Statistical analysis shows pattern consistent with pre-industrial temperature swings, study concludes
From McGill University’s Shaun Lovejoy
Statistical analysis of average global temperatures between 1998 and 2013 shows that the slowdown in global warming during this period is consistent with natural variations in temperature, according to research by McGill University physics professor Shaun Lovejoy.
In a paper published this month in Geophysical Research Letters, Lovejoy concludes that a natural cooling fluctuation during this period largely masked the warming effects of a continued increase in man-made emissions of carbon dioxide and other greenhouse gases.
The new study applies a statistical methodology developed by the McGill researcher in a previous paper, published in April in the journal Climate Dynamics. The earlier study — which used pre-industrial temperature proxies to analyze historical climate patterns — ruled out, with more than 99% certainty, the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate.
In his new paper, Lovejoy applies the same approach to the 15-year period after 1998, during which globally averaged temperatures remained high by historical standards, but were somewhat below most predictions generated by the complex computer models used by scientists to estimate the effects of greenhouse-gas emissions.
The deceleration in rising temperatures during this 15-year period is sometimes referred to as a “pause” or “hiatus” in global warming, and has raised questions about why the rate of surface warming on Earth has been markedly slower than in previous decades. Since levels of greenhouse gases have continued to rise throughout the period, some skeptics have argued that the recent pattern undercuts the theory that global warming in the industrial era has been caused largely by man-made emissions from the burning of fossil fuels.
Lovejoy’s new study concludes that there has been a natural cooling fluctuation of about 0.28 to 0.37 degrees Celsius since 1998 — a pattern that is in line with variations that occur historically every 20 to 50 years, according to the analysis. “We find many examples of these variations in pre-industrial temperature reconstructions” based on proxies such as tree rings, ice cores, and lake sediment, Lovejoy says. “Being based on climate records, this approach avoids any biases that might affect the sophisticated computer models that are commonly used for understanding global warming.”
What’s more, the cooling effect observed between 1998 and 2013 “exactly follows a slightly larger pre-pause warming event, from 1992 to 1998,” so that the natural cooling during the “pause” is no more than a return to the longer term natural variability, Lovejoy concludes. “The pause thus has a convincing statistical explanation.”
The methodology developed in Lovejoy’s two recent papers could also be used by researchers to help analyze precipitation trends and regional climate variability and to develop new stochastic methods of climate forecasting, he adds.
—————————-
The paper:
“Return periods of global climate fluctuations and the pause”, Shaun Lovejoy, Geophysical Research Letters, published online July 14, 2014. DOI: 10.1002/2014GL060478
Abstract
An approach complementary to General Circulation Models (GCMs), using the anthropogenic CO2 radiative forcing as a linear surrogate for all anthropogenic forcings [Lovejoy, 2014], was recently developed for quantifying human impacts. Using preindustrial multiproxy series and scaling arguments, the probabilities of natural fluctuations at time lags up to 125 years were determined. The hypothesis that the industrial epoch warming was a giant natural fluctuation was rejected with 99.9% confidence. In this paper, this method is extended to the determination of event return times. Over the period 1880–2013, the largest 32 year event is expected to be 0.47 K, effectively explaining the postwar cooling (amplitude 0.42–0.47 K). Similarly, the “pause” since 1998 (0.28–0.37 K) has a return period of 20–50 years (not so unusual). It is nearly cancelled by the pre-pause warming event (1992–1998, return period 30–40 years); the pause is no more than natural variability.
Preprint paper here:
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“Hang on a minute, I was under the impression that the post war cooling that Lovejoy attributes to natural variation, was firmly attributed to fine particulate and SO2 aerosol cooling. So which one do they want. They cant have it both ways.”
More recent research suggests that particulates don’t have as powerful a cooling effect as originally assumed by models. This means that natural variability must be greater than first assumed, however that opens up a new can of worms.
How many “reasons” have now been proposed for the lack of warming?
We’ve had “It’s in the deep oceans” (Kalamity Kevin!), “It’s hiding in the North Pole”, “It’s masked by aerosols”. Probably a few more that I’ve missed.
So, which one is it folks?
Adam Gallon,
I found the global warming! It was under the cushions on my sofa. I also found $1.47 in loose change.
The selection of this Lovejoy post must have had in mind the James Risby paper in Nature that came out today that Mr. Watts had a post on over the weekend. The Risby paper makes the case that climate models proved themselves useful in understanding the 15 year “pause” in the long term trend of temperature rise. The Lovejoy paper seems to attempt to put a statistical framework on “natural” variation while the Risby paper takes it a step forward in saying climate models were “skillful” in picking up that “natural” trend.
