Climate change, The Economist and The Irish Times

The Irish Times have kindly published an article of mine on climate change today. Two apparently contradictory facts have recently emerged that I thought worth discussing in my regular column on the IT science page:

A. The buildup of greenhouse gases in the atmosphere has increased over the last few decades, despite the warnings of climate scientists (this month, the concentration of carbon dioxide in the atmosphere exceeded a value of 400 parts per million for the first time in millions of years).

B. There has been a slight slowing in the rise in average global surface temperatures in the last ten years in comparison with the preceding decade.

Some commentators have sought to reconcile these two facts by suggesting that scientists may have over-estimated our climate’s sensitivity to greenhouse gases. In particular, a recent article in The Economist making this argument has been widely cited. However, the Economist article makes heavy use of a single Norwegian study that has yet to be published (why?) and I don’t know any physicists who agree with the hypothesis , for several reasons:

(i) Climate sensitivity is a complex issue and measurements of global surface temperatures do not tell the whole story: about 90% of global warming is estimated to occur in the oceans

(ii) Heat and temperature are not the same thing: temperature response to heating can be significantly delayed, particularly in the case of large bodies of water

(iii) Sometimes significant heating can occur without any discernible change in temperature, for example when ice melts to water: just such a ‘change of state’ is happening on a massive scale at the poles and will result in inexorably lead to increased sea levels and reduced reflectivity, causing further warming



Images from the Skeptical Science website

Some climate scientists fear that we may be entering a new phase of global warming, where a dangerous amount of heat will be stored in the ecosystem without an appreciable change in temperature at first (known as latent heat). Significant temperature rise will eventually follow, but we can expect climate change skeptics to use this delay to deny the reality of climate change.

You can read my full article on the subject on the Irish Times website

Update and correction

In a follow-up letter to The Irish Times, Tony Carey points out that the figures I gave in the article for the increase in greenhouse gas concentrations are actually those for CO2 only.  He is absolutely right in this, the error crept in at the very last draft of the article, aargh. He is also right to point out that while the concentrations of other GHGs are also rising, the rate of increase has in fact slowed for these gases. Well spotted.

However, this doesn’t really affect the argument I make in my article simply because the CO2 concentration is much larger than that of the other long lived greenhouse gases. Indeed, figures for CO2 are often quoted as a proxy for all longlived greenhouse gases for this reason, although this is not strictly accurate.  The diagram below from NOAA illustrates the dominant effect of CO2 very well (turquoise line). Note that ‘radiative forcing’ relates to the effect of GHGs on climate, involving calaculations I won’t go into here. Note also that climate sensitivity is defined in terms of a doubling of CO2, because of its dominance.



Filed under Global warming

28 responses to “Climate change, The Economist and The Irish Times

  1. Pingback: Ninth Level Ireland » Blog Archive » Climate change, The Economist and The Irish Times

  2. Tom Barry

    Hi Cormac,

    Here’s a topic you might want to write a blog on : A friend of mine read in a book ”Edge of the Universe” that the known universe is 92 billion light years wide. But at 13.7 billion years old should it not be just 2×13.7 plus some expansion. Surely the expansion does not give us an extra 60 billion? Can you explain.

    Regards, Tom

  3. cormac

    Haha. I think that is what is known as an off-topic comment! However, this is indeed primarily a cosmology blog so I’ll post on this in a few days!

  4. Hi Cormac,

    The key problem here is the inherent assumption (made first by Arrhenius) that CO2 and other greenhouse gases have some kind of effect on temperature and climate. The assumption Arrhenius made neglects the cloud cover mechanism which opposes a rise in temperature or change in climate.

    There’s peer-reviewed published research that demonstrates negative feedback from increasing cloud H2O (shadowing the earth, a cooling effect) and a fall in humidity which cancels out CO2 increases. In other words, there’s a built in thermostat (clouds fogging up the atmosphere, cooling the lower altitudes) that prevent a Venus-type runaway greenhouse effect on Earth by water vapour’s wide-band IR absorption, and this is ignored totally in all 21 IPCC 2007 climate models.

