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Global Dimming may have a brighter future Un avenir brillant pour l’assombrissement global ?

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A while ago, we wrote about Global Dimming – a reduction in downward solar radiation of about 4% or about 7W/m2 from 1961 to 1990 was found at stations worldwide. We said at the time that there were hints of a recovery underway post-1990; now research has been published showing this. From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth’s Surface by Martin Wild et al. (Science 6 May 2005; 308: 847-850; subscription required for link) uses surface measurements; Do Satellites Detect Trends in Surface Solar Radiation? by Pinker et al., Science 2005 308: 850-854 uses satellites; both find a recovery of surface downward radiation since about 1990.
Il y a quelques temps, nous écrivions à propos de l’assombrissement global – une réduction de l’irradiation solaire de 4% ou environ 7W/m_ entre 1961 et 1990 observée dans des stations météorologiques autour du monde. Nous disions alors qu’il y avait des indices de reprise en cours après 1990. Des recherches qui le montrent ont maintenant été publiée. De l’assombrissement à l’éclaircissement: changements décennaux de l’irradiation solaire à la surface de la Terre (From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth’s Surface) de Martin Wild et al. (Science 6 Mai 2005; 308: 847-850; abonnement nécessaire pour lire l’article) utilise des mesures faites en surface; Les satellittes détectent-ils des tendances dans l’irradiation solaire ai niveau de la surface? (Do Satellites Detect Trends in Surface Solar Radiation?) de Pinker et al., Science 2005 308: 850-854, utilise des satellites. Les deux études identifient une reprise de l’irradiation solaire de la surface depuis environ 1990.

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2005 Record Arctic Ozone Loss

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You read it here first!


Update (09/05/05): Markus Rex was kind enough to send us the full figure from which Nature made their thumbnail, and which is a little clearer. He also cautions that the 2005 numbers are still preliminary, however there is a clear trend towards increasing potential for Arctic ozone loss, which is realised or not depending on the vagaries of each individual winter.

Technical problem apology

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Due to some odd behaviour with our blog software, many people have had problems this week posting comments. We would like to apologise to our readers if they encountered these problems (bizarre redirections and WordPress login screens appearing where they shouldn’t).

We appear to have fixed the problem (fix from here for those interested), but please let us know if anything weird or unusual continues to occur. Thanks for your patience.

Normal service will resume after the break.

Pollution-Climate Connections Liens entre Pollution et Climat

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Guest commentary by Loretta Mickley, Harvard University

Every summer over much of the United States, we brace ourselves for heat waves. During these periods, the air turns muggy and usually smoggy. After a few days, a cold front moves in, sweeping away the pollution and ending the heat. Given that we are on a path towards global warming, atmospheric chemists are asking how climate change could affect air quality. Will warmer temperatures mean more pollution during these episodes? Will episodes last longer? Most importantly, what effect will changes in air quality have on human health?
Article invité par Loretta Mickley, Harvard University (Traduit par Pierre Allemand)

Tous les étés, dans la plupart des régions des USA, nous nous préparons aux vagues de chaleur. Pendant ces périodes, l’air devient très humide et généralement brumeux. Après quelques jours, un front froid survient, balayant la pollution et mettant fin à la chaleur. Etant donné que nous nous acheminons vers un réchauffement global, les spécialistes de la chimie de l’atmosphère se demandent de quelle façon le changement climatique pourrait affecter la qualité de l’air. Des températures plus élevées signifieront-elles plus de pollution durant ces épisodes ? Ces épisodes dureront-ils plus longtemps ? Plus important : quels sont les effets des changements dans la qualité de l’air sur la santé humaine ?
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Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century Recul du Front des Glaciers de la Péninsule Antarctique au cours des 50 dernières années

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Guest commentary by David Vaughan

The recent retreat of ice shelves on the Antarctic Peninsula has been widely attributed to warming atmospheric temperatures. There is, however, little published work describing the response of glacier margin positions to this regional climate change. In the paper Retreating Glacier Fronts on the Antarctic Peninsula over the Past Half-Century published this week in Science, we presented new data describing trends in 244 marine glacier fronts on the Antarctic Peninsula over the last 50 years. The data come from matching archives of over 2000 aerial photographs of the Antarctic Peninsula to satellite images, and represent about three years of work by Alison Cook. The work was carried out at British Antarctic Survey, but was funded by the US Geological Survey, as part of a larger programme to map change in the coastline of all Antarctica.

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How rapid-response works

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Nature this week published a letter from Dr. Huang (U. Mich) highlighting how this ‘brave new world’ of science blogging works. He writes:

I was concerned to find that … [a figure] included an outdated and erroneous reconstruction of borehole data. … In my view, the website should have used a later version … To be fair, the authors of the website added a correction after I drew their attention to this.

