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New Floods Study Not Supported By The Data

August 26, 2017
tags:

By Paul Homewood

 

 

A few have asked me to review this recent study about European floods, highlighted by the BBC a couple of weeks ago.

 

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Climate change has had a significant impact on the timing of river floods across Europe over the past 50 years, according to a new study.

In some regions, such as southern England, floods are now occurring 15 days earlier than they did half a century ago.

 

But the changes aren’t uniform, with rivers around the North Sea seeing floods delayed by around eight days.

The study has been published in the journal Science.

Floods caused by rivers impact more people than any other natural hazard, and the estimated global damages run to over a $100bn a year.

Researchers have long predicted that a warming world would have direct impacts on these events but until now the evidence has been hard to establish.

Floods are affected by many different factors in addition to rainfall, such as the amount of moisture already in the soil and other questions such as changes in land-use that can speed up water run-off from hillsides.

This new study looks at this issue in some depth, by creating a Europe-wide database of observations from 4,262 hydrometric stations in 38 countries, dating back to 1960.

The analysis finds a clear but complex impact of climate change on river flooding.

 

map

Image copyright Günter Blöschl Image caption

The blue arrows indicate earlier flooding due to changes in the soil moisture levels. The yellow and green indicate earlier floods due to earlier snow melt

 

 

The most consistent changes are in north-eastern Europe around Scandinavia where earlier snow melt due to warmer temperatures is leading to earlier spring floods. Around 50% of monitoring stations are seeing floods eight days earlier than they did 50 years ago.

The biggest changes are seen along the western edge of Europe, from Portugal up to Southern England. Half the stations recorded floods at least 15 days earlier than previously. A quarter of the stations saw flooding more than 36 days earlier than in 1960.

In these regions, the issue isn’t snow melt – it’s more about saturated soils. Maximum rainfall tends to occur in the autumn and gets stored in the soils. Heavier and earlier rain means that the groundwater reaches capacity earlier.

“It’s the interplay between extreme rainfall and the abundance of rainfall,” lead author Prof Günter Blöschl, from the Technical University of Vienna, told BBC News.

“In southern England, it has been raining more, longer and more intensely than in the past. This has created a rising groundwater table and higher soil moisture than usual and combined with intense rainfall this produces earlier river floods.”

However, around the North Sea, in the Netherlands, Denmark and Scotland, the trend is towards later floods.

The scientists believe this is due to changes in the North Atlantic Oscillation (NAO), the weather phenomenon that pushes storms across the ocean into Europe.

 

flood map

Image copyright Günter Blöschl Image caption

Across Europe, regions experienced different shifts in the timing of floods, both earlier and later

 

 

The NAO is driven by differences in atmospheric pressure between the North Pole and the Equator. Recent, rapid changes in temperatures in the Arctic are interfering with these pressure levels and changing the track of the oscillation and storms as well.

According to this study, the storms are arriving later and as a result some river flooding happens later too.

Prof Blöschl says that this study shows clear evidence of the impact of human-induced climate change in many regions – but there are still some areas of uncertainty.

“Where the human imprint is obvious is in the northeast of Europe. It is quite a direct link, with a warming climate and earlier snow melt,” he said.

“However, the areas impacted by the NAO are more difficult to attribute to anthropogenic global warming. The jury is still out on that aspect.”

The study foresees subtle but significant impacts that could arise from the change in flood timing. There could be effects on river ecosystems with salmon spawning later in the year. There could also be implications for hydropower stations, and for agriculture if fields stay wetter for longer.

“The more serious concern is that if warming impacts the seasonality it may also impact the scale of flooding,” said Prof Blöschl.

“You could think of timing changes as the harbinger of future changes of flood magnitude. That is the more serious concern. If that happens, flood risk management will have to adapt and that will be different in different parts of Europe.”

Other experts believe that the changes in flood timing identified by this study have significant implications for how we understand the risk of river floods and how we deal with them.

“Nearly every major city and town in Europe is built on a river and we protect this urban infrastructure by using past floods as a gauge of the potential risk,” said Mark Maslin, Professor of Climatology at University College London.

“The study shows that this approach underestimates the risk, as climate change has made European floods occur earlier in the year, increasing their potential impact.

“This means all the infrastructure that we have built to protect our cities needs to be reviewed as much of it will be inadequate to protect us from future climate change-induced extreme flooding.”

http://www.bbc.co.uk/news/science-environment-40889934

 

 

Xmetman Bruce has already written a detailed post on this paper here, which is well worth a read.

My immediate thoughts are:

1) Over the last 50 years, some areas have experienced earlier winter/spring floods, while others are later.

To which I can only reply –”And?”