The authors of the Risby paper looked at the models that were best in sync with the ENSO cycles and then looked at how well their temperature predictions had performed. Apparently they performed rather well.
They also did looked at the models that were ‘worst’ (most out of sync) with the ENSO cycle and their temperature predictions did quite poorly. This tells us that the models do quite well when they accurately reflect ENSO cycles, and poorly when they don’t.
The implication also is that ENSO is the “natural” variation that Lovejoy speaks of. Maybe this is a clue to help us better understand climate science. At the least, reading of the summary of the Risby paper over at the Guardian will let you see how people that think climate models are a good tool view them. theguardian.com/environment/climate-consensus-97-per-cent/2014/jul/21/realistic-climate-models-accurately-predicted-global-warming
peakweather says:
Confused and genuine question – every year on Jan 1st for the last 10 years, the BBC have stated that the previous year was the warmest on record and something similar to saying the last 10 years have been the warmest on record. How on Earth can thus statement fit in with the Earth has been cooling for the last 17 years?
Yes. It couldn’t be that they are just making things up, could it?
Satellite data — the most accurate data available — shows that the planet has been cooling slightly.
Satellite data and the BBC cannot both be right.
So someone’s lyin’. <——- Lookin' at you, BBC.
DW says:
dbstealey,
Thank you for the link to woodfortrees, but could I get a clarification of the significance of 1997? I was under the impression that an interval of less than twenty years was not typically considered to be of statistical significance when calculating temperature trend, but when I insert pretty much any year prior to ’97, a warming trend seems apparent. This applies to (I believe) every temperature record available via the site, calculated over any timeframe greater than 20 years. I’m clearly confused, could you assist? Is this due to fudged/corrupted datasets, or am I using the site incorrectly? Thanks in advance.
The year 1997 was selected by über-Warmist Phil Jones, who had been asked in a 1999 interview about the apparent halt to global warming. Jones thought he was on safe ground by declaring that global warming would have had to stop for fifteen years in order to be statistically significant. In 1999 it had been only 2 years, so Jones was playing it safe.
But now global warming has been stopped for more than 17 years, causing the alarmist crowd immense consternation. They were wrong. In their wildest dreams they never expected that global warming would still not have resumed. But it hasn’t. And Jones, for his part, is hiding out.
The base year of 1997 was designated by the Warmist crowd, not by skeptics. Live by the sword, die by the sword.
re
Sparks says:
July 21, 2014 at 8:26 pm
Steven Mosher
“noting snark”
Is an anagram for what?
No T Rankings
Instead of speaking about “above average temperatures”, wouldn’t it be more interesting to speak about “above (or under) average temperatures since the 1998’s start of the pause” ?
Then we would easily understand if the temperatures are resuming climbing (or falling).
Applying Occam the warming before the pause, all things being equal, would have been a natural variation as well and any surplus CO2 signal has been voided by natural feedback mechanisms.
But hasn’t NOAA just said June was the hottest month ever? Is this true? If so, what should we do?
Just how ‘lucky’ can you get natural variation just happens to be in near perfect balance to the warming the AGW should has caused. Why do this people work at all , with that types of ‘luck’ they should be winning the lottery ever week.
If you consider that AGW is real, and unless you consider that the temperature data sets are erroneously under recording the change in temperature anomaly these past 17 (or so years), the conclusion of this paper is a necessity. It is an inevitable conclusion deriving from the theory itself. I am putting it kindly elevating it to theory status, since it is in reality AGW is simply conjecture
The basic physics of CO2 as a radiative gas (and ignoring how it may behave outside the laboratory in the real life atmoshere of planet Earth) is that whenever there is an icrease in CO2, unitl fully staurated, temperatures MUST ALWAYS go up Not may go up. Not sometimes go up. Not sometime stay steady or sometimes decline. Not some times go into the atmosphere and at other times bypass the atmosphere and go in to the ocean (still less by pass the top of the ocean and go without trace into the deep ocean). The upward trend in temperature is an inevitable consequence that must always take place.
So if temperatures have not gone up when there has been an increase in CO2, either CO2 has become fully saturated at today’s levels, or there must be some other downward acting forcing in play, either natural (including volcanoes), or manmade.
Accordingly, the conclusion of this paper adds nothing to the debate. It is what all Climate Scientists, who consider the AGW meme as being correct, must inevitably hold 9whether they admit it or not is a different issue).
