Paul Williams, Professor of Atmospheric Science at Reading University, has issued a strict edict on Twitter regarding the rules of engagement for critics of his research:


Screenshot_2020-02-20 Paul Williams on Twitter Okay haters, here are my new rules of engagement If you want to criticize my[...]

What that basically says is don’t engage with me if you have any criticism of my studies because I will block you if you do. Which is odd for a winner of the Royal Meteorological Society’s Michael Hunt Award who “has a sustained and extensive record of engagement with the public and their concerns over weather and climate” and “is just the sort of person worthy of recognition and encouragement from the Society in the area of increasing the understanding of meteorology among members of the general public”. But then again, maybe it’s not that surprising: Mann and Hayhoe have both won awards for science communication. In climate science, the more censorious you are of critics it seems, the greater your chance of picking up an award for engaging with the public.

I don’t doubt that Williams puts up with his fair share of insults and unfair criticism on social media. Everyone does; it’s par for the course. He has been the subject of some silly name calling in the past:

But he’s a public figure, with a public profile and he shares the results of his research on Twitter, so he’s responsible for responding to questions and to valid criticism of his work, especially with regard to climate change and its impacts, which we, the public, are being asked (nay, forced) to pay trillions for, in taxes and for the purchase and subsidising of new, low carbon technology to replace perfectly working ‘old’ technology which is a lot cheaper and more effective. That gives the public the right to question him, not via peer-review, but on social media and elsewhere online, wherever commenting on articles is enabled. Articles, for instance, like this latest Conversation piece where he and a fellow author explain why Climate change means longer take-offs and fewer passengers per aeroplane.

Paul has in the past been highly critical of Williams’s research when the Prof previously demonstrated a ‘significant’ increase (1 minute 18 secs) in travel time of a 12 hour transatlantic flight – due to projected changes in the jet stream caused by climate change. Ken Rice, bless him, defended Williams to the hilt, saying that the blog post made Paul “seem like a nasty, intolerant piece of work who simply likes to smear anyone who presents anything with which you happen disagree”. But of course it was not simply disagreeing with Williams, it was criticising his absurd claims in the Guardian article where he was quoted as saying:

“The aviation industry is facing pressure to reduce its environmental impacts, but this study shows a new way in which aviation is itself susceptible to the effects of climate change,” Williams said. “This effect will increase the fuel costs to airlines, potentially raising ticket prices, and it will worsen the environmental impacts of aviation.” Fuel costs are a critical factor in the competitiveness of airlines.

“The jet stream does not just live in the Atlantic, it goes all the way around the world and there is another one in the southern hemisphere too,” Williams said. “So it is plausible that similar flight routes around the world will be affected and when you look at those numbers, it is just enormous.”

An increase in flight time of of a six hour flight from London to New York of 5 minutes 18 secs and a decrese in flight time of 4 minutes on the return, making a net increase of 1 min 18 secs on a 12 hour flight has ‘enormous’ implications for global air travel according to Williams. Paul called it out as bullshit and Ken didn’t like that; neither, I suspect did Williams but like all good climate communicators, he did not appear in the comments to defend the integrity of his research.

Now he’s claiming another ‘significant’ impact of climate change on airline flights – an increase in take off distance. I quote:

Our new research suggests that higher temperatures and weaker winds are making take-off more difficult. In the long run, this means that airlines are delivering fewer passengers and cargo for the same amount of fuel.

We have been recording the weather at ten Greek airports since 1955. For each year, we took the average wind and overnight minimum temperatures, and then plugged that into performance graphs. These are used to calculate the safe runway lengths and aeroplane weights that are needed to ensure that airlines can carry their passengers safely.

We found that in every case the conditions had changed over the 62 years to make aeroplane take-off more difficult. Safety regulations ensure that aeroplanes are never allowed to take off without enough runway, but on the longer runways we studied, the take-off distances necessary to get a large jet plane into the air had increased by about 1.5% every decade, and about 1% for a smaller turboprop airliner.”

Finally, Williams and his co-author are quoted on the seemingly ‘terrible consequences’ of climate change on airline flights worldwide:

“That could mean that airlines must reduce the numbers of passengers they carry on flights, or search for ways to lengthen their runways. In some extreme cases, it could become impossible for some aeroplanes to use some airports altogether. This is another reminder of how rapidly and extensively human actions are transforming the world around us, and how ill equipped we are to deal with the consequences.”

