Cooling: one we missed: Petersen and Larsen, 1978

Global cooling again; via a comment on this rather dodgy page I find Stockton, C. W. and W. R. Boggess, Geohydrological implications of climate change on water resource development, Contract Report DACW 72-78-C-0031, for U. S. Army Coastal Engineering Res. Center. That isn't P-R, but contains on p 159 a "Projected Climatic Trends" which in turn references A statistical study of a composite isotopic paleotemperature series from the last 700,000 years, Erik Lundtang Petersen, Søren E. Larsen. Tellus Volume 30, Issue 3, pages 193–200, June 1978; which is of course P-R. And which sayeth:

An attempt is made to identify a stochastic model that makes the best fit to a generalized temperature curve covering the last 700,000 years. A search is made for the model within the family of auto-regressive, integrated, moving average models. All the models presented forecast a decline in temperature during the next 5000 years.

That forecast, now, isn't of any value to science; only to history of science. Of the model: "only models based on the apparent memory in the series will be discussed" and "By excluding models containing a forcing term, e.g. Milankovitch's insolation theory (Monin, 1974), we avoid the difliculties ssociated with assigning the form of the forcing, as discussed by Kukla (1975) and Hays et al. (1976), and more-over we avoid linking our results to any specific physical model". That seems a rather dodgy basis to me, but nevermind, its what they did. I think it tells you why its wrong: (a) it omits the greenhouse gas forcing, so its completely wrong as a forecast, but (b) it omits the differences in Milankovitch type forcing now as opposed to the past interglacials, and so is wrong there too (actually I suspect its even wronger than that, for reasons analogous to those mt has discussed elsewhere re the inevitable tendency of Fourier-type-fitting to "predict" cooling after warming, but never mind).

I think that, even for a bunch of palaeogeographers, they are curiously unaware of the world around them. The conclusion does note that its only valid if the mechanisms controlling the future are still the same as the past; the only way to rescue this is to realise that they are wrapped up in their world, which was not anywhere near as politicised as it is now. Palaeogeographers were free to speculate on what would happen restricting themselves only to their patch.

[Update: thinking about this, I should really have looked at the timescale and size of change more carefully. Their prediction has a timestep of 5 kyr, so arguably we could ignore it if we're interested in the "near future" - say the next few decades or century. But if you do try the next say 50 years, and assume linear interpolation to 5 kyr, then their prediction of 1 oC cooling over 5 kyr translates into 0.01 oC over 50 years. Which is so small it would get overwhelmed by natural variability; its equivalent to "no change / neutral".]

More like this

Camp century cycles.
-> predict global cooling.
No global cooling
-> there must be some dark force preventing global cooling
-> there must be something warming the globe
A period of two decades warming
-> predictions that ? is causing a lot more warming than is needed to prevent the camp century cycle prediction coming true.

Now what on earth could that ?

[I'm not quite sure what you're trying to say. I *think* you're taking this paper seriously, in the sense of having something useful to say about predicting the future; if so, that would be a mistake. As I explained in the post -W]

By Mike Haseler (… (not verified) on 08 Jan 2014 #permalink

By excluding models containing a forcing term, e.g. Milankovitch’s insolation theory (Monin, 1974)

Wait, what? This puts the paper in question firmly in the "not even wrong" category. I can see, as an intellectual exercise, neglecting greenhouse gas forcings to see what the climate would do under the Milankovitch cycles alone--a paper that did that would at least be wrong. But the forcings due to Milankovitch cycles would still be there, and IIRC these forcings were known by 1978. Neglecting them in favor of a straight Fourier extrapolation is, at best, cargo cult science.

By Eric Lund (not verified) on 08 Jan 2014 #permalink

If this were the old days, I'd steal that as a .signature:

" ... only valid if the mechanisms controlling the future are still the same as the past"

By Hank Roberts (not verified) on 08 Jan 2014 #permalink

Consider when it was written. There's been quite a bit of improvement in data analysis technology and methodology since 1978. This paper's has long been superseded. Even without forcings included, the paper is useful. If without forcings the global temp stays about the same, then any warming (or cooling) can be ascribed to the forcings.

By Paul Kelly (not verified) on 08 Jan 2014 #permalink

"This, of course, being under the assumption that the time series used here is representative for the past climate and that the mechanisms controlling the climate are still the same as they have been for the last 700,000 years"

By David Sanger (not verified) on 09 Jan 2014 #permalink

Even through 1979 deforestation albedo effects were being juxtaposed against greenhouse gases. The threat of "Nuclear Winter" was created to augment the popular belief of cooling. Climatology didn't really exist as a science so decadal variation dominated popular thought. Natural climate cycles are longer than a generation so the fact that a tropical storm like "Sandy" would be equated to the hurricanes that routinely hit the US northeast is not surprising. It's like asking a person whether Haley's comet was more or less intense when they saw it for the first time. But to the point, the near term is rather irrelevant wrt Milankovitch. There is no doubt that an ice age is coming, rather it's whether we can survive the interglacial warm period with more than natural warming. Lets not forget we are "interglacial" and there has yet to be any scientific reason to believe we will not enter another glacial period. The only discussion is short vs. long positions. I will be dead long before global warming or glaciation kills me.

By Tim Beatty (not verified) on 10 Jan 2014 #permalink

Tim Beatty: "The threat of 'Nuclear Winter' was created to augment the popular belief of cooling. "

Huh? Are you saying Carl Sagan was involved in a plot to augment the popular belief in cooling? Oh nos! If that's true, then everything I thought I knew is a lie!!11!!

By Mal Adapted (not verified) on 10 Jan 2014 #permalink

Drat- does this mean we have refight the Cold War?…

"Gwynne, now 72, is a bit chagrinned that from a long career of distinguished science and technology reporting, he is most remembered for this one story.

"I have, in fact, won prizes for science writing," he said, with just a whiff of annoyance, in an interview this week."

[Nice, thanks. As the article says, this was only an inside piece given greater prominence now, and only by liars. But I don't think Gwynne is being entirely honest though. And still, Gwynne notes of his story, "I stand by it. It was accurate at the time." I don't think I really buy that. "Newsweek being Newsweek, we might have pushed the envelope a little bit more than I would have wanted," Gwynne offered is closer -W]

By Hank Roberts (not verified) on 16 Jan 2014 #permalink