Further to our post about whether 2005 will be a year of record warmth, Jim Hansen has put out a brief discussion on the Washington Post report and some of the subsequent discussion. One minor clarification to his statements is that the reporter involved (Juliet Eilperin) did in fact leave messages for the relevant people at GISS (including me) prior to publication, but sometimes people can just be difficult to track down. Oh….and for those who are counting, with the preliminary October data in, 2005 has pulled ahead of 1998 in both the GISS land based met. station index (0.76 to 0.73°C) and the GISS land-ocean index (0.59 to 0.58°C). All previous caveats still apply….
Instrumental Record
Update on 2005 temperatures
Global warming on Earth Réchauffement global sur Terre ?
The Washington Post picked up on the latest update to the 2005 temperature anomaly analysis from NASA GISS. The 2005 Jan-Sep land data (which is adjusted for urban biases) is higher than the previously warmest year (0.76°C compared to the 1998 anomaly of 0.75°C for the same months, and a 0.71°C anomaly for the whole year) , while the land-ocean temperature index (which includes sea surface temperature data) is trailing slightly behind (0.58°C compared to 0.60°C Jan-Sep, 0.56°C for the whole of 1998). The GISS team (of which I am not a part) had predicted that it was likely the 2005 would exceed the 1998 record (when there was a very large El Niño at the beginning of that year) based on the long term trends in surface temperature and the estimated continuing large imbalance in the Earth’s radiation budget.
In 1998 the last three months of the year were relatively cool as the El Niño pattern had faded. For the 2005 global land-ocean index to exceed the annual 1998 record, the mean anomaly needs to stay above 0.51°C for the next three months. Since there was no El Niño this year, and the mean so far is significantly above that, this seems likely. [Read more…] about Global warming on Earth
Hurricanes and Global Warming – Is There a Connection? Huracanes y calentamiento global ¿Hay conexión? Ouragans et réchauffement global – existe t’il un lien ?
by Stefan Rahmstorf, Michael Mann, Rasmus Benestad, Gavin Schmidt, and William Connolley
On Monday August 29, Hurricane Katrina ravaged New Orleans, Louisiana and Missisippi, leaving a trail of destruction in her wake. It will be some time until the full toll of this hurricane can be assessed, but the devastating human and environmental impacts are already obvious.
Katrina was the most feared of all meteorological events, a major hurricane making landfall in a highly-populated low-lying region. In the wake of this devastation, many have questioned whether global warming may have contributed to this disaster. Could New Orleans be the first major U.S. city ravaged by human-caused climate change?
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by Stefan Rahmstorf, Michael Mann, Rasmus Benestad, Gavin Schmidt, and William Connolley (traduit par Claire Rollion Bard)
Le lundi 29 août, l’ouragan Katrina a ravagé la Nouvelle-Orléans, la Louisiane et le Mississipi, laissant une traînée de destruction dans son sillage. Il va se passer du temps avant que le bilan total de cet ouragan soit estimé, mais les impacts environnementaux et humains sont déjà apparents.
Katrina était le plus craint des évènements météorologiques, un ouragan majeur laissant un terrain vide dans une région très peuplée de faible élévation. Dans le sillage de sa dévastation, beaucoup se sont demandés si le réchauffement global pouvait avoir contribué à ce désastre. La Nouvelle-Orléans pourrait-elle être la première ville majeure des Etats-Unis à être ravagée par le changement climatique causé par les humains ?
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The tropical lapse rate quandary
Guest commentary by Steve Sherwood
There are four independent instrumental records of sufficient length and potential accuracy to tell us about 20th-century climate change. The two longest ones are of temperature near the Earth’s surface: a vast network of weather stations over land areas, and ship data from the oceans. While land surface observations go back hundreds of years in a few places, data of sufficient coverage for estimating global temperature have been available only since the end of the 19th century. These have shown about a 0.7 C warming over land during the last century, with somewhat less increase indicated over oceans. The land records contain artifacts due to things like urbanization or tree growth around station locations, buildings or air conditioners being installed near stations, etc., but laborious data screening, correction procedures, and a-posteriori tests have convinced nearly all researchers that the reported land warming trend must be largely correct. Qualitative indicators like sea ice coverage, spring thaw dates, and melting permafrost provide strong additional evidence that trends have been positive at middle and high northern latitudes, while glacier retreat suggests warming aloft at lower latitudes.
Et Tu LT?
In previous posts we have stressed that discrepancies between models and observations force scientists to re-examine the foundations of both the modelling and the interpretation of the data. So it has been for the apparent discrepancies between the Microwave Sounding Unit (MSU) lower tropospheric temperature records (MSU 2LT), radiosonde records and the climate models that try to simulate the climate of the last few decades. Three papers this week in Science Express, Mears et al, Santer et al (on which I’m a co-author) and Sherwood et al show that the discrepancy has been mostly resolved – in favour of the models.
