There was another twist to the hurricanes/global warming issue in Science Express on Friday where a new paper from the Webster/Curry team just appeared. This study, lead by Carlos Hoyos, crosses a few t’s and dots a couple of i’s on the connection of increasing numbers of intense hurricanes (Cat. 4 and 5) to sea surface temperatures (SST). Basically, they looked at a number of other key variables for hurricane intensity (like wind shear and humidity) and examined whether there was any pattern to those variables across the different ocean basins that they study. Bottom line? None of the other variables have as much explanatory power for the long term trends as SST which is the only consistently trending constituent in the mix. So far, so un-surprising. However, one interesting aspect of this story is that almost all the key players in the ongoing debate were interviewed by different journalists in various media and those comments are probably more useful for gauging the state of play than the details of the new paper itself. [Read more…] about Reactions to tighter hurricane intensity/SST link
Meteors, Nuclear Tests and Global Warming
What is one to make of a recent press release and submitted preprint blaming global warming on the Tunguska meteor event in 1908? Well, although it is not unknown for impact events to affect climate (the K/T boundary event springs to mind) there are a number of hurdles for any such theory to overcome before it moves into the mainstream from the wilder shores of unsubstantiated speculation.
Firstly, one would anticipate that immediate effects of the impact on climate would be strongest near the time of the impact (allowing for some inertia in the system) and decay away subsequently. Secondly, the timescales for any mechanism associated with the impact (in this case disruption of the atmopsheric water vapour) would need to be in line with the change one hopes to explain. And thirdly, one has to show that this explanation is better than the alternatives. Unfortunately, none of of these requirements are met by this hypothesis. [Read more…] about Meteors, Nuclear Tests and Global Warming
Art and climate
As anecdotal evidence of past climate change goes, some of the most pleasant to contemplate involve paintings of supposedly typical events that involve the weather. Given the flourishing of secular themes in European art from the Renaissance on, most of this art comes from the 16th to 19th centuries. As readers here will know, this coincides (in the public mind at least) with the so-called ‘Little Ice Age’ and somewhat inevitably this canon of work has been combed over with a fine tooth comb for evidence of particularly cold conditions.
The image that brought this issue to mind was seeing ‘Washington crossing the Delaware’ at the Met the other day and seeing the iceberg-like ice it was imagined (75 years after the event) that the rebels had had to row through in 1776. The first thing I noticed was that the ice is completely wrong for a river (which is just one of the errors associated with this picture apparently). River ice is almost always of the ‘pancake’ variety (as this photo from the Hudson river shows), and doesn’t form ‘growlers’. However, the confusion of artistic license with climatology appears to be a bit of a theme in other oft-cited works as well…. [Read more…] about Art and climate
Those pesky scientific facts…
We would be remiss in not bringing today’s Doonesbury cartoon to a wider audience.
Hat Tip: Pharyngula and Hank Roberts.
Richard Lindzen’s HoL testimony
Prof. Richard Lindzen (MIT) is often described as the most respectable of the climate ‘sceptics’ and is frequently cited in discussions here and elsewhere. Lindzen clearly has many fundamentally important papers under his belt (work on the QBO and basic atmospheric dynamics), and a number of papers that have been much less well received by the community (the ‘Iris’ effect etc.). Last year, he gave evidence to and answered questions from, a UK House of Lords Committee investigating the economics of climate change, in which he discoursed freely on the science. I’ll try here to sort out what he said. [Read more…] about Richard Lindzen’s HoL testimony
Hansen in the New York Times
The more astute of you may have noticed the headline NYT story this weekend on Jim Hansen’s ongoing tussles with the (politically appointed) public affairs people at NASA HQ (Jim is my immediate boss so you need to read this with that in mind!). Most of the recent fuss has been about the GISS analysis of surface air temperatures (GISTEMP), which used to routinely be made available as soon as the analysis was done (usually a week or so after the end of any particular month). This data was generally released with little or no fuss (and no press releases) except for the end of year summary. However, as it started to become clearer that 2005 was a contender for warmest year, journalists and others started paying direct attention to the raw figures and writing stories that were bypassing public affairs. For instance, Juliet Eilperin’s October story in WaPo (discussed here and here) was one of the stories that they were most definitely not happy with (as alluded to in today’s WaPo). No follow-up media requests to interview relevant scientists were approved.
[Read more…] about Hansen in the New York Times
Calculating the greenhouse effect
In another forum (on a planet far, far away), the following quote recently came up:
….the combined effect of these greenhouse gases is to warm Earth’s atmosphere by about 33 ºC, from a chilly -18 ºC in their absence to a pleasant +15 ºC in their presence. 95% (31.35 ºC) of this warming is produced by water vapour, which is far and away the most important greenhouse gas. The other trace gases contribute 5% (1.65 ºC) of the greenhouse warming, amongst which carbon dioxide corresponds to 3.65% (1.19 ºC). The human-caused contribution corresponds to about 3% of the total carbon dioxide in the present atmosphere, the great majority of which is derived from natural sources. Therefore, the probable effect of human-injected carbon dioxide is a miniscule 0.12% of the greenhouse warming, that is a temperature rise of 0.036 ºC. Put another way, 99.88% of the greenhouse effect has nothing to do with carbon dioxide emissions from human activity8.
We’ve discussed the magnitude of the greenhouse effect before, but it might be helpful to step through this ‘back-of-the-agenda’ calculation and see what the numbers really give. (Deltoid has also had a go at some of these mis-statements). [Read more…] about Calculating the greenhouse effect
Atlantic circulation change summary
) Nature this week has an excellent summary of the state of the science with regards to possible changes in the ocean thermohaline (or meridional) circulation in the Atlantic and its impact on climate. Even though it quotes a couple of us, it’s still worth reading if you want to understand how results like the Bryden et al paper – that suggested that the Atlantic overturning had reduced by 30% in recent decades – are assimilated into the scientific picture. [Read more…] about Atlantic circulation change summary
Scientists baffled!
) 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.
How to be a real sceptic
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