Barrage over climate change link to floods

 
Flooding

As the barrage of bad weather eases, another kind of turbulence is brewing over one of the potential causes.

Listen to some environmental campaigners and you might think that there is total certainty that global warming led to the recent rain; listen to some climate sceptics and there is absolutely no connection at all.

Viewers have berated me either for failing to explicitly blame climate change in my reporting of the floods - or for suggesting that the rain may conceivably have been made more likely by the rising presence of manmade greenhouse gases.

For anyone coping with clearing up a flooded home, this question will not exactly be the highest priority.

However, political figures have raised its profile, making the connection rather more forcefully than many scientists.

The Prime Minister, David Cameron, set the tone by telling the Commons that he "very much" suspects that climate change is involved. And the Labour leader, Ed Miliband, warned that "we are sleepwalking into a national security crisis on climate change".

Of course not every politician agrees. Lord Lawson, on the Today programme, dismissed any link to the weather, saying, "the question is whether global warming has marginally exacerbated it. Nobody knows that".

Different takes

If we stand back from the Westminster hothouse, what do the scientists actually say?

The fact is that attributing a human influence to individual weather events is an emerging area of research and is acknowledged by those involved to be extremely challenging because so many factors are at work.

One leading figure in climate science, Professor Sir Brian Hoskins, summed it up bluntly: "There's no simple link - we can't say 'yes' or 'no' this is climate change."

Instead, he and others point to a range of factors which would make intense downpours more likely.

The key one is a basic physical relationship: since warmer air can hold more moisture, it makes sense that our warming atmosphere would produce more intense rain.

But how much rain? And where? The computer models used to explore scenarios for the impacts of different levels of greenhouse gases are recognised to be weaker on rainfall than on temperature.

Surely, you might think, the UN's Intergovernmental Panel on Climate Change (IPCC), the consensus assessment of the latest science, might clear this up? As so often, you can read its documents in different ways.

If you think global warming is overplayed, you focus on this conclusion in the most recent IPCC report:

"There continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale."

Translated, that means we're not seeing more floods, story over.

However, if you do think climate change is serious, your eye may fall, first, on the line that "the frequency or intensity of heavy precipitation events has likely increased in North America and Europe."

Second, the IPCC predicts that "extreme precipitation events" over the mid-latitudes (which includes Europe) will very likely become more intense and more frequent. Doesn't this explain the recent British weather? Is this the smoking gun? No, because this scenario will unfold "by the end of this century" rather than right now.

Looking for answers

Another take comes in a report by the European Academies Science Advisory Council published in November last year.

It suggests a future in northern Europe in which "high intensity and extreme precipitation become more frequent…" and that "future projections suggest increases in flood risk over a wide area of Europe…"

So bad news on the way, clearly, but none of this categorically nails the question we began with - exactly how much manmade greenhouse gases are involved in the current weather.

A study by the Met Office and Centre for Ecology and Hydrology concluded that "it is not possible, yet, to give a definitive answer on whether climate change has been a contributor or not."

Their report points to the sea level rising and an increase in storminess in the North Atlantic as factors consistent with climate change. But it also highlights what is not properly understood, including the path of the jet stream, which has acted as a conveyor belt, delivering storm after storm.

At the launch of the report, the Met Office chief scientist, Dame Julia Slingo, seemed to go a bit beyond what appeared in print.

She said: "All the evidence suggests there is a link to climate change." Not some of the evidence, but all of it.

So what about that unexplained path of the jet stream? The Mail on Sunday quoted one Met Office scientist, Professor Mat Collins, as saying that "there is no evidence that global warming can cause the jet stream to get stuck in the way it has this winter."

The Met Office scrambled to produce a statement to assert that there was no disagreement. It also confirmed the "uncertainty" about the storm track in the North Atlantic but did not address whether the chief scientist had gone beyond the conclusions of their own report.

Does this leave us any wiser? No. In my experience scientists always disagree - that's how research advances.

Dr Tim Osborn of the University of East Anglia is among climate researchers concerned about the science of extreme weather being portrayed as a little more certain than it might appear.

"You've got a lot of natural variability superimposed on the long term trend - in the next 20 years, the frequency of weather like this winter's could drop below the trend or rise above it. We're not expecting a year on year change."

The only way to detect a human fingerprint on weather is to run simulations of the event as it actually happened - and then to repeat them having stripped out the greenhouse gas component in the models.

Previous studies of this kind, for example into the 2000 floods in England, have found that the storms were made more likely because of manmade climate change - likely but not certain.

The answer is framed as an increased probability. A categoric answer may never be possible.

As the country copes with the floods and starts repairs and thinks about making things safer for the next one, people will look up at the skies and want certainty about whether wild winters will become normal. And at the moment, the science cannot provide that.

 
David Shukman Article written by David Shukman David Shukman Science editor

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  • rate this
    +3

    Comment number 41.

    Burning fossil fuels with abandon is a bad idea, full stop. It is a limited resource, makes us more vulnerable to world politics, and costs us money if we are inefficient, particularly noticeable with increasing global demand. Regardless of the arguments over the causes and effects, we should be aiming to be less reliant on fossil fuels. Denying manmade causes is pointless.

  • rate this
    0

    Comment number 40.

    The recent floods are NOT unprecedented. Records may have been broken in one or two areas, but severe weather has happened many times in the past, long before the reported build-up of 'greenhouse gases'. Climate does change from time to time, for many reasons, most of them natural. All we can do is to make our infrastructure more robust for the next time, which will probably be many years hence.

  • rate this
    +2

    Comment number 39.

