http://www.climateprediction.net/professor-myles-allen-speaking-at-egu-about-weatherhome-2014-uk-flooding-experiment/

Professor Myles Allen will be presenting the results from our weather@home 2014 UK Flooding experiment at a press conference at the EGU (European Geophysical Union) General Assembly in Vienna tomorrow.

The press conference will be streamed live, and you can watch it on the EGU website.

We will be formally releasing the results tomorrow morning, to coincide with the press conference.

The press conference is entitled, �The IPCC Assessment Climate Change 2013 and beyond: making sense of recent climate change� and as well as Professor Myles Allen, involves Thomas Stocker, Co-Chair Working Group I, Gian-Kasper Plattner, Head Technical Support Unit Working Group I and Jochem Marotzke, Max Planck Institute of Meteorology, Hamburg.

At EGU 2014, the Working Group I of the Intergovernmental Panel on Climate Change (WGI IPCC) is convening three scientific sessions and a Union Session to mark the completion of a five year effort by thousands of scientists worldwide. In this press conference, the Co-Chair of WGI IPCC will summarise the lessons learnt from the past assessment and reflect on the implications for future assessments carried out by the IPCC. The Head of the Technical Support Unit will report on the assessment process and highlight particular challenges. Finally, WGI authors will discuss two issues regarding recent climate change: (i) the �warming pause� observed during the past 15 years, and (ii) the role of man-made climate change in recent extreme weather events. The latest research findings are put into the context of the comprehensive assessment by IPCC completed in September 2013.

The EGU is Europe�s premier geosciences union, dedicated to the pursuit of excellence in the geosciences and the planetary and space sciences for the benefit of humanity, worldwide. The EGU General Assembly 2014 will bring together geoscientists from all over the world to one meeting covering all disciplines of the Earth, planetary and space sciences. The EGU aims to provide a forum where scientists, especially early career researchers, can present their work and discuss their ideas with experts in all fields of geosciences.

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Hannah Rowlands
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No longer Communications Officer for climateprediction.net, as of October 2015

Up until the past day or so several thousand hadam3p_eu WUs have been on the server. I have three of them here. If you're presenting the results of the study, does this mean you don't still want these WUs done, or will they go in a later paper?

This project is continually adding data to the big pile that already exists, so that it's there for future researchers.
This is talked about here on the About page at the front of the web site.

The ensemble that we've accumulated so far is HUGE, and we hope to make it MUCH bigger over the coming years. And that includes adding every model that gets completed from this experiment, both before and after it finishes. Some people running very slowly could take months yet to return all of their data.

Okay. This is me being confused about the distinctions (or lack of same) between:
* Ongoing ensemble runs (see the about page) and
* the winter flooding attribution study.

Those hadam3p_eu WUs on my hard drive will add to the ensemble data and may be used for improved analysis of the winter flooding attribution question?

and may be used for improved analysis of the winter flooding attribution question?

Yes

Or anything else that some climatologist thinks of in the far distant future.
Next Tuesday, perhaps. :)

Climate data is climate data.

Hi Niall,

Sorry about the confusion.

Yes, there are still a few model simulations from the UK Flooding experiment that are still running, even though we're announcing the results of this experiment today.

Those additional runs will still be very useful to us and will contribute to a published journal article later in the year which will include further analysis beyond what we're announcing today.

Thanks for your support,

Best wishes,
Hannah

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Hannah Rowlands
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No longer Communications Officer for climateprediction.net, as of October 2015

Announcement of Results from weather@home 2014 UK Flooding Experiment

http://www.climateprediction.net/results-from-weatherhome-2014-uk-flooding-experiment-climate-change-makes-very-wet-winters-a-bit-more-likely/

Results from weather@home 2014 UK Flooding Experiment: climate change makes very wet winters �a bit more likely�

Our recent weather@home 2014 UK Flooding experiment, that assessed the effects of global warming, has found a small but statistically significant increase in the probability of extremely wet winters in southern England.

We used the spare capacity on volunteers� home computers to compare tens of thousands of simulations of possible weather in our present-day climate with tens of thousands of simulations of a hypothetical world without the influence of past greenhouse gas emissions in the atmosphere using the same climate model. Comparing numbers of extremely wet winters between these two groups provides estimates of the influence of climate change on the UK weather.

