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A barrier to understanding?

Filed under: — gavin @ 27 December 2007

People don’t seem to embrace global measures of temperature rise (~0.2ºC/decade) or sea level rise (> 3mm/yr) very strongly. They much prefer more iconic signs – The National Park formerly-known-as-Glacier, No-snows of Kilimanjaro, Frost Fairs on the Thames etc. As has been discussed here on many occasions, any single example often has any number of complicating factors, but seen as part of a pattern (Kilimanjaro as an example of the other receding tropical glaciers), they can be useful for making a general point. However, the use of an icon as an example of change runs into difficulty if it is then interpreted to be proof of that change.

With respect to sea level, the Thames Barrier is a concrete example that has been frequently raised.

The trends in its ‘raising’ have been linked to increasing sea levels and storm surges. But how often is it being raised? why? and does it give us any real insight into sea level rises on a wider basis? Looking into it, I was fortunate to get an exceptionally comprehensive set of data on the closings and reasons for them from Anthony Hammond at the Environment Agency in the UK. The results are interesting, but complicated….

The background to the Thames barrier is available here, but suffice to say it started operating in 1983, and is raised whenever there is a forecast danger of high tides, river flow and storm surges combining to threaten London. It has been raised over 100 times operationally since being constructed.

Lest you think this isn’t really a problem, I recall a friend’s car being parked near the boathouses in Putney. After a particularly high tide (this would have been in 1992 maybe), she returned to the car to find it filled with river water. No amount of cleaning ever got rid of the rather pungent odour. Flooding along the riverwalk in Chiswick near where I lived at the time, is frequent. And of course, the city has been flooded many times in the past – most recently in 1953 when over 300 people died.

The raw data on the closings (per winter season – the 2007 number is for Mar 2006 to Mar 2007) is seen here:

It is clear there has been a strong upswing in closings over time. The last year alone there were almost 3 times as many closing as during the first 5 years of operation put together. The three-year running mean is possibly a little clearer, showing two definite periods of more frequent closings, 1992 to 1995 and 2002 to the present.

Is this a sign of increased sea level, increased storminess, increased river flow, or changes in river management policy? As always, local factors in short records are important. Over the two and half decades of barrier operation, understanding of the Thames river hydrology has grown and models are now more accurate than they used to be, allowing for more precision in decisions to raise the barrier. The decisions depend on three main factors, the river flow at Teddington (which is where the first weir is), the forecast high tide and the (more uncertain) accompanying surge. Thus if the river flow is strong, an unexceptional high tide could cause problems, while even an exceptional tide might not if the river is particularly low. In the data, closings are distinguished by whether they are due to tidal issues, or to the combined effect of tides and high river flow (fluvial), but there is not necessarily a clean distinction.

In the 25 years of operation, global sea levels have risen around 5 cm, but it’s not at all clear that such a change would be registered in the very noisy extreme surges. The two peak years for closure (2001 and 2003) had very strong river flows, making the tidal threshold for closure much lower than normal.

Overall, the tidal height over time associated with a closure decision has actually decreased (by about 2cm a year just looking at the tidally driven closures). This hints at a possibly increasingly risk-averse management policy, or it might reflect changes in the river models used for predictions (for instance, if including more detail increased the variance). However, the highest tides do come towards the end of the record – the very highest tides at Southend (above 3.9m) occurred in 1994, 2004 and (the highest at 4.04m) 2007. For tides > 3.7m, there were 12 in the last ten years, compared to only 3 in the first ten years in line with generally increasing sea level. However, tidal records are probably best examined directly for these kinds of statistics. The raw data for the barrier closings are available here if anyone wants to look into it further.

This might be a good point to address some confusion that is knocking around. For instance, there is a statement from an official UK govt. (Defra) report on whether the closings are a useful indicator of climate change that states:

Because the Thames River Barrier is now subject to different operating rules, it may be less useful as an indicator. The barrier is now closed to retain water in the Thames River as well as to lessen the risk of flooding. (It was closed on 9 successive tides at the start of 2003.) Thus, the number of closures has increased greatly in recent years. This indicator would only be useful if it were possible to distinguish the number of closures made specifically to lessen flood risk.

