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The weirdest millennium

Filed under: — stefan @ 29 May 2007

Much research effort over the past years has gone into reconstructing the temperature history of the last millennium and beyond. The new IPCC report compiles a dozen reconstructions for the temperature of the Northern Hemisphere (including of course the original “hockey stick” reconstruction, despite opposite claims by the Wall Street Journal). Lack of data does not permit robust reconstructions for the Southern Hemisphere. Without exception, the reconstructions show that Northern Hemisphere temperatures are now higher than at any time during the past 1,000 years (Figure 1), confirming and strengthening the conclusions drawn in the previous IPCC report of 2001.

Fig. 1: Figure 6.10 (panel b) from the paleoclimate chapter of the current IPCC report (see there for details).

“Climate sceptics” do not like this and keep coming up with their own temperature histories. One of the weirdest has been circulated for years by German high-school teacher E.G. Beck (notorious for his equally weird CO2 curve). This history shows a medieval warm phase that is warmer than current climate by more than 1 ºC (see Figure 2). So how did Beck get this curve?


Fig. 2, modified from E.G. Beck (we added the green parts).

The curve is a fake in several respects. It originally is taken from the first IPCC report of 1990: a scan of the original is shown in Figure 3. At that time, no large-scale temperature reconstructions were available yet. To give an indication of past climate variability, the report showed Lamb’s Central England estimate. (Unfortunately this was not stated in the report – an oversight which shows that IPCC review procedures in the early days were not what they are now. We will post in more detail on the history of this curve another time.)


Fig. 3. The past millennium as shown in the first IPCC report of 1990, before quantitative large-scale reconstructions were available. This curve was based on Lamb’s estimated climate history for central England.

But Beck did not stop at simply using this outdated curve, he modified it as highlighted in green in Figure 2. First, he added a wrong temperature scale – the tick marks in the old IPCC report represent 1 ºC, so Beck’s claimed range of 5 ºC exaggerates the past temperature variations by more than a factor of three. Second, the original curve only goes up to the 1970’s. Since then, Northern Hemisphere temperatures have increased by about 0.6 ºC and those in central England even more – so whatever you take this curve for, if it were continued to present, the current temperature would be above the Medieval level, as in the proper reconstructions available today. As this would destroy his message, Beck applied another fakery: he extended the curve flat up to the year 2000, thereby denying the measured warming since the 1970s. With this trick, his curve looks as if it was warmer in Medieval times than now.

When approached directly about these issues, Beck published a modified curve on a website. He changed the temperature range from 5 ºC to 4.5 ºC – but he shortened the arrow as well, so this was just cosmetics. He also added instrumental temperatures for the 20th Century at the end – but with his wrong temperature scale, they are completely out of proportion. (In fact his version suggests temperatures have warmed by 2 ºC since 1900, more than twice of what is actually observed!)

Beck goes even further: in a recent article (in German), he has the audacity to claim that his manipulated curve is right and the more recent scientific results shown by IPCC are wrong. And for years, he has offered his curve on an internet site (biokurs.de) that distributes teaching materials for schools, with support from German school authorities. It is quite likely that his fake curve has been shown (and will continue to be shown) to many school children.


507 Responses to “The weirdest millennium”

  1. 51
    Jim Cross says:

    I wouldn’t attempt to defend Beck’s rigged graphs; nevertheless, there is significant variation (~1 degree) temperature variation in the last thousand years even when we eliminate the last hundred years.

    What accounts for that?

    [Response:There is a large literature on this. In my view one of the clearest papers is that by Crowley and Lowry in Science a few years ago. Here's a link to the abstract.
    The temperature variations are probably much less than 1 degree C by the way. One of the points of his paper is that we understand the response of the climate to forcing (e.g. sun, CO2, aerosols) rather well, and looking at the past variations gives us about the same for the climate sensitivity (how much temperature will change for a given forcing) as we already had calculated from first principles. --eric]

  2. 52
    J.S. McIntyre says:

    re 47:

    *chuckle*

    re 49

    “I actually do not get why skeptics think that it is SO important what the temperature of the MWP was. Both events, recent anthropogenic warming and the MWP, to me are independent.”

    This is much like similar arguments we see from Creationists when they say the fossil record is incomplete and thus fossils cannot be seen as evidence for evolution. (Of course, the argument ignores the fact we do have nearly complete records, as in the case of Whales, but I digress).

