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Réchauffement global sur Terre ?

Classé dans: — gavin @ 13 octobre 2005 - (English)

Le Washington Post a choisi de se pencher sur la derniere mise a jour de l’analyse des anomalies de température en 2005 développées par le laboratoire GISS de la NASA. La valeur de cette anomalie terrestre de janvier a septembre 2005 (ajustée pour prendre en compte les biais urbains) est plus chaude que la précédente année la plus chaude (0.76°C a comparer a l’anomalie de 0.75°C pour les memes mois de l’année 1998, et une anomalie de 0.71°C pour l’année complete) , alors que l’index terre-océan (qui prend en compte les températures de surface océaniques) est tres légerement inférieure (0.58°C a comparer a 0.60°C Jan-Sep 1998, et 0.56°C pour la moyenne annuelle 1998). L’équipe du GISS (dans laquelle je ne participe pas) a prédit qu’il était probable que 2005 allait dépasser le record de 1998 (quand avait eu lieu un large événement El Niño au début de l’année) en se basant sur les tendances a long terme de la température de surface et la continuation d’un déséquilibre persistant du bilan radiatif terrestre.

En 1998 les trois derniers mois de l’année ont été relativement froids en raison de la disparition progressive d’El Niño. Pour que l’index global terre-océan 2005 dépasse celui de l’année 1998, l’anomalie moyenne doit rester supérieure a 0.51°C au cours des trois prochains mois. Comme il n’y a pas eu d’El Niño cette année, et que la moyenne est, jusqu’a maintenant, significativement au dessus de celle-ci, cette hypothese semble probable.

Est-qu’un nouveau record de quelques centiemes de degrés signifie vraiment quelque chose ? Les tendances importantes du climat ne sont pas fondées sur des années spécifiques, mais sur les tendances sous-jacentes qui sont “robustement” positives au cours des dernieres décennies. Chaque nouvelle année ne sera pas systématiquement plus chaude que la précédente en raison de la variabilité intrinseque (‘météo’) de la température globale moyenne (0.1 a 0.2°C), mais a la vitesse actuelle de réchauffement global (~0.17°C/décennie), de nouveaux records peuvent etre attendus assez fréquemment. Restez en ligne pour de plus amples informations sur ce sujet…

Mise a Jour: Les chiffres fournis par le CRU/Met Office numbers sont legerement différent de ceux du GISS/NASA, mais il faut faire attention a comparer des objets strictement similaires. L’anomalie terrestre de Janvier a Aout 2005 Jan-du CRU est de 0.81°C par rapport a 0.84°C pour la meme période en 1998.

25 Responses to “Réchauffement global sur Terre ?”

  1. 1
    Reinout says:

    Also the following site gives this data (on the 15th of each month).

  2. 2
    Steve Latham says:

    2005 wasn’t really an El Nino year, as Gavin points out above, but there were many similarities with El Nino years. Or so I have been told. There was little coastal upwelling on the Pacific coast (of North America at least) and I believe several other oceanographic features mimicked El Nino. Sorry for the lack of citations, but I am only recalling what I was told when I was trying to understand why Fraser River sockeye were showing up much later than usual and similar in timing to El Nino years. My understanding is that these oceanographic anomalies are subsiding (like the ’98 El Nino, I guess), so it may not be reasonable to assume that temperature trends for the remaining months will contrast strongly with ’98.

  3. 3


    Good point, North Pacific Ocean temps were also seen higher than usual ….

    Check out the current temp anomaly over the North Pacific:

    I read the same article as above, and became curious about another lame excuse, a world wide warming cycle theory. Wow, I must say all these cycles are everywhere:
    South Atlantic, Arctic, Pacific and now the entire world! The argument for natural variability is based on a false premise, that the world’s environment of today was the same as lets say the year 1535 , with a small exception of 6 billion people and hundreds of millions of internal combustion engines constantly belching out fumes in the air we breathe. Those adhering to multiple temperature cycle theories need to review all their environmental parameters, througout time, and especially explain what is natural about man made pollution?

  4. 4
    David Wojick says:

    Can you explain, or refer me to, how the data is adjusted for urban biases? To my knowedge we have not measured the biases.