In an early post, we used a figure that contained a minor error regarding how a borehole temperature reconstruction had been scaled. This mistake had been properly corrected in the literature, and so this was indeed an oversight on our part. Dr Huang was kind enough to remind us of this and we amended the caption immediately to point this out and direct readers to the correction should they be interested. Since this mistake was not central to the point being made in the post, we left the original figure in place.

The Internet is nothing if not flexible, and unlike in journals where mistakes can persist an awfully long time, we are able to correct such problems very quickly. In this respect, Dr. Huang’s letter seems to indicate that things are actually working quite well here.

We would like to take this opportunity to re-iterate our commitment to getting the science right, and as importantly, getting it right in real-time. We welcome all corrections or clarifications and we will endeavour to fix any errors, great or small, as quickly as we can.

RealClimate

Moberg et al: Highly variable Northern Hemisphere temperatures? Moberg et coll. : une plus grande variabilité climatique passée dans l’Hémisphere Nord ?

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by William Connolley and Eric Steig

The 10th Feb edition of Nature has a nice paper “Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data” by Anders Moberg, DM. Sonechkin, K Holmgren, NM Datsenko, & W Karlin (doi:10.1038/nature03265). This paper takes a novel approach to the problem of reconstructing past temperatures from paleoclimate proxy data. A key result is a reconstruction showing more century-scale variability in mean Northern Hemisphere temperatures than is shown in previous reconstructions. This result will undoubtedly lead to much discussion and further debate over the validity of previous work. The result, though, does not fundamentally change one of the most discussed aspects of that previous work: temperatures since 1990 still appear to be the warmest in the last 2000 years.
par William Connolley et Eric Steig (traduit par Pierre Allemand)

L’édition du 10 février de Nature contient un intéressant article “Les grandes variations de températures de l’hémisphère Nord reconstituées à partir d’observations à basse et haute résolution ” par Anders Moberg, DM Sonechkin, K Holmgren, NM Datsenko, et W Karlin (doi:10.1038/nature03265). Cet article adopte une nouvelle approche du problème de la reconstitution des températures passées à partir de marqueurs (“proxies”) des paléoclimats. Un des principaux résultats est une reconstitution montrant une variabilité à l’échelle du siècle dans les moyennes des températures de l’hémisphère nord plus importante que celle montrée dans les reconstitutions précédentes. Ce résultat amènera sans doute beaucoup de discussions et de débats futurs concernant la validité des travaux précédents. Néanmoins, le résultat ne change pas fondamentalement un des aspects les plus discutés de ces travaux, à savoir que les températures depuis 1990 semblent être les plus chaudes des 2000 dernières années.

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Exeter conference: Avoiding Dangerous Climate Change Conférence d’Exeter (G-B): éviter un changement climatique dangereux

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The conference last week in Exeter on “Avoiding Dangerous Climate Change” grew out of a speech by UK Prime Minister Tony Blair. He asked “What level of greenhouse gases in the atmosphere is self-evidently too much?” and “What options do we have to avoid such levels?”. The first question is very interesting, but also very difficult. As Roger Pielke has noted the conference organisers actually choose three “key questions”:

  1. For different levels of climate change what are the key impacts, for different regions and sectors, and for the world as a whole?
  2. What would such levels of climate change imply in terms of greenhouse gas stabilisation concentrations and emission pathways required to achieve such levels?
  3. What technological options are there for achieving stabilisation of greenhouse gases at different stabilisation concentrations in the atmosphere, taking into account costs and uncertainties?

It is worth thinking about the difference between the initial aim and the “key questions” chosen. Question 1 is essentially IPCC WGII impacts); question 2 is firmly WGI (how-much-climate-change); question 3 is fairly WG III (mitigation, including technical options). I guess they switched questions 1 and 2 round to avoid making the identification too obvious. The conference steering committee report makes it very clear that they are building on the IPCC TAR foundation.


Par William Connoley (traduit par Thibault de Garidel)

La conférence ayant eu lieu la semaine dernière à Exeter intitulée “Eviter un changement climatique dangereux” a pour origine un discours du premier ministre britannique Tony Blair. Celui-ci avait alors posé deux questions “quel niveau de concentration de gaz à effet de serre dans l’atmosphère peut être considéré comme excessif ?” et “quelles options avons-nous pour éviter de tels niveaux ?”. La première question est très intéressante, mais également problématique. Comme Roger Pielke l’a noté, les organisateurs de cette conférence ont en fait choisi trois “questions principales” :

1. Pour différents niveaux de changement climatique, quels sont les impacts principaux, pour les différentes régions et secteurs, et pour le monde entier ?
2. Pour que de tels niveaux de changement climatique soient atteints, quelles sont les implications en terme de stabilisation des concentrations en gaz à effet de serre, et des options d’émission ?
3. Quelles options technologiques existent pour arriver à stabiliser les gaz à effet de serre à différentes concentrations, en tenant compte des coûts et incertitudes?

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