The real point of interest is that this conclusion acknowledges that CO2 has not overcome natural variation, and acknowledges that natural variation can (presently at any rate) still equal and oppose the forcing of CO2, ie., that CO2 is not paramount and/or dominat.
As Ian W says:(July 21, 2014 at 4:58 pm) “…It is also amazing that during the ‘pause’ the natural variations have been precisely enough to keep the change in global average temperatures statistically zero.” The chances of that are presumably rather small (but since we do not know what natural variation consists of nor the upper and lower bounds of any forcings encompassed therein, we cannot begin to assess the likelihood). And as we go forward should the pause continue (let alone should there be a fall in temperatures), the likelihood of that becomes ever more small and unlikely.
Of course as others have posted, the take home conclusion really confirms that until one can identify precisely what natural variation comprises, identify each and every consitituent forcing, the upper and lower bounds of each and every forcing, and what drives those forcings to change, one cannot begin to dispklace the null hypothesis, ie., such changes that we have observed in the temperature rwecord is due to natural variation.
In short: having ruled in natural variation, natural variation cannot be ruled out.
richard verney, you describe CO2 effect as though it were a linear effect, like the sun. As you know, the atmosphere is very nuanced with lots of positive and negative feedbacks. If the CO2 effect were linear, you would not be able to explain why the warming trend is most notable for winter nights when the insulating effect of the atmosphere is least affected by the sun.
“… ruled out, with more than 99% certainty, the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate.”
okay
What is the real value of total RF (+ positive, minus negative feedback) for ant. GHGFs?
… contra the size – the net value of the natural variations?
Significant?
It is possible that this value is so large so that was really important (compared to the size the natural variations – repeat once again) – require our prevention?
We should remember what is most important: theory of global warming is not (primarily) the direct impact of RF GHGs (especially CO2) on global temperature but are decisive here (the main component of the total RF) feedback: positive.
Feedback – the positive – they have (?) a value much higher than the negative …
But here is especially a lot of: “… too many uncertainties … ”
This is not as he will, eg, Richard B. Alley: “Ultimately, it boils down to simple physics.”
It’s: “… most predictions generated by the complex computer models …”
For example, what do we really know about solar cycles, other natural, for exclude them as significant?
(http://www.nhm-wien.ac.at/jart/prj3/nhm/data/uploads/mitarbeiter_dokumente/harzhauser/Kern-et-al-2012a.pdf):
“A best fit adjustment of sedimentation rate results in signals which fit to the lower and upper Gleissberg cycle, the de Vries cycle, the unnamed 500-year- and 1000-year-cycles …”
“Each of these cycles has a distinct and unique expression in the investigated environmental proxies, reflecting a complex forcing-system. Hence, a single-proxy-analysis, as often performed on Holocene records, should be considered cautiously as it might fail to capture the full range of solar cycles …”
Let me give you another example: aerosols as the main reason for pause (by Hansen).
In models with a dominant role – influence, GHG’s to changes in temperature, the impact of aerosols is underestimated. Therefore, it is obvious, undisputed that the impact of GHGs in these models is likely to be significantly overestimated.
Neely (2013 http://onlinelibrary.wiley.com/doi/10.1002/grl.50263/abstract): “Comparison of the model results to observations reveals that moderate volcanic eruptions, rather than anthropogenic influences, are the primary source of the observed increases in stratospheric aerosol.”
We can not “hope” that abruptly we have a “volcanic silence ” and anthropogenic GHGs “will triumph” …
“Today, Hansen’s team estimates the human forcing from greenhouse gases to be about 3 watts per square meter (warming) and the forcing from aerosols to be about minus 1.5 watts per square meter (cooling).”
“… 1.5 watts per square meter …” however, is “burdened” with a big mistake, because: “… the aerosol effect is complicated because aerosols are distributed inhomogeneously …” Hansen said.”( http://earthobservatory.nasa.gov/Features/GISSTemperature/giss_temperature4.php).
… but why not 2, 2.5, 3 watts? Because even such range of error is possible …
Furthermore we can not have the “hope” that abruptly we have a “volcanic silence ” and anthropogenic GHGs “will triumph” …
R. Alley says that “survived” to pause the 60-70’s, 80’s and current pause is not anything new for him. The problem, however, is that the current pause was not to be, because current RF CO2
(for the existence of a pause) is too great …
semczyszakarkadiusz, you mentioned every potential “natural” cause for the “pause” except ENSO. 98 was an especially warm El Nino phase and we have been in a mostly La Nina phase since.
