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Arctic Sea Ice decline in the 21st CenturyDéclin de la banquise de l’Arctique au 21ème siècle

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Guest Commentary by Cecilia Bitz, University of Washington

Last month a paper I co-authored received considerable media attention. Headlines read “Experts warn North Pole will be ‘ice free’ by 2040”, “The Big Melt: Loss of Sea Ice Snowballs“, and “Arctic Clear for Summer Sailing by 2040: Models Predict Rapid Decline of Sea Ice”. The story also reached NPR, BBC, CBC, the Discovery channel, and Fox News, among others. Dr. Marika Holland, the first author of the paper, was inundated with media attention. About a dozen journalists contacted me too. I was impressed by the questions they posed — questions that probably reflect what the public most wants to know. However, after giving lengthy interviews, I would read the resulting article and see my explanations boiled down to a few lines. In this essay, I’d like to explain the science in the paper and give my answers to the most often asked questions.
Cécilia Bitz, Université de Washington (traduit par Valérie Masson-Delmotte)

Ce mois-ci, un article dont j’étais co-auteur a attiré considérablement l’attention des médias. Les unes des journaux titraient : “Les experts tirent la sonnette d’alarme : le Pôle Nord libre de glace d’ici à 2040”; ““Fonte massive : perte de banquise en boule de neige”; et “L’Arctique dégagée pour la navigation d’été d’ici 2040 : les modèles prévoient un déclin rapide de la banquise”. Cette histoire a aussi gagné les chaînes de télévision : NPR, BBC, CBC, Discovery Channel et Fox News, parmi d’autres. Le Dr Marika Holland, premier auteur de cet article, a été submergée par les sollicitations médiatiques. Parmi les douzaines de journalistes qui m’ont également contactée, j’ai été impressionnée par les questions qui m’ont été posées – des questions qui reflètent probablement ce que le grand public veut savoir en priorité. Cependant, après avoir donné de longues interviews, je vois souvent mes explications réduites à quelques lignes dans les articles… Dans cet essai, je voudrais expliquer les résultats scientifiques de notre publication et mes réponses aux questions les plus fréquentes.

(suite…)

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El Nino, Global Warming, and Anomalous U.S. Winter Warmth

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A slovak translation of this piece (by Alexander Ač) can be found here.
Det finns en svensk översättning tillgänglig här.

It has now become all too common. Peculiar weather precipitates immediate blame on global warming by some, and equally immediate pronouncements by others (curiously, quite often the National Oceanic and Atmospheric Administration in recent years) that global warming can’t possibly be to blame. The reality, as we’ve often remarked here before, is that absolute statements of neither sort are scientifically defensible. Meteorological anomalies cannot be purely attributed to deterministic factors, let alone any one specific such factor (e.g. either global warming or a hypothetical long-term climate oscillation).

Lets consider the latest such example. In an odd repeat of last year (the ‘groundhog day’ analogy growing ever more appropriate), we find ourselves well into the meteorological Northern Hemisphere winter (Dec-Feb) with little evidence over large parts of the country (most noteably the eastern and central U.S.) that it ever really began. Unsurprisingly, numerous news stories have popped up asking whether global warming might be to blame. Almost as if on cue, representatives from NOAA’s National Weather Service have been dispatched to tell us that the event e.g. “has absolutely nothing to do with global warming”, but instead is entirely due to the impact of the current El Nino event.

[Update 1/9/07: NOAA coincidentally has announced today that 2006 was officially the warmest year on record for the U.S.]
[Update 2/11/08: It got bumped to second place. ]
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Consensus as the New Heresy

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Gavin Schmidt, Michael Mann, David Archer, Stefan Rahmstorf, William Connolley, and Raymond Bradley

Andy Revkin, who’s one of the best journalists on the climate beat, wrote a curious piece in the NY Times discussing the ‘middle stance’ of the climate debate. It’s nice to see news pieces on climate that aren’t breathless accounts of a new breakthough and that take the time to point out that the vast majority of relevant scientists take climate change extremely seriously. To that extent, the message of this piece was a welcome one. The curious part, however, was the thread running through the piece that this middle ground is only now emerging, and even curiouser, that this middle ground can be characterized as representing some sort of ‘heresy’.