I read the study and I commented at the Conversation thus:

Firstly, this is not an attribution study. As such this article should not be entitled ‘climate change causes’. Secondly, the period of data measurement is not 62 years, that is the longest data series. The shortest was 28 years.

The geographical location of the airports was Greece, therefore it can hardly be said to be representative of the changing global climate over 28 to 62 years. The authors admit that pbserved headwind changes not formally attributed to climate change:

“It is beyond the scope of this study to formally attribute the observed secular headwind changes to anthropogenic carbon dioxide emissions.”

And what of the observed changes in temperature? Are the observed increases in temperature at the airport uniquely attributable to climate change in their entirety? We get a clue to that answer when the authors attempt to explain reasons for why the headwinds may have changed:

“A final possible explanation is an increase in surface roughness, caused by an increase in vegetation or (in our case) development around the airports. For the purposes of this paper, however, the main point of interest is that the wind vectors have modified.”

Spot that? Development has occurred around the airports during the 28 to 62 years of wind speed and temperature data. Not only might this have impacted secular wind speed trends via ‘surface roughness’ but it is highly likely that that it has affected temperatures (especially at night) which have impacted take off distances.

Barring a formal attribution analysis of climatic conditions at these airports, it is not possible to say that ‘climate change caused’. So please don’t.


Paul and John Ridgway have also commented and Williams responded to Paul with a cynical short reply, but he has not bothered to answer my points, so I am calling bullshit once again at Cliscep on this latest research which purports to demonstrate the significant negative impacts of climate change™ on airline flights, but doesn’t do that because it cannot quantitatively attribute the changes in temperature and windspeed at the test locations to the mean global increase in surface temperature over the periods in question. This is regardless of whether you think a 1-1.5% increase in take-off length per decade is significant or not.

This is not just a dig at Professor Paul Williams. I have noticed that climate and other scientists contributing to climate change research are becomingly increasingly thin-skinned and defensive on social media in respect of any public criticism of their work. Why? When the public are being required to make such huge sacrifices to mitigate climate change and its projected impacts, they should surely be engaging ever more frequently and enthusiastically to convince the public of the validity of the science which supposedly demonstrates the magnitude of that change and the nature of those impacts. It seems to me to be the complete opposite. They are retreating into the bunker.


  1. In response to my rather light-hearted comment, Paul Williams is trying to deny what he wrote in the article about winds getting weaker. I’ve pointed this out and said that I await his apology.

    Screenshot here

    Liked by 1 person

  2. Indeed, Jaime. I thought it inappropriate that someone who is so intolerant of his ‘haters’ on twitter should be so quick to resort to hateful trolling when his Conversation article was challenged by Paul Mathews. I’ve pointed out his hypocrisy, but Dr Williams doesn’t seem too concerned to defend himself. I think it is a case of ‘don’t feed the person who points out that you are a troll’.


  3. Paul, John, yes, Prof Williams’ reply was not that smart. His study suggests that surface winds have generally become weaker and changed direction (due to climate change). So the headwind vector magnitude has been reduced on average (due to both a change in direction and decrease in magnitude), making take off more difficult. This effect might be due to a global ‘stilling’ of surface winds (supposedly due to climate change) or it might simply be because of development around the airport, or both. No attempt is made to attribute the changes to climate change, beyond mere hand-waving about faster warming at the poles and expanding Hadley cells, so portraying his research as ‘climate change means’ is not honest communication in my opinion.


  4. I always believed that the airline industry was so sensitive to anything that affects its performance that one company did not paint its aircraft to reduce weight.
    If the results of these studies are as significant as the good (but sensitive) Professor believes is his research funded by a Greek airline or is he dipping into British Research Funds (and having free holidays on he side?)


  5. I note that the Paul Williams article speaks of “in-flight turbulence, which is getting worse”. This intrigued me, because I was not aware that there was a database of historical measurements of in-flight turbulence upon which one could form such a judgement. So I decided to follow the link. The link, of course, didn’t work, but I wasn’t going to be put off so easily. Not long after, I found the following:

    In the abstract, one can find the following:

    “Here we show using climate model simulations that clear-air turbulence changes significantly within the transatlantic flight corridor when the concentration of carbon dioxide in the atmosphere is doubled.”