My contact at the Environment Agency noted that “I have read the Defra statement that you mentioned; it seems that it is a misunderstanding or simply a poor written account of what the Barrier does. The barrier does not maintain river levels during low tides and it never has.” However, he counsels that “the pattern [of closings] is erratic and the years of operation too short for it to be an indicator of sea level rise”.

To summarise, Thames Barrier closings tell a complicated story which mix climate information with management issues and are probably too erratic to be particularly meaningful – if you want to say something about global sea level, then look at the integrated picture from satellites and tide gauges. But it is a good illustration of adaptive measures that are, and will increasingly be, needed to deal with ongoing climate change.


129 Responses to “A barrier to understanding?”

  1. 1
    S. Molnar says:

    Gavin writes “With respect to sea level, the Thames Barrier is a concrete example that has been frequently raised.” I don’t know if the phrasing was intended to amuse, but I burst out laughing. One quibble, however: it’s actually concrete and steel.

    [Response: Pedant! ;) - gavin]

  2. 2

    The Environment Agency has just completed a comprehensive review of some of these issues, pulling together GPS, tide gauges, absolute gravimeters and InSAR data. It shows London continues to subside at 1-2mm a year. With waters rising in the region by about 1mm a year, the combined effect is a 2-3mm a year rise in sea level with respect to the land. With some slight modifications, the barrier is good for a number of years yet. The engineers who built it were very far-sighted. I’ve written about it at:

    http://news.bbc.co.uk/2/hi/science/nature/6231334.stm

  3. 3
    Jim Redden says:

    I’ve seen the Thames River Barrier, but impressive as it is, some very large lurking problems of climate change are harder to envision.

    While the concerns of rising sea levels due to thermal expansion and melting polar glacial ice are very provoking, my primary concern of anthropegenic forcing remains disruption of bio-geochemical cycles.

    Not to sound like a broken record, but, the food chains of the oceans have been polluted and gutted by overfishing; the result of these pressures is a weakening adaptive ability to climate change of any kind.

    Huge swaths of terrestrial biomes in have been placed in service to agriculture.

    In both cases, the destabilizing loss of diversity, and the commensurate diversion of energy, space, and life activity, to sustain humans is more than dangerous.

    Given that we are in the midst of massive unprecedented changes in the chemical makeup of the atmosphere, one can see how James Lovelock arrives at such pessimistic conclusions. Natural systems may break rather than adapt.

    I am not one to give up hope, but given the politics at hand, we might just end up watching the end on TV.

  4. 4
    Fernando Magyar says:

    Re#1, Ah Mr Molnar, you beat me to that one, I too laughed out loud at the ebb and flow of the puns in that phrasing.

  5. 5
    Pat Neuman says:

    In the U.S., a barrier to understanding global warming was created by misinformation from agencies in NOAA on weather, climate change and hydrology. Examples at:

    http://npat.newsvine.com/_news/2007/12/21/1179815-national-weather-service-minnesota-offices-downplayed-climate-change-for-more-than-13-years

  6. 6
    Pat Neuman says:

    Regarding the Thames, increasing river flows in many regions of the world suggest that the frequency of Thames Barrier closings may be a result of increases in river flow.

    Photos and graphs of recent heavy runoff in the Midwest are at:

    http://picasaweb.google.com/npatnew/UpperMidwestHydrology

  7. 7

    I too am pessimistic. Population growth has to be considered as a major factor in climate change, given the technologies available. The human race must forget about the Biblical injunction to be fruitful & multiply. Fertility rates everywhere must be given incentives to become less than 2 children per woman. A rational approach to this can be found at http://www.npg.org–Negative Population Growth.