We found a 1-in-100-year winter rainfall event (ie. 1% risk of extreme rainfall in the winter of any given year) is now estimated to be a 1-in-80 year event (i.e. 1.25% risk of extreme rainfall in any given winter) so the risk of a very wet winter has increased by around 25%. This change is statistically significant thanks to the number of computer simulations we were able to run� over 33,000 computer models run in the experiment.

However, while our finding is statistically robust the result depends on how man-made climate change is represented in the experiment. We used different climate models to estimate the pattern of global warming which provided a range of possible changes in risk. In several cases, the models gave no change or even a reduction in risk, but overall the simulations showed a small increase in the likelihood of extremely wet winters in the south of England.

Researcher Dr Friederike Otto, from the weather@home project based in the University�s School of Geography and the Environment, said: �It will never be possible to say that any specific flood was caused by human-induced climate change. We have shown, however, that the odds of getting an extremely wet winter are changing due to man-made climate change. Past greenhouse gas emissions and other forms of pollution have �loaded the weather dice� so the probability of the south of England experiencing extremely wet winters again has slightly increased.�

She added: �Total winter rainfall, although useful as a benchmark, is not the direct cause of flood damage, so we are working with collaborators, such as the Centre for Ecology and Hydrology, to explore the implications of our results for river flows, flooding and ultimately property damage.�

Graphs displaying the results of the weather@home project can be viewed on our Results page.

Read coverage of this story in the Guardian.

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Hannah Rowlands
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No longer Communications Officer for climateprediction.net, as of October 2015

The results of the flooding attribution experiment show the complexity of interpreting anything that involves probability.

The climateprediction.net project itself emphasises how small the effect is, both explicitly in the written and video press releases, and implicitly in the names of links ('...a-bit-more-likely') and the discussion of the large ensemble sizes needed to establish statistical significance.

The Guardian takes a different line, reporting "Climate change caused by humans has made the likelihood of extreme rainfall similar to that seen in England this winter significantly higher, according to analysis seen by the Guardian." This may simply be journalists reading the phrase "statistically significant" as if it means "significant (and justified by statistics)". As anyone using statistics knows, statistical significance is not immediately about magnitude but about confidence, although less immediately it might be harder to be confident about small differences than large ones. Or perhaps it's just editorial exaggeration. In any event, I am beginning to wonder whether it's a wrong that makes a right.

The headline figure is 25%, meaning that a "once every 100 years" event becomes a "once every 80 years". In other words, the event would occur four times in 400 years (4 x 100) in the world as it might have been, but five times in 400 years (5 x 80) in the world as it is. It wouldn't be quite right to say that four of those events are natural and the fifth caused by climate change but the weaker statement "there's about one extra event per 400 years due to climate change" should be acceptable. Suppose there were an insurance policy that paid out on a 100-year event or worse: its premium would rise 25% (though in practice diluted by other risks not affected by climate change - the whole country wasn't flooded, for example). The question for me is whether this change amounts to "a little bit more". It might also be argued that anything that's measured in units of 100 years isn't worth worrying about, except we've just had such an event. Except also that, as Myles points out in his EGU press conference (here; main session - here), the events in southern England this year were actually a "once in 250 years" event; the 250 years limit might just be because the record doesn't go back any further. Added to this are the comments that there appear to be amplifying effects that convert a "bad" rainfall rate into "worse" flooding (farming practices, housing etc.). Most of all, as Thomas Stocker illustrates early in the EGU press conference (3:44), the aggressive-mitigation 21st century world is +2C but the business-as-usual world is +4.5C: in the winter of 2013/14 we in the UK aren't anywhere near even the +2C point but nonetheless the probability of something bad is already 25% higher. I find that shocking.

There's also a higher level narrative going on: asked to comment on the IPCC process the press conference panel make it clear that scientific interests move on - to paraphrase Myles, the headline cannot always be "Earth goes around Sun". So climate impacts are now the focus of efforts, as here on CPDN: this flooding attribution goes one step further - not only does it say what is likely to happen in some far-off region of the world at some point in the future, it ties the impacts to an actual event. In other words, modelling is now two stages on - global temperatures will rise, areas of the world will be affected, and risk increases are detectable now. As Bruce Willis complains in his recent Sky TV ad, "Does that sound small to you?"