    The point is, this is not about trying to convince you, any more than creationists are trying to convince me of the veracity of their claims; what is really happening is the denialist industry is putting up smoke screen, creating straw man arguments that are used to appeal to an underinformed public.

    The sad part is it works.

    Here’s another (rhetorical) question regarding the U.S. and its position on global warming: Many of us expend quite a bit of energy planning for the future of our children; where they will go to school, figuring out what appeals to them, encouraging them to grow, to branch out and learn. We put money away to insure they can afford a good education, dedicate huge blocks of our time to them, are there for them when they need us and generally demonstrate the nuturing tendencies for successful child rearing. It goes even further: when they have children, we are often there for them, helping them when they hit difficult times, providing moral support and the benefit of our own experience to help them through. In short, we evidence the behavior of people who look far into the future with a concern for our offspring and descendants. Also, let’s not forget that as a nation we make a lot of noise about being concerned for our children and their future.

    Yet when perhaps the gravest crisis to face civilization rears its ugly head, is shown to be a threat to the future we are trying to prepare for our children, and that we are part of the problem, what do a large segment of us do?

    Exactly.

  3. 53
    Jim Prall says:

    Beck’s graph of historical “chemical” CO2 measurements (all over the map, often over 400 ppm) gets picked up as “unpublished” source material in Tim Ball’s slide show for the Frontier Centre for Public Policy:
    http://www.fcpp.org/pdf/TimBallJan2607handouts.pdf
    It’s on page 17 of this PDF (top slide – it’s handout format with two slides per page.)
    I note as well the sketchy temperature graph at the top of p. 11 of this PDF. It’s somewhat similar to the 1990 one above but not identical. It lists IPCC 1995 as the source. Is it in fact picked up from the 1995 report, and if so it is a fair reflection of the original? (Sorry I haven’t dug back myself tonight – I’m already up way too late.)

  4. 54
    danny bloom says:

    Stefan, great post and thanks. have you ever considered the need for teaching people about polar cities….?

  5. 55
    Hank Roberts says:

    Mr. Jones (or Shell?) #47 — the link (as I said in #28) was in the main article — in the line that says: “… from the paleoclimate chapter of the current IPCC report (see there for details).” The link gets you that chapter — it’s a large PDF, and you should really read the whole thing.

    In #28, the link was to a temporary copy of the one image ( now expired) for anyone who couldn’t get the PDF.
    That’s via the Firefox extension PDFDownload, by the way; they provide the 24-hour temporary copies.

    Mike again, thanks for the explanation of the smoothing — worth saving that one as a good explanation of what the picture means. (And, the figure as Spencer notes in #12 could be described a bit more clearly in the main post)

    Aside to Robert Rohde — can you include Mike’s explanation in his response to #47 above, if you use the image on globalwarmingart? It really helps understand what the ‘error bars’ mean in the original — clearly it takes reading the whole IPCC report to understand that stuff. I”m as always in y’all’s debt for making it clearer.

  6. 56

    Re: Ender and Mc Intyre. What is for sure as evidenced in core ice samples over the past 650,000 years is that NOW is easily and dramatically the highest the level of CO2 has ever been. Also there is always a slight time lag between when a CO2 spike occurs and the air/sea temp heating up. And the two graphs practically mirror each other. CO2 has a spike and sure enough (every time) temp follows. Look at An Inconvenient truth..Gore has been meticulous to keep the science accurate and transparent. However this current rise in CO2 is not a anomaly or transient spike it is instead an UNPRECEDENTED and disturbing rapid trend. Temp will very very soon follow the CO2 graph up-up and away. Can we hold on the the tigers tail long enough to shoot a tranquilizing dart into her?? Logic says nope..I’m praying to all gods and sundry that I’m wrong.

  7. 57
    Timothy Chase says:

    Lawrence Coleman (#56) wrote:

    Re: Ender and Mc Intyre. What is for sure as evidenced in core ice samples over the past 650,000 years is that NOW is easily and dramatically the highest the level of CO2 has ever been. Also there is always a slight time lag between when a CO2 spike occurs and the air/sea temp heating up. And the two graphs practically mirror each other. CO2 has a spike and sure enough (every time) temp follows.