Storms and Climate Change
The Atlantic hurricane season will soon be upon us again , and no doubt many people will recall last year’s devastating Hurricanes that swept across Florida. There was a great deal of press about these storms, as 3 major hurricanes and 5 tropical storms made landfall in the US. According to HurricaneProtection.com, the last time eight different tropical cyclones impacted the United States coastline in a single season was 1916. There were a total of 15 tropical storms and hurricanes, which means that the total number of storms that year was higher than 95% of the previous years of hurricane observations. There was also a record number of Typhoons over Japan in 2004 (10! The previous record was 6 from 1996) . Typhoons are the same as Hurricanes, but have a different name over the Indian ocean and the western Pacific. They are also known as ‘tropical cyclones’. Furthermore, it was the first time that a tropical cyclone had been observed in the south Atlantic (see WMO Climate News, Jan 2005, p. 12)! So, what’s going on?
Doubts about the Advent of Spring
A “consensus view” amongst climate scientists holds that the Northern Hemisphere will be warming this month, as spring is coming. This is thought to be due to the Earth’s orbit around the sun and the inclination of the Earth’s axis, tilting the Northern Hemisphere progressively towards the sun throughout March and April and increasing the amount of solar radiation received at northern latitudes.
In a new novel, State of Euphoria, bestselling author Michael Crikey uncovers major flaws in this theory and warns against false hopes for the arrival of spring.
[Read more…] about Doubts about the Advent of Spring
Worldwide glacier retreat Recul mondial des glaciers
One of the most visually compelling examples of recent climate change is the retreat of glaciers in mountain regions. In the U.S. this is perhaps most famously observed in Glacier National Park, where the terminus of glaciers have retreated by several kilometers in the past century, and could be gone before the next century (see e.g. the USGS web site, here, and here). In Europe, where there is abundant historical information (in the form of paintings, photographs, as well as more formal record-keeping), retreat has been virtually monotonic since the mid 19th century (see e.g. images of the glaciers at Chamonix). These changes are extremely well documented, and no serious person questions that they demonstrate long term warming of climate in these regions. New work published in Science (“Extracting a Climate Signal from 169 Glacier Records”) highlights these results, and uses them to make a new estimate of global temperature history since about 1600 A.D., which agrees rather well with previous, independent temperature reconstructions.
Un des exemples les plus irrésistibles visuellement du récent changement climatique est le recul des glaciers dans les régions montagneuses. Aux Etats-Unis, c’est peut-être ce qui est le plus fameusement observé au Glacier National Park où les terminus des glaciers se sont retirés de quelques kilomètres au cours du dernier siècle (voir e.g. le site web de USGS, ici, and ici)ici et ici). En Europe, où il y a des informations historiques importantes (sous la forme de peintures, photographies, aussi bien que sous forme d’enregistrements plus formels), le recul a été virtuellement monotone depuis le milieu du 19ème siècle (voir e.g. images de glaciers à Chamonix). Ces changements sont extrêmement bien documentés si bien qu’aucune personne sérieuse ne doute que cela démontre le réchauffement à long terme du climat dans ces régions. Un travail récent publié dans Science (“Extracting a Climate Signal from 169 Glacier Records”) souligne ces résultats et les utilise pour faire une nouvelle estimation de l’histoire globale des températures depuis environ 1600 A.D., et qui est en assez bon accord avec les précédentes reconstructions indépendantes de la température.
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[Read more…] about Worldwide glacier retreat
Moberg et al: Highly variable Northern Hemisphere temperatures? Moberg et coll. : une plus grande variabilité climatique passée dans l’Hémisphere Nord ?
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.
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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[Read more…] about Moberg et al: Highly variable Northern Hemisphere temperatures?
What If … the “Hockey Stick” Were Wrong? Et si …. la “Crosse de Hockey” était fausse ?
The “hockey stick” reconstruction of temperatures of the past millennium has attracted much attention – partly as it was high-lighted in the 2001 IPCC report as one of the important new results since the previous IPCC report of 1995, and partly as it has become the focus of a number of challenges. Discussion about the “hockey stick” is conducted with considerable fervor in the public media, where this curve is often presented as if it were a proof, or even the most important proof, of anthropogenic influence on climate.
As someone who has not worked on the past millennium, I do not want to discuss the merits of the often rather technical challenges (which have been dealt with elsewhere on this site). Rather, I want to discuss the “what if…” question: what if really some serious flaw was discovered in the “hockey stick” curve? What would that mean?
Par Stefan Rahmstorf (traduit par Claire Rollion-Bard)
La reconstruction “crosse de hockey” des températures du dernier millénaire a beaucoup attiré l’attention – en partie car elle a été mise en avant dans le rapport IPCC 2001 comme l’un des nouveaux résultats importants depuis le précédent rapport IPCC de 1995, et en partie car elle est devenue le point de mire d’un certain nombre de défis. La discussion sur la “crosse de hockey” est transmise avec une ferveur considérable dans les médias, où cette courbe est souvent présentée comme une preuve ou même la preuve la plus importante de l’influence anthropogénique sur le climat.
En tant que personne n’ayant pas travaillé sur le dernier millénaire, je ne veux pas discuter des mérites des défis techniques (qui sont discutés dans une autre section du site). Je veux plutôt discuter de la question “et si…” : et si de sérieux défauts étaient trouvés dans la courbe “crosse de hockey” ? Qu’est ce que cela signifierait ?