Model Based Extreme Rainfall Claims Not Supported By Actual Data

By Paul Homewood

The Guardian, reporting on some recent research from Oxford University, comment:

image

They say:

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.

Rainfall events that would previously have occurred only once in a century are now likely to be witnessed once every eighty years in the south of England, the Oxford University work shows.

That will mean far more frequent severe floods for residents of the crowded region, with what were once extremely rare events now happening much more often than the infrastructure of the region is equipped for. The research shows an increase in the rate of such events of about 20 to 25%, which significantly alters the number of homes likely to be vulnerable to flooding.

http://www.theguardian.com/environment/2014/apr/30/climate-change-extreme-rainfall-england-flooding

The first thing to point out is that these results are based on climate models, rather than real world data. As the authors point out:

However, while our findings are 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.

 

They also describe their study thus:

Following preliminary assessments from the Met Office, Oxford University researchers undertook the first scientific experiment to analyse whether the risk of extreme rainfall has changed owing to climate change after the winter deluge between December 2013 and February 2014. Total rainfall in Oxford over the three months was the highest ever recorded by the University’s Radcliffe Observatory since it was set up 200 years ago.

Scientists 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. They found that a one-in-100-year winter rainfall event (i.e. a 1% risk of extreme rainfall in the winter of any given year) is now estimated to be a one-in-80 year event (i.e. a 1.25% risk of extreme rainfall in any given winter), so the risk of a very wet winter has increased by around 25%.

http://www.ox.ac.uk/news/2014-04-30-global-warming-makes-very-wet-winters-more-likely

Still, let’s see what the real data tells us.

Despite last winter being the wettest on record since 1910 in the South of England, there is no evidence to suggest that wet winters are becoming more common. The wettest 10 years were between 1911 & 1920.

 

imageFigure 1

However, we need to recognise that the selection of the narrowly defined period of “December to February” has very little relevance. If there are concerns about “extreme rainfall and flooding”, we should be looking at the months that are traditionally the wettest. In the South of England, these are October to December.

image

http://www.metoffice.gov.uk/public/weather/climate/oxford-oxfordshire#?tab=climateGraphs

When we analyse these months, we find that the wettest year was 1929, followed by 2000 and 1960. (Oct-Dec rainfall in 1929 totalled 457.7mm, compared to 408.5mm this last winter).

Wet years in 2000 and 2002 pushed the 10-Year trend up to similar levels seen in the 1910’s, but the trend has fallen again since.

Also evident is the well accepted “dry period” of the 1960’s and 70’s. As with the winter trends, there is no evidence that Oct-Dec periods are becoming wetter.

imageFigure 2

Of course, the study talks about “extreme rainfall”, rather than averages, so is there any evidence that this is becoming more common?

It is important to recognise that the reason why the winter of 2013/14 was so wet was because the wet weather persisted for three months. (It is also worth recalling that the even wetter weather of 1929 persisted for four months, from October to January).

This persistence is a factor of weather and coincidence, rather than having anything to do with a warmer climate. Therefore, to establish whether rainfall, per se, is becoming more extreme and intense, we need to look at monthly figures, rather than seasonal ones.

Figure 3 shows the top 20 wettest months, falling in the October – December period, since 1910 for England South.

Clearly, the wettest months occurred in the early decades. Since 1970, only one month, Oct 2000, has exceeded 160mm, compared with nine such months up to 1970.

imageFigure 3

Finally, let’s take a look at the Oct-Dec rainfall trends at Oxford itself, where data is available back to 1853. As with England South, the three stand out years are 1929, 1960 and 2000.

In the last decade, we have seen nothing that was not commonplace between 1870 and 1920.

imageFigure 4

Conclusions

There is no evidence that “extreme rainfall” is becoming more common.

The study’s authors seem to have gone to a lot of bother, trying to establish a link to global warming. They would have saved themselves a lot of work, if they had simply gone and analysed the data.

