Science for Sustainability

David MacKay

It is appropriate that my first post here should be about David MacKay, but utterly sad that it should be prompted by his untimely death at just 48, on 14th April 2016. MacKay's unparalleled contribution in applying science to the issues around the sustainability of human life on this planet is the inspiration behind my somewhat more modest efforts to try to foster science- and evidence-based discussions of these issues.

I met David once, briefly, at an audience-participatory demonstration of his DECC 2050 Pathways Calculator at the 2014 Hay Festival, compered by Mark Lynas (who also does great work in communicating scientific issues related to sustainability). Afterwards I asked David whether he would give a talk to our Cafe Scientifique or Skeptics in the Pub groups, which he said he might do when he finished working at DECC and had more time. (I also produced my copy of SEWTHA and asked him to sign it: he seemed to find that amusing, but obliged graciously.) Over the last couple of years I exchanged occasional tweets with him, asking his opinion on technologies like kite power, sharing egregious greenwash and flagging up misrepresentations of his work. But I didn't know of his cancer until I heard that he had died.

There have been many well-informed and moving obituaries and I have collected those I could find here. Mark Lynas has written a formal obituary in the Guardian and a more personal piece on his own blog. Mark also recorded an interview with David shortly before he died.

Niall Mansfield, his publisher at UIT Cambridge, has written about his recollections, especially of working with MacKay on SEWTHA. Fellow Cambridge academics Dr Emily Shuckburgh and Professor Athene Donald have written their own accounts. Mythic Beasts, an internet hosting company set up by some of MacKay's former students (and the host of his Without Hot Air website) posted their own tribute (including, en passant, a scathing evisceration of a piece of egregious greenwash, which would surely have pleased MacKay). Matthew Garrett has written of being recruited to develop David's "Dasher" computer accessibility software. Prolific science and technology blogger Brian Wang at Next Big Future also added his mark, noting that MacKay had founded software company Transversal (whose software provides the SEWTHA "metafaq" (sadly now mostly lost to link rot)). Euan Mearns (and his frequent guest-blogger Roger Andrews) at the Energy Matters blog (which specialises in numerically geeky analyses of energy scenarios somewhat like MacKay's own analyses) offer their tributes. The Daily Telegraph, Cambridge University's Varsity and the Science Media Centre have also published obituaries. BBC Radio 4's "The Last Word" included a tribute to "the cleverest man in Cambridge" featuring MacKay's friend and colleague (and collaborator on Dasher) Dr Alan Blackwell, and Mark Lynas (at 17' 57" in podcast or whole segment here). Bill Gates offered his tribute on his blog.

On 14th and 15th March — barely a month before his death — a symposium "Information, Inference and Energy" was held at Cambridge to celebrate David's work, with talks covering a variety of topics including the Global Calculator, Dasher, information theory, and a surprise lecture from MacKay himself on the information-carrying capabilities of wooden blocks, and an examination — including derivation of two "Brio Theorems" — of popular children's wooden railways as Finite State Machines.

David also maintained a blog - "Everything Is Connected" - up until a couple of days before he died.

Life and work

Wikipedia's article gives a brief and (at the time I write this) incomplete account of David's life and work. Wikipedia and many obituaries mention MacKay's contribution to information theory and machine learning, his "Dasher" computer accessibility tool, Sustainable Energy Without The Hot Air and his work at the Department of Energy and Climate Change including development of the 2050 Pathways and Global calculators.


Like many others I first heard of David MacKay through his book Sustainable Energy Without The Hot Air, reading it initially online and later buying the book. I have yet to read every page of it - and in any case it's not that sort of a book: it's partly a course in sustainable energy, partly a reference book on the subject. The gist is that we can work out, from a mixture of physical principles and practical data, how much energy we use for heating (and/or cooling) our homes, for transport, agriculture etc, and we can also work out how much energy we could generate from the sun, wind, water, and the natural alchemy within atoms of the Earth which make life itself possible on our planet. Then we can compare the figures — and it becomes apparent that getting the second to match the first is quite a challenge. MacKay shows the sources for his data and all his workings-out so anybody can check them and, if they think have better data or more correct workings-out they can try their own. He is also quite blunt, often in his characteristic wryly humorous way, about the shortcomings and problems with all of them.