As a good sceptic I don’t care very much about what statisticians say. I believe in the art of adaptation, which has been and still is the driving force of mankind. Meanwhile, the Aussies have realized that squandering money by the megaton on dubious CO2-schemes of all kind won’t change anything. They have the potential in becoming the pioneer in common climate sense.
Peakweather
What you have to understand is that the powers-that-be at the BBC have little or no knowledge about climate science – witness their response to the Lawson saga – but they do know what will get them approving nods from those jolly nice chaps who keep them supplied with headline friendly press releases.
Has for those claiming they cannot have it both ways , you forget the second rule of climate ‘science’ heads I win tails you lose .
Not only is it ‘science’ which was born perfect but its that ,ironically , very anti-science idea something which is impossible to be wrong .
TBear
“But hasn’t NOAA just said June was the hottest month ever? Is this true? If so, what should we do?”
Reach for a pinch of salt, would be my advice.
It’s unlikely that the others will agree with NOAA: and given that NOAA keeps adjusting its own figures, it’s unlikely that NOAA will even agree with itself in due course.
dbstealey says:
July 22, 2014 at 2:01 am
peakweather says:
Confused and genuine question – every year on Jan 1st for the last 10 years, the BBC have stated that the previous year was the warmest on record and something similar to saying the last 10 years have been the warmest on record. How on Earth can thus statement fit in with the Earth has been cooling for the last 17 years?
///////////////////
The BBC are frequently economical with the trutjh.
Since their primary target is the British viewer, it maight have been relevant for them to comment on CET. Since 2000, temperatures, according to CET, have fallen by about 0.5 degC..
Perhaps more significant, winter CET temperatures (this is December to February inclussive) have, since 2000, fallen by almost 1.5degC. The UK has suffered a spate of cold winters these past 10 or so years.
If such a trend continues (and I am not saying it will), the UK citizen will require more energy, which is fast becoming punitively expensive and unaffordable for many. The spate of harsh winters and high energy costs have led to between 20,000 to 40,000 premature deaths each year, again a matter that the BBC does not like to report on.
But the BBC has long given up on reporting news, instead it churns out the opinion according to the BBC. Should you ever watch its news bulletins, you will note that most news items involve the newsreader interviewing the news reporter, (the BBC correspondent), for their opinion!
Re Will Nitschke says:
July 22, 2014 at 1:26 am
Indeed, but the thesis of the paper is that the expected forcing “as predicted by the models” is being moderated by natural variation. Now either the models got it wrong w.r.t. the post war cooling becuase of over-correction including vulcanism (in which case they are overpredicting), or they have it wrong w.r.t. the extent of the natural variation. As I said above, they cant have it both ways.
Re: Bob Tisdale says:
July 21, 2014 at 5:14 pm
“And if the hiatus last for another 15 years, making it a total of 30 years, it will still be ‘consistent with pre-industrial temperature swings’.”
According to NOAA’s most recent announcement, the “hiatus” is over and the first half of 2014 was the highest average global land and sea temperature ever recorded. It would seem the GISS record has again been tortured into revealing the answer some wish to see.
http://hosted.ap.org/dynamic/stories/U/US_SCI_RECORD_HOT_WORLD?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2014-07-21-12-31-37
“99.9% confidence.”
Gerraway!
Of course. Trouble is they can’t deny it was, because they are not deniers, are they? Otherwise they were fifty times more confident on this point than the latest IPCC report, which fact needs much elaboration beyond claiming to be expert rejecters.
This Lovejoy fellow is apparently smarter then all the wrong computer models. His physics is apparently better. Perhaps he should be creating his own computer program. Does his paper explain what factors the computers models missed?
Felix says, The combined average temperature over global land and ocean surfaces for June 2014 showed the greatest divergence from the satellites ever recorded”
There, fixed it for you.
Changing sea surface readings (throwing out the cold ones) may have something to do with this ever growing divergence…
https://chiefio.wordpress.com/2014/07/22/gistemp-who-needs-antarctic-data-or-temps-near-ice/
I’m hoping McIntyre, Briggs, or one of the other resident statisticians take a look at this.
dbstealey says:
July 21, 2014 at 9:25 pm
Who ya gonna believe?
Phil.?
So you only believe in the null hypothesis when it suits you, I’ll remember that when you inevitably trot it out in your future posts. As stated before according to the null hypothesis the “Satellite data — the most accurate data available”—does not show that the planet has been cooling slightly.