Heresy, is commonly defined as ‘an opinion or doctrine at variance with the official or orthodox position’. So where does this idea come from, and why is it now ’emerging’?
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The Physics of Climate Modelling La physique de la modélisation du climat

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This is just a pointer to a ‘Quick Study’ guide on The physics of climate modelling that appears in Physics Today this month, and to welcome anyone following through from that magazine. Feel free to post comments or questions about the article here and I’ll try and answer as many as I can.

Cet article est aussi disponible en français.

The main article is also available in Portugeuse.

On Mid-latitude Storms

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Statements often appear in the media about suggesting that more extreme mid-latitude storms will result from global warming. For instance, western Norway was recently battered by an unusually strong storm which triggered many such speculations. But scientific papers on how global warming may affect the mid-latitude storms give a more mixed picture. In a recent paper by Bengtsson & Hodges (2006), simulations with the ECHAM5 Global Climate Model (GCM) were analysed, but they found no increase in the number of mid-latitude storms world-wide. Another study by Leckebusch et al. (2006) showed that the projection of storm characteristics was model-dependent. (Note that the dynamics of tropical and mid-latitude (often called ‘extra-tropical’) storms involve different processes, and tropical storms have been discussed in previous posts here on RC: here, here, here, and here).

The factors that control this are often confounding and so make this a tricky prediction. Simple arguments based on the expected ‘polar amplification‘ and the fact that the surface temperature gradient between the tropics and the poles will likely decrease would reduce the scope for ‘baroclinic instability’ (the main generator of mid-latitudes storms). However, there are also increases in the upper troposphere/lower stratospheric gradients (due to the stratosphere cooling and the troposphere warming) and that has been shown to lead to increases in wind speeds at the surface. And finally, although latent heat release (from condensing water vapour) is not a fundamental driver of mid-latitude storms, it does play a role and that is likely to increase the intensity of the storms since there is generally more water vapour available in warmer world. It should also be clear that for any one locality, a shift in the storm tracks (associated with phenomena like the NAO or the sea ice edge) will often be more of an issue than the overall change in storm statistics.
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2006 Year in review Revue de l’année 2006

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A lighthearted look at the climate science goings-on over the last year:

Best highlight of the gap between the ‘two cultures’:
Justice Scalia: ‘Troposphere, whatever. I told you before I’m not a scientist. That’s why I don’t want to have to deal with global warming’ .

Least effective muzzling of government climate scientist by a junior public affairs political appointee:
George Deutsch met his match in Jim Hansen.

Most puzzling finding that has yet to be replicated:
Methane from plants

Worst reported story and least effectual follow-up press release:
Methane from plants

Best (err… only) climate science documentary on public release:
An Inconvenient Truth.

Most worn out contrarian cliche:
Medieval English vineyards.

Previously prominent contrarian cliche curiously not being used any more:
“The satellites show cooling”

Most bizarre new contrarian claim:
“Global warming stopped in 1998”.
By the same logic, it also stopped in 1973, 1983, and 1990 (only it didn’t).

Most ironic complaint about ‘un-balanced’ climate coverage on CNN:
Pat Michaels (the most interviewed commentator by a factor of two) complaining that he doesn’t get enough exposure.

Most dizzying turn-around of a climate skeptic:
Fred Singer “global warming is not happening” (1998,2000, 2002, 2005) to global warming is “unstoppable” (2006)

Best popular book on the climate change:
Elizabeth Kolbert’s “Field Notes from a Catastrophe”

Least unexpected observations:
(Joint winners) 2006 near-record minima in Arctic sea ice extent, near-record maxima in Northern Hemisphere temperatures, resumed increase in ocean heat content, record increases in CO2 emissions

Best resource for future climate model analyses:
PCMDI database of IPCC AR4 simulations. The gift that will keep on giving.

Best actual good news:
Methane concentrations appear to have stabilised. Maybe they can even be coaxed downward….