  8. 8
    BlogReader says:

    [ It shows London continues to subside at 1-2mm a year. With waters rising in the region by about 1mm a year ]

    Didn’t know that London was sinking into the ocean, and at twice the rate of any climate change.

  9. 9
    Marchand says:

    Re N°8 : Yes, London is sinking, while Scotland is rising (a souvenir of the end of the last glaciation).

  10. 10

    Since GW has already been proven beyond a 5% doubt, attribution of single events is more like “deconstructing” the statistical level of climate, and getting back down to the micro-level.

    I’m thinking like this. We live in a globally warming world. Events that are expected in such a world could be attributed to GW, with the idea it would be up to the skeptics or scientists to prove at scientific certainty the event is in no way impacted by GW (e.g., by finding other factors that more greatly overshadow any GW effect). So from a layperson’s perspective (one not out to sue for damages), I feel OK with linking single events expected in a globally warming world to GW. Afterall, the stats are just a collection of many such above average or above baseline events.

  11. 11

    Sea level rising in millimeters and temperature rising in degrees are too small. At the other end, the collapse of civilization and the extinction of Homo Sap are too big and evoke surrender. Perhaps the drought in Atlanta, Georgia, California, Australia, Greece, Turkey, the Sahel, China and other places would be closer to the right size. Changes in soil moisture affect crop yields, and everybody knows this. Both Jared Diamond and Brian Fagan, the author of “The Long Summer,” blame minor climate changes for the collapse or as a factor in the collapse of many civilizations. Jared Diamond points out that present time environmentally stressed countries are the same countries that are suffering breakdowns of government, genocide, terrorism, and so on, because the citizens of those countries are hungry or starving. Food is the issue to communicate to the masses. If it doesn’t rain in Iowa, what are Americans to eat?
    Another thing you have going against you is religion. In “Collapse, How Societies Choose to Fail or Succeed,” Jared Diamond discusses how religion has played a role in the collapse of some civilizations. Christianity contributed to the collapse of the Greenland Viking civilization. Religionists will, of course, resist any change in values regardless of the fact that a change in values is necessary for survival. This is an issue of the preachers’ income. In the end, the preachers may be eaten, but it is too late by that time. Yes, “Collapse” has its gory points.

  12. 12
    henning says:

    Thanks a lot for that one, Gavin. Understanding what can be linked directly to AGW and what can’t is very important in the political debate. Blaming AGW for everything and seeing “evidence” everywhere would not lead to more public awareness – in the long run it would be rather the opposite. Personally, I would have liked to see somewhat more of this in the “Gore” thread… but never mind. ;-)

  13. 13
    A. Simmons says:

    I’m surprised the article made no mention of the UK government’s (recently retired) Chief Scientific Officer Sir David King, who has frequently used Thames Barrier statistics as an example of real-world evidence for AGW. (See for instance this 2004 address to the AAAS, and Google has many more examples.)

  14. 14
    Akseli says:

    Scotland, Norway, Sweden, Finland and many other places are rising and pushing away water from their coasts. Where is all that water going ?

  15. 15
    rick says:

    #5 Very interesting info.
    I’ve had my own doubts about my local NWS in New York. They always seem to be understating the actual temperatures we experience here, especially during the Winter.

  16. 16
    Ricks says:

    Mount Kilimanjaro seems a poor example.
    “Kilimanjaro’s ice has been melting away for more than a century, and most of that melt occurred before 1953, prior to the period where science begins to be conclusive about atmospheric warming in that region, according to Philip Mote of the University of Washington and Georg Kaser of the University of Innsbruck in Austria. “

    [Response: This is precisely what my bigger point was. Kilimanjaro, like almost all other tropical glaciers, is receding fast. These glaciers have existed continuously for 1000's of years, and now the one on Kilimanjaro is disappearing (and it really is). The important point is that tropical glaciers are receding everywhere (see our previous post) and that is much more easily attributable to global climate change than any one glacier. However, Kilimanjaro is a great example of tropical glacier retreat, even if on it's own it is not proof of the attribution. What gets lost in these discussions is the whole balance of evidence from other sources. - gavin]

