Claim: natural variation 'masked' global warming, creating 'the pause'

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:

http://www.physics.mcgill.ca/~gang/eprints/eprintLovejoy/neweprint/Anthropause.GRL.final.13.6.14bbis.pdf

 

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Severian

Funny thing, natural variation can only cause temps to go down, if they to up its, da da daaaaa, Globul Warming!

Tom Moran

“The hypothesis that the industrial epoch warming was a giant natural fluctuation was rejected with 99.9% confidence. ” Lovejoy
=================
Naturally. All those other giant natural fluctuations were natural, but, this one….this one is special.

It is stronger than we thought.

Frank

So, the author should make some predictions with error bars. Let’s see if they come true.

“A sadistical variation destroyed our theory”

Ian W

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 the natural cyclic variations matching the ‘anthropogenic forcing’ for more than 17 years must be incalculably small. I rather fancy Professor Lovejoy talks to the faeries at the bottom of his garden, or has a real problem with understanding of probabilities.

Good thing I got me a SUV. No telin’ how colt it a be iffin I was drvin’ one a them volts.

joelobryan

curious that Lovejoy found 0.28 – 0.37 deg C over 20- 50 yr periods, JUST enough to explain the hiatus. What abpout -1.0 to -1.5 deg C over 100-200 years, enough to explain the LIA? A period that Mann tried to hide the decline with “Nature trick.”
Just more evidence of the crisis in which mainstream Climate Scientists currently find themselves in with the hiatus and climate model-randon number generators.
I bought [a] couple of Anthony’s “I Believe In Climate ^Science Change” bumper stickers last year. More applicable than ever.

So when temps go down it’s natural variation, when they go up it’s climate change?
Isn’t that called observer bias?

Sparks

I can not wrap my head around this type of logic.. the reverse engineering of a flaw to correct it is one thing, but to reinvent a square wheel and call it round is just absurd.

So, they expect warming to commence any minute now, then. Could be fun to watch.

So these slight declines are “natural variation”, but only man can make the temperature go up? And how long have these natural declines been happening? Since the last ice age maybe? Is he saying that were it not for man’s CO2 emissions, Earth would be much colder than it was during the last ice age? Or is the climate like some kind of Escher lithograph ?(http://www.mcescher.com/gallery/lithograph/ascending-and-descending/)

Konrad

“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.”
It’s just getting sad. Eventually climastrologists are going to have to admit the truth, that radiative gases don’t have a net warming effect in our atmosphere. Yet the models they defend say the opposite. They are just delaying the inevitable and ultimately there is no point. Everything built on this failed hypothesis from careers, subsidies and hot air trading systems will collapse. Every day, every hour and every second this foolishness goes on just makes the final fallout worse and worse and worse.
At the very foundation of this inanity is a scientific mistake, and it’s not a small one. It’s black or white, right or wrong. The political techniques of “slow walkback” and “issue fade and replace” cannot work in these circumstances. There is nothing to be gained from delaying the end. Band-aid off fast? Or Band-aid off slow and painful? Those are the only choices now. The authors of this paper have chosen “slow and painful”…

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”.
So what did the statistical exercise performed as part of the paper tell us? Nothing.

Steve O

If natural variation can cause “the pause” how much of “the hockey stick” can that cause?

MattN

So natural variation can cause cooling, but absolutely cannot cause warming. Right?

So how did they statistically factor out those 500 to 1500 year natural cycles that gave us the MWP and LIA?

Steve

Hey all you guys who know lots more about this than I do….what’s up with all the latest hoopla this week about 2013 being the hottest on record? I’ve been searching WUWT and some other sites to see what the scientific response is, but not seeing anything yet. Is anyone disputing it yet with substantive analysis? From my purely objective perspective, the 2013/2014 winter was setting all kinds of cold and ice records…coldest temps, latest snows, latest ice cover, etc. Seems like the “pause” is still continuing so these wild claims always baffle me.

cnxtim

CAGW is absurd.
i was just watching an episode of the Sagan show Cosmos – remade mostly it seems to include doom and gloom CAGW of course!
The presenter (Mike Tyson?) ran through all the massive geo shifts in the earths history and the incredible changes they wrought to the shape and climate of the earth – all pre-date the miniscule increase in anthropogenic CO2 and all were monumentally catastrophic…
BUT – these changes were only catastrophic when extreme cold occurred compared to heat which was mostly beneficial to life on earth..
Give it up guys, get a real job and start making a genuine contribution

This paper is going to be a short lived event – they’re still trying for a sensitivity of 3c / doubling, which implicitly posits that the pause is an extreme cooling event which cannot last for much longer.
This is going to be fun.

Natural variation seems to be masking everything – probably because the null hypothesis remains in effect.

“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.”
Yeah, I would consider zero temperature rise to be something of a “deceleration” and “markedly slower” also.
On the other hand, they did use the term “skeptics” instead of the alternative, so it could have been worse.

