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.
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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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Funny thing, natural variation can only cause temps to go down, if they to up its, da da daaaaa, Globul Warming!
“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.
So, the author should make some predictions with error bars. Let’s see if they come true.
“A sadistical variation destroyed our theory”
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.
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?
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/)
“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.
If natural variation can cause “the pause” how much of “the hockey stick” can that cause?
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?
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.
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
Natural variation seems to be masking everything – probably because the null hypothesis remains in effect.
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.
“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 😉
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
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]