  17. 17
    Don says:

    response to Bird Thompson
    Actually, population growth is trending the right way. http://www.worldbank.org/depweb/english/modules/social/pgr/
    Global rates of growth, though still positive, are falling. Averaged over all of humanity, fertility rates were about 6 children per woman 35 years ago; now the number is less than 3. We have a huge task ahead of us in feeding 6 billion people now and probably about 9 billion before the total number starts to fall. Certainly GW will make feeding the world much more difficult, and the knock-on effects of secondary pollution will aggravate environmental damage Most overall growth is now in the age structure rather in the number of children per woman. The contribution to greenhouse gases is small among peoples with the highest growth rates. Burning the coal for air conditioning in the southeastern US probably contributes more CO2 to the atmosphere than does Africa and the parts of Asia and the Middle East where poverty and high birth rates are found. GW will harm these impoverished people much more than they will contribute to global warming.

  18. 18

    Edward Greisch posts:

    [[Another thing you have going against you is religion. In “Collapse, How Societies Choose to Fail or Succeed,” Jared Diamond discusses how religion has played a role in the collapse of some civilizations. Christianity contributed to the collapse of the Greenland Viking civilization. Religionists will, of course, resist any change in values regardless of the fact that a change in values is necessary for survival. This is an issue of the preachers’ income. In the end, the preachers may be eaten, but it is too late by that time. Yes, “Collapse” has its gory points.]]

    And yet the Pope has said that global warming is a serious problem and 83 leading evangelicals have signed a statement saying Christians need to act to prevent global warming. How about that?

    [Response: No more discussion of religious issues please. - gavin]

  19. 19
    pete best says:

    Re #18, what would the pope know on this issue really. Although AGW is a serious problem I doubt that it is the main threat in the near term for the first world is some decades off. No, that accolade goes to peak oil, the cost of oil and its global availability. Come 2020 we are really going to be struggling with adequate supply. All IPCC climate models vastly overestimate global fossil fuels reserves and hence peak fossil fuels will come first with oil happening first of all.

    Maybe we can delay the onset of peak oil by a decade by mining increasingly energy poor oil reserves but the writing is on the wall. Once oil peaks extracting coal and gas becomes very difficult so its doubtful they will scale.

    21st century issues eh

  20. 20
    henning says:

    I don’t understand, how even all glaciers put together (or all tide barriers or whatever) could possibly provide “proof” for global warming. We measure temperatures using termometers, we measure percipitation using a bucket on a stick and we measure gas concentrations and radiation using sophisticated sensoring. Obviously, filming a termometer slowly rising by .2C per decade for 90 minutes won’t win you an oscar – but when you want to find out, how the temperature behaved during the last couple of decades, you fire up GISTEMP – you certainly don’t hike up the Kilimajaro with a yardstick or penetrate your garden with a core-driller, right?

  21. 21
    Martin says:

    Just a point of detail. The floods in 1953 referred to in the article did not actually reach the City of London, only going as far as dockland and the east end. The 307 deaths were all along the east coast of England from Northumberland to Essex. (Central London is about 25 miles in-land).

    This is something of a technical point because it is certainly true that the people of London were very worried by the 1953 floods and that the case for a Thames Barrier was made, but as far as I can tell there were few, if any, casualties in 1953 up-river of the site of barrier.

  22. 22

    Aleksi #14 kirjoitti:

    Scotland, Norway, Sweden, Finland and many other places are rising and pushing away water from their coasts. Where is all that water going ?

    Well, to London, for instance. :-)

    Seriously, for every post-glacial uplift area there is a “remote zone” that’s downlifting, very slowly. For Fennoscandia it includes Central Europe.