    27 Apr 2007
    The lag between temperature and CO2. (Goreâ??s got it right.)
    Filed under: Climate Science Paleoclimate Greenhouse gases Arctic and Antarcticâ?? eric @ 2:45 pm
    http://www.realclimate.org/index.php/archives/2007/04/the-lag-between-temp-and-co2/

    Actually the paleoclimatoligcal record at least appears to show temperature lagging behind carbon dioxide. There has been some recent debate – and it may possibly have even lead, but it appears to lag by approximately 99 yrs. Feedback. Warming ocens and plants lead to higher levels of carbon dioxide by putting more of the co2 sequetered t0 the atmpospher – for exmple, they reduce the capaicty of the ocean to to but carbon dioxide leads to the buldup of thermalradiation and thus temperatio.

  8. 58
    Ovind Seland says:

    Re: Greenland and MWP. I have an interesting paper that,although very qualitative, disagrees with the notion of an medieval warm period on Greenland, and for that matter also over the northern hemisphere in general. Nansen F. (1926) Klima-vekslinger in historisk and post-glacial time (“Klimate shifts in historical and post-glcacial times”)

    His argument include that the graves dug in the medieval period coincides, with the present day (1920 in this case) depth of the permafrost. The graves were typically 2-3 feet deep, not 6. Also description of the ice-conditions from Norwegian 13. century sources said that the the drift-ice even in august usually extended slightly to the west of the southernmost cape. BTW as seen even from Beck’s curve any Chinese expedition in 1421 is already within the “little ice-age” so I do not see why this should support a theory on medieval warm periods.

    On a larger scale Nansen cites from papers on water-level in the Caspian sea that the 12. century likely experienced dry (warm?) conditions, while written sources from Hangchow in China indicate colder temperatures in China than around 1900. The Chinese source described the date of latest snowfall in the spring.

  9. 59

    Thanks Tim, I think the ocean temps have a 100yr lag? Air temp is mainly a result of greenhouse effect. Good point about the warmer it gets the more CO2 released by plants..although..some countries get drier and some wetter..australia for one is getting much drier..so is many countires of europe..so I’m not sure about the net effect of botanical CO2 release. CO2 release is dependant on the concentration of nitrogen in the soil…again drier country’s plants generally have little nitrogen in the soil so as the weather warms the plants will not produce much more CO2. But in wetter area that are getting wetter..plants have an almost unlimited potential to pump out CO2 due to the humous of the soil. In those arid countries or the ones getting nmore arid…vegetation will probably die off with say a doubling of atmospheric CO2 as has been proven to occur.

  10. 60
    Urs Neu says:

    Re 47

    There might be some problems with the tree ring-temperature relationship. It is known that the tree ring-temperature relationship has changed in the last about 20 years compared to the time between 1850-1980. This also partly explains the differences at the end of the period. It shows that climate change might also influence this relationsip (there are several possible reasons). However, the reconstructions use the time period before 1980 for calibration, and secondly, proxies other than tree rings show a similar temperature evolution. It is very unlikely that a possible change of the proxy-temperature relationship is just similar for a broad variety of different proxies and thus would introduce a considerable bias in the overall picture.

  11. 61
    Harold Pierce Jr says:

    The most conspicious human activity of the 20th century was continuous hot and cold warfare which has continued unabated to this date. World War II saw the formation of the military-industrial complex (MIC),now immense world-wide enterprise which consumes enormous of amounts energy and resources which also requires even energy for their aquisition and manufacture into weapons. In Fig 1 there is a distinct peak in the temperature curve in the WW II years. Has any consideration been given to assigning a forcing factor for warfare and the MIC’s? The extensive use of jet planes for transport of men and materials to the front (and for removal of injured and dead soldiers from the war theater) must be consuming colossal amounts of fuel, which is probably the real reasons for the increase in prices of gasoline, diesel and commercial jet fuel and of copper and zinc which are used for the production brass for ammuntion. Or put another way, how much carbon dioxide is produced by these activities and other government activities such as intelligence. If world peace were to break out and the MIC’s reduced to near nil, how much cabon dioxide would not be produced?

    Will swords ever be beaten into plowshares? We can only hope.

  12. 62
    Paul says:

    Becks graph stops in 1970, the IPCC graph in about 1985. Why are the last 20 years of data missing from the IPCC graph?

  13. 63
    Timothy Chase says:

    Re #57

    Good grief – I should know better than to post when I am falling asleep at the keyboard. Typos. Missing lettes. 99 yrs instead of 900 yrs. Oy!

  14. 64
    Timothy Chase says:

    Lawrence Coleman (#59) wrote:

    Thanks Tim, I think the ocean temps have a 100yr lag?

