Wally Broecker’s Dumb Luck

 

Doug McNeall tweeted a link to this somewhat enigmatic essay yesterday. It’s by Wally Broecker, the so-called “Father of Global Warming”, an epithet which he earned by virtue of his fairly accurate prediction of global temperature rise (predicted to be mainly due to rising CO2 emissions) in 1975.

It’s pretty obvious that Wally Broecker does not nowadays care much for the accolade, if he ever did:

screenshot-link.springer.com 2017-03-07 13-24-25

screenshot-link-springer-com-2017-03-06-16-57-20

It’s also very obvious, from the main subject of his essay, that he considers his prediction of global warming for the 40 odd years hence from 1975 to have been correct – but for the wrong reasons.

screenshot-link.springer.com 2017-03-06 17-10-22Given that those reasons were:

  1. A cessation of the natural cooling influence of the Dansgaard cycle
  2. The commencement of dominant CO2 GHG warming

We are left to ponder the possibility that Wally Broecker is not quite as certain as he once was that GHG warming is mainly responsible for the rapid temperature rise after the late 1970s.

I can’t imagine that this revelation, this scientific epiphany, has come to Broecker very suddenly. He’s probably known for years that his scientific reasoning re. natural variability at least, was faulty. But he has waited until now, when establishment climate science is going through a particularly rough period, to write this rather enigmatic essay which hints that all might not be quite as it seems with respect to natural climate variability and hence, by logical deduction, the attribution of modern climate change mainly to anthropogenic GHG warming.

Broecker recently became aware of the fact that Dansgaard’s Arctic oxygen isotope record – which he used as a proxy for global temperature in 1975 – was in fact far more closely related to the phase and amplitude of the North Atlantic Oscillation. This in itself is rather interesting because the NAO, during winter, governs the severity of northern European winters especially. Take a look at the standardized winter NAO index since 1950:

season-jfm-nao

We can see the deep trough which gave us the very severe winters of the 1960s and early 70s, the partial recovery to 1975/76, the dip into the late 70s/early 80s, followed by the pronounced rise to the mid 90s, coincident with the rapid phase of global warming. Thereafter, the winter NAO index began to decline again, resulting in the severe winter of 2009/10 and the exceptionally cold December of 2010. Remarkably, after 2010, it did a very sharp about turn and went very positive in 2014/15/16, which explains the extremely wet, very warm winters we experienced during those years. So, although NAO is not a very accurate proxy for global temperature, there is a link there somewhere, and it is probably via a teleconnection to ENSO.

And speaking of ENSO, Broecker, identifying 1976-77 as a significant turning point in global climate, indicates that at the time (coincident with an El Nino event) the equatorial Pacific underwent a marked change whereby upwelling weakened considerably, resulting in significant warming of the California current plus other effects in South America and elsewhere. Broecker also notes that that the PDO underwent a sharp phase change from “unusually large negative” to positive at the time. All of these events signify what is known as the Pacific Ocean Climate Shift of 1976/77. It is obvious that a major and abrupt shift in global atmospheric/oceanic circulation took place at that time, the physics of which still eludes scientists today.

Broecker speculates that “perhaps in the new circulation regimen [initiated during 1976/77], the ocean absorbed less of the heat generated by the atmosphere’s growing CO2 content”. If so, then naturally we would expect global mean surface temperature to rise considerably as heat stayed in the upper layers of the Pacific during this period of decreased upwelling. It is equally plausible of course that incident solar UV (perhaps boosted by clearer tropical skies) also warmed the ocean surface considerably more during this period – energy which was not mixed into deeper layers, thus leading to accelerated surface warming. Whatever the case, natural variability almost certainly has played a part in the rapid warming post 1976. Broecker speculates that the same mechanism, in reverse, may be responsible for the 21st century pause:

screenshot-link.springer.com 2017-03-07 14-06-38

Which, if we are brutally honest, is a version of the ‘ocean ate my warming’ explanation for the Pause. But I do wonder if it is more than that, if Wally Broecker is saying not that the Pacific is responsible for moderating and enhancing global warming due only to humans, but that it is responsible of itself for moderating natural global warming via the absorption and release of incident short wave solar radiation, hence bringing into question the attribution of all global warming post 1950 to CO2 emissions. I could be misinterpreting his essay of course, but it is rather enigmatic. It’s also worth noting that Broecker based his calculations in 1975 on a transient climate response of 2.4°C, which is considerably higher than many current estimates, so the amount of warming which he predicted due mainly to GHGs, may need to be augmented by unaccounted for natural forcings (internal/external).

Finally, a rash of new science papers recently released tends to confirm the increasing recognition by scientists of the role played by natural variability in climate change.

 

9 thoughts on “Wally Broecker’s Dumb Luck

  1. Broecker also promoted the view that ocean currents drive climate change. He popularized the notion of the ocean “conveyor belt” by which the thermocline circulation fluctuates over centuries. That idea is also needing more observational support, such as the RAPID array in the N. Atlantic is beginning to provide.

    Still the main import of the ocean dynamics is to show why earth’s climate changes so little and so slowly that people get excited about a degree rise in 150 years.

    https://rclutz.wordpress.com/2015/07/20/follow-the-water-arctic-ocean-flywheels/

    Liked by 1 person

  2. Very interesting and curiously worded. I hope this trickle becomes a flood quite soon.

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  3. The observational TCR is about 1.3C, see Lewis and Curry 2014. So it was dumb luck because the paper is wrong. But, enigmatic as it is, this is still a bit of a climb down. Another sign the tide has turned.

    Liked by 1 person

  4. Scott Adams has made so many funny, penetrating insights into the corporate business world that when I was in amongst it, his cartoons were a regular tonic. But recently he has been getting some good jabs in on the CO2 Melodrama, and this new one is a fine example. Basic stats perhaps, but well explained. Bit by bit. inch by inch, the sloppiness is being exposed whether it be by an Adams rapier jab, or a McIntyre and McKitrick broadside, or even this pause for thought by Broecker. Not quickly enough to have stopped the excesses so far, but maybe the Trump administration will see us turn the corner on them.

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  5. There are a lot of holes in all the arguments now eg the Permian Triassic extinction was supposed to be caused by CO2 warming but now it might be an ice age (I really have no more confidence in this research but it’s the warmists argument, not mine). Apart from a bit of warming and a bit of ice melting, what have the alrmists got left? We ought to do a round up of all the scares that have bitten the dust.

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  6. Tiny

    Or that the earth has no natural thermostat because ‘runaway global warming’ in the Paleocene-Eocene Thermal Maximum. They’re getting really desperate. Like 9Gt annual carbon emissions is in any way comparable to a probable 3000Gt effectively instantaneous atmospheric carbon excursion during the PETM (most likely due to an extraterrestrial impact! I don’t think so.

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  7. Meanwhile, The New Scientist uncritically reports on a Welsh psych professor who thinks that more than a 100% of climate change in the last century was due to man and that 90-97% of scientists agree with him but the idiot public doesn’t. Dr Lew’s got competition.

    https://www.newscientist.com/article/2123819-most-people-dont-know-climate-change-is-entirely-human-made/

    They haven’t just jumped the shark, they’ve got it pregnant and refuse to pay child support.

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  8. CO2 levels are not in ‘lock-step’ with temperatures at all. It’s a myth.

    Significant changes usually happen around El Nino/La Nina, not CO2. Then there’s ‘the pause’, plus the fact that most GHG is water vapour not absurdly overrated CO2.

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