    BTW Gavin, the Eastern Schelde Barrier in the Netherlands may be interesting to look at, as it is a cleaner example (and a longer time base)

  23. 23
    Ray Ladbury says:

    Henning, Actually, Gavin’s point is very important. The balance of evidence or the aggregate of the evidence is crucial. Drawing conclusions based on data from multiple independent lines of evidence and reasoning makes it much less likely you’ll draw erroneous conclusions. So it is not the thermometers or the yard sticks or the laser altimetry by themselves that make us so confident about our conclusions, but rather all of them together.
    Likewise in evolution, it is not any particular fossil that establishes evolution, but the aggregate of the entire fossil record.

  24. 24
    P. Lewis says:

    Sorry, that should have read:

    Full(ish) details on the UK 1953 floods can be found at the Met Office.

  25. 25
    Ray Ladbury says:

    Pete Best,
    Oh, I suspect we will find a way to use the coal–plenty of that for decades to come. Then there are the clathrate deposits at the bottoms of the oceans–already looking into how to use that. Humans have plenty of ingenuity to release all the carbon we need to cook our own goose. The question is whether we will have the wisdom to apply our ingenuity to making the situation better rather than worse.

  26. 26
    James says:

    Re #20: [I don’t understand, how even all glaciers put together (or all tide barriers or whatever) could possibly provide “proof” for global warming.]

    It’s a cold morning, your outside thermometer says 20F. You want to know if it gets above freezing while you’re away at work (and you have a bunch of skeptics claiming your thermometer is out of whack), so what do you do? Simple: put an ice cube outside. Go to work. If the ice cube’s melted when you get home, it’s a pretty good indication that the temperature got above freezing, isn’t it? If you want to get a bit fancier, you could measure how much of the ice had melted, do a little math, and come up with a figure for degree-hours.

    So that’s glaciers: handy natural sensing devices that integrate temperature and precipitation for you :-)

  27. 27

    Likewise in evolution, it is not any particular fossil that establishes evolution, but the aggregate of the entire fossil record.

    Stronger still: the fossil record, and Linnaeus’s family tree, and molecular genetics: several methodologically different lines of evidence, all telling essentially the same story.

  28. 28
    pete best says:

    Re #25, that just not reality if you study the subject Ray. There are many interpretations but the IPCC projections for fossil fuel energy reserves are extreme best case scrnarios (worse case really) and not reality (well in many peoples eyes anyway).

    You see OPEC all bumped up their quotas in the 1980′s in order to be able to pump more oil. Those rises were not real, they were economic and since then many billions of barrels have been used by their proven reserves remain the same. However the IPCC took data from these reserves and more besides in the ultimately recoverable reserves range.

    No, peak oil or economically more expensive oil is going to be a major destabaliser and if we somehow do find enough oil then climate change will be worse than I expect.

  29. 29
    Ray Ladbury says:

    Re 27. Exactly! A single fossil or measurement can mislead. A single trend can be misinterpreted. However, when all the data are telling you anthropogenic CO2 is behind the warming, it’s bloody unlikely that all the people analyzing all these data are making mistakes in the same direction. That seems to be what denialists–of anthropogenic climate change or of evolution–seem to miss.

  30. 30
    VirgilM says:

    Pat Neuman Re #5…

    A particular climatic event like the 1993 Midwest Flood in itself isn’t proof of anything. There has been paleoclimatic research published on such events (Midwest River Floods) and many such events have occurred in the last 1000 years before significant human arthoprogenic climate forcing. Some of those events were much more severe than what was experienced in 1993. So how can you be so sure that the 1993 Midwest Floods was not a natural event?

    Yesterday, I read a paper in the journal Earth-Science Reviews: Cook et al (2007) North American drought: Reconstructions, causes, and consequences. In the abstract, this paper notes: “Of central importance to drought formation is the development of cool “La Nina-like” SSTs in the eastern tropical Pacific region.” So if persistant La Nina conditions causes drought over significant portions of the United States, then could it be that persistant El Nino conditions causes floods over significant portions of the United States? Going back to the ENSO record during that time, Neutral to Moderate El Nino conditions was present over the equatorial Pacific from 1990 to the onset of the 1993 Midwest floods. I wonder if such a connection has already been made in published research?

