17545379_10155148769467350_6493523413752513322_o Or so says the Graun: A plan to halve carbon emissions every decade, while green energy continues to double every five years, provides a simple but rigorous roadmap to tackle climate change, scientists say. Well you can’t fault the simplicity; then again “everyone should be nice to everyone else” is also simple. The obvious flaw is that Moore’s law is descriptive, not prescriptive: it describes a situation that is observed to exist. It is not a “law” in the legislative sense of a thing that we want to happen1.

You’d hope the distinction would be obvious; for the Graun, sometimes it is, sometimes it isn’t. Prof John Schellnhuber… said the aim of the carbon law was to provide “a really compelling story of how decarbonisation can be achieved”, and to bridge the gap between the pledges made by nations in Paris and what will be needed in the long term to keep global warming well below the danger limit of 2C. The bit I’ve bolded appears to be the key, and calling it a “story” makes it much much weaker than the headline. Which isn’t terrible in itself; headlines are always stupid2.

Enough of the Graun; let’s look at A roadmap for rapid decarbonization by Johan Rockström… Malte Meinshausen, Nebojsa Nakicenovic and Hans Joachim Schellnhuber in Science 24 Mar 2017: Vol. 355, Issue 6331, pp. 1269-1271. DOI: 10.1126/science.aah3443. Which begins Although the Paris Agreement’s goals (1) are aligned with science (2) and can, in principle, be technically and economically achieved (3), alarming inconsistencies remain between science-based targets and national commitments… “aligned with science” is a slightly odd phrase, don’t you think? Designed to slip past without triggering any reaction in the unwary mind. What’s “(2)”? It’s our old friend HJS, in H. J. Schellnhuber, S. Rahmstorf, R. Winkelmann, Nat. Clim. Chang. 6, 649 (2016), not that self-citation is any crime. Although that’s only a Nature Climate Change commentary not a proper paper. I’m somewhat cautious about the links between physical science, cost/ benefit analysis, and politics; but happily the paper is paywalled so I don’t have to pretend to want to read it. But I’ll note that and can, in principle, be technically and economically achieved (3) is somewhat odd, because the aforecited “(2)” already contains Limiting the anthropogenic temperature anomaly to 1.5–2 °C is possible, yet requires transformational change across the board of modernity so what exactly is the need for ref 3, other than to make the text look respectable by having lots of nice references?

But enough nit-picking, what do they actually say? I’m glad you asked: propose framing the decarbonization challenge in terms of a global decadal roadmap based on a simple heuristic—a “carbon law”—of halving gross anthropogenic carbon-dioxide (CO2) emissions every decade. Complemented by immediately instigated, scalable carbon removal… so it’s a heuristic. Or, looked at another way, a slogan; but that wouldn’t sound so academic. I’m dubious about the need for scaling up carbon removal; and if you can halve CO2 emissions every decade, you don’t need it anyway. Perhaps one of the authors was desperately interested in removal.

2017–2020: No-Brainers

Oh dear. Scrolling down just a little bit more in the hope of discovering if there was anything to this paper, or if it really was no more than a slogan, I discovered this section header. I hate the phrase “no brainer”. It is so stupid, so ill-bred, so uncultured, so dismissive of debate. And now it appears in journals – admittedly, USAnian, not British, journals – like Science?

Naturally, I stopped reading at that point. What else could I do?

Update: another thought

There’s another obvious thought, though, which is: why would you expect any response to follow a half-every-decade law? An S-shaped curve is more likely: things begin slowly – arguably we’re round about that point – then progress becomes faster, then the easy stuff is done and you’re left with the hard bits and progress slows again. If you were decarbonising by, say, producing solar panels, why would that kick in so suddenly in the next decade? and if it did: why would you then slow down in the following decade?


1. Originally. After being articulated it did become a rough plan for chip makers and foundaries to work towards.

2. Except mine.


  1. #1 Phil Hays

    There are not the technologies to rapidly halve carbon release on this “heuristic”.
    Example: To vastly reduce carbon release from transportation, changing cars from gasoline/diesel to electric. How low carbon this is depends partly on how low carbon the electric grid is. If the grid is low carbon, this is pretty good, if the grid is all coal is about the same as the best gasoline cars.
    Growth rate of EVs is is significant, but is starting at tiny numbers. Just passed 1% of cars sold in the USA. Might be able to double this every 5 years… That hits half the of new cars in about 6 doublings: or about 30 years. Need about another 10 years to get to half of all cars on the road as the useful like of a car is well over 10 years. Probably can’t do much faster for a long list of good reasons.

  2. #2 Phil Hays

    “useful life” not “useful like”

    Pointer to one of my favorite resources:


    Hat tip to Mr Kelly comment on Science.

  3. #3 Everett F Sargent
    United States of no peer review?

    (Science Issue containing said Policy Forum)
    (note PRE (Peer Review Evaluation) section at page bottom)
    (Instructions for Reviewers of Policy Forums)



    Science’s Insight section presents analysis by scientists and other experts on issues of interest to Science readers. With the exception of Letters and Comments, most items in these sections are commissioned by the editors, but unsolicited contributions are welcome. Perspective and Policy Forums should include an abstract. Commentary material may be peer-reviewed at the Editors’ discretion.

    So a CO2 emissions half-life of 10-years and a renewables doubling time of 5.5-years as opposed to a SLR doubling time of 10-years (e. g. you know who). I’d really like to see the same analysis for 20-year half-life for CO2 emissions and 11-year doubling times for renewables.

    … the east and the west are mine … the north and the south are mine … all looks beautiful to me … :(

  4. #4 Andrew Dodds
    United Kingdom

    The problem is, Moore’s law is a special case.. namely that an ongoing linear decrease in feature size on silicon chips causes an exponential increase in the number of components per unit area.

    Which is very nice, all well and good, but there is nothing in there that says that any other technology or process should follow such a law.

    There are some quite obvious problems with exponential growth in the energy sector. We imply that, for instance, at the end of this doubling process we’d have enough PV panel production capacity to power the world every 10 years; this isn’t the tech sector with a near limitless market for more CPU power and storage, so that capacity would quickly become idle.

  5. #5 David B. Benson
    United States

    There is no need to remove carbon, which is harmless. There is a need to remove some of the carbon dioxide in the atmosphere. If the current concentration of 400 ppm is maintained, much land will eventually be drowned by the 25 meter sea level rise.
    for the mid-Pliocene.

  6. #6 Magma

    “Easier said than done” and “saying doesn’t make it so” are a couple of old phrases that sprang to mind.

  7. #7 Hank Roberts
    at the reference desk again

    What we need is a way to collect energy from English Ivy.
    Or kudzu. Something green that doubles annually and will grow anywhere on anything ….

  8. #8 Julian Frost
    Gauteng East Rand

    Didn’t know where to put this, but thought it was germane.

    The City of Tshwane announced its flagship policy on Embedded Power Generation (EPG), which is aimed to promote small-scale solar power generation by residents.

    Speaking at a media briefing on Thursday, executive mayor Solly Msimanga said this is an opportunity for residents to sell their excess power to the city.

  9. #9 Russell Seitz
    Decreasingly rural North America

    Given that population growth has gone from ~ 1 billlion per century to nearly 1 billion per decade, and despite new energy tech, longer lifetimes still mean more carbon burned per capita,
    the Graun has more than one wrong tree tom bark up.