    As a civil engineer is was a shame so much rubbish was talked about the flooding and about flood defences especially by the TV reporters who probably studied English rather than science at school.

    I live in Shepperton and people have been badly affected by the floods. There needs to be re-think about building in floodplains as flood defence walls in this area will not work.

  • rate this
    -4

    Comment number 38.

    "Blaming it all on "climate change" is too easy. Any excuse for inactivity"
    My concern is that call me dave and his wet friends will use it as an excuse to raise even more taxes on us. I bought my house on a hill, I'm not stupid but unlike CMDs mates I cant afford to not ay my taxes, leave off squeezing us any more Dave.

  • rate this
    -3

    Comment number 37.

    28.TLs..

    see 31 as to why AGW by CO2 is economically preferred against policies designed to alleviate the consequences.

    The idea that we can change our lifestyle and fix climate change is perhaps the greatest folly of the last 25 years.

    We can't...

    But what we must do is to take steps to alleviate the worst of the consequences. Unfortunately AGW by CO2 blocks these necessary steps.

  • rate this
    -1

    Comment number 36.

    Sunspot activity at a very low level, which should cause a reduction in solar radiation and hence temperature - last time we saw this was Little Ice Age in C18th with Frost Fairs on the Thames. Not happening this time.

    Climatology is a comparatively new science. Jet Stream only discovered in 1940s. In 1970s scientists correctly mapped the history of past Ice Ages...

  • rate this
    -1

    Comment number 35.

    "The effects of climate change can only be analyzed retrospectively",

    This is the problem with "post-mortem" approach of the 'Modern Era'.. The Victorians had to learn hard lessons about the impact of large-scale urban- industrial living and had really begun to tackle them by the 1860s, before the worship of the large-scale possibilities of the State unleashed the era of "Yes we can"

  • rate this
    +2

    Comment number 34.

    First we need to untangle possible links between climate change and flooding and weather abnormalities. There's a big difference. Flooding goes beyond rainfall intensity, a function of climate, and involves consideration of risk exposure of populations and societal responses to those perceived risks. I haven't seen the National Adaptation Programme of 2013 mentioned once during this debate.

  • rate this
    -3

    Comment number 33.

    Most people labelled as deniers don't deny anything. They simply grasp that these changes have been happening for billions of years with or without mankinds help. They understand that one day we will be gone and the changes will still continue. They understand the bigger picture, the world cannot be maintained simply for the comfort of mankind.

  • rate this
    0

    Comment number 32.

    Why not use coal to build the flood barriers and kill two birds at once?

  • rate this
    -1

    Comment number 31.

    Economic Cause of the belief in AGW by CO2

    We (are persuaded to) believe in AGW by CO2 because banks and businesses can make huge sums of money 'investing' in product changes. Low energy light bulbs etc. (I concede more energy efficiency in products is a good thing.)

    BUT this stops us doing Civil Engineering solutions as these cannot be turned into a huge profit stream for business & banks.

  • rate this
    +20

    Comment number 30.

    Until excessive human population growth is addressed, any further discussion on this article is just p*ssing in the (strengthening) wind.

  • rate this
    +32

    Comment number 29.

    Anyone who thinks that shoving trillions upon trillions of tons of co2 and other man produced gasses into the atmosphere in a very short space of time is delusional if they think it will have little or no effect. None of this is about 'save the planet', it doesn't care, it's survived much worse than anything we can throw at it! But will we survive as a species because of our actions? Maybe not.

  • rate this
    -2

    Comment number 28.

    Of course climate change is involved just as it has been for past few billion years
    Climate change is undisputable, it's just the human element that is in dispute

    We can measure climate & its variances/changes & extremes throughout the ages by various soil/rock/plant & ice tests, but this comparable information is denied to public

    Climate change is deceitfully abused for political purposes

  • rate this
    +3

    Comment number 27.

    The evidence is all around us, but some deluded fools choose to ignore the uncomfortable truth.

  • rate this
    -3

    Comment number 26.

    To help the flooding problem;
    A: Minimum service level from the Environment Agency need to be set out in law i.e. dredging rivers etc.
    B: Building firms should be libel for flood damage to properties they construct for 25 years (or more) after construction (unless A has not been carried out, then the Environment agency should be libel).
    This would help stop building in inappropriate areas.

  • rate this
    -2

    Comment number 25.

    When will people learn that the water resources of the UK have been managed for a VERY long time?
    I live below sea-level in the Fens and parts of it were drained by the Romans and if you don't maintain the waterways it will flood - it's a known fact!
    And why does climate change have to be man-made? It's something else that has changed for years - as has sun-spot activity or inactivity.

  • rate this
    -25

    Comment number 24.

    Why Anthropomorphic Climate Change is a dangerous illusion.

    1. Climate is changing.

    2. Deludedly, we think the changes are caused by us so we can do something about it.

    3. My opinion is that the changes are solar related.

    4. Because we think we can change the cause (CO2) we do not take protective steps - this is the grand delusion!

    5. We need to take steps to alleviate the consequences.

  • rate this
    +2

    Comment number 23.

    Following my previous- the change in the Jetstream is quite a predicable consequence of measurable changes. Bigger surface area of water on the Earth. Warmer temperatures. Result more evaporation. In a warmer atmosphere vapour has to rise higher to get condensed. . Energy released by condensation into upper atmosphere. Winds become stronger. Jetstream has more centrifugal power, slipping south.

  • rate this
    -25

    Comment number 22.

    In the 1970s they were trying to scare us to death about the forthcoming ice-age that was going to wipe us out.

 

Page 40 of 42

 

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