    The point here is that while the National Weather Service sees it’s mission to publicize major climatic events as they happen, they don’t have the research published in journals available to them that tells them if the climatic event is human caused or natural caused. Such research only gets published years after the event. Many NWS offices have chosen to take the conservative approach in this area to preserve credibility and trust rather than in enguaging in non-peer reviewed speculation on the causes of climatic events.

  31. 31
    henning says:

    “However, when all the data are telling you anthropogenic CO2 is behind the warming…”

    Does it? A rise in sea-level is just that – a rise in sea-level. It can be measured and it can be broken down to various contributions by further investigation. The frequency of the closing of some human controlled barrier surely does not even remotely clarify whether there is a rise in sea-level, let alone that it’s cause lies in the warming of our planet and even less so when it comes to the question of what caused this warming. You don’t have to be a denialist to see that you can stretch an argument only so far.

  32. 32
    Ray Ladbury says:

    Pete, I don’t doubt that Peak Oil will be a factor, but it will be short term. I have greate faith in human ingenuity. I’ve seen it work time and again–mostly digging us deeper and deeper into a hole. Peak oil means there’s more incentive to find new ways to use other energy resources. Now those resources could be renewables, or they could be coal, and clathrates and nukes, etc. Indeed, there may be only a tiny difference in cost between them. But that tiny cost multiplied by billions of consumers will make somebody very, very rich.
    Look at India. When the wood was gone, they went further and go more wood. When that was gone, they used the stubble from their fields. Now they use animal dung. There’s a whole industry processing animal dung for use in cook stoves. Economics doesn’t stop when things get expensive, or even when things are used up. It goes on as long as there are sufficient resources to support life–just like bacteria in a bottle.

  33. 33
    Ray Ladbury says:

    Henning, Yes, a rise in sea level says little in and of itself. However, if a theory predicts a priori that sea levels will rise, the rise is evidence that favors that theory over those that predict no rise or falling sea levels. Moreover, if the theory predicts the rise quantitatively within errors, the support for the theory is stronger.
    Similar arguments apply to melting glaciers and sea ice. Likewise if one model predicts that night-time temperatures will see greater effects than daytime temperatures–that favors said model. You cannot look at an isolated result or line of reasoning. However, if you have lots of favor a particular theory moderately strongly, the result is no less convincing–and maybe moreso–than a single smoking gun.

  34. 34
    John Mashey says:

    re: #28 peak Oil

    1) I recommend the recent paper by Kharecha & Hansen, “Implications of “peak oil” for atmospheric CO2 and climate”, which is submitted (so its name may change), but rather than talk about that here, perhaps RC might start a thread for it?

    2) As far as I can tell:

    a) IF that paper is reasonable.

    b) IF The Ayres+Warr work is reasonable, i.e., that GDP growth is more dependent on exergy = efficiency * energy-used than any other factor, i.e., the “Solow residual” isn’t jsut “technology”.

    c) THEN the idea held by many economists that one can defer climate change mitigation because people in 2100, 2200… will be much richer and they can do it (i.e., sometimes described a positive discount rate) … is seriously wrong.

    d) In particular, no matter how cheap an iPod with a Terabyte of memory gets, things that actually require energy in the real world won’t, especially when there’s effectively no petroleum left:
    - Water
    - Nitrogen-based fertilizer [natural gas]
    - Food (The Economist: “The End of Cheap Food a week or two ago)
    - Required transport of food & needed materials
    - Concrete & steel
    - Building dikes and sea-walls, earthmoving in general

    As economists would say, iPods are not substitutes for these goods. [Of course, we can get more efficient, we can electrify, use biofuels for the necessary transport, stretch the oil&gas longer (to avoid coal-to-liquid and burning a lot more coal), and maybe it won’t be worldwide depression, but it’s just hard to see how there is *not* going to be a negative discount rate during much of the next century.

