In a recent paper in Geophysical Research Letters, Scafetta & West (S&W) estimate that as much as 25-35% of the global warming in the 1980-2000 period can be attributed changes in the solar output. They used some crude estimates of ‘climate sensitivity’ and estimates of Total Solar Irradiance (TSI) to calculate temperature signal (in form of anomalies). They also argue that their estimate, which is based on statistical models only, has a major advantage over physically based considerations (theoretical models), because the latter would require a perfect knowledge about the underlying physical and chemical mechanisms.
Climate Science
Pielke père et fils in Nature
There’s an interesting profile on Roger Pielke Jr. and Sr. in Nature this week. As readers here are probably aware, both of them have blogs (Prometheus for Jr., Climate Science for Sr.) and both have contributed to the discussions on RealClimate. Readers will also be aware that the discussions have at times been heated, though have usually remained collegial. There have been a few times when the discussion may have seemed to be at cross-purposes, but overall the exchanges have been enlightening.
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How much future sea level rise? More evidence from models and ice sheet observations.
Lots of press has been devoted to four papers in this week’s Science, on the topic of ice sheets and sea level.
We’ve already discussed the new evidence that Greenland’s glaciers are speeding up. What is new this week is an effort to evaluate the impact of future warming on Greenland by looking at what happened to it last time it got very warm — namely during the Last InterGlacial (LIG) period, about 125,000 years ago. The same group of authors looked at this in two ways, using NCAR’s Community Climate System model (CCSM) coupled to a state-of-the-art 3-D ice sheet model.
[Read more…] about How much future sea level rise? More evidence from models and ice sheet observations.
Climate sensitivity: Plus ça change…
Almost 30 years ago, Jule Charney made the first modern estimate of the range of climate sensitivity to a doubling of CO2. He took the average from two climate models (2ºC from Suki Manabe at GFDL, 4ºC from Jim Hansen at GISS) to get a mean of 3ºC, added half a degree on either side for the error and produced the canonical 1.5-4.5ºC range which survived unscathed even up to the IPCC TAR (2001) report. Admittedly, this was not the most sophisticated calculation ever, but individual analyses based on various approaches have not generally been able to improve substantially on this rough estimate, and indeed, have often suggested that quite high numbers (>6ºC) were difficult to completely rule out. However, a new paper in GRL this week by Annan and Hargreaves combines a number of these independent estimates to come up with the strong statement that the most likely value is about 2.9ºC with a 95% probability that the value is less than 4.5ºC. [Read more…] about Climate sensitivity: Plus ça change…
Reactions to tighter hurricane intensity/SST link
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
Good climate debate FAQ
There are a number of topics in climate science that are frequently misunderstood or mis-characterised (often by those trying to ‘scientize’ their political opinions) that come up again and again in climate-related discussions. RealClimate tries to provide context on many of these issues, and commentaries on the 1970s ‘global cooling myth‘ or whether water vapour is a feedback or a forcing are among our most referenced pieces (see our FAQ category). However, our explanations of specific points have often appeared in the middle of a larger piece, or in the comment section and are not clearly referencable. Since many of these same points keep coming up in comments and discussions, having a clear and precise resource for these explanations would be very useful and we have thought about doing just that. But it now appears that we have been beaten to the punch by a new blog run by Coby Beck, a frequent commenter here and at sci.env. His new blog ‘A few things ill-considered‘ has a point-by-point rebuttal of almost all the most common ‘contrarian’ talking points. The list of topics by category is a good place to start, and it shows the huge amount of work done so far. We’re very impressed!
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.
The Greenland Ice
by Rasmus Benestad, Eric Steig and Gavin Schmidt
In a recent paper in Science, Eric Rignot and Pannir Kanagaratnam present new satellite observations of the speed of glaciers of Greenland, and find that they are sliding towards the sea almost twice as fast as previously thought. Additionally, between 1996 and 2005, they detected a widespread glacier acceleration and consequently an increased rate of ice discharge from the Greenland ice sheet. However, previous papers have recently noted an increase in snow accumulation in the interior (i.e. Johannessen et al., 2005), so how do these different measurements fit into the larger picture of Greenland’s net mass balance?
[Read more…] about The Greenland Ice