    My paper gives a summary of the data and references to the research:

  5. cormac

    Good point, yes – water vapour plays a major role in climate, and it’s frustrating the way there is never enough room to mention such factors in newspaper articles. However, the main point there is that water vapour is a condensing gas, as you know. Thus it plays a dynamic role in climate, condensing to sleet, rain and snow, while in contast about 50% of the CO2 we emit sits stubbornly in the atmosphere.
    Looking forward to reading your paper…Cormac

  6. Alan Millar

    Hi Cormac

    Hi Cormac

    I am a little confused by your choice of words.

    Now we know that climate scientists were predicting, for the 21st Century, a massive acceleration in the average warming rate seen in 20th Century, to more than four times the rate in fact.

    So far this century this is the ‘warming’ trend.

    Now saying “There has been a slight slowing in the rise in average global surface temperatures in the last ten years in comparison with the preceding decade” is an odd way of describing actual cooling.

    I have asked this question before but there seems a reluctance to answer it in some quarters.

    ‘By what years can we expect the average warming rate to hit 4, 3, and 2, times the 20th Century rate?

    Indeed by what year will there be any warming this century?



  7. cormac

    Hi Alan,
    the point I’m making in the blogpost and in the article is that *warming* and *surface temperature rise* are not the same thing. There are many circumstances under which significant warming can occur without a temperature rise. Of course, you might wonder how anyone could know whether any heat exchange is happening under such circumstances – the answer is that the warming shows up in other ways, notably significant loss of land ice and rise in sea level.

    Re cooling, I am unaware of any major peer-reviewed study that reports a cooling over a decade (the shortest timespan for climate trends). Collations of all known studies of surface temperature show as rise in average global surface temperature of 0.1 degree C in the decade 2000-2010. This is indeed smaller than the 0.2 degree rise in the preceding decade, but although the rate of change is not as steep, the temp is still rising (good old calculus).

    You occasionally see references to global cooling outside of the scientific literature, but that is usually either one isolated study (in the normal way of obsevational science) , or a misrepresentation of the data. For example, if you measure temp relative to some arbitary peak you like to pick (such as 1998), of course it will look like a cooling! One or two ‘skeptic’ scientists have done this in the grey literature, and been heavily cited in the blogosphere. However, the vast majority of climate and non-climate scientists agree that temp should be measured relative to a baseline, not a fixed point, in order to investiagte any trend relative to the background random variation (calculus again).

    P.S. V interesting website, I’ll have a proper look when I get home

    • Alan Millar

      Hi Cormac

      Thanks for your response.

      I agree with your point about various proponents ‘cherry picking’ start dates to suit a particular point. That is why I just stick to the average warming rates of the centuries involved.

      The 20th century average rate is fairly well estimated and nearly all the forecasts and predictions in climate science relate to what is going to happen in the 21st century, so that is what my questions always relate to. (can hardly cherry pick between centuries!)

      So we have a warming rate of about 0.7c for the 20th century and no warming at all in the 21st century. Of course you can always look at other metrics as a proxy for increased energy input but apart from the Arctic I see nothing unusual from the 20th century average, including sea level rise. It would appear that the Arctic could very well be a Regional effect as Antarctic ice is running at record levels, not something you would expect in a truly global warming.

      Again I just wonder by what years we can be expecting this centuries warming rate to start rising at multiples of the 20th century rate as has been forecast by many scientists. I mean, in normative science if the predictions of your theory don’t work out you normally have to question the theory not reality.

      Yes, the Wood for Forest site is a great resource for looking at the trends in various data sets linked to climate.



  8. Pingback: Another Week of Global Warming News, June 2, 2013 – A Few Things Ill Considered

  9. cormac

    Again: no physicist would talk about a ‘warming’ rate of 0.7 C per century – that’s a rate of temperature change , not a rate of warming. Temperature can be a measure of heat absorption, but not always.
    As regards the temp rise, I’m not sure where you are getting the figure of 0.7 C per century from, or your quote of ‘no rise at all’ for the century after that. I suspect these estimates do not include expected feedback effects, notably the loss of albedo (almost certainly significant over longer periods).
    Re quantitative timwe predictions, I know what you mean. Although the effects of GW are all too predictable, estimating when exactly such and such an effect will occur is very difficult because of feedback mechanisms, both slow and fast (not all positive, but a net positive effect).
    However, this difficulty in prediction is not at all unusual in science. In medicine, for example, a doctor cannot predict exactly when smoking 40 ciggies a day will start to damage your cells, or even give a rough estimate of which cancer will set in first or even at all. What they can say is to that the ciggies have a very high probablility of damaging you. Exactly when is difficult to predict and in one sense slightly moot!