Biggest increase in uncertainty as a function of more research:
Anything to do with aerosols.

Least apologetic excuse for getting a climate story wrong:
Newsweek explains its 1975 ‘The Cooling World’ story.

Most promising newcomer on the contrarian comedy circuit:
Viscount Monckton of Brenchley

Least accurate attempted insinuation about RealClimate by a congressional staffer:
‘There’s so much money’: Marc Morano (Senate EPW outgoing majority committee staff, 5:30 into the mp3 file)

Boldest impractical policy idea:
Geo-engineering

Boldest practical policy idea:
Creation of a National Climate Service, which could more effecitvely provide useful climate information to policymakers.

Most revealing insight into the disinformation industry (fiction):
Thank you for smoking

Most revealing insight into the disinformation industry (non-fiction) and year’s best self-parody:
‘CO2 is life’

Feel free to suggest your own categories and winners…


Traduit par Etienne Pesnelle

Un regard humoristique sur les événements de la climatologie de l’année passée :

La meilleure illustration de la fracture entre les “deux cultures” :
Justice Scalia : “La troposphère ou que sais-je encore. Je vous ai déjà dit que je n’étais pas une scientifique. C’est pourquoi je ne veux pas m’occuper du réchauffement planétaire.”

Le musèlement de climatologiste gouvernemental par haut fonctionnaire
novice le moins efficace :
George Deutsch a trouvé quelqu’un à sa hauteur en la personne de Jim Hansen

La découverte la plus curieuse qui reste à reproduire :
L’émission de
méthane par les plantes.

Le sujet le plus mal rapporté et le communiqué de presse le moins efficace :
L’émission de méthane par les plantes.

Le meilleur (erreur… le seul) documentaire grand public sur la climatologie :
Une vérité qui dérange.

Le cliché négateur le plus éculé :
les vignerons anglais du Moyen-Age.

Le cliché négateur auparavant très répandu et curieusement plus du tout utilisé :
“Les satellites montrent un refroidissement.”

Le nouvel argument négateur le plus bizarre :
“Le réchauffement planétaire s’est interrompu en 1998.” Avec le même raisonnement, il s’est également interrompu en 1973, 1983 et 1990 (mais en fait il ne s’est pas arrêté)

Le reproche le plus ironique à propos de la couverture “déséquilibrée” de la question climatique sur CNN :
Pat Michaels (un commentateur qui intervient deux fois plus que les autres) se plaignant que sa présence médiatique est insuffisante.

Le revirement de sceptique climatique le plus vertigineux :
Fred Singer, passant de : “le réchauffement planétaire ne se produit pas” (1998,2000, 2002, 2005) à un réchauffement “qu’on ne peut plus arrêter” (2006)

Le livre sur le changement climatique le plus populaire:
“Notes prises sur le terrain d’une catastrophe”, d’Elizabeth Kolbert

Les observations les moins inattendues
(ex-aequo) l’étendue de la glace de mer arctique en 2006, proche des minimums record, les températures dans l’hémisphère Nord proches des maximums record, lareprise
de l’augmentation de la chaleur contenue dans l’océan, les augmentations record des émissions de CO2.

La meilleure source d’information pour les futures analyses des modèles climatiques:
La base de données PCMDI issues des simulations IPCC AR4. Le cadeau qui continuera à s’offrir.

La meilleure bonne nouvelle:
Les concentrations en méthane semblent s’être stabilisées. Peut-être peut-on même les persuader gentiment de redescendre…

L’incertitude qui augmente le plus avec les recherches scientifiques :
Tout ce qui a à voir avec les aérosols.

L’excuse la moins contrite pour avoir publié une fausse nouvelle :
Newsweek, expliquant son article de 1975 “Le monde se refroidit”.

Le nouvel espoir de la tournée de la comédie des négateurs :
Le vicomte Monckton of Brenchley

La tentative d’insinuation envers RealClimate par assistant parlementaire la moins pertinente :
“Il y a tant d’argent”, Marc Morano, assistant parlementaire de la majorité sortante à la Commission du Sénat sur l’Environnement et les Travaux Publics (à 5 minutes 30 après le début du fichier MP3).