The idea that weather stays the same every year is frankly laughable. By its very nature, weather is highly variable and unpredictable.

As the second graphic shows, there is very little pattern to the trends, other than the Scandinavian ones resulting from earlier snowmelt.

There is a clear attempt to link all of this to worse floods

According to the BBC report, Mark Maslin, Professor of Climatology at University College London, says:

The study shows that this approach underestimates the risk, as climate change has made European floods occur earlier in the year, increasing their potential impact.”

While the report’s author Bloschl states:

The more serious concern is that if warming impacts the seasonality it may also impact the scale of flooding. You could think of timing changes as the harbinger of future changes of flood magnitude. That is the more serious concern.”

 

In fact, the earlier snow melt would surely mean the opposite, as the later the melt is, the more snow is accumulated. You only have to think to the UK in March 1947 to understand this point.

 

 

2) As I have often pointed out, flood experts in the UK tell us that the period from 1960-90 was a notable flood dry period in the UK. As far as the UK is concerned, at least, 50-year trends are meaningless, and much longer periods need to be looked at.

 

 

But let’s look at the specific claims about southern England. First, the Abstract:

Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.

http://science.sciencemag.org/content/357/6351/588

And this is what the BBC has reported:

The biggest changes are seen along the western edge of Europe, from Portugal up to Southern England. Half the stations recorded floods at least 15 days earlier than previously. A quarter of the stations saw flooding more than 36 days earlier than in 1960.

In these regions, the issue isn’t snow melt – it’s more about saturated soils. Maximum rainfall tends to occur in the autumn and gets stored in the soils. Heavier and earlier rain means that the groundwater reaches capacity earlier.

“It’s the interplay between extreme rainfall and the abundance of rainfall,” lead author Prof Günter Blöschl, from the Technical University of Vienna, told BBC News.

In southern England, it has been raining more, longer and more intensely than in the past. This has created a rising groundwater table and higher soil moisture than usual and combined with intense rainfall this produces earlier river floods.”

So they are essentially referring to heavier rainfall in autumn, which they conclude leads to earlier winter floods.

But what are the facts?

The Met Office have regional data since 1910.

Shows the standard areas (general regions) used by the Met Office when generating climatologies.

image

http://www.metoffice.gov.uk/pub/data/weather/uk/climate/datasets/Rainfall/date/England_S.txt

 

The obvious standout year was the notoriously wet autumn of 2000, when 415mm fell.

Yet even that was hardly unprecedented, as 1960 was almost as wet with 408mm.

But apart from that year, there appears to be no meaningful trends at all, simply the usual year to year noise we always expect to see.

As already mentioned, the 1960-90 period was a flood dry one, and there were certainly some particularly dry autumns, notably 1978 which was by far the driest on record. The autumns of 1985 and 1964 were also third and fourth driest. But changes in rainfall patterns since that time have nothing at all to do with “global warming”.

 

The Met Office also publishes the longer running HADUKP series, with regional data going back to 1873.

This splits the south of England into 3 districts, Central, SE and SW:

Region definitions for EWP

image

image

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http://www.metoffice.gov.uk/hadobs/hadukp/data/download.html

None of these regions show any evidence of the paper’s claim about increasing autumn rainfall.

What particularly stands out are some extremely wet autumns in the 1870s.

 

I have only looked at southern England. But if the Bloschl paper has got it so badly wrong there, how much confidence can there be in the rest of his analysis?

Although Bloschl is the Lead Author, there are 46 authors in total, so there must be a lot of funding involved here.

The first part of the Abstract rather gives the game away about what they are up to:

“A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far.”

We are constantly told by climate scientists that global warming has already made floods worse. Yet they now admit that they can find no evidence to support this.

Left with this dilemma, they have shifted their attention to timing. But, as we have seen, their new claims don’t stand up to scrutiny either.

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26 Comments
  1. dave permalink
    August 26, 2017 12:21 pm

    These climatologists have futile brains – they think of ways of explaining everything.*
    Surely, the joke is wearing very thin now, even for true believers?

    Adapted from ‘The Phoenix and the Carpet,’ by E.E. Nesbit.

  2. dave permalink
    August 26, 2017 12:29 pm

    They leave us – brain-washed masses and pathetic Pavlovian dogs, they fondly imagine – to equate ‘climate change’ with ‘man-made climate change’ and beat ourselves up about it.

    • dave permalink
      August 26, 2017 12:56 pm

      Oh cute!

      The headline of the BBC talks about “floods” which 99.9% of people will understand as an inconvenient overflow of water onto normally dry land, while the study actually was of the timing each Spring of when rivers “go into flood (i.e. rise)” which is an archaic meaning.