    Followed by:

    “Our results suggest that climate change will lead to bumpier transatlantic flights by the middle of this century.”

    That’s right folks. No data, no measurements, and absolutely no factual evidence presented to show that in-flight turbulence is actually getting worse. Just more climate model simulations and ‘results’ that ‘suggest’ that something may happen in the future.

    It’s this sort of deceitful misrepresentation that attracts the attention of sceptics – or, to use Paul Williams’s terminology, ‘haters’.

    Liked by 4 people

  6. Williams the denier continues to deny that he said what he said about winds getting weaker.

    It’s also right at the top of the article that presumably he wrote at his university blog,
    “Warmer, less dense air and weaker winds thanks to climate change result in more difficult take-offs for aeroplanes”.

    John, this sort of behaviour from supposed scientists doesn’t just attract sceptics, it creates them, as I say in my latest comment over there. It was this type of thing from people like Mann, Schmidt, Connolley and Rahmstorf that turned me from an agnostic into a sceptic in about 2008.

    Liked by 1 person

  7. “We have been recording the weather at ten Greek airports since 1955.”

    Strange. His photograph doesn’t suggest that he is in his eighties at least.

    If you view everything through the lens of CO2, everything starts to get a bit fuzzy. Cooking with gas takes on a new meaning.

    Liked by 1 person

  8. John, here is the full PDF of that paper on turbulence.

    Click to access nclimate1866.pdf

    Near the end it says:

    “Observational evidence suggests that this increase in bumpiness has already begun 17,23″

    I haven’t looked at those references but the fact that they only ‘suggest’ probably means that the observational evidence of increasing turbulence is not that convincing.

    In a Guardian article, Williams states:

    “There has already been a steady rise in incidents of severe turbulence affecting flights over the past few decades.”

    There is no reference given for the source of this data.


  9. And here, Williams demonstrates the global response of clear air turbulence to climate change during the period 2050-2080:

    “Two HadGEM2‐ES simulations are analyzed to calculate how climate change could impact CAT in the upper troposphere and lower stratosphere in future. Specifically, a preindustrial control simulation (picontrol) is compared with a climate change simulation using the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathway 8.5 (RCP8.5) (Flato et al., 2013). The picontrol run is a base state that uses constant preindustrial greenhouse gas concentrations to simulate the global climate before the industrial revolution. The RCP8.5 run assumes a net radiative forcing increase of 8.5 W m−2 by 2100 (Van Vuuren et al., 2011), which implies greenhouse gas concentrations equivalent to around 1,370 ppmv of CO2. We analyze 30 years of data for the future period 2050–2080 from RCP8.5 compared to 30 years of historic data from picontrol.”

    Yep, RCP8.5 sure does come in handy when you want to generate scary climate change impacts. But it’s only climate scientists and rich celebs who will be knocking their heads on the overhead luggage storage by then because all the proles will have been banned from flying, so we needn’t be too concerned.

    Liked by 1 person

  10. Jaime,

    Thanks for the link. It’s the observational evidence that I’m interested in. That’s the only thing that can justify a claim that something ‘is getting worse’. But I think you must be right; the evidence cannot be that compelling, otherwise I would expect it to have found its way into the paper’s abstract, rather than be mentioned in a throwaway line. The fact remains that his paper is all about modelling and theorising, rather than measuring a trend.

    Meanwhile, over at The Conversation, Paul Williams is digging himself a deeper hole in his dispute with Paul Mathews. I’d wade in to help, but Williams would only play the victim card again. The poor dear is surrounded by haters who don’t appreciate that when he said that winds are slowing down due to climate change, it should have been obvious that he only meant the component aligned with the runway.

    Liked by 1 person

  11. i had the why are you using only RCP8.5 in your work conversation with Dr Paul Williams a few years back… And I called back to that, tweeting to him, recently about the RCP8.5 not being business as usual, but he said at the time he was too busy to read it.. (click on, to see discussion)

    hopefully he will read the Nature paper, it is very interesting.