    No – its 900 yrs. Or at least that is what it would appear to be. And not a problem: I just didn’t want to leave an opening for some denialist to come along and give you trouble. Still, I wish I had been a little more awake. No alcohol – it interferes with my meds – just sleep deprivation, which isn’t really a good idea, either. And now my wife woke me up early and the kitten insisted that I come out.

    Oh well – maybe I will get more sleep tonight.

  15. 65
    RichardT says:

    #62
    Because it was drawn in 1990?

  16. 66
    J Bloom says:

    Re #52 – most global warming deniers are just cultural misfits looking for attention.

  17. 67
    Steve Reynolds says:

    > I actually do not get why skeptics think that it is SO important what the temperature of the MWP was.

    For myself (not a skeptic of AGW), it is very important in understanding what the effect of AGW will be. If the MWP was warmer that currently, that is evidence that current warming is not as harmful as some claim.

  18. 68
    catman306 says:

    “Re #52 – most global warming deniers are just cultural misfits looking for attention.”

    Or, perhaps they are paid shills for wealthy corporations and individuals who are profiting from maintaining the status quo in energy and consumerism. This is certainly true of right wing talk radio in the US.

  19. 69
    Hank Roberts says:

    >62,

    It’s explained in the original chapter from which it’s taken (the link is in the main article, before the comments). Look at the chapter text for the table (6.1) identifying the records charted.

    The figure shown here at RC is 6.10(b) from the chapter:
    ———
    Reconstructions using multiple climate proxy records, identified in Table 6.1, including three records (JBB..1998, MBH..1999 and BOS..2001) shown in the TAR, and the HadCRUT2v instrumental temperature record in black.
    ———

    >65, RichardT: No, it wasn’t drawn in 1990. You can look this stuff up.

  20. 70
    unconvinced says:

    The inline response to #47 is, in fact, incorrect – please read the caption of this graphic, which clearly explains the smoothing process used.

    [Response:No, actually the inline response is probably correct. The caption doesn't indicate how many adjacent values were used in calculating the mean used to pad the series. If the number of adjacent values used was one half filter width, then the boundary constraint is essentially identical to that achieved by reflecting the series about the terminal boundary, i.e. the 'minimum slope' constraint. Even if few adjacent values were used, the method still supresses any trend near the boundary. --mike]

  21. 71
    James says:

    Re #67: [ If the MWP was warmer that currently, that is evidence that current warming is not as harmful as some claim.]

    Except that the current warming (by which I mean the warming that has happened so far) is not a big problem, and would be even less of a problem if we had reason to believe that it was just another wiggle in the curve, which would soon reverse itself. The problems come from the warming that is predicted to happen; warming that is either “in the pipeline” from existing CO2, or which will be caused by future increases in CO2.

  22. 72
    Paul M says:

    That’s what I like to see, healthy discourse about the accuracy of postings. With accurate science, the truth will show itself with a wink and a smile, though the topic may be bleak.

  23. 73
    John Mashey says:

    re: #67 Steve Reynolds

    Suppose you know that:
    a) Today’s temperature (Tnow) is going up very fast, for pretty-well-understood physics, which will make the temperature keep going up (with the usual jiggles) for decades. I.e., the first derivative is certainly positive.

    b) There are 6.5B people on the planet, with more to come, compared to ~300M people around 1000AD (http://www.census.gov/ipc/www/worldhis.html), with more people living on the coasts that existed in 1000AD, and stress on water supplies, etc.

    c) Now, let us just suppose that you could magically transport today’s instruments back to 1000AD and measure the temperature (T1000AD), so that you got much tighter error bars than one can get with reconstructions.

    What exactly would you do different if today:

    T1000AD > Tnow ( a little cooler today) OR
    T1000AD == Tnow (same) OR
    T1000AD < Tnow ( a little warmer already)

    Put a different way, if the temperature keeps heading up, does it matter whether the date at which T1000AD == Tnow happens is 5 years from now, or 5 years ago? I.e., does one say: "It won't happen for 5 years, so we're OK ... but in 5 years, I'll decide there's trouble"?
    ====
    For what it's worth, suppose you didn't believe the usual reconstructions. How about glacier records (as discussed in another thread), but more specifically:

    a) See Figure 5 in
    http://www.unige.ch/forel/PapersQG06/Holzhauser2005.pdf,
    which shows the Great Aletsch Glacier’s advances & retreats [a long glacier, which tends to smooth out short-term fluctuations, and is only now responding to 1980s temperatures.]