      They are all just twisters.

      • August 26, 2017 1:13 pm

        The authors are actually duplicitous in the way they use the term flood. They measure date of highest flow which in the vast majority of cases will not involve over-flow. But then they say things like this:

        River flooding affects more people world- wide than any other natural hazard, with an estimated global annual average loss of US $104 billion.

        and

        If the trends in flood timing continue, considerable economic and environmental consequences may arise

        From which it is clear the article is about over-flow events. Its also worth noting that some of the trends have already reversed.

  3. August 26, 2017 12:45 pm

    The MAIN problem with the Blöschl et al approach is that they don’t actually present any data on flooding. They begin with the date of highest flow in a river andy year and then average this over a region, e.g. southern England. So the starting point is a big average which will itself obscure any evidence of actual flooding in a single catchment. And then they run a 10 year mean through the time series obliterating any extreme events which flooding is connected to. The approach is non-science – budget €2.2 million.

    • dave permalink
      August 26, 2017 1:01 pm

      2.2 million euro? Seriously? I could have done that analysis for 2.2 thousand.

      I would have insisted, however, my name NOT go on such a piece of sh*.

      • dave permalink
        August 26, 2017 1:06 pm

        At the other end of the world the usual suspects were pretending, a few months ago, to be worried about the ice extent in ANTARCTICA :

      • August 26, 2017 1:20 pm

        ERC “FloodChange,” project no. 291152 (budget €2.2 million) – the budget is for the whole program. Probability of them not finding a link between flooding and climate change = 0!

  4. August 26, 2017 12:57 pm

    “Floods caused by rivers impact more people than any other natural hazard, and the estimated global damages run to over a $100bn a year.”
    This nonsense is regularly trotted out to presumably show that climate change is getting worse because the figures for damage climb every year. Of course they do because populations are increasing, towns and cities are expanding, and everyone wants, for some unaccountable reason, to live on a flood plain.

  5. August 26, 2017 1:47 pm

    As you may know the so called “Event Attribution Science” has attributed the 2000 floods in England and Wales to fossil fuel emissions. Here is a critical analysis of that attribution
    https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2929159

    • Jack Broughton permalink
      August 30, 2017 8:08 pm

      Fascinating statistical analysis of rainfall: shows that weather is variable but not trending.
      An odd point, not directly related, is the distribution of UK weather stations graphic in the paper: mainly south of England and central Scotland. Seem to be very few on coasts or in NW, where we had floods recently. Wonder why?

  6. Broadlands permalink
    August 26, 2017 1:55 pm

    This sentence says it all?

    “The scientists believe this is due to changes in the North Atlantic Oscillation (NAO), the weather phenomenon that pushes storms across the ocean into Europe.”

    The NATURAL phenomenon that humans have no control over.

    • dave permalink
      August 26, 2017 3:48 pm

      The following is interesting as an example of there being little new under the Sun – except for attitudes:

      “Was it wholly right that palm fronds should rustle in New York City on the first of January? It was a miracle of the weather-control towers that increased the greenhouse effect in the atmosphere, enabling it to retain more of the Sun’s heat.”

      From a short science-fiction story called “The Restless Tide” by Raymond Z Gallum published in….

      1951.

  7. leescott290822035 permalink
    August 26, 2017 3:06 pm

    Of what consequence is a change in the timing if the overall amount of water is the same. Do I really care if the date of maximum flow occurs 2 weeks earlier than it used to? It seems like the only thing I should be concerned about is, is it going to rise over the banks and flood my house? If that happens, I don’t see that it’s any worse happening mid-April than the first of May.

    They’ve already said they don’t see any increase in the incidence of actual flood events, so about all I can infer from this study is that good summer weather for the growing season is now also arriving two weeks early. I see that as a good thing.

  8. michael hart permalink
    August 26, 2017 4:02 pm

    In much of the UK and Europe, rivers are ‘managed’ and floods are often the result of changes in land-management and building on flood plains. The alarmists have less than no evidence for their claims.

  9. August 26, 2017 5:15 pm

    ‘I have only looked at southern England.’

    Jet stream variability can easily transfer Scottish weather patterns further south during some seasons, as per this 2012 BBC weather item written by a forecaster:

    ‘In a normal summer, the jet stream would typically pass to the northwest of Scotland, bringing rain to the northwest of Britain and drier weather to the southeast.

    This year, the jet stream has often got ‘stuck’ – more or less across southern England – which brings the low pressure systems straight across England and Wales.