  10. Tony Carey

    From: Tony Carey
    Cc: Dick Ahlstrom
    Sent: Friday, May 31, 2013 12:41 AM
    Subject: Greenhouse Gases

    To: The Editor
    The Irish Times

    Sir, – Cormac O’Raifeartaigh
    (Life Science, May 30th) is in
    serious error in claiming that
    greenhouse gas emissions
    are accelerating because he
    only cites figures for one of
    the greenhouse gases, CO2.
    However, when the other
    greenhouse gases are included
    the warming effect of all the
    gases has actually decelerated
    since 1990!
    This is because the other
    greenhouse gases – mainly CFC’s
    and methane -have not been
    increasing as fast since 1990
    as they did in the period 1960 -1990.
    Of course this slower rate
    of increase in the warming effect
    since 1990 does not mean that
    we can ignore Climate Change, but
    it may give us more time to
    innovate our way out of the
    problem. – Yours, etc,

    Glencree Rd,
    Enniskerry, Co Wicklow

    Full address:
    Curtlestown Lower
    Glencree Rd
    Co Wicklow

  11. careytj

    Just wondering if you would care to comment
    on my letter which the Irish Times published on June 11th.
    Your article also contained at least one other misleading statement – the
    reference to “massive” melting of Antarctic ice.
    In fact the sea area of Antarctic ice has been
    increasing for reasons that are under debate and
    there is insufficient evidence to know whether the
    actual mass of the ice cap itself is increasing or decreasing.
    Kind regards,
    Tony Carey

  12. cormac

    Hi Tony, just a brief response as I am trying to keep up with things here in Oxford
    Re ‘serious error’ for stating that greenhouse gas emissions are accelerating because I cite figures for only one greenhouse gas: CO2 is routinely used by climate scientists as a proxy for all non-condensing greenhouse gases simply because of the combination of its abundance and strength relative to the other non-condensing greenhouse gases. This is not an error but an approximation widely used in climate science.

    You’re of course right that other greenhouse gases play a role, but far from giving us ‘more time to innovate our way out of the problem’, a big concern is that the current warming could lead to the release of buried methane – an extremely strong greenhouse gas – from the ocean vents and the permafrost, causing an acceleration in global warming.

    Re last comment on ice,it’s very important to distinguish between sea and land ice. Please bear in mind that the article above is not one individual opinion -all my articles on climate are drawn from peer-reviewed literature and checked against two experts before publication

    • careytj

      Thanks Cormac for that clarification. However, I think the focus on CO2 by you and others is more political than scientific in that it diverts public knowledge away from inconvenient facts. There are many more of these that the alarmist – lets fear runaway warming from methane – end of the climate change agenda seeks to avoid, like *the positives from higher CO2 levels such as greater drought resistance from plants due to the stomata response, like *global cooling from aerosols and probably too from con trails, like *the increasing evidence that climate models may have over-estimated ‘climate sensitivity’ [ temperature increase from a CO2 doubling] and *the evidence for factors that can amplify solar variability effects. Another example, from your own blog on heat input and where it goes, is that you ignore the area of increased radiation loss to deep space and the possible ways in which this might be influenced by greenhouse gases.

      A result of this hidden agenda by yourself and many others to influence public opinion is that it will tend to play into the hands of the ‘brown’ lobby’ and the ‘deniers’ as and when these ‘inconvenient truths’ emerge. So I urge you to join the Climate ‘realists’ and communicate from a scientifically balanced perspective. All the very best, Tony

  13. cormac

    Oh dear. As so often, I mistook Tony’s first comment above as genuine curiosity, but now the same old conspiracy theory is revealed. I don’t know any cure for this common distrust of science; I guess all I can do is emphasize two simple facts
    (i) Nothing in my recent Irish Times article (or any other such articles) is my own opinion – it represents what you will find in every modern climate textbook and in the peer-reviewed literature
    (ii) Politically-driven agendas don’t last very long in science – there are simply too many young experimentalists and theoreticians who happy to prove any consensus wrong. While not perfect, the scientific method has proven to be a remarkably robust way of knowing the world.
    Sadly, a great many commentators like Tony reject the findings scientists, never realising that their own views are far less robust. Tony, I see no point in continuing this conversation, in my opnion there is nothing that will convince you