    Liked by 1 person

  12. In Greece –
    “The shitty personal abuse that climate scientists receive has reached ridiculous levels. Twitter takes no action. It has to stop”
    said the scientist at the all night free bar.


  13. Cognitive Dissonance
    #1 Wokemob, libmob live in a happy Guardian bubble world

    #2 Gets called out
    #3 Fake-Worldview is shattered
    #4 Cognitive Dissonance kicks in, he’s real angry
    #5 Lashes-out .. rather than face up to his own problem
    #6 Deflects by saying, you are the problem
    #7 Dehumanises you with a power label like “denier” ,”troll”, “fascist” etc
    #8 Projects, cos he behaves in the very manner of the dehumanising-label
    eg He tells you to “delete your account, you are a non-person” etc.
    .. that is of course fascist behaviour.

    Then what ??
    .. Well, if you persist he’ll lash out more
    but I have seen people quietly come around


  14. The court said that Trump cannot block on Twitter
    cos his account is a public servant so must not be a bubble only preaching to his bubble.

    Williams is ultimately paid by the public
    so similar would apply
    He can choose not to tweet
    but from his public platform he should not stay in a bubble but rather be open to all.

    It’s late but that’s what I think, I think.

    BTW a technical note
    scrolling works fine direct at
    but I normally view via WordPress Reader cos it gives you buttons like Reply & Like
    but today it’s not scrolling properly.


  15. Small boy to Emperor “OMG you are naked”

    Tailor “Shut up, unless you have read the paper about the magic suit
    which was peer reviewed by my pal Mr Tailor2 here”

    Small Boy “I part pay for this suit, so I will speak”


  16. Barry on the new Twitter thread I see he is being civil to you.
    I think he wrote that initial tweet in anger and doesn’t mean it literally.

    After all skeptics have like the small boy been valuable.
    When they have spotted an error in a paper, and pointed it out.
    …. without actually reading the whole paper.


  17. Hi Stew. I’m not at war on twitter, some people have piled on the guy, complete strangers, so they rightly would get short shrift.. vs people that have interacted before. Had a chat a few times in the past. Also Iwent to same university and know people at that Uni still. Doesn’t matter how right anyone thinks they are, go in full tilt, people will block you. It is social media, people can block who they want, for any reason


  18. You can block obvious idiots and time wasting trolls on Twitter very easily and then you are no longer bothered by them. Williams appears to want to censor valid criticism as well though, using as his excuse so called ‘haters’ on social media. He promotes his own research, fine, but he does not have the right to apparently overstate the results of his research in particular with regard to climate change impacts without being publicly questioned by sceptics.

    Liked by 1 person

  19. Barry as I said that angry tweet he posted does accord with my list on the pattern of wokemob behaviour when they get Cog Diss
    .. now it seems he is backtracking and is only angry with true trolls.


  20. Re ‘Deniers are bots’ article in the Guardian and now in the BBC report ‘The Guardian says’

    when science reports get published in the media BEFORE proper publication, then that is almost a sign of “PR NOT science”

    It probably took also 3 years so far cos team Lew have been TORTURING the data to get “the correct” narrative.
    … it’s their habit isn’t it ?


  21. Jaime,

    I couldn’t resist it after all. I have posted the following at The Conversation, in response to Williams’s last rebuke aimed at Paul:

    “’We’ve been here before, haven’t we Paul?’

    Well, I haven’t been here before. I have neither previously commented upon your work nor have I challenged you on twitter. But I have to say my first impressions are not favourable. Clearly, the issue here is not a failure to understand the difference between wind and headwind, nor is it anything to do with a failure to appreciate how a vector works. Rather, you have clearly stated that climate change is affecting both the strength and direction of winds (“winds are slowing down and changing direction”). Paul responded by pointing out the apparent paradox that both strengthening and weakening of wind both appear to be attributed to climate change. You had the opportunity of clarifying that issue for the benefit of this article’s readers but (if you’ll pardon the pun) you blew it, preferring instead to indulge in a professional slur that completely missed the point. You still have the chance to return to a scientific debate, but I am not holding my breath – your reticence in response to Jaime’s comment is not encouraging.”

    Liked by 2 people

  22. John, good for you. I’ll be surprised if you get a substantive reply from either author and I will be surprised if the Con do not now close comments.