Sources

1) All precipitation data for England South from Met Office

http://www.metoffice.gov.uk/climate/uk/summaries/datasets

2) Oxford rainfall data

http://www.metoffice.gov.uk/pub/data/weather/uk/climate/stationdata/oxforddata.txt

3) Details of the Oxford University study.

http://www.ox.ac.uk/news/2014-04-30-global-warming-makes-very-wet-winters-more-likely

http://www.climateprediction.net/weatherathome/weatherhome-2014/results/

49 thoughts on “Model Based Extreme Rainfall Claims Not Supported By Actual Data

  1. Anbother set of numpties who think that running a climate model is an experiment. No wonder the UK is in serious decline if this is what Oxford University is doing these days.

  2. now happening much more often than the infrastructure of the region is equipped for….

    huh?…..the infrastructure can support a flood every 100 years…
    …but not every 80 years?

    Dear Lord, what kind of infrastructure do you guys have over there?

  3. Nice work, but tell us something we don’t know.
    The Guardian is frantically going out of its way to ‘prove’ global warming by whatever means necessary. This latest ‘definitive report’ is just another piece of absurdly biased climate propaganda.
    It’s what they do. They won’t come out of this well.

  4. Should we begin building an ark now, or wait till later?
    Sorry about that, I’ve been reading all of these rent-a-catastrophe reports, and between extreme rains and rising sea levels it appears we’re being sold the idea that Man is capable of creating catastrophes of biblical proportions. Without, apparently, angering a god who the warming alarmists will say doesn’t exist anyway. Nope, gonna do it all by ourselves.

    OK. It rains in England. A lot. The Gulf Stream and prevailing Westerlies blow in moisture from the Atlantic and it drops as rain over England. It’s been doing that a long time now. It’s going to keep right on doing that regardless of any decrees coming from Whitehall or the White House. Buy a decent foul-weather outfit and get used to it.

  5. It has to be remembered that in the old days the citizens of the UK thought for themselves. They lived on high ground and graised their livestock on the floodplains in summer. Nowadays the Government decrees that farming for food is not necessary and encourages people to live and work on the floodplains. The dumbing down of education means that millions of people are quitre happy to buy a house on a floodplain.

  6. “They would have saved themselves a lot of work, if they had simply gone and analysed the data.”

    True on almost all alarmist claims, but then alarmists couldn’t make alarming claims if they actually used data. Tough to be an alarmist and a scientist of integrity.

  7. They would have saved themselves a lot of work, if they had simply gone and analysed the data.
    but results would have been ‘worthless ‘ from the fill your boots with grant cash , point of view.

    Lets face it ‘the cause ‘ has [led] to wide scale use of science by press release , and great claims made on little or no evidence , while its created a ,models mean more than facts outlook . You want to get published , you want to get paid , then you know what results you need to produce!

  8. They say: ” Rainfall events that would previously have occurred only once in a century are now likely to be witnessed once every eighty years in the south of England, the Oxford University work shows.”

    Correct me if I am wrong but that means this type of rain event will occur 5 times every 400 years instead of 4 times.

    Yet they claim “the likelihood of extreme rainfall similar to that seen in England this winter significantly higher” . How is 1 more time per 400 years a “significantly higher” occurrence?

    They also claim “That will mean far more frequent severe floods for residents of the crowded region, with what were once extremely rare events now happening much more often”. How is 1 more time per 400 years “far more frequent” and how does that 1 extra event per 400 years change a “once extremely rare event” into something else?

  9. A computer model science study should be illegal to publish without scientific observations/evidence to verify it using scientific method. A computer model on its own means absolutely nothing and no paper should report this rubbish.

  10. If you take the report seriously (or if “one” takes the report seriously), isn’t the most important implication that you should invest in better flood control in the affected region? Flooding every 80 years instead of every 100 years does not strike me as a reason to sacrifice your economy to wind farms.

  11. Tom in Florida: Correct me if I am wrong but that means this type of rain event will occur 5 times every 400 years instead of 4 times.

    That’s about the size of it.