    • Cormac, I never suggested that there was a “conspiracy”, merely a political agenda. If the scientific facts justify an alarmist view, then it is ethically entirely acceptable to focus on facts that support this view and an an associated political agenda to take appropriate action. As evidence that there is a political agenda let me quote the following from a recent email from someone in Ireland’s Environmental Protection Agency: “The EPA is a policy implementation agency and we implement elements of national and EU policy on climate change. This is obviously agreed at political levels e.g. the need to keep the global temperature increase below 2C with respect to pre-industrial temperatures.” If you send me an email, I am happy to copy you with confirmatory evidence for this statement. Incidentally, there is nothing wrong with such a policy per se. What should be debated is just how urgent is it, in pursuing this policy, to take the sort of severe action that will increase hardship and unemployment and whether the facts justify the alarmist position. Kind regards, Tony

      • cormac

        Again: Scientists are not concerned with political agendas, they are concerned with science. They are not concerned with alarmist agendas, they are concerned with the laws of physics. Agendas are for other people, including the EPA.
        If it seems like an agenda to you, it’s because you don’t understand the science – you just think you do. Please stop wasting my time and yours articulating your random opinions and pick up any textbook on climate science and try to understand the science as best you can.

    • They start out so reasonable, and so quickly descend into baked and fudged figures. Then comes the name calling. Deniers argue like the tea party in the us.

  14. Cormac, Your belief that scientists are not concerned with the social & political implications of their science is not true. I am sure you remember that Einstein wrote a letter to the US president on nuclear power and its explosive potential. Another example is that Dr James Hansen, a prominent US climate change scientist, has been campaigning against coal fired power stations for some years. Politics is largely about policy and the mandate of the IPCC “is to make policy relevant – as opposed to policy prescriptive – assessments of the existing worldwide literature on the scientific, technical and socio-economic aspects of climate change.” [ quote from foreword to “Climate Change 2007 – The Physical Science Basis – part of an IPCC report – not a bad ‘text book’ that I consulted in drafting my letter to the Irish Times!].
    With regard to my not understanding “the science”, in 1990 I made a presentation to the Energy Policy sub-committee of the Confederation of Irish Industry on the physics of greenhouse gases and its implications for climate change.
    Kind regards, Tony [ BA (Natural Sciences), Clare College, Cambridge,]

    • cormac

      IPCC summaries are written by policy makers and administrators, not by climate scientists. My point is the *science* is not based on a political agenda, or any other agenda. Of course some scientists may lobby based on the science, good for them.

      By the way, if you’re a recognized expert on the topic then you presumably know that it is standard practice to quote CO2 as a proxy for all non-condensing greenhouse gases (because of its prevalence) – therefore to publicly accuse me of a “serious error” is dishonest. Either that or you you didn’t know the science despite posing as an expert for the CII – which is it?

      • careytj

        Cormac, The answer to your question is ‘neither’. As I said in my June 18 comment : “I think the focus on CO2 by you and others is more political than scientific in that it diverts public knowledge away from inconvenient facts.” ie the facts about the other greenhouse gases and the slowing in the total rate of warming. The actual facts, based on the IPCC reports of 1990 & 2007 and the Feb 2013 data from CIADC – see – are that radiative forcing due to long lived greenhouse gases increased at a rate of 0.43 watts per sq. metre per decade during the period 1960 – 1990, and slowed to 0.19
        watts per sq. metre per decade in the period from 1990 – 2013 (Feb). This is a fall of more than 50% in the rate of warming – something that is decidedly inconvenient if one is trying to persuade politicians to impose higher carbon taxes etc.
        With regard to the error in your article and the claim that this is because of some convention of CO2 as a proxy, a leading expert at the national level on climate change commented to me on your article with: ” Having had a quick look I would say that this is an editorial problem. I would think a physicist would not have mixed up the units of emissions with the units of atmospheric concentration which is done in this article.” ie mixing up a reference to greenhouse gases [plural] with the concentration of CO2.
        With regard to the honesty or otherwise of my letter, before it was published I sent a copy to Ireland’s leading international expert on Climate Change who commented ” Good letter. I hope it gets published”.
        Again, if you email me I am happy to cite the two experts.
        Kind regards, Tony.