  23. I looked around for some information on turbulence incidents affecting aircraft, which Paul Williams claims are on the rise:

    “It is predicted there will be more and more incidents of severe clear-air turbulence, which typically comes out of the blue with no warning, occurring in the near future as climate change takes its effect in the stratosphere,” Dr Paul Williams, a Royal Society research fellow at Reading University, said last week. “There has already been a steady rise in incidents of severe turbulence affecting flights over the past few decades. Globally, turbulence causes dozens of fatalities a year on small private planes and hundreds of injuries to passengers in big jets. And as carbon dioxide levels in the atmosphere keep on rising, so will the numbers of incidents.”

    The only information I could find pretty quickly was the statistics for injuries to passengers and crew due to turbulence collected by FAA (which has control of US airspace) since 2009:

    Year Passengers Crew Total
    2009 74 27 101
    2010 35 23 58
    2011 4 25 29
    2012 4 19 23
    2013 2 4 6
    2014 19 9 28
    2015 11 16 27
    2016 29 13 42
    2017 9 8 17
    2018 4 5 9

    The overall trend for injuries due to turbulence seems to be going downwards. There also seems to be some cyclic behaviour in the variation of injuries from year to year.


  24. Dave,

    Thanks very much for that. Little evidence there of a ‘steady rise’. And I can’t see where the ‘hundreds of injuries’ could be coming from.

    Once again, good work.


  25. The science here is exceptionally weak even for climate science where it often is weak. There is zero expectation that climate models will be able to predict changes in atmospheric turbulence. To do so one would need much finer grids and to turn on a turbulence model everywhere, not just in the boundary layer.

    In any case, these changes are immaterial to anything of consequence. Travel times are vastly more impacted by getting to and from the airport, any intermediate stops, and even which aircraft is used than by climatic changes.


  26. More on Paul Williams’s claim that in-flight turbulence ‘is getting worse’:

    In the introduction to his 2013 paper, he states:

    “Although there have been suggestions of recent increases in aircraft bumpiness, the evidence has not been compelling.”

    But he then states in his conclusion:

    “Observational evidence suggests that this increase in bumpiness has already begun.”

    Both statements, although seemingly inconsistent, cite the same source. Notwithstanding, it appears that his concluding remark is the one behind the ‘is getting worse’ claim within his Conversation article. It’s funny how the caveats seem to dissolve whenever an award-winning science communicator gets into his stride. For example, no mention of:

    “…moderate-or-greater upper-level turbulence has been found to increase over the period 1994_2005 in pilot reports in the United States. However, it is difficult to assign much significance to this trend, because of the shortness of the data set.”

    Or again, taken from the same paper’s conclusion:

    “We infer that turbulence diagnostics are generally functions of the spacetime sampling, and that they may be biased when calculated from gridded or averaged data.”

    Oh, you don’t say! Oh yes, I forgot, he didn’t say!

    Professor Paul Williams objects to on-line ‘haters’ who comment without reading and understanding his papers. I wonder how he feels about those who comment after reading them.

    Liked by 1 person

  27. DPY6629,

    I’m sorry for the delayed response. I hope you are still tuning in.

    You said:

    “There is zero expectation that climate models will be able to predict changes in atmospheric turbulence. To do so one would need much finer grids and to turn on a turbulence model everywhere, not just in the boundary layer.”

    On this issue, Williams’s 2013 paper states:

    “At present, it is not computationally feasible to forecast turbulent eddies on horizontal scales of 100m–2km through explicit simulation with a global model of the troposphere and lower stratosphere. Instead, clear-air turbulence is forecast by computing various diagnostic measures derived from simulations of the larger-scale flow. Examples are the Colson-Panofsky index, the Brown index and the Ellrod indices. The instabilities diagnosed by these indices are necessary but not sufficient conditions for clear-air turbulence.”

    So the author is falling back on a heuristic approach. Smaller scales indeed cannot be directly modelled, but operationally calibrated diagnostics are available that enable the smaller scale phenomena to be inferred from the larger scale flow. That said, there must be an awful lot of devil lurking in this detail, not the least of which would be the subjectivity undermining the calibration provided by pilot testimony. And, of course, there is always the small matter of the credence that may be placed in the climate model used to predict the larger-scale flow.


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