Refroidissement de l’Antarctique, réchauffement global ?

Thomson et Salomon (2002) ont montré que le Mode Annulaire Austral (une variabilité qui affecte les vents ouest autour de l’Antarctique) avait été dans une phase plus positive (vents plus forts) au cours des dernières années, et que cela joue comme une frontière, empêchant l’air plus chaud d’atteindre le continent. Il y a aussi quelques indications des modèles que cela pourrait avoir été causé par une combinaison de l’appauvrissement de l’ozone stratosphérique et le refroidissement stratosphérique à cause du CO2 (Gillet et Thompson, 2002 ; Shindell et Schmidt, 2004). Il est important de noter qu’il y a des preuves, à partir des reconstructions climatiques basées sur les cernes d’arbres, que la phase du Mode Annulaire Austral a changé de manière comparable dans le passé (Jones et Widman, 2004). On ne peut pas, alors, attribuer les changements de températures récemment observés à une seule cause en particulier.

Alors qu’est-ce que tout cela implique ? Tout d’abord, les observations à court terme devraient être interprétées avec prudence : nous avons besoin de plus de données sur l’Antarctique, sur des périodes de temps plus longues, pour dire avec certitude ce qu’est la tendance à long terme.

Deuxièmement, un changement régional n’est pas pareil à un changement global moyen.

Troisièmement, il y a des explications très raisonnables pour le refroidissement récemment observé qui ont été reconnues, il y a déjà quelques temps, à partir des simulations des modèles. Cependant, les modèles suggèrent aussi que, plus on va dans le temps et plus l’importance relative des effets radiatifs qui augmentent, comparés avec les effets de la dynamique de l’atmosphère et de l’océan, est susceptible d’augmenter. En résumé, nous nous attendons pleinement à ce que l’Antarctique se réchauffe dans le futur.

Page 2 of 2 | Previous page

11 comments on this post.
  1. William:

    It is worth pointing out that the myth of bipolar amplification of global warming is remarkably strong and appears in even otherwise sensible places (e.g. 1, at the end) as well as the standard skeptic press.

    The IPCC TAR actually says:

    For the change in annual mean surface air temperature in the various cases, the model experiments show the familiar pattern documented in the SAR with a maximum warming in the high latitudes of the Northern Hemisphere and a minimum in the Southern Ocean (due to ocean heat uptake) (2)

    and the zonal mean pic (fig 9.8) on that page shows it clearly.

    The myth probably arises from the very early days of equilibrium change runs, where the ocean heat sink effect did not apply.

  2. Doug:

    The fact that the southern oceans are absorbing heat may set up another interesting lag effect. Warming oceans will increase rates of evaporation which will pump more heat-trapping large molecules (i.e. gaseous H2O) into the atmosphere. So, while the oceans are a heat sink in the short-term, warmer oceans are a source of climate gases in the long-term. More positive feedback …

    See for instance, http://www.gcrio.org/ipcc/qa/09.html

  3. David Risen:

    I agree that local events should not be used as evidence for or against global warming. Do you apply the same degree of criticism to authors who use local warming to argue for global warming? Discover Magazine’s #1 story in science for 2004 is that ‘Evidence of global warming became so overwhelming in 2004 that now the question is: What can we do about it?’

    http://www.discover.com/issues/jan-05/cover/

    Read the article. You will see that the ‘overwhelming evidence’ listed is based on LOCAL conditions. I look forward to your editorial comments debunking this dishonest use of science.

  4. Oscar:

    Wouldn’t the real issue about Antarctic cooling be: if the amount of water locked up in the ice cap increasing or decreasing, and at what rate? There is a lot of water down there now, but given the fact that parts of the continent are getting cooler and parts are getting warmers, plus the effects on air currents, etc. this seems like an interesting question to answer. Any studies on the depth of the ice cap?

  5. Understanding Global Warming « Understanding Global Warming:

    […] of extra water vapor, and is not inconsistent with a warming world. Despite this, and a slight cooling in parts of Antarctica (now abating), most of the world’s glaciers have been receding as part of an inter-decadal […]

  6. Understanding Global Warming:

    […] of extra water vapor, and is not inconsistent with a warming world. Despite this, and a slight cooling in parts of Antarctica (now abating), most of the world’s glaciers have been receding as part of an inter-decadal […]

  7. Right-wing agenda in the public schools - Page 4 - Political Forum:

    […] the level of man’s role in global climate change (don’t call it "global warming", since some areas of the earth get cooler as a result of the change). But maintaining clean water and air, to stay on the safe side, seems like a good idea. I don’t […]

  8. Cardinal Pell: Australia’s Climate Change Lyre Bird « Under The Milky Way:

    […] short, on Antarctica, Pell was selective to the point of myopia. Really, he doesn’t want to know and if Pell is serious about being open to further evidence he will be interested in this report […]

  9. Man Based Global Warming.... - Page 39:

    […] a rising temperature trend: "Our results do not contradict earlier studies suggesting that some regions of Antarctica have cooled. Why? Because those studies were based on shorter records (20-30 years, not 50 years) …" […]

  10. Understanding the Basics of Global Holocene Climate Change « Understanding Global Warming:

    […] precipitation of extra moisture, and is not inconsistent with a warming world. Despite this, and a slight cooling in parts of Antarctica, most of the world’s glaciers have been receding as part of an inter-decadal trend, ice loss […]

  11. Understanding Global Warming:

    […] precipitation of extra moisture, and is not inconsistent with a warming world. Despite this, and a slight cooling in parts of Antarctica, most of the world’s glaciers have been receding as part of an inter-decadal trend, ice loss […]