  15. cormac

    Many thanks for CIADC link, that is a very useful website. However, I don’t see any data contradicting the simple assertion that CO2 is the most abundant non-condensing GHG by several orders of magnitude, and therefore the continued rise in CO2 is a matter of great concern.
    Re ‘experts’, the article was taken directly from two recent textbooks, and vetted by Prof Ray Bates and Prof Richard Sommerville, both world-recognized physicists in this area. If you email me the names of the experts you quote, I will be happy to contact them directly, rather than rely on third party interpretations of what they said. I have yet to receive any criticism of one of my climate articles from a working climate scientist, so I would be most interested (while few scientists disagree on the basics, I expect we might well disagree on how best to present climate data – in any event, I am all for dialogue with fellow scientists).
    Just the names, please , no more essays necessary!
    Best, Cormac
    P.S. I’m trawling through that great CDIAC website. Almost every single graph and table presents GHG emissions in terms of carbon only, just as my article did. Indeed, the entire website supports the focus on CO2, as far as I can see so far.

  16. careytj

    Cormac, It seems that we don’t have each others email address. So I have emailed Ray Bates asking for yours. Kind regards Tony
    PS The table on the web page on the CIADC link presents all the GHGs not in terms of carbon but through their common units of increased radiative forcing. Yes, I agree that rising CO2 is indeed a source of considerable concern. My view is that the correct best action at this time would be an internationally co-ordinated mega-programme of R&D aimed at low carbon energy generation.

  17. cormac

    Btw, I wrote to CIADC directly and they disagree with your analysis of their data. The graph you really want is the last graph at
    The rise in all long-living GHGs is perfectly clear. The reason is that while the rate of increase has indeed decreased for some GHGs, Co2 dominates, just as I have said all along

    • careytj

      I am puzzled! The CIADC graph you refer to starts in 1979, but your article refers to “in the 1960’s” and what I said [June 22] was:

      “The actual facts, based on the IPCC reports of 1990 & 2007 and the Feb 2013 data from CIADC – see – are that radiative forcing due to long lived greenhouse gases increased at a rate of 0.43 watts per sq. metre per decade during the period 1960 – 1990, and slowed to 0.19 watts per sq. metre per decade in the period from 1990 – 2013 (Feb).”

      Anyway I did very little analysis on their data – just used it to calculate the current radiative forcing – most of my data came from the two IPCC reports cited above.
      Have the CIADC given you their figures for those two rates of increase of radiative forcing [ie for 1960-1990 & 1990 -2013] and if so what are they?
      With regard to your previous requests for the names of the experts I quoted, I sent you their names yesterday in an email to your email address, the one on the WIT website. Did it get through? If not, please send a test email to Professor Ray Bates asking him to forward it on to me so that we can properly connect. Kind regards, Tony

  18. cormac

    Again: you keep talking of forcing, nitpicking about years, and ignoring the obvious point of the huge difference in CO2 concentration vs the other GHGs. Remember that in communicating science to the public, clarity is key. I concentrate on CO2 because of its dominance – there is a reason climate sensitivity is defined in terms of CO2, as the CDIAC pointed out. See graph in update section of blog.

    Remember also that all stats are taken from the Economist article, because it was their assumption I was questioning. I note that not a single one of your many comments refers to the Economist article, or to the central point I made concerning the difference between heat and surface temperature.

    Yes , I got your email. Please do not contact Ray on this again as I think he is annoyed to be dragged into this.
    I am now closing comments on this post as it has gone on very long. Many thanks for the CIADC link and here is a tip in return: few scientists publicly accuse one another of being’ in serious error’ in a newspaper. We say we disagree or we are puzzled, especially when dealing with science writing for the public, an art rather than a science. Apart from questioning someone’s competence (hardly helpful if you agree GHGs are a genuine probem), it also states an opinion as a fact – the mark of the amateur – and closes a dialogue instead of opening it.
    For example, you mention in your letter to the IT that “other greenhouse gases have not been increasing as fast since 1990 as they did in the period 1960-1990”. This is true, but in my opinion very misleading if you do not mention that their concentration is far below that of CO2. Even more importantly, the main message , that GHG emissions continue to increase, is obscured
    Best, Cormac

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  20. Gary

    Cormac, Thank you for the insight – I am a ‘change of state’ proponent, as the amount of energy transfer is comparatively a very large one – and the ice is quite definitely melting. I wonder if the amount of heat energy to accomplish the melt is being underestimated