  12. Calling computer program outputs “experiments” gives new meaning to the term “artificial intelligence.”

  13. How can you statistically extract periodicities of events from data that is only about the same length as the period of interest?

  14. ClimatePrediction.Net is the source of the projections. The same crowd (e.g. Myles Allen) who predicted up to 11 degrees celsius increase in temperature before the end of the centurydue to AGW.

  15. AJB says:
    May 7, 2014 at 11:54 am

    “Follow up project coming soon here.”

    Mod.: Spam? (link, “here”)

    [Good find, thank you. Mod]

  16. Of course they should have analysed the data, but there is an inherent problem in doing that using real-world (unadulterated) records. As these are typically unable to conform to the assumptions (wishful thinking) used by climate scientists in their heat-seeking models they would never have been able to publish scary ‘research’.

    If all climate science were based on accurate, unadulterated and un-cherry-picked data the world would be a much better and much happier place. Except for the politicians who would be unable to keep justifying their new tax raising abilities and of course those whose livelihoods and often massive wealth are entirely dependant on maintaining the gullible warming scare.

    ps Don’t you just love the creative thinking in describing the model output which showed a 1 in 100 chance changing to a 1.25 in 100 chance (i.e nothing here to worry about) as a ‘25% increase’ in likelihood of extremely wet winters which sounds a whole lot scarier ….

  17. 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.

    Overall they torture the models until the desired result is reached. Here is what happens when you are more humane and desist from cruel torture.

    Abstract
    …….Climate model simulations disagree on whether future precipitation will increase or decrease over California, which has impeded efforts to anticipate and adapt to human-induced climate change……..Between these conflicting tendencies, 12 projections show drier annual conditions by the 2060s and 13 show wetter. These results are obtained from 16 global general circulation models downscaled with different combinations of dynamical methods…

    http://dx.doi.org/10.1175/JCLI-D-12-00766.1

    UK to get more drought

    http://dx.doi.org/10.1016/j.jhydrol.2010.04.035

    UK to get more rain

    http://dx.doi.org/10.1002/joc.1827

  18. Hey that wasn’t spam! There’s little difference between this crowd sourced nonsense that writing a shared game. Maybe I shoulda used the /sarc tag.

    [Yes, that would have helped. Mod]
    [Then again, the crowd-sourced game might be a more accurate GCM. Mod]

  19. They found that a one-in-100-year winter rainfall event (i.e. a 1% risk of extreme rainfall in the winter of any given year) is now estimated to be a one-in-80 year event ……

    So the next one is in 80 years time. If their simulation is wrong they would have been just a thing of the past. Children won’t know what an Oxford researcher is. Next.

  20. Just over 18 inches of total precipitation in 3 months
    is “extreme”?

    As was pointed out by Paul Homewood
    and poster mjmsprt40, it simply rains
    a lot in England on average basis.

  21. Reminds me of one of our local climate ‘experts’ here in Oz, Tim Flannery, who infamously [predicted] that [our] rivers would dry up, our dams would never fill and that we effectively faced endless drought. This was in spite of the data recorded by our Bureau of [Meteorology] (OzBOM) that showed about a 20% increase in rainfall across the continent, higher in the tropical north but pretty [much] every where except SW Western Australia ( which is now thought to be more [about] land clearing over the wheat belt area) and the island state of Tasmania which had seen about a 10% fall ( Tas has twice the mainland’s rainfall to start with).

    Now in Oz we have a weather god named Huey who I think may be the same god as the playful trickster Norse god Loki. Huey is very approachable by sailor’s and surfers in particular, as many here are aware, but Professor F’s arrogant, empty headed distortion of his works, never mind not even acknowledging Huey, [severely] pissed the god off and so he sent us some floods centred on Queensland and NSW where the foolish professor F lives ( by the shore and vulnerable to the catastrophic rising sea levels he also endorses – but that’s another story). The dams are now full and how the rivers run.

    At least these turkey’s in the UK are using that old stalking horse, a model, so as to not piss the gods off directly. They can’t be that dumb I suppose, about as smart as your typical hillbilly I venture.