    [Response:Hansen et al (2001). -gavin]

  5. 5
    Gil Pearson says:

    I thought the WP article was fair until I saw the graphic at the end. They used a new way to show the surface temperature. They put the mean at the 1980 temperature and coloured everything below the temperature at that time blue, everything above red. The reader is invited to think that the only warming that occured last century was after 1980. The temperature rise that occured from 1900 to 1940 ends up in the blue section and gets lost in the cold part of the century. I am always troubled when I see dishonesty like this. I think that the credibility of those who are concerned about global warming is reduced. Do they need to hide the fact that there was warming from 1900 to 1940? Where did the WP get this graphic from?

    [Response:The NCAR dataset is with respect to the 1961-1990 mean and that appears to be what was plotted. I don’t see any dishonesty there. -gavin]

  6. 6
    Stephen Berg says:

    Re: #4,

    David Parker’s study shows the UHI plays no significant role in the temperature record.

    The article is profiled here:

  7. 7
    Dano says:

    That’s fine snark, wayne, and:

    Those adhering to multiple temperature cycle theories need to review all their environmental parameters, througout time, and especially explain what is natural about man made pollution?

    It’s natural, wayne, because we are a part of nature. We are not separate from nature, therefore it is natural.

    An argument that the CO2 ppmv levels are unprecedented certainly can be made, which obviates any ‘natural cycle’ hand-waving. But anything any species on the planet does in its normal metabolism and life processes is natural.

    What’s not natural, IMHO, is our society’s separation from nature and thus the resultant inability to apprehend natural processes [which is difficult with our limited sensory input anyway].



  8. 8
    Stephen Berg says:

    Re: #7, “It’s natural, wayne, because we are a part of nature. We are not separate from nature, therefore it is natural.”

    I disagree. If we were to live out a natural life, we wouldn’t have created such infrastructure (power plants, high-pollution industries, etc.) that has devastated the environment at many times in history.

    We would have been a hunter-gatherer society and technology would have consisted with, at most, flint sticks to start fires for cooking the catch of the day (whether bison, moose, or deer). In short, we would live out life as the Aboriginals did in North America prior to European conquest.

    Now, Iâ??m not saying that would be the desired lifestyle today, but what I am saying is that we are no longer living a naturalistic lifestyle. Heck, look at the chemical compounds weâ??ve created in laboratories that would have NEVER been made a century ago and would be essentially impossible for nature to create on her own.

  9. 9
    David Wojick says:

    Re #4, Hansen et al say “We find evidence of local human effects (“urban warming”) even in suburban and small-town surface air temperature records, but the effect is modest in magnitude and conceivably could be an artifact of inhomogeneities in the station records. We suggest further studies, including more complete satellite night light analyses, which may clarify the potential urban effect.”

    This hardly sounds like they think they have “corrected” for it, as you claim. I think a fair assessment is that we know there is a UHI effect but we don’t know what it is and so cannot correct for it. Bad data is bad data.

    [Response: You think wrong. The above statement is about a potential residual trend, after the main impact in the urban centers has been corrected for. Whether this residual trend is significant was tested by Parker (2004) (ref above) (as you well know) and found not to be detectable. – gavin]

  10. 10
    Dano says:

    Re: #8:

    Steven: the environment is not a separate “thing” from us. We are part of it. Our cultural evolution made the technological revolution while we lived in nature, and increased the CO2 ppmv as a result. We certainly are not living a ‘naturalistic’ lifestyle [which I take to mean ‘with nature’], but our pollution was created by us living as a part of nature, and is natural. If we call pollution ‘unnatural’, this implies we don’t live in nature.

    Anyway, there is a big debate occurring now about framing this issue and how your phraseology is completely…er…natural here.

    Re: #9, if I can expand on gavin’s reply, Karl first quantified the effect of the UHI in 1989. Sixteen years ago. We knew what it was then and it is corrected for now.

    But it might be useful for all of us if David could actually back his claim that the data are bad, and what constitutes ‘bad’. Set some parameters ahead of time, DW.



  11. 11
    dan allan says:

    I have a general question on the temperature anomalies. As I understand it, they refer to the anomaly versus the previous 100 years of global average temperatures. But if this is so, that suggests that 1998 anomaly is against a different 100 years than the 2005 anomaly…which I have trouble believing, because it would serve to downplay the rate of GW. Anyone care to clarify?