Joel O’Bryan;
What abpout -1.0 to -1.5 deg C over 100-200 years, enough to explain the LIA? A period that Mann tried to hide the decline with “Nature trick.”
>>>>>>>>>>>>>>>
Hide the decline and make the MWP go away were two separate things. I suggest you hit the search bar on WUWT and read the details of both, there should be plenty of articles. A good skeptic is most effective when armed with facts, but correct facts are even better 😉

Latitude

Question….did he use the temp history that showed temps falling?….or the one that showed temps flat?….or the one that showed temps rising?
Lovejoy’s new study concludes that there has been a natural cooling fluctuation of about 0.28 to 0.37 degrees Celsius since 1998….about the time the internet kicked in
So he says cooling was ~ 1/4 degree…..on top of their adjustment to the temp
…that should put us with temps falling

Felix

Give it up guys ….
“The combined average temperature over global land and ocean surfaces for June 2014 was the highest on record for the month, at 0.72°C (1.30°F) above the 20th century average of 15.5°C (59.9°F).”
http://www.ncdc.noaa.gov/sotc/global/2014/6
[what, you think the temperature won’t ever go back down? -mod]

So we’re kinda going full circle here.
Before the pause sank its roots deep into the data, skeptics pointed out that the warming we were seeing was well within natural variability. We were poo pooed as complete morons by climate “scientists” who insisted that natural variability was far to small to account for the anthropegenic warming signal being measured. Now they wish to argue that, in fact, natural variability is large enough to not only swamp the anthropogenic signal, but large enough to do so for 15+ years.
Given that the earth has been warming since the LIA, some 300 to 400 years, I see no reason why we should expect anything different for the next few hundred years. Fact is though, that should warming return, natural variability can’t be discounted as too small to cause it, because they’ve just stipulated that it must be large enough to explain the pause.
They can only flip flop so often. I am constantly shocked at how often, but there has to be an end to it at some point. I think.

Jared

Did you guys know that global warming makes people shorter? The only reason it looks like people are getting taller is because better nutrition is masking the effects of CO2 on height. Just wait we will all be tiny by 2100.

Cameron

HEADLINE: Scientists from NASA and NOAA have discovered Global Pausing!
The one thing for sure now is “the pause” or “the hiatus” or whatever is starting to make more and more headlines. Only a few months ago we were being told there was no pause or slight cooling, it was still rising.
Now we are being told that natural variations in the climate cycle are stronger than AGW! They are contradicting their own story now.

Catcracking

The sad thing here we probably paid quite a few bucks for this useless study.
With this crowd, anytime they mention statistics it means the data has been twisted beyond all belief and it is impossible to give it any credibility. ,

pat

would love comments from roy spencer, bob tisdale etc on this one, which does discuss the pause/”hiatus” etc…
AUDIO 29 MINS: 21 July: BBC Discovery: What has Happened to El Nino?
At the start of 2014 meteorologists warned of a possible El Nino event this year. The portents were persuasive – a warming of the central Pacific much like that which preceded the powerful El Nino event of 1997. But since then the Pacific climate system seems to have stalled. What’s going on? What are the prospects for an El Nino to develop later this year? What impacts might it have? Roland Pease delves below the Pacific surface to find out what drives El Nino cycles, the most powerful single climate fluctuation on the planet, and asks the experts why it is so hard to forecast. “The year started with a bang,” one expert tells Discovery – will it end with a whimper?
http://www.bbc.co.uk/programmes/p022tlhq

Brock Way

So, Lovejoy reports a belief that the principle driver is natural variation. Welcome to the flat-earth denier camp, Lovejoy. Have a seat right over there with the other deniers like the GISTEMP data set.

Pat Frank

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..”
Statistics is not a substitute for physics.
Lovejoy’s previous statistical study could only have ruled out to 99% confidence that the present increase in temperature is not statistically equivalent to historically previous temperature swings.
Such a study says nothing whatever about physical causality.
Lovejoy’s study must also have assumed the consensus confidence intervals of the global surface air temperature record. You’ll remember those intervals — the ones that reflect the consensus assumption that systematic measurement error is stochastic.

brockway32

You believe natural variation is the cause for temperature trend? GASP! Welcome to the denier camp, Lovejoy, you flat-earther.

Latitude

Felix says:
July 21, 2014 at 5:36 pm
Give it up guys …
——
yep, I’ll give it to them…..it beat the old record by 1/20th of a degree
we’re all going to die………….

Dave the Engineer

The Cult members always have an explanation for why things are not as they previously predicted. More proof that it is a Cult. But look at it this way: with all the twisting and turning they are doing now they will not have any credible outs as it gets colder and colder. At least this idiot is not saying the heat is hiding in the deep ocean. He is actually admitting the the heat is not increasing. Progress!