  22. semi automatic spellchecker kicking in
    … predicted that our rivers…..of Meteorology… … more about land clearing…

  23. Computer models of journalists reporting on climate issues show 50% of articles sympathetic to AGW and 50% of articles skeptical of AGW.

    Reality is that 97% of journalists advance the left leaning AGW agenda.

    Computer models… pshaw!

  24. Rain in the UK? Cor wot a shocker!

    And let’s not forget the Somerset floods were caused by deliberate government policy.

  25. never mind. Stanford & Steyer will save the planet:

    7 May: Reuters: Rory Carroll: Stanford University ending investments in coal companies
    Stanford University said on Tuesday it will no longer use any of its $18.7 billion endowment to invest in coal mining companies, a move aimed at combating climate change that could influence college administrations elsewhere…
    The university’s board of trustees agreed with recommendations from a panel of students, faculty, staff and alumni that found investments in alternatives to coal would be less harmful to the environment…
    It was announced on the same day the White House released a report warning that climate change was already affecting the United States in the form of more severe droughts in some areas and more intense storms in others.
    He added that Stanford, which is located on the edge of Silicon Valley, is working to develop sustainable energy sources…
    ***Billionaire hedge fund investor-turned-environmental activist Tom Steyer, who has supported a number of colleges in their campaign to purge coal investments, is an alumnus of Palo Alto-based Stanford, a member of its board of trustees and founder of two clean energy research institutes on campus…
    Jay Carmona, divestment campaign manager for 350.org, said he hopes Stanford’s decision will influence other universities.
    “Now that one of the biggest endowments on earth has acknowledged that it can’t keep investing in climate change, others can follow,” he said…

    http://www.reuters.com/article/2014/05/07/us-carbonstanford-divestment-idUSBREA460L620140507

    8 May: UK Independent: For sale: Norway’s pristine Arctic wilderness – the coal-rich Svalbard Islands
    But while about 65 per cent of the archipelago is protected, mining has been part of the landscape on the Svalbard Islands since its settlement in the early 20th century, and the 217 square kilometres of land put up for sale recently is believed to hold about 25 million tons of coal…
    “China is in constant search of coal and other natural resources,” Mr Ostreng said. “By purchasing this property they can use Svalbard as a platform for a long-term plan in the Arctic Ocean Basin.”…
    Searching for the natural resources to fuel its economic growth, China is already one of the biggest mining investors in Greenland, and last year was granted observer status on The Arctic Council, a body coordinating policy in the region…
    Norway’s Green Party is fighting to preserve the wilderness of Svalbard, and at a party congress this week proposed closing down all the coal mines on the archipelago.

    http://www.independent.co.uk/news/world/europe/for-sale-norways-pristine-arctic-wilderness–the-coalrich-svalbard-islands-9307546.html

  26. 7 May: UcaNews: George Moya: Greenpeace slams Philippines’ reliance on coal
    “This report should make President Aquino and his energy officials to re-think about approving more coal fired plants, aside from the 45 plants currently in the pipeline,” said Reuben Andrew Muni, climate and energy campaigner for Greenpeace…
    The report claims that the Philippines can cut its reliance on fossil fuels by as much as 45 percent by 2020, and renewable energy sources can provide 55 percent of the power needs of the country.

    http://www.ucanews.com/news/greenpeace-slams-philippines-reliance-on-coal/70881

    8 May: Economic Times India: Finance Ministry seeks details on coal availability for power sector
    The power ministry envisages capacity addition of 66,014 Mw of coal-based generation during the 12th Five-Year Plan (2012-17), of which fuel supply
    agreements for about 21,300 Mw plants are yet to be signed, while 27,760 Mw is proposed to be met through captive coal blocks.
    Fresh coal supply agreements are required for another 12,400-Mw power plants…

    http://economictimes.indiatimes.com/industry/energy/power/finance-ministry-seeks-details-on-coal-availability-for-power-sector/articleshow/34802016.cms

  27. What was once a lifetime event might become a once in a lifetime event…? That is about as save a ‘prediction’ as can be made. Tough to prove wrong, rather easy to dismiss by anyone without blinders.