L’idée politique peu réalisable la plus téméraire :
La géo-ingéniérie.

L’idée politique réalisable la plus téméraire :
La création d’un ServiceNational
du Climat, qui pourrait fournir plus efficacement de l’information climatique utile aux décideurs.

L’aperçu le plus révélateur sur l’industrie de la désinformation (fiction) :
“Thank you for smoking”

L’aperçu le plus révélateur sur l’industrie de la désinformation (nonfiction) et la meilleure auto-parodie de l’année :
“CO2: We Call It Life” (NdT: spots publicitaires de 60 secondes diffusés sur les chaînes TV états-uniennes en mai 2006)

N’hésitez pas à suggérer vos propres catégories et gagnants…

AGU Hangover

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It turns out that there were almost 14,000 attendees at AGU last week, which apparently makes it the largest Earth Science meeting ever held. To be sure, not all of that is climate related – there was lots of seismology, planetary and more theoretical/small-scale stuff, but a lot of it was. At most times there were at least half a dozen sessions that I would have been interested to attend – and they were often discussing overlapping themes.

It used to be that one could go to a meeting like this and get a wide overview of the work being done much more efficiently (and speedily) than reading the journals. However, that is clearly no longer true. And of course, we can’t keep up with all the relevant journal articies in the wider field either, and so how do scientists manage?
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Not just ice albedo Ce n’est pas qu’une histoire d’albédo de la glace…

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A recent paper by Francis & Hunter provides an interesting discussion about reasons for the recent decline in the Arctic sea-ice extent, based on new satellite observations. One common proposition about sea ice is that it involves a positive feed-back because the ice affects the planetary albedo (how the planet reflects the sunlight back to space before the energy enters the ‘climate system’). Yet, there is more to the story, as the ice acts more-or-less like an insulating lid on top of the sea. There are subtle effects such as the planet losing more heat from the open sea than from ice-covered region (some of this heat is absorbed by the atmosphere, but climates over ice-covered regions are of more continental winter character: dry and cold). The oceanic heat loss depends of course on the sea surface temperature (SST). Open water also is a source of humidity, as opposed to sea-ice (because its cold, not because its dry), but the atmospheric humidity is also influenced by the moisture transport associated with the wind (moisture advection). Francis & Hunter found a positive correlation between lack of ice and the downward long-wave radiation, something they attributed primarily to cloudiness. Hence, clouds play a role, both in terms of influencing the albedo as well as trapping out-going heat. Francis & Hunter suggest that the changes in the long-wave radiation is stronger than the clouds’ modulation of the direct sunlight.
[Read more…] about Not just ice albedo Ce n’est pas qu’une histoire d’albédo de la glace…

Fall AGU

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The Fall AGU meeting in San Francisco is always an exhilarating/exhausting (take your pick) fixture of the Earth Science calendar. This year will be no different, and since about half of us will be there, RealClimate will probably be a little quiet next week. Hopefully, we should be able to report on any highlights when we get back.

N.B. If any readers will be attending and want to say hi, I will be giving a talk on ‘Science blogging: RealClimate.org and the Global Warming debate‘ on Friday (PA53A, 13:40, MCS 309).

Update: AGU went well – lot’s of good stuff. The actual RealClimate presentation is available here – it’s pretty basic though (only 15 minutes worth)).

Inhofe’s last stand

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Part of me felt a little nostalgic yesterday watching the last Senate hearing on climate change that will be chaired by Sen. James Inhofe. It all felt very familiar and comforting in some strange way. There was the well-spoken ‘expert’ flown in from Australia (no-one available a little closer to home?), the media ‘expert’ from the think tank (plenty of those about) and a rather out-of-place geologist. There were the same talking points (CO2 leads the warming during the ice ages! the Medieval Warm Period was warm! it’s all a hoax!*) that are always brought up. These easy certainties and predictable responses are so well worn that they feel like a pair of old slippers.
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