    b) It is worth looking at the chart of Great Aletsch:
    http://glaciology.ethz.ch/messnetz/glaciers/aletsch.html

    c) and read the actual data, especially the last column, which shows the total length change, which is ~-700m since 1986.
    http://glaciology.ethz.ch/messnetz/data/aletsch.html

    d) The scale is inverted between a) and d), but if you draw the line from (2000AD, 3300m) to (2027AD, 3300+700=4000m), you get a gross approximation to what you’d expect if the glacier keeps retreating at the same rate. [It may be looks almost vertical, and the point (2027AD, 4000m) is slightly below the bottom edge of the chart.

    e) Anyway, read the article (with the caveats & speculations), and assess whether or not the charts make sense, and whether or not something unusual is happening right now.

  24. 74
    unconvinced says:

    Very well, I will accept your explaination as the math is beyond my competence (alas!). I would be pleased if you could explain why a number of proxy records, despite being available up until 1980 or so, have been truncated at earlier times – some end in 1960, some as early as 1930 (eg, Briffa et al) Would any doubts about the reliability of the proxies in this period cast doubt on the same proxies for earlier periods? If not, why not?

  25. 75
    Craig Allen says:

    Beck and the rest of his deluded ilk don’t seem to be convincing anyone with their nutty ideas:

    275 Australian economists today issued a joint statement, calling on the Australian Government to stop undermining international efforts to tackle climate change and to ratify the Kyoto Protocol without delay.

    The statement draws attention to the likely economic damage to Australia that will come from failing to reduce greenhouse gas emissions. They acknowledge that the latest Intergovernmental Panel on Climate Change report presents of new and stronger evidence that global warming is attributable to human activities. They also acknowledge warnings from the CSIRO (Australia’s peak science organisation) that climate change has the potential to seriously disrupt agricultural output, water flows and natural systems in Australia.

    Some quotes from the statement:

    â��Policy measures are available that would greatly reduce emissions of carbon dioxide and other greenhouse gases at modest economic cost.”

    �Australia has shown over the last two decades that it can manage significant change without major negative consequences for incomes or employment and, in fact, with change being a stimulus to improving innovation in the longer term.�

    �The Kyoto Protocol represents the first step towards a major international effort to deal with climate change in the long term. The refusal by Australia and the United States to ratify the Kyoto Protocol is undermining global efforts to tackle climate change.�

    The statement can be found here. (The first page is the media release. Skip to page two to read the statement.)

  26. 76
    Rod B says:

    56: “What is for sure as evidenced in core ice samples over the past 650,000 years is that NOW is easily and dramatically the highest the level of CO2 has ever been.”

    I hope you’re referring to the last 650,00 years as “ever”. There’s been many times, millions of years back, when CO2 concentration was much greater than today — and much greater than current projections for 2100+.

  27. 77
    Rod B says:

    66, 68: Who wake you guys up? Can you be a little more creative with your ad hominems? And check your non sequiturs at the door, please.

  28. 78
    Lynn Vincentnathan says:

    This is a bit OT, but I just read THE RISING, a novel about global warming. The premise seems plausible to me (tho perhaps not likely), but what do I know. The Rone & Ross ice sheet distintegrate (like the Larsen B), and this causes the land glaciers to slip into the sea, which causes a 1 foot sea rise. The loss of the weight of so much land ice then causes local Antarctic earthquakes (as noted to happen in Iceland & Greenland), and this causes more ice to break up & fall into the sea….and volcanoes under the antarctic (3 known, one unknown heretofore by scientists) erupt, and that really causes more ice to melt into the sea, and a part of a mountain & lots of big ice chunks to plunge in, causing a tsunami up the Atlantic ocean, wiping out inhabitants on both littorals. And there’s a 3 foot sea rise, which overflows the California aquaducts, making agri there impossible (who knew a 3 ft rise could do that??).

    Now the worst is not what global warming does, but how the government and people react. That’s the really scary part. It’s a good, near-future sci fi read, and I thought somewhat more plausible than DAY AFTER TOMORROW.