So it was a surprise to me when I found that some people were accusing him of being biased - mostly towards nuclear though I have also heard him accused of treating renewables too favourably. According to MacKay the book arose from his defence of solar power and a need for numerical evidence on which to base that defence, but he made clear that he was overridingly just pro-arithmetic. Of the five example scenarios for a sustainable Britain he gave in SEWTHA, two were non-nuclear, one of which was explicitly aimed at the sensibilities of the Greens. Even so at a local Green Party meeting that their leader Natalie Bennett addressed a few years ago, when I asked her if the party might produce a MacKay-style numerate energy plan (and held aloft my copy of SEWTHA) her instant response was "We don't need nuclear!". I later heard from a couple of other Green activists that MacKay had been "exposed" as pro-nuclear and therefore SEWTHA was discredited. It's an extraordinary claim given that the transparency of his work allows anyone suspicious of his specific findings on, say, the energy density of wind or solar, or the likely reserves of Uranium, to check for themselves, but it seemed to have spooked some people and one of them led me to the source: an anti-nuclear activist called Jim Hickey who had published a diatribe against MacKay and SEWTHA. As an example of evidence-free rhetoric it stands in stark contrast to MacKay's meticulously sourced work and annoyed me so much I wrote a response to it. (I also more recently came across, and responded to, an attack by Dr Chris Vernon.)

Another attack on SEWTHA is that it is "out of date". This came up in a February 2016 episode of Radio 4's The Bottom Line on Renewable Energy when the presenter, Evan Davis, cited MacKay's estimate that we would have to cover about 5% of the UK with solar panels to get less than half our total energy from PV. Jeremy Leggett, the founder of PV sales company "Solarcentury" responded by claiming that SEWTHA was "out of date" and that he didn't think "that doctor MacKay even believes that any more". (The conversation is at 9' 38" into the podcast.) "Doctor" MacKay disagreed: "He is wrong. Laws of physics not changed".

Of course technology has changed over the years since SEWTHA was first published: bigger, more powerful wind turbines are being developed which, due to their greater height, enjoy more consistent wind and can produce energy more of the time (they have higher capacity factors), and the more efficient types of solar panels are getting cheaper. Also there are new designs of wave and tide generators, and batteries and other storage systems being developed; however these can all be accommodated within the framework David laid out in SEWTHA by changing numbers accordingly. And much of SEWTHA is based on back-of-envelope figures which are close enough to make realistic estimates rather than precise to Physical Laboratory standards, so it really doesn't matter if the efficiency of solar panels has increased from, say, 19% to 21%: unless Britain moves several thousand kilometres closer to the equator, we'd still need to cover the area of Devon and half of Cornwall in the most efficient PV panels to generate the energy we need (not to mention somehow storing much of that generated during the summer to use in the winter when we need it).

I Will if You Will

In SEWTHA David MacKay made it possible for the lay person to understand sustainable energy in a straightforward but numerate way. But as Bennett, Hickey, Leggett and others have demonstrated, this is not enough if one is in denial of the truths thus revealed (but we knew that from climate change deniers anyway). However even when people accept the realities of nature, our human nature gets in the way of us acting on the problems we face. In the case of climate change a continuing impediment to effective world-wide action has been nations' reluctance to commit effectively to reducing carbon emissions unless other nations make matching commitments.

In October 2015, in what he described as the most important piece of writing he had ever co-authored, David MacKay, Peter Cramton, Axel Ockenfels & Steven Stoft, published a paper in Nature: Price carbon — I will if you will. In it they advocated an elegant game-theory based approach to carbon pricing negotiations at the then-upcoming COP21 Paris summit which could replace an incentive to minimise individual nations' carbon-reduction commitments with a system which would create an incentive to maximise commitments.

I have no idea how many of the negotiators at the Paris conference were aware of this work, or how much influence it had amongst them. I don't suppose MacKay expected it to bring about a miraculous overnight transformation in international cooperation. But it seems to me that he regarded all the problems we face in safeguarding the sustainability of human life on this planet, from the physics of energy to the psychology of motivation, as being amenable to scientific investigation and solution, which he would simply, and without fanfare, set about applying his seemingly boundless intellect and energies to doing. It is tantalising to think where his enquiring, incisive genius would have taken him in this quest, and disheartening to contemplate humanity's loss from his untimely death. The cancer which robbed David MacKay of his life may indirectly end up claiming many, many more.

John Stumbles — April 2016 (updated Dec 2019, mostly correcting for link rot)