    Anyway, the article mentioned above is very useful.

  35. 35
    John Mashey says:

    Oops, sorry, the URL for previous post was:
    http://pubs.giss.nasa.gov/docs/notyet/submitted_Kharecha_Hansen.pdf

  36. 36
    Hans Kiesewetter says:

    Re 22: the Eastern Schelde Barrier in the Netherlands may be interesting to look at, as it is a cleaner example (and a longer time base)

    Not interesting (sorry). Had a quick look, see: Wiki NL”

    Construction finished in 26 june 1986.
    Number of closures period 1986-1995: 13.
    Number in period 1996 – 2007: 5.
    (Counting two closures on same day, or following day as one.)

    Also in this case weather is dominant. Climate change is (still) of minor impact. Only a few cm SLR in this period.

  37. 37
    Tom M says:

    There is quite a bit of discussion in RC comments about short vs. long term trends. Mostly with persons cherry picking short term data to justify arguments against long term climate modeling. Can someone answer at what durations could temperature observations contrary to predictions begin to represent real issues? For example SST.

  38. 38
    Stu1211 says:

    Actually temperatures dont necessarily get through to people like other markers do. But it seems people in these cities do get the point. This website http://forum.skyscraperpage.com/showthread.php?p=3225220 lists the greenest cities in the US. This shows that municipalities care about climate change. I guess the general population cares about the environment and global warming. My score on their calculator was 400 but at least I am trying. Here is the link to the website that published the list of cites and where the carbon calculator can be found: http://www.earthlab.com. The test took me like 5 minutes tops, and then maybe another 2 minutes to find the pledges I wanted. Pretty cool application.

  39. 39
    Stu1211 says:

    On a different note, I found this article (http://forum.skyscraperpage.com/showthread.php?p=3225220) listing the greenest cities in the US. This shows that municipalities care about climate change. I guess the general population cares about the environment and global warming. My score on their calculator was 400 but at least I am trying. Here is the link to the website that published the list of cites and where the carbon calculator can be found: http://www.earthlab.com. The test took me like 5 minutes tops, and then maybe another 2 minutes to find the pledges I wanted. Pretty cool application.

  40. 40
    Norman Page says:

    Britain’s CRU data show the following. Global temperature in Nov 2007 was 0.22 degrees colder than in Nov 1997. Warming peaked in 1998. Granted that year was unusually hot, 2006 was still cooler than 2002,2003,2004 and 2005 . This year 2007 is going to end up cooler than 2006. During this period CO2 rose by >5%. There has been no net warming during this 10 year period.
    Many investigators conclude that the sun is the main climate driver and that we may be entering a cooling period for the next 20 years and perhaps until mid century.
    I would like to pose a serious multiple choice question to the Realclimate people. How many more years of rising CO2 and flat or falling temperatures would it take to make y’all begin to question the Anthropgenic CO2 – warming paradigm? A 2, B 3, C 5,D 10 E 15.
    I would seriously like to hear your considered response to this question Regards Norman Page.

    [Response: How many times do we need to say that short term trends are too noisy and cherry picking start dates is a no-no? CRU trends are all positive for this period, but they are noisy. 1998-2007 (crutem3v) is 0.12+/- 0.3 C/dec. Note the error bar. Why is this so hard to do for your self? - gavin]

  41. 41
    Johnno says:

    I think indisputable effects of sea level rise are only a few years away. For example a nearby fresh water intake to a pumping station is about 20km from a river mouth. Recent salt water incursions have come within a kilometre or so. When they have to move the intake further upstream there can be little doubt.

    Some concrete walkways at boat marinas are barely a centimetre or two above mild surge levels; they will have to be rebuilt.