  29. 79

    Their latest crusade is to try to dent the IPCC’s review of the urban heat island literature by saying it’s just one guy [edited]. How valid is this criticism? Note that I’ve read the relevant bits in the IPCC WG1 report, but they’re trying to make an end-run around the IPCC by charging that its review of the UHI literature was biased.
    I don’t trust ice sheet modelers because I suspect that they ignore terrestrial heat flow, and the reduction in ice sheet friction when sea water floats ice sheets so reducing the normal force from the ice that remains grounded.

  30. 80
    stuart says:

    I hope you’re referring to the last 650,00 years as “ever”. There’s been many times, millions of years back, when CO2 concentration was much greater than today

    True. Of course multicelled life didn’t appear on earth until around 600 million years ago, so as long as we aren’t concerned about having multicelled life anywhere on earth we could use those higher CO2 levels to feel fairly safe about the earth’s future.

    Personally I have an interest in the continued existence of multicelled life, so I feel it safe to ignore conditions that existed more than 600 million years ago as irrelevant to what conditions may or may not be acceptable in the modern era.

  31. 81

    [[For myself (not a skeptic of AGW), it is very important in understanding what the effect of AGW will be. If the MWP was warmer that currently, that is evidence that current warming is not as harmful as some claim. ]]

    And evidence that heavier-than-air flight was impractical would show there’s no threat to the railroads from an air travel industry.

  32. 82

    Re 81:

    True. Of course multicelled life didn’t appear on earth until around 600 million years ago, so as long as we aren’t concerned about having multicelled life anywhere on earth we could use those higher CO2 levels to feel fairly safe about the earth’s future.

    Personally I have an interest in the continued existence of multicelled life, so I feel it safe to ignore conditions that existed more than 600 million years ago as irrelevant to what conditions may or may not be acceptable in the modern era.

    I think we need to keep in mind that 4.6Bya there was not only no any celled life on this planet, but there was no planet on this planet. Prior to the Cambrian Explosion, there were no advanced civilizations, much less not-so-advanced one, or even cockroaches, rats, used car salesmen, or any of the other scourge of society.

    We should also keep in mind that there are parts of this planet where multi-celled intelligent life live that are a heck of a lot warmer than other places, and particularly, a heck of a lot warmer than what the more northern and southern extremes are ever going to be under any global warming scenario. Some of y’all might think 40C/104F is a hot day. But some of us are grateful for days that are only that hot. If things start getting over 45C/113F, then I might think it’s really hot.

    There are plenty of reasons to be concerned about the things that are believed to lead to global warming. Suggesting all higher life forms are going to go extinct any time soon is the sort of doom and gloom that people use to discredit the underlying science.

  33. 83
    Mike Donald says:

    #67 #81
    [[For myself (not a skeptic of AGW), it is very important in understanding what the effect of AGW will be. If the MWP was warmer that currently, that is evidence that current warming is not as harmful as some claim. ]]

    If the MWP was warmer than today it means the earth’s more susceptible to feedbacks, forcings, influences etc. The exact opposite of what you’ve said.

    [Response: In my opinion, the magnitude of the MWP would have to be (globally) much greater than today's level to have any implication at all. That is, given the current uncertainties in the forcings (principally solar and volcanic) and the continued uncertainty in the climate sensitivity only a dramatically warmer MWP will be any kind of constraint. Thus the couple of tenths of deg C that are in dispute here are simply just not that relevant for the questions of future climate. They are very interesting in terms of climate history and spatial patterns of change of course, but the MWP question is just not that important. - gavin]

  34. 84

    Re:76 Rob B. But I bet you’re glad you weren’t around thouse millions of years back. Think you’re missing a little piece of the puzzle..this time it’s us who have changed the biochemistry..not comets, not dinousaurs breaking wind…this time Rob..it’s US!

  35. 85
    catman306 says:

    “66, 68: Who wake you guys up?” -Rod B

    It was this guy that awakened me:
    The Greenhouse Effect: Science and Policy
    Stephen H. Schneider
    Science 10 February 1989 243: 771-781 [DOI: 10.1126/science.243.4892.771] (in Articles)
    ……of Science Article Article The Greenhouse Effect: Science and Policy Stephen…Global warming from the increase in greenhouse gases has become a major scientific…That infrared radiation is trapped by greenhouse gases and particles in a planetary atmosphere……

    (Perhaps someone can produce the abstract.)

    Even back then it was apparent that the unpredictability of climate (and therefore local weather) was going to have major detrimental effects on our global civilization and the planetary biosphere.

