Friday, July 31, 2015

EGU Open discussions

The Hansen paper (submitted manuscript!) has provoked me into mentioning that the EGU are in the process of revamping the discussion phase of their on-line open access publications. There have been a number of complaints over the years that the open publication of the pre-review manuscript can be confusing, as it may lead people to think that these are peer-reviewed publications (which they are not). I've never been particularly convinced by this, and you only have to look at the process to see what is going on, but then again, if people are going to be confused, maybe it is reasonable to wonder if the process could be clarified. A “watermark” on the title page was already added a few years ago, and they have also recently improved the way that the website links and indexes the manuscripts - pointing more clearly to the final paper when available, so people do not read and cite the original version unless they specifically want to.

I'm not sure quite how finalised the new plans are, but at the time of the last EGU meeting one of the proposals was that the authors' own typset manuscript (eg a fairly plain LaTeX template) would be posted up as-is rather than being formatted into the in-house EGU online style. I don't really like the EGU style so that's already an improvement from my perspective. Another potential benefit is that this would eliminate one source of up-front cost which may pave the way for normalising the publiction fee model to a pay-on-(peer-reviewed)-publication model rather than pay-on-submission. There are arguments on both sides of this - pay on submission may reduce the number of poor submissions, but it can be administratively difficult and may lead to both a presumption of acceptance and hard feelings when a paper is rejected.

Ultimately, I don't think these changes will have much effect on the rare cases where people deliberately publicise their submitted manuscrips, as Hansen appears to have done. Most journalists won't understand, or care about, the details of the peer-review process. Nevertheless, I don't have much sympathy for Ken Caldeira's claim that publishing the review process is a form of “pollution” of the peer reviewed literature. No-one sane would routinely read the discussion phase of the journal, and the point behind the publication of these manuscripts is not to double the amount of material that scientists are supposed to read, but to give people the chance both to look at how a particular paper passed through the peer-review process, or to comment on a manuscript that is particularly noteworthy. To that end, I'm happy to see that the Hansen manuscript is well on its way to being the most heavily-commented paper on ACPD, though predictably most of the comments seem to be from crazies. At least they are thereby distracted from commenting on my blog :-)

Monday, July 27, 2015 Evaluation of CMIP5 palaeo-simulations to improve climate projections

Our latest paper has just appeared in Nature Climate Change: "Evaluation of CMIP5 palaeo-simulations to improve climate projections". It was mainly the brainchild of Sandy Harrison, intended as a response/update to the "preview" paper "Evaluation of climate models using palaeoclimatic data" which promised that the PMIP component of CMIP5 would
provide assessments of model performance, including whether a model is sufficiently sensitive to changes in atmospheric composition, as well as providing estimates of the strength of biosphere and other feedbacks that could amplify the model response to these changes and modify the characteristics of climate variability.
So, how did PMIP do? Well, when we started writing the paper, we looked to see what work had been published that addressed these questions. There was not perhaps quite as much as we might have hoped, but enough to say that
Palaeo-evaluation has shown that the large-scale changes seen in twenty-first-century projections, including enhanced land–sea temperature contrast, latitudinal amplification, changes in temperature seasonality and scaling of precipitation with temperature, are likely to be realistic. Although models generally simulate changes in large-scale circula- tion sufficiently well to shift regional climates in the right direction, they often do not predict the correct magnitude of these changes. Differences in performance are only weakly related to modern-day biases or climate sensitivity, and more sophisti- cated models are not better at simulating climate changes. Although models correctly capture the broad patterns of climate change, improvements are required to produce reliable regional projections.

We started work on the paper around the time we visited Reading last summer, and mostly finished it during our trip to France. Most of the time since then it’s been sitting in limbo waiting for space to be published. It’s pleasing that this travel actually generated a tangible result, which doesn’t always turn out to be the case. And also pleasing that jules and I can continue to make contributions to the literature despite the lack of grey cubicles to spend our days in :-)

4 figures summarise the main results. The first shows that large scale behaviour of the models is consistent between past and future climates (top plots) and that the past climates are consistent with data (bottom plots).
However, when we look at some smaller (but still quite large) areas there are substantial problems, with the modelled mid-Holocene monsoon not adequate to support the vegetation that was present in what is now the Sahara desert. In some places, the models barely register any changes at that time, or move in the opposite direction to the data.
We summarised the climatologies with a Taylor diagram: the Last Glacial Maximum results show at least a positive correlation between models and data (the temperature results are fairly good), whereas for the mid-Holocene, the model results are clustered close to the zero correlation line (vertical line in the diagram below) and have far too little spatial variability. Pale colours are the older PMIP2/CMIP3 results where available, showing that things have not changed significantly with the new generation of models.
We also re-examined the question of equilibrium climate sensitivity. This had been raised in the context of CMIP3 by Hargreaves et al in 2012 who asked "Can the Last Glacial Maximum constrain climate sensitivity?" Our answer there did point to the importance of checking this somewhat tentative result with the new CMIP5 results when they became available, and the new results are not so encouraging. In short, there is no detectable correlation between the equilibrium sensitivity of the models, and their simulated LGM cooling. Not that the results are particularly incompatible with the correlation we had previously found either, they just form a rough ball in the right place without a slope either way. There is, perhaps, room to explore this in more detail, and a new paper by Hopcroft and Valdes (which seems to have been written while our paper was in the publication queue) does exactly this. There are question marks over one or two of the models but it’s perhaps a mistake to go too far down this route, as the risks of cherry-picking and post-hoc justification are strong when the ensemble is so small to begin with.

Not much of Harrison et al. will come as a huge surprise to those working in the field, as this paper is basically a review of recent literature rather than hot-off-the-press results. We hope it will serve as a useful summary and perhaps provoke further research in this area.


Thursday, July 16, 2015

[jules' pics] Baaaa!

A sheeps
Lake District Lamb.

Posted By Blogger to jules' pics at 7/16/2015 12:45:00 PM

Sunday, July 12, 2015

'Mini ice age' coming in next fifteen years!

Oh no it isn't, despite what you can read in the Indescribablyoverhyped. At most, a solar min might make a detectable reduction in the warming trend. It won't cause significant cooling.

It is not clear to me who is responsible for this made-up story, it could be due to exaggeration from the scientists, a badly worded press release, or a journalist trying to get their story published. But in any case, it's not true.

Oh, thanks to ATTP, the press release seems ok, I can see how the journalist might have got confused. I wonder if she actually spoke to any scientists - solar or climate - before writing her piece.