  28. phillipbratby says:
    May 7, 2014 at 12:04 pm
    They lived on high ground and graised their livestock on the floodplains in summer.
    … millions of people are quitre happy to buy a house on a floodplain.

    Try “grazed” and “quite”. They work better.

  29. Old England — thank you for the concept of the ‘heat-seeking model’ — made me envisage a virtual Sidewinder aimed at the ‘advanced’ economies of the world. Oh — wait a bit…

  30. Chris

    The floods this winter were not caused by short term, heavy rainfall, but by persistent rainfall over several weeks. Indeed, there is no evidence at all that such heavy rainfall has been more common or intense this winter.
    Indeed, the evidence shows the opposite.

    http://notalotofpeopleknowthat.wordpress.com/2014/02/22/no-julia-rainfall/

    The study you quote only has a handul of stations up to 1960. and therefore is not statistically sound (note the huge error bands).

    Besides, the Oxford study is specifically on the seasonal totals, and not daily rainfall.

  31. Paul, the WordPress link you refer to is looking at something different – the amount of rainfall that falls on the wettest days. That is not the same thing as the % of all rainfall that occurs on heavy rainfall days. So that data does not disprove the conclusions of the study. In Singapore, where I live, the government is spending 100s of millions of dollars to expand the capacity of the storm drains, due in part to more frequent occurrences of very heavy rainfall days, defined as those in which more the 100mm of rain falls in less than 4 hours.

  32. I ran some control charts on our recent rainfall using the Met Office records from 1766 and 1910 and it suggests that what we have seen is nothing particularly out of the ordinary. A lot depends on over what period you take for your rainfall measurements. I used the Met Office Winter figures.

    http://oldgifford.wordpress.com

  33. Given as rainfall is estimated from weather radar and not measured as it was in the past, how reliable is the time series data?

  34. Chris

    That is not the same thing as the % of all rainfall that occurs on heavy rainfall days

    There is another analysis here of Oxford, which replicates another more up to date Met Office analysis on extreme rainfall.

    Again it show no long term changes.

    http://notalotofpeopleknowthat.wordpress.com/2014/03/27/extreme-daily-rainfall-at-oxford/

    The reality though is that the Osborn paper invalidates itself:-

    First part of record – 37 rain gauges

    Final part since 1960 – 544 rain gauges.

    You simply cannot splice two totally different sets of data together, and expect to come up with a statistically meaningful result.

  35. Cheshirered says:

    The Guardian is frantically going out of its way to ‘prove’ global warming by whatever means necessary

    Rather missing the point that the way you “prove” something using science is generally to attempt to “falsify” it and fail to do so :)

  36. Matthew R Marler says:

    If you take the report seriously (or if “one” takes the report seriously), isn’t the most important implication that you should invest in better flood control in the affected region?

    Remembering that bad “flood control” can be worst than doing nothing.
    Also at least some of the recent UK flooding actually appears to have been down to a failure to carry out well understood activities.

  37. Chris R. says: May 7, 2014 at 2:55 pm
    Just over 18 inches of total precipitation in 3 months is “extreme”?

    VALSETZ, OREGON (358833) Period of Record Monthly Climate Summary
    Period of Record : 10/25/1936 to 10/12/1986
    Average Total Precipitation (in.)
    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
    20.97 17.18 15.07 8.42 4.64 3.28 1.16 1.95 4.54 10.69 19.53 23.14 130.56

    So for 50 years, 3 Months average over 18″ and any 3 months from Sept to May average over 18″, so the answer is “no or not everywhere.” And no the town was not washed away.

  38. I attempted to submit a comment to this article in the Guardian. I simply asked the question why weather was blamed for the recent cold snowy winters whereas the mild wet conditions of last winter were due to man made climate change. The comment was instantly removed because it did not abide by their community standards.

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