    The science is mostly in, local climates almost everywhere are changing in unpredictable ways, worldwide agriculture is starting to feel these changes, species die-offs are an almost daily occurrence, global average temperatures are up, but the denialists continue to spew their scientific sounding nonsense. Maintenance of the social and economic status quo seems to be a principal explanation. Got a better one?

  36. 86
    James Rigby says:

    I have a question about temperature. There is plenty of talk about the global rise in mean temperature. What I am curious about is the projections for temperature variability. It’s well documented that the diurnal temperature range is declining, and thus that the rise in mean temperature is due to disproportionate rise in daily minimum temperature. If we look at a time series of daily temperature (min, max, or average), how is the variance and correlation structure expected to change, if at all? Can someone give a brief answer and perhaps point to references on this?

  37. 87
    pete best says:

    Earth Nears Tipping Point

    http://www.csmonitor.com/2007/0530/p02s01-wogi.html

    Looks like we have 10 years once again to mitigate climate change and here is the reason why I doubt it will happen even with all of the noises coming from the climate science community.

    http://gristmill.grist.org/story/2007/5/29/14713/4957

    Looks like those with the money (ie the fossil fuels industry) will gets its way with the present US administration anyway and with the present administrations policy comes no hope for the rest of the emerging world economies as well.

    So it looks like no matter what exerts say politicians and fossil fuel lobbyists are going to screw us in a manner of speaking.

    [edit]

  38. 88
    Hank Roberts says:

    > a little more creative with your ad hominems? And check your non sequiturs

    The Contributors here are quite good at pruning that sort of thing. Trust me on this. If they’d let every draft I tried to post appear in public, I’d be recognized as a far more caustic and intemperate writer. “Are you sure you’re not from [a lobby, a thinktank, the flying saucer] isn’t an ad hominem, tho’ it’s not snugglebunny-grade writing. An ad hominem would be “look at what this person wrote elsewhere, he makes clear he’s from (or soon going to) [a lobby, a thinktank, Antares] his argument’s not worth considering” —- the point is to try to get the source and documentation, to understand what’s real, on the facts.

    Always the facts, the cites, the careful reading of the text and the explanation by those who understand the particular area of the science.

  39. 89
    Kenny says:

    Thank you for doing everything here at realclimate. It is definitely clearing a lt of things. However, i’ve heard of some new papers in geophysical research letters that seem to suggest warming on neptune and mars or something, and that the warming correlates well with the solar output and earth’s temperature trend. Now even though correlation is not causation, they were very convincing…any chance you could cover those articles? I’m being bombarded by so much criticism and it would be great to have an argument back at them. Thanks!

  40. 90
    J.C.H says:

    The Russians are coming…to save the day!

    http://en.rian.ru/russia/20070530/66362712.html

  41. 91
    Timothy Chase says:

    Re #85

    You might want to have a look at these two posts. The first is specifically about Mars – but touches on Pluto’s presumed “global warming.” (Didn’t know it got that much sunlight.)

    5 Oct 2005
    Global warming on Mars?
    Guest contribution by Steinn Sigurdsson
    http://www.realclimate.org/index.php/archives/2005/10/global-warming-on-mars/

    3 Aug 2005
    Did the Sun hit record highs over the last few decades?
    Guest commentary by Raimund Muscheler
    http://www.realclimate.org/index.php?p=180

    Anyway, some others might have more information for you – and I might be able to get back later today.

  42. 92
    Jeff Stevens says:

    I have read this article with interest, and read the paleoclimate section of the IPCC report, and there are two things that still bother me:

    1. In the graph shown above from the IPCC report, what makes the “hockey stick” shape is the temperature record appended to the end of the proxy record. Without the temperature record the time period from 1800-2000 looks very much like the time period from 800-1000. The proxy records are truncated earlier than the temperature record, but to be consistent with the temperature record, they would need to show a dramatic change between the end of the time series and now. Has anyone looked for this?

    2. I haven’t seen an explanation of what caused the Medieval Warm Period and the Little Ice Age. The IPCC report shows some correlation with solar output, but the difference does not seem to be large enough (<0.5 W/m^2). Is there a generally accepted explanation for what caused these climate changes?

  43. 93
    John Mashey says:

    re: #73: sorry, I messed up an edit: should have said:

    T1000AD < Tnow (already warmer)
    If one says "(T1000AD > Tnow) = OK, but thinks in terms of time instead, with (smoothed) rising temperatures, all this means is that on some date in recent past or near future), the world suddenly goes from OK to not-OK, which makes no sense at all. The first derivative of the temperature is positive, and I don’t see any evidence of a negative second derivative to change that.