    [Response: When you see a graph of anomalies, they are usually against a 30 year (not 100 year) reference period. Usually 1960-90 nowadays. But on any one graph the same ref period would be used for all the data, it would indeed be very confusing is each year were anomaly from the 30y before that very year (if thats what you’re wondering) – William]



    BTW, Dano, your definition of “natural” is pretty silly, since you have succeeded in encompassing everything that has ever happened and could ever happen into “natural” events. So we no longer need the word, do we? Of course, we are just another species and what we do, arguably, is therefore “natural”. But we all know what is meant by the word, it is a useful term, and your version of it renders it useless. Just my opinion.

  12. 12
    nanny_govt_sucks says:

    Isn’t a flat, or slight cooling trend in the surface data over the last 3 years some “good” news to crow about? Or has no one noticed this in all the alarmist hysteria?

  13. 13
    Andrew Dodds says:

    Re: 12

    Just as a thought experiment, if the last 3 years had each gotten progressively warmer, would you accept it as definitive proof of global warming? Since you consider 3 years long enough to establish a stastically valid trend in climate.. (Or would that be ‘different’?).

    Actually, this news is quite bad. Previously, is was claimed by skeptics that the 1998 anomoly made the temperature trend look far worse than it was. The fact that we are now seeing global temperatures exceeding this without such strong el nino effects is a confirmation that AGW theories are correct.

  14. 14
    Janne Sinkkonen says:

    Re: #12

    If you look at the same dataset at the NASA site, you find out a yearly variation around the trend, with standard deviation about 0.12 degrees. The “trend” of last three years has been about 0.06 degrees in 2002-2003 and 0.04 degrees in 2003-2004, which as absolute yearly differences are actually below average. During the last 30 years, there have been four such three-year downward “trends”. IMO there is nothing to write home about.

    By the way, by all likelihood, 2005 will be warmer than 1998, currently the hottest year on record.

  15. 15
    Timothy says:

    Re: #12 and more generally…

    As pointed out in the body of the post above: “The important climate trends aren’t based on individual years, but on … decades.” Three years isn’t enough for a trend. Since ENSO variability is a big driver of the global temperature variability [around the trend] you’d want a decrease to be sustained over a couple of ENSO cycles [>10 yrs] rather than three years.

    What is significant about this year is that it would be a new record warmest year without there being a strong El-Nino as in 1998. This suggests that the next time there is a strong El-Nino [comparable to 1998] you’d set a new record even higher than 1998 and 2005.

    As long as the trend in rising temperature continues [as CO2 continues to rise], then eventually even the “coldest” years that happen due to variability will be warmer than 1998.

  16. 16
    Dano says:

    BTW, Dano, your definition of “natural” is pretty silly, since you have succeeded in encompassing everything that has ever happened and could ever happen into “natural” events. So we no longer need the word, do we?

    Thanks for the critique of my argument dan; obviously this needs work. We do need the word. What prompted my reply was the statement that man-made pollution was ‘unnatural’, when that is not the case. If the only conclusion drawn from my argumentation is that every event is natural, that’s OK, but my linky and larger point was that there is a larger discussion over the environment as a “thing”, a distinction which allows the environment to be devalued (and allows the environmental movement to be seen as a special interest). We see evidence of this in this very thread – ‘alarmist hysteria’.

    Highlighting the distinction is a semiotic and framing exercise, intended to show that the environment isn’t separate from man, therefore when we pollute into the environment, that pollution doesn’t go somewhere that doesn’t affect man – it’s not an ‘externality’, but rather an accounting error.

    Arguments made – and entered into the public discourse – about the effects of AGW and our response to them should be seen as affecting all of us, not just as an argument by special interest or about “thing”.



  17. 17
    Lynn Vincentnathan says:

    RE 7,8,10,11. Let me try to clear this up. All is one (nature/culture, etc) – no doubt about it. That’s why were in a fix with GW & other environmental dangers now.

    However, we can make ANALYTIC distinctions for the sake of better understanding. These are not concrete distintions. So we can speak of culture or the cultural dimension, as analytically distinct from the environmental (biological, other natural & physical sci dimensions). We can speak of the cultural, psychological, and social dimensions — in addition to the “natural” or phys sci dimensions. Each dimension has its own dynamics, properties, patterns that cannot be reduced to another dimension or combination of dimensions, but they are all impacting and interpentrating each other and the “whole.” Now it might be different on Mars, where there are no people…yet (we’d have to subtract a lot of these dimensions).

