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about Gavin Schmidt

Gavin Schmidt is a climate modeler, working for NASA and with Columbia University.

Scientists baffled! Une surprise pour les scientifiques !

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Every so often a scientific paper comes out that truly surprises. The results of Keppler et al in Nature this week is clearly one of those. They showed that a heretofore unrecognised process causes living plant material to emit methane (CH4, the second most important trace greenhouse gas), in quantities that appear to be very significant globally. This is surprising in two ways – firstly, CH4 emission is normally associated with anaerobic (oxygen-limited) environments (like swamps or landfills) but chemistry in plants is generally thought of as ‘aerobic’ i.e. not oxygen-limited, and secondly, because although the total budget for methane has some significant uncertainty associated with it (see the IPCC assessment here), the initial estimates of this effect (between 62–236 Tg/yr out of a total source of 500+ Tg/yr!) give numbers that might be difficult to incorporate without some significant re-evaluations elsewhere.

Reactions so far have been guarded, and there will undoubtedly be a scramble to check and refine the estimates of this process’s importance. Once the dust settles though, the situation may not be so different to before – some emissions may turn out to have been mis-identified, this source may not be as large as these initial estimates (10-30% of total sources) suggest, or it might radically challenge our current understanding of methane’s sources and sinks. However, the process by which this is decided will demonstrate clearly that the scientific method is alive and well in the climate sciences. That is, as long as a work is careful and the conclusions sound, papers that upset the apple cart can appear in the major journals and have a good chance of ending up being accepted by the rest of the field (providing the conclusions hold up of course!).

Update 19 Jan: The authors of the study have released a clarification of their study to counter some of the misleading conclusions that had appeared in the press.

De temps en temps, un papier scientifique crée de véritables surprises. Les résultats de Keppler et al. publiés cette semaine dans la revue Nature est clairement un de ceux-çi. Ces auteurs ont prouvé qu’un processus jusqu’ici non reconnu fait que les plantes vivantes émettent du méthane (CH4, le deuxième gaz à effet de serre après le CO2), dans des quantités qui semblent être très significatives globalement. Ceci étonne de deux manières – premièrement, l’émission de CH4est normalement associée aux environnements anaérobies (c’est-à-dire pauvres en oxygène) comme les marais ou décharges, alors que la chimie dans les plantes est généralement considérée comme étant ‘aérobie ‘ c.-à-d. non limitée en oxygène, et deuxièmement, parce que les évaluations initiales de cet effet (entre 62-236 Tg/an sur une source totale de 500+ Tg/an!) donne des valeurs qu’il sera difficile d’incorporer dans le budget total du méthane sans des ré-évaluations majeures (et ce malgré les incertitudes liées au budget total – voir l’évaluation de celui-ci par le GIEC).

Les réactions jusqu’ici ont été réservées, et il y aura assurément un grand nombre d’études pour vérifier et raffiner les évaluations de l’importance de ce processus. Une fois que la poussière se sera redéposé, la situation pourrait ne pas être si différente que celle précédent cette étude – certaines émissions pouvant s’avérer avoir été mal interprétées, cette source pouvant ne pas être aussi importante que suggérée par ces évaluations initiales (10-30% de sources totales), ou au contraire elle pourrait radicalement défier notre compréhension actuelle des sources et puits du méthane. Cependant, le processus par lequel cette étude sera confirmée ou pas démontrera clairement que la méthode scientifique est belle-et-bien vivante dans les sciences de climat. C’est-à-dire, aussi longtemps qu’un travail est soigné et rigoureux, et que les conclusions sont justifiées, les papiers bousculant le courant de pensée dominant peuvent paraître dans les journaux les plus importants, et ont une bonne chance à la fin d’être accepté par le reste des scientifiques (si les conclusions tiennent la route bien sûr !).

How to be a real sceptic

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Scepticism is often discussed in connection with climate change, although the concept is often abused. I therefore thought it might be interesting to go back and see what the epitome of 20th Century sceptics, Bertrand Russell, had to say on the subject. This is extracted from the Introduction to his ‘Sceptical Essays’ (1928):
[Read more…] about How to be a real sceptic

Climate meeting blogging

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Two climate-related meetings are being covered quite extensively this week, the American Geophsyical Union meeting in San Francisco is being blogged for Woods Hole Oceanographic Institution, and the COP/MOP meeting in Montreal is being podcasted by the New York Times and blogged by other attendees. Hopefully this is a sign that scientists are starting to use these tools more effectively than they have so far.

Debate over the Early Anthropogenic Hypothesis

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There have been a few mentions of the ‘early anthropocene’ hypothesis recently (cf. the EPICA CO2 results, and Strange Bedfellows). We therefore welcome Bill Ruddiman to RealClimate to present his viewpoint and hopefully stimulate further discussion – gavin.