    This stuck weather pattern has resulted in us having the wettest April on record.’

    http://www.bbc.co.uk/news/uk-18367583

  10. Athelstan permalink
    August 26, 2017 5:39 pm

    Image copyright Günter Blöschl Image caption

    Across Europe, regions experienced different shifts in the timing of floods, both earlier and later

    So, “earlier AND”…………erm

    “later” and the subtext ‘this is purely speculative bilge’.

    However, always interesting stuff Paul these sorts of factual and historical graphs even if they do emanate out of Exeter always make me wonder – why was this, that the other years so out of the unusual and what might have been partial cause – you’ll never find out the actual combination but as in Krakatoa going off in 1883 or Tambora [1815] – some ‘event’s cannot be ignored nor erased though Mann tried to do something akin to rewriting the MWP off/out of the surface T record of the whole bloody globe……what a knavish fookwit he REALLY iis.
    What is interesting are the UK autumnal rainfall figures in 1870-1890 some major rainfall amounts and the 1960 figure really stands out, as does Autumn 2000, clearly, certainly volcanic events are a factor but no way can they provide the full picture, the conveyor Jet stream has focused a series of troughs and depressions bearing rain and concentrated on particular parts of this mainland, Somerset and the South west drenched in 2013/14, the Lakes in 2015 but although everyone remembers the south of England flooding in 2000 the country got a drenching, as we all did in 2007 but the annual amounts did not count as aught significant – not ‘record’ breaking as in 1960 etc. Again 1870s and 1880s [7 peaks] and 1960 – I wonder why………………?

  11. August 26, 2017 7:11 pm

    “Researchers have long predicted that a warming world would have direct impacts on these events”

    “Impact” is rather vague – is that really what they predicted? I’m pretty sure the prediction was lots more flooding, and disaster.

    Not that the river would be at a higher point a few days/weeks earlier in the year.

  12. tom0mason permalink
    August 26, 2017 8:14 pm

    So from these tidbit –

    The scientists believe this is due to changes in the North Atlantic Oscillation (NAO), the weather phenomenon that pushes storms across the ocean into Europe.
    … and
    “However, the areas impacted by the NAO are more difficult to attribute to anthropogenic global warming. The jury is still out on that aspect.”
    … and
    “The more serious concern is that if warming impacts the seasonality it may also impact the scale of flooding,”
    … and
    “The study shows that this approach underestimates the risk, as climate change has made European floods occur earlier in the year, increasing their potential impact.
    “This means all the infrastructure that we have built to protect our cities needs to be reviewed as much of it will be inadequate to protect us from future climate change-induced extreme flooding.”

    All it really says is

    We don’t know what controls the variability of flooding in Europe, but we believe it is the NAO (no grounds or data given for this).
    We don’t know that the NAO is affected by human activity but we are assuming it’s so through some mysterious ‘climate change’ mechanism.
    We are trying to alarm people but using words like “more serious concern” when all we can say afterward is a bunch of ‘ifs’ ‘may’ and ‘coulds’.
    And finally they recommend flood defenses should be improved because of “potential impact” and the unspecified probability that ‘climate change’ may make floods worse.
    ~~~~~~~~~~~

    Regardless of what this paper says flood defenses should be periodically reassessed anyway. There should be money put aside for it, and NOT spent on worthless reports like this. Flood defenses are an ongoing maintenance requirement throughout Europe, and these defenses are always changing to reflect the varying requirements of waterway and land use. Anything less is a negation of public duty.

    • tom0mason permalink
      August 26, 2017 8:16 pm

      Oops forgot that closing HTML tag…

  13. Jack Broughton permalink
    August 26, 2017 8:41 pm

    Great assessment of the junk-science and junk news again Paul.
    Whenever the BBC etc, want to make something that is untrue credible they cite “scientists say”: when they are really trying to cover up nonsense they find some so-called “professors” and the plebs are supposed to say “I’m now convinced”.

    Sadly, professors and scientists have become tools of the establishment and seem to believe that they are saving the world from itself, no matter how strongly the evidence refutes this. Climate is far, far longer than 50 years!

  14. Paddy permalink
    August 27, 2017 6:17 am

    ….. and they insist on not dredging the rivers.

  15. tom0mason permalink
    August 27, 2017 9:08 am

    So who could be inspiring such use of the English language?

    Hammering out their version all the while staying hidden?

  16. Tim Hammond permalink
    August 27, 2017 11:17 am

    If this is linked to snow melt then the two variables are the amount of snow and how quickly it melts. So do we have more snow and/or is there evidence it is melting any more rapidly?

    Simply waving your hands around instead of presenting the underlying data seems like not-science.

    • August 27, 2017 12:06 pm

      They do acknowledge that the snowmelt is not a factor in most of the “Western Europe” area, hence they are forced to hunt around for other factors

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