    This is a non-deterministic model (sort of ecological), but each dimension has impact. For instance, the cultural dimension would include beliefs, knowledge (incl scientific), values, world view, ethos, technology. How we see, view, value, and use the world has an impact. But not total impact, because the social (other people, group dynamics, relationships (political/power, econ, family/friendship)), the psychological (emotion/affect/drive, cognitive processes & content at individ level), and all the phys. sci dimensions are also impacting the cultural….and “the whole.”

    Almost all of these dimensions play a role in AGW, its causes & consequences.

    I’m an anthropologist, Dano. Don’t put me out of work!

  18. 18
    Dan Allan says:

    I have no objection to your overall point. I could have worded my criticism a little more delicately.
    – Dan

  19. 19

    “Alarmist hysteria” is a pejorative slogan designed to bring down Global Warming from a very serious topic to a kindergarten name calling level of discussion.

    I am finally glad to read high level dedicated climatologists being published a little more than not. Those who want to diminish their work are only fooling themselves.

  20. 20
    Michael Jankowski says:

    RE:”Global Warming on Earth,” plus #14, #15, etc.

    Not that it’s particularly important where 2005 ranks in “recorded history,” but Britain’s Met Office is saying it will likely be #2 or possibly even #3. At least according to the Met Office, it’s quite premature to claim it is “likely” or “in all likelihood” that 2005 will be hotter than 1998.

    Reuters: 2005 set to be second hottest year on record

    ***2005 will be the second or third warmest year on record globally, Britain’s national weather service said on Friday…

    …”Whether it is second or third depends on how Siberia reacts between now and the end of the year,” said Wayne Elliott, Met Office spokesman.***

  21. 21

    #20 May be so, but likely #1 for the Northern Hemisphere, a quite interesting Hemispheric split so to speak.

  22. 22
    Steve Bloom says:

    Re #20: We of course won’t know for sure until January, but if temps for the last quarter of this year are no less than the same quarter in either of the last two years, 2005 will be the new record. The Met Office must be assuming some part of the globe (apparently Siberia) is going to be cooler (relative to those years) than does GISS. Another interesting difference is that the Met Office thinks the reliable global record goes 20 years farther back than GISS does.

  23. 23

    Differential refraction forecasting method as explained on my website, disagrees with the British Met office, at least with aspects of a cooling for the Canadian High Arctic (next to Siberia). Latest September and October data indicates a continuance of warm or warmer temperatures when compared with 2002-04 data. This will likely make 2005 # 1 warmest year in history for Northern Hemisphere. Sun Oblateness method successfully predicted this past warmest summer in history for Northern Hemisphere. Odds are very strong that 2005 will be called #1. If I am not mistaken, NASA Giss recognizes the year ending on November 30.

  24. 24
    Timothy says:

    Re: #22: “We of course won’t know for sure until January…”

    Or perhaps later. There’ll be all sorts of quality control checks that will be applied to the raw data. I imagine that various institutions will want to be the first to announce it were it to be the warmest year, though.

  25. 25
    John Finn says:

    Why is the GISS record being quoted?

    The CRU record suggests that 2005 might be 2nd warmest but will be nowhere near the warmest.

    The satellite record agrees with the CRU record – at least as far as the relative warmth of 2005 to previous years is concerned.

    The GISS record is out of step.

    [Response: There is a reasonable point to be made here about comparing with what the CRU record shows. However, such a comparison hardly justifies the description “nowhere near the warmest”. Preliminary CRU land-only estimates are not yet provided publically. Moreover, September data is not yet available which makes any direct comparison with the cited GISS values impossible. However, the CRU global mean combined land air/sea surface temperature estimates for Jan-Aug 2005 lag behind the 1998 annual mean estimate by 0.08C (0.50C vs. 58C for 1998) while GISS indicates a lag of 0.02C. A difference perhaps, but certainly not enough to say that the GISS record is “out of step”, particularly when one notes that the Sep value is not included for CRU. In both cases, 2005 is well in front of the next warmest year (2002 and 2003 tie at 0.475C in the case of CRU). What is most significant about the global mean warmth of 2005 is that, unlike 1998, it occurs during an essentially El Nino-neutral year. In other words, El Nino cannot be implicated with the anomalous global mean warmth recorded this year. -mike]