[Addendum: For a non-technical backgrounder on the ‘early anthropocene’ hypothesis and its significance in the context of anthropogenic climate change, see Bill Ruddiman’s article “How Did Humans First Alter Global Climate?” from the March 2005 issue of “Scientific American” (first two paragraphs available for free; full article must be purchased). -mike]

Guest posting from Bill Ruddiman, University of Virginia

The hypothesis (Ruddiman, 2003) that early agriculture caused large enough emissions of greenhouse gases millennia ago to offset a natural climatic cooling remains controversial. The centerpiece of the hypothesis was a comparison of the increases of CO2 and CH4 values in Vostok ice during the current (Holocene) interglaciation versus the (natural) drops during similar portions of the three previous interglaciations. [Read more…] about Debate over the Early Anthropogenic Hypothesis

650,000 years of greenhouse gas concentrations 650 000 années de concentrations de gaz à effet de serre

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The latest results from the EPICA core in Antarctica have just been published this week in Science (Siegenthaler et al. and Spahni et al.). This ice core extended the record of Antarctic climate back to maybe 800,000 years, and the first 650,000 years of ice have now been analysed for greenhouse gas concentrations saved in tiny bubbles. The records for CO2, CH4 and N2O both confirm the Vostok records that have been available for a few years now, and extend them over another 4 glacial-interglacial cycles. This is a landmark result and a strong testament to the almost heroic efforts in the field to bring back these samples from over 3km deep in the Antarctica ice. So what do these new data tell us, and where might they lead? Les derniers résultats du forage EPICA en Antarctique viennent juste d’être publiés dans le numéro de cette semaine de Science (Siegenthaler et al. et Spahni et al.). Cette carotte glaciaire a permis d’étendre l’enregistrement du climat Antarctique jusqu’à 800 000 ans, alors que les concentrations de gaz à effet de serre, piégées sous forme de minuscules bulles de gas, ont été analysées pour les 650 000 dernières années. Ces enregistrements de CO2, CH4 et N2O sont en accord avec ceux de Vostok (également en Antarctique) disponibles depuis quelques années, et permettent d’observer 4 cycles d’alternance glaciaire/interglaciaire supplémentaires. Ces travaux sont remarquables, et justifient des efforts gigantesques effectués sur le terrain pour ramener des échantillons enfouis jusqu’à 3km de profondeur dans la glace Antarctique. Que nous disent ces nouvelles données, et dans quelle direction peuvent elles nous mener ?
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 [Read more…] about 650,000 years of greenhouse gas concentrations 650 000 années de concentrations de gaz à effet de serre

Update on 2005 temperatures Mise à Jour sur les températures 2005

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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….

En complément du message sur le record de température possible de l’année 2005, Jim Hansen a écrit une courte discussion (en anglais) sur l’article du Washington Post report et des discussions sur cet article. Et pour le record, avec les données disponibles d’octobre, 2005 est passé devant 1998 dans les deux types de données du GISS, l’index “GISS land” sur des stations météo terrestres (0.76 comparé a 0.73°C) ainsi que pour l’index “GISS land-ocean” (0.59 to 0.58°C). Les mises en garde précédentes sont toujours valables…

Lawson vs. the IPCC

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Nigel Lawson, one of Britain’s Chancellors of the Exchequer during the Thatcher Era (Secretary of the Treasury for those needing a US translation) and more recently known as the father of Nigella Lawson (a UK cooking diva), has weighed into the climate debate with a recent broadside calling for the abolition of the IPCC (Intergovernmental Panel on Climate Change). Based on a curious report by the UK House of Lords Economics Affairs committee (in which they made clear that they had no scientific expertise), Lawson demands that the only global scientific assessment process on climate change be shut down, and replaced with ….well what exactly? [Read more…] about Lawson vs. the IPCC

Global warming on Earth Réchauffement global sur Terre ?

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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 Réchauffement global sur Terre ?

What is a first-order climate forcing?

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Roger Pielke Sr. (Colorado State) has a blog (Climate Science) that gives his personal perspective on climate change issues. In it, he has made clear that he feels that apart from greenhouse gases, other climate forcings (the changes that affect the energy balance of the planet) are being neglected in the scientific discussion. Specifically, he feels that many of these other forcings have sufficient ‘first-order’ effects to prevent a clear attribution of recent climate change to greenhouse gases.

In general, I heartily agree – other forcings are important, even essential, for understanding observed climate variability and, as a community, we are only just starting to get to grips with some of the more complicated effects. Obviously, though, not all forcings are of the same magnitude (either globally or regionally) and so it is useful to separate the ‘first-order’ forcings from those that are relatively minor. But what exactly is ‘first-order’ and what is not? [Read more…] about What is a first-order climate forcing?