    Anyway, if you don’t like the usual proxy reconstructions, how about glaciers?
    a) Look at Figure 5 in
    http://www.unige.ch/forel/PapersQG06/Holzhauser2005.pdf,

  44. 94
    SomeBeans says:

    There is this article on Mars:
    http://www.realclimate.org/index.php/archives/2005/10/global-warming-on-mars/#more-192

    I thought I remembered something around here about Neptune but I can’t find it at the moment…

  45. 95
    Timothy Chase says:

    Rod B (#76) wrote:

    56: “What is for sure as evidenced in core ice samples over the past 650,000 years is that NOW is easily and dramatically the highest the level of CO2 has ever been.”

    I hope you’re referring to the last 650,00 years as “ever”. There’s been many times, millions of years back, when CO2 concentration was much greater than today — and much greater than current projections for 2100+.

    I don’t know specifically how many times they have been above today’s level of 378 ppm (is that the current?), but with the strong feedbacks for the carbon cycle (not included in the IPCC WG1 AR4 estimations), models are projecting between 730 and 1020 ppm by 2100. Levels of 1000 ppm or more have been associated with ocean anoxia and mass extinctions, both on land and in the ocean. Of course, the anoxia due to temperature would take a while to work its way through the ocean. Centuries, most likely. Algae blooms and the anoxic deadzones they leave behind are of more immediate relevance as far as the ocean is concerned.

  46. 96
    Ray Ladbury says:

    Kenny, keep in mind that each planet has different drivers. Solar radiation on Mars is only 36% what is on Earth. And for Neptune, the energy from the Sun is tiny (about 0.1% what Earth receives). The Mars climate models explain the effect on Mars quite well, and we have yet to see a full “year” for Neptune. Anybody who makes this argument is either ignorant or deliberately trying to obfuscate the issue.

  47. 97
    SomeBeans says:

    Here’s a link to the “Neptune’s warming” paper:
    http://www.agu.org/pubs/crossref/2007/2006GL028764.shtml

    Ray Ladbury paraphrased the abstract:
    “Just because there’s no statistically significant correlation and we have no mechansim how this would occur doesn’t mean we’re wrong.”

  48. 98

    Re #83 (comment)

    Gavin, the height of the MWP is less important than the variation of temperature between MWP-LIA-current. Depending of the temperature reconstruction, the variation is 0.1 to 0.7 °C and additional some 0.1 °C at maximum average induced by volcanic explosions in all reconstructions. The range is pretty wide, as that represents natural (mainly solar) variability in the past.

    I know that some (like Briffa) assume that a larger natural variability in the past is a sign of a larger sensitivity for any forcing (assuming, as in most climate models, that the different forcings have similar sensitivities). Others like Esper, Luterbacher, Moberg, ea. have the opposite opinion:

    “So, what would it mean, if the reconstructions indicate a larger (Esper et al., 2002; Pollack and Smerdon, 2004; Moberg et al., 2005) or smaller (Jones et al., 1998; Mann et al., 1999) temperature amplitude?
    We suggest that the former situation, i.e. enhanced variability during pre-industrial times, would result in a redistribution of weight towards the role of natural factors in forcing temperature changes, thereby relatively devaluing the impact of anthropogenic emissions and affecting future predicted scenarios.”

    I agree with the latter (but you know, that I am convinced that the role of solar is underestimated in current models)…

  49. 99

    #43, You must also talk to an Icelander, as I did, and the story of Greenland was a practical joke by Icelanders who were perfectly happy to keep away unwanted visitors by diverting them to greener pastures.

  50. 100
    Timothy Chase says:

    Re SomeBeans (#87):

    Some more info on Neptune…

    The following post analyzes the paper on the statistically insignificant correlations (by the authors’ own admission) between Neptune’s brightness and Earth’s temperature, then in an update includes a link to a tech paper which concludes that the evidence regarding Neptune is most easily explained by seasonal variability (seasons last longer out there). Given the problems Connelly cites, it seems odd that the orginal paper ever made it through peer review.

    Suggestive correlations between the brightness of Neptune, solar variability, and Earth’s temperature?
    Posted on: May 10, 2007 4:02 PM, by William M. Connolley
    http://scienceblogs.com/stoat/2007/05/suggestive_correlations_betwee.php


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