Felix says:
July 21, 2014 at 5:36 pm
Give it up guys ….
“The combined average temperature over global land and ocean surfaces for June 2014 was the highest on record for the month, at 0.72°C (1.30°F) above the 20th century average of 15.5°C (59.9°F).”
>>>>>>>>>>>>>>>>>.
Which changes the fact that the temps haven’t changed by an amount worth talking about for 15+ years how?
Let’s try and put your alarming “news” about the recent temps in perspective.
Say you start a bank account, and ever year for 100 years, you put $1,000.00 in it. You’ve picked a really sh*tty bank though, they don’t pay interest, so after 100 years, you’ve got 100,000.00 in the bank. In year 101, you put in a single penny. Congrats, you’ve now got 100,000.01 in the bank. In year 102, you put another penny in. Congrats, you’ve now got 100,000.02 in the bank. In year 103, another penny goes in, and you’ve got 100,000.03 in the bank.
Now Felix, it would be quite accurate to say you’ve had the most money ever in year 103. In fact, you could even say that the last 3 years have all set new records for the amount of money you have in the bank. Those statements would both be true. But the fact of the matter is that years 101 thru 103 are meaningless. You’ve had a pause in your savings, and trying to claim otherwise is just silly. Your savings from the last 3 years are effectively zero.
We’ve been warming since the LIA, several hundred years ago at a reasonably constant rate. This century was warmer than the last, and that one was warmer than the one before. But the warming is no longer happening at $1000.00 per year, it is happening at $.01 per year. Hence all the scientists trying to explain the reasons why, for they would look rather silly trying to explain that $.01 is significant, so they stick to announcing records instead, no matter by how small.

F. Ross

davidmhoffer says:
July 21, 2014 at 5:39 pm
Good post!
(except for this part: “They can only flip flop so often.”)
🙂

Come on guys, we can measure CO2, we can determine the (wrong) climate sensitivity the delta-T for a doubling of CO2, but the authors here don’t say what natural variability is made of, how to measure it, or how to predict its impact.
Perhaps the NSF, NOAA, or some proactive agency should start to study it. 🙂

ch

The headline that would make sense: Natural variation mistaken for global warming

Bruce Cobb

The dog must have been very hungry.

Evan Jones

So natural variation can cause cooling, but absolutely cannot cause warming. Right?
Oh, I think it is generally conceded that the pre-CO2 Age warming prior to 1950 was largely natural.
We need to be real about this. I think that ENSO/PDO may be keeping things flat now: We are in a negative PDO, but not much cooling. That would account for a lot of Trenberth’s “missing heat”. I think T. was pretty much just “rediscovering” the PDO, actually. OTOH, with this new OHC study, maybe not so much. The flip side being that when SO was positive, a lot of that warming was natural. The figures do have to add up. Sort of. Somehow.

Michael F

This has become a Soap Oprah. At the end of every episode there is another twist to the story. Will climate change, change it’s name again? will they find the hiding place of the lost heat? will the main character “Climate change” have a personality change and morph into global cooling? Will Al Gore convert to climate cooling and star in the new movie a convenient lie? will Michael Mann finally purge his conscience and admit his mistakes. Stay tuned for the next exciting episode of Climate Change.

bit chilly

felix,the data manipulation to come to the conclusion that june somehow broke a global temperature record was quite frankly painful . the notion of global temperature being measured accurately over any period is farcical. i do not care who disagrees with that statement ,from agw advocate to sceptic,they are all wrong.
the simple fact is the data is insufficient to draw any meaningful conclusion ,so lovejoy ,along with countless others is full of s***

Lovejoy. Isn’t he the guy who says the uncertainty for global mean temperature is only 0.03 deg C, so can be safely ignored?
NOAA would beg to differ . . .
http://www.ncdc.noaa.gov/sotc/service/global/global-land-ocean-mntp-anom/201301-201312.png

RoHa

“shows that the slowdown in global warming during this period is consistent with natural variations in temperature”
But the preceding warming wasn’t?

Lenny

I’m new to this but, if the warmists recognize a pause how can the Guardian claim 352 consecutive months of above average temperatures. Would that not refute a pause?

norah4you

Is there anyone out there who have an English version of Huff’s How to lie with Statistic unfortunatly my own is in Swedish, had it when studying matematic statistic in 70’s know those who still uses Swedish translation today at University’s basic course in ms. Had I had one in English I would have donated that examplar to the McGill University. Guess they never got an examplar or anything alike….. 🙂

Lenny,
The Guardian is feeding the public a load of crap. Satellite data — the most accurate of all — shows that global warming stopped many years ago.
In fact, the planet is slightly cooling. [See the green trend line in the chart.]
There is lots of false propaganda in the media. The Guardian is not the only prevaricator. Even Scientific American lies about the “carbon” scare.
Stick with this site. You will learn to sift the truth from the chaff.

I’ll focus on Equation (1) of the paper at http://www.physics.mcgill.ca/~gang/eprints/eprintLovejoy/neweprint/Anthropause.GRL.final.13.6.14bbis.pdf. What, if anything, is the author’s justification for assuming this equation? He does not say. Should we assume the paper’s conclusions to be true? Obviously not.

AnonyMoose

I’ll have to read his earlier paper to see how he dismissed the warming before 1945 as not being as significant as the warming after 1976.