

  45. 95
    John H. says:

    77. Comment by Andrew Hobbs — 19 November 2009 @ 1:15 AM
    “I too have read lots in that time and I can’t seem to find anything, anything at all, that would make me less convinced.”

    That really is an astounding comment Andrew.

    You had to have been shletered by some means from the plethera of material produced by the dozen or so major skpetics and their troops.
    Even Gavin has acknowledged their existence and work.

    Respone: I doubt the issue is that Andrew doesn’t think they exist. Rather that they are not convincing. And indeed they are not. – gavin]

    Many of us who have long followed the issue by devouring both sides of the “campaign” grow more conviced there is insufficient science to sustain the IPCC/AGW theory.

    Respone: It’s a well known trick to strengthen your convictions by convincing yourself that more and more people are agreeing with you. That may or may not be true, but it makes no difference to the truth or falsity of your actual belief. – gavin]

    For one to state that they can’t find anything at all is a little too convenient.

    Perhaps the debate here is insufficient. Offering or allowing too little of what you appear to be missing.

    It may be a result of challenging posts recieving a less than welcome response.

    Round we go.

    Respone: Round we go? Who are the people keep stating that Gerlich has proved the greenhouse effect doesn’t exist? Who brings up Miskolciz who says it exists but can’t change? Who brings up Essex saying that there is no such thing as a surface temperature in any case? Not us. If there is round-and-round arguments happening, it’s because the ‘anything-but-carbon’ crowd can’t let anything go and refuse to spend even one iota of critical thinking on dumping the nonsense. Why you find it surprising that this isn’t convincing to people who know something about the subject is the real surprise. – gavin]

  46. 96
    Hank Roberts says:

    Pat, you link to the Freakonomics/Geoengineering notion and an earlier notion about covering deserts with something shiny — you must have missed the extended discussion of both of those ideas; the Search box (top of the page) will find it. Try ‘geoengineering’ and ‘albedo’ as search terms.

  47. 97
    Jim Bouldin says:

    Some people have asked about the causes of the wide ring widths in the graph about 3500 years ago. In addition to what’s already been said on that, I did some quick analyses on the data from the 3 treeline sites in the study, using a simple robust biweight mean of the ring widths, all trees included.

    Couple of points. First, the pattern of that spike differs between the two sites where there is any decent sample size (SHP and MWA), and even at those it is very marginal (n = 20) (which generally takes one back about 1100 to 1500 years b.p.) the recent increase is very coherent among the sites, and unprecedented at each, as per the authors’ Fig 4b, but taken further back in time.

  48. 98
    Jim Bouldin says:

    That post was apparently mangled by inequality signs. Second try here.

    Some people have asked about the causes of the wide ring widths in the graph about 3500 years ago. In addition to what’s already been said on that, I did some quick analyses on the data from the 3 treeline sites in the study, using a simple robust biweight mean of the ring widths, all trees included.

    Couple of points. First, the pattern of that spike differs between the two sites where there is any decent sample size (SHP and MWA), and even at those it is very marginal (n under 10). At SHP the spike is very pronouned about 3800 years ago, whereas at MWA it is lower but broader, covering several hundred years to about 3300 years ago. The third site (PRL) had only a couple samples that old, and is thus very unreliable. Conversely, for each period, across the sites, having a respectable sample size (n over 20) (which generally takes one back about 1100 to 1500 years b.p.) the recent increase is very coherent among the sites, and unprecedented at each, as per the authors’ Fig 4b, but taken further back in time.

  49. 99
    Rod B says:

    Since it does little good (and Gavin dislikes it) I won’t go into any detail but just say, in my perfunctory response to refute Ike (72), use my tobacco rebuttals #3 and #4.

    In a more helpful topical vein and in keeping with Guy’s concern (if not his recommendation) I do not think hyperbole and conspiracy theories peppered with hubris and arrogance is a good way to win hearts and minds.

  50. 100
    D MacKenzie says:

    Ok, my post from last night on GCMs doesn’t seem to have appeared for some reason, but..

    @ Donald Oats: Haven’t read Pilmer, but web-sites, blogs and source articles where I can and time allows. Tried to cover the full spectrum of views in order to establish my own.

    @ Lynn Vincentnathan: Thanks for the link to the Hansen article; hadn’t come across that before. His ideas are interesting, and personally more palatable than the creation of a carbon market. As for Galeleo, that’s just an example. The point I was trying to make is that just because the current wisdom supports a certain hypothesis about how a system works, then someone else comes along with an alternative hypothesis, that person isn’t necessarily dumb, stupid, ignorant, uncaring, etc. They’re not necessarily right either. Knowledge advances when information is collected to determine the degree of support for the different hypotheses. If you want to get all Popperian about it you’d be trying to falsify hypotheses although there no reason you can’t do science under a multiple hypothesis framework either. I’m not trying to suggest I’m right and you’re wrong, I’m just saying I don’t view things the same as you at this point in time and that as I read and learn more, my view may change and so may yours ( ;-) ), that’s the way of life.

    @ Hank Roberts: I’m actually an ecological statistician with a PhD and 10 years experience behind me. I’m well versed with models and computer simulations as such are aware of the pros and cons of such approaches. GCM’s are a couple of orders of magnitude more complex that anything I’ve ever dealt with, but the basics are still the same. I also think hard about appropriately accounting for and expressing uncertainty in estimated quantities. Things like error bars on quantities that are clearly estimates seem to be in short supply in much of the literature I’ve read to date. Data quality and sample sizes are also something I think hard about. When you’re working with data that wasn’t expressly collected for the current topic of interest and/or very small samples sizes then it is possible for the statistics to mislead you.

    I know about the physics side of thing with CO2, but my understanding is that that only contributes a certain percentage of the projected warming (can’t recall the figure off the top of my head), the rest comes from hypothesized positive feedbacks.

    Constructive comments and links appreciated.