  42. 42
    Norman Page says:

    Gavin. I really would like a response to the question I posed.I will rephrase it.By what year would you reconsider the CO2 – Warming paradigm if the CRU Global annual mean temperature is cooler than 2005 – 2009, 2010 2012 ,2017 or 2022.?
    Regards Norman Page

    [Response: Long term trends from the forcing are expected to be around 0.2 - 0.3 deg/decade. Therefore you need to be able to get uncertainties down to well below those values in order to find a clear discrepancy. Judging from the last thirty years, that period is around a decade. All trends starting before 1996 are unambiguously positive and significant. But so is starting from 1999 or 2000 - 0.31+/-0.22 and 0.34+/-0.29 (95% confidence). Therefore the only significant trends you can find are spot on projections. Even the non-sig trends are still positive and with uncertainties that encompass the predictions. We would start to worry if that didn't stay true, but there is no sign of it. It's never going to be about a single month or a single year. You need a greater than a decade non-trend that is significantly different from projections. Going from the numbers recently, that isn't even plausible in the next 5 years (and I don't consider it likely at all). - gavin]

  43. 43
    per says:

    Re #33

    The important part is make the predictions before searching for the evidence, the more odd the better.

    For instance, because of the indirect and nonlinear nature of climate/weather, I as an amateur that does not know better, thinks it is pretty obvious that ‘necessary but not sufficient’ single event teleconnections does not exist.

  44. 44
    pete best says:

    Re #33, you misunderstand me Ray. Peak oil will make us forget climate change. So many things are made from oil, it will depress our first world economy far too much. We may however create plastics from something else or find additional oil reserves but soon that AGW comes the economic crash or peak oil.

  45. 45
    David B. Benson says:

    pete best (44) — There are already bioplastic products on the market. More coming soon. So I deeply doubt that lack of petrochemical feedstocks will ever be an issue.

  46. 46
    Eli Rabett says:

    Rick #15 if you are talking about NYC the Central Park weater station is in a shaded grove protected from wind. is a picture. The station is maintained in this location because the NWS does not want to break a long historical series

  47. 47
    Daniel Klein says:

    Gavin:

    You write at comment 42:

    “You need a greater than a decade non-trend that is significantly different from projections.”

    OK, lets start with 1998. There is a significant cooling over the past 10 years:
    http://www.remss.com/msu/msu_data_description.html#msu_amsu_trend_map_tlt

    You suggest that trends from 1999 are appropriate to interpret, how about 1998?

    [Response: Oh please. Almost by definition, if you only get a negative trend by picking one specific start date that means that the trend will not be significant. Plus, all the surface records even have positive (non-significant) trends, even starting from then. The issue is significance . - gavin]

  48. 48
    Anthony Watts says:

    RE46 Since “Eli Rabett” is fond of referencing a picture of the NYC weather station, but didn’t actually have one to share, I thought I’d help him out by offering these pictures:

    http://gallery.surfacestations.org/main.php?g2_itemId=3139

  49. 49
    pete best says:

    Re #45, I doubt that they scale as yet. It is all about scale and I would imagine that Oil provides nearly 100% of the volume required for all plastics and petrochemicals.

    It is early days for all alternatives to oil such is its grip on the market.

    In fact recent work by a caltech professor seems to demonstrate that peak fossil fuels will become an issue much sooner that climate change becomes one. Although both are linked to alternative sustainable energy sources, there is still a huge gap between what people propose and reality.

  50. 50

    #36 thanks!

    Construction finished in 26 june 1986.
    Number of closures period 1986-1995: 13.
    Number in period 1996 – 2007: 5.
    (Counting two closures on same day, or following day as one.)

    So using a cleaner data source than London gives a null result :-)

    Not only is the closure data very noisy due to the weather, it is also not properly reduced for, e.g., the lunar declinational tide (saros period, 18.03 a) and who knows what. Sounds like a hopeless exercise.

    I calculated for the heck of it the percentage of closures where the “trigger” of 3.00 m over NAP actually materialized. 69% and 70%, respectively, for both periods. Doesn’t seem they are getting any better at predicting…


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