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Global warming overestimated by factor of two

A new paper in PNAS entitled 'Using data to attribute episodes of warming and cooling in instrumental records' looks important. Ka-Kit Tung and Jiansong Zhou of the University of Washington report that anthropogenic global warming has been overcooked. A lot.

The observed global-warming rate has been nonuniform, and the cause of each episode of slowing in the expected warming rate is the subject of intense debate. To explain this, nonrecurrent events have commonly been invoked for each episode separately. After reviewing evidence in both the latest global data (HadCRUT4) and the longest instrumental record, Central England Temperature, a revised picture is emerging that gives a consistent attribution for each multidecadal episode of warming and cooling in recent history, and suggests that the anthropogenic global warming trends might have been overestimated by a factor of two in the second half of the 20th century. A recurrent multidecadal oscillation is found to extend to the preindustrial era in the 353-y Central England Temperature and is likely an internal variability related to the Atlantic Multidecadal Oscillation (AMO), possibly caused by the thermohaline circulation variability. The perspective of a long record helps in quantifying the contribution from internal variability, especially one with a period so long that it is often confused with secular trends in shorter records. Solar contribution is found to be minimal for the second half of the 20th century and less than 10% for the first half. The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07–0.08 °C/decade, with superimposed AMO-related ups and downs that included the early 20th century warming, the cooling of the 1960s and 1970s, the accelerated warming of the 1980s and 1990s, and the recent slowing of the warming rates. Quantitatively, the recurrent multidecadal internal variability, often underestimated in attribution studies, accounts for 40% of the observed recent 50-y warming trend.

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    great resources here. Ill be back for the next your posting. keep writing and happy blogging.

Reader Comments (30)

Sounds plausible.

Feb 9, 2013 at 9:45 AM | Registered CommenterPhilip Richens

I'm sure the team is being mobilised now to counter this heresy!!!


Feb 9, 2013 at 10:11 AM | Unregistered CommenterMailman

"The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07–0.08 °C/decade"

So the massive increase in anthropogenic CO2 production in the late 20th century and early 21st century has had no effect at all? If this were true does it not blow the CAGW hypothesis out of the water?

Feb 9, 2013 at 10:14 AM | Unregistered CommenterRoger Longstaff

This sort of examining of the data might have been more prevalent and influential but for the distraction of GCMs which reflect absurd aspirations (we can replicate a poorly-understood, sparsely observed, stochastically complex system just by running and running the code) and Heath-Robinson-like in practice (CO2 represented by an 'external forcing' at the top of the atmosphere, flux adjustments ad hoc down below to stop people laughing at the results, and who knows what other pampering and tampering to get 'usable' outputs given enough parameters to create not just an elephant and wag its tail but a whole menagerie).

Feb 9, 2013 at 10:20 AM | Unregistered CommenterJohn Shade

Good news.

Let's hope what's happening is that the signal has come down that it is now preferred that they tell the truth rather than wildly exaggerate as they had been doing before.

"Solar contribution is found to be minimal for the second half of the 20th century and less than 10% for the first half. "

That in itself should tell any rational person that this is voodoo, not science unless they can explain it.

One year to the next IPCC report.

Feb 9, 2013 at 10:29 AM | Unregistered CommentereSmiff

Is there any way to alert the politicos currently committing 20% of EU spending to solving this problem, that they can immediately announce a 50% reduction in spending, thereby immediately saving 300B Euros by 2020, which is probably enough to fix Greece?

Feb 9, 2013 at 11:09 AM | Registered Commentersteve ta

I wonder if the founders of the CET had a clue to what a debt we would owe them?

Feb 9, 2013 at 12:05 PM | Unregistered CommenterBloke down the pub

A particularly valuable thought, Bloke down the pub (he writes on his new MacBook Air down the pub). May we act in our own generation in such a manner that others will say the same of us.

Feb 9, 2013 at 12:32 PM | Registered CommenterRichard Drake

Bloke down the pub
Raise a glass to them next time you go down to the pub

Feb 9, 2013 at 12:37 PM | Unregistered CommenterSandyS

The important bit is the fact that this comes from the National Academy of Sciences of the United States. Now, will the "consensus" scientists begin to recognize the obvious?

Feb 9, 2013 at 1:10 PM | Unregistered CommenterJack Maloney

What a bizarre approach - using actual data rather than multi-million dollar computer models, and trying to account for the ongoing recovery fron the Little Ice Age. But we all surely realize that the current paradigm of IPCC climate science is confined to GCM's. Any aspects that cannot be subjected to a fully reductionist approach and codified within the models or, even worse, not requiring such models, has no part in legitimate climate science. Real data does not come from real world observations, it comes from GCM's. What were these characters thinking?

Most egregiously of all, they purport to reject the IPCC's canonical and irrefutable statement, in AR4, that most of the observed warming since the mid 20th century is the result of anthropogenic greenhouse gas emissions! The IPCC expressed a confidence of >90% in that finding. Now these guys come along and tell us that natural variability continues to dominate, despite the fact that it has done so for 4.5 billion years?

Again, simply bizarre. But no worries, this paper is easily refuted - it came out of data analysis, not a reductionist model within a grant-fed GCM.

End of story, just move right along folks nothing to see here.

Feb 9, 2013 at 1:41 PM | Unregistered CommenterTodd Martin

A sane voice in Bedlam, crying out amidst the ululations of the consensus.

Feb 9, 2013 at 2:23 PM | Unregistered Commenterjorgekafkazar

Jack Maloney -
The paper isn't truly from the National Academy of Sciences, that is to say, it's not an NAS report. It appears in their Proceedings, but that's really just another journal. With, I must say, a rather uneven quality -- some of the worst papers I've seen are from the PNAS.
This appears to cover the same ground as their prior paper at the Journal of Atmospheric Sciences, discussed at WUWT and Crok's website.
Does anyone have a non-paywalled link to the new paper?

Feb 9, 2013 at 2:36 PM | Registered CommenterHaroldW

I have a concerns with this study.

First, it states that "The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07–0.08 °C/decade,". This totals to pretty much the whole warming identified for the 20th Century doesn't it? They seem to be saying that natural changes (AMO etc.) cancel themselves out over the period. Seems to support the CAGW story pretty well (except for the spread of the anthropogenic effect), even though they are stating that the anthropogenic rate is greatly overstated.

There seem to be a lot of questions to answer here. Is their finding of a steady underlying anthropogenic warming rate credible? How does their interpretation of the natural changes (AMO etc.) compare with others? Are their findings on solar in line with current views?

I do not see how, with these findings, they also find that the anthropogenic warming rate has been greatly exagerated. What does that say about natural forcings in the scenarios they (effectively) criticise?

Feb 9, 2013 at 2:40 PM | Unregistered Commentermiket

Uncanny - Overestimated by factor 2 is what Steve Mc said in his recent interview.

Feb 9, 2013 at 3:00 PM | Registered CommenterPaul Matthews

Nice to see you around, Richard

Feb 9, 2013 at 3:31 PM | Registered Commentershub

HaroldW - The fact that PNAS and AMS journals are publishing a paper that undermines "the consensus" is, IMHO, another significant crack in the CAGW edifice.

Feb 9, 2013 at 3:40 PM | Unregistered CommenterJack Maloney

My prediction is that this paper will turn out to have exaggerated the anthropogenic influence, rather than have under-estimated it.
The relevent quote:-

The underlying net anthropogenic warming rate in the industrial era is found to have been steady since 1910 at 0.07–0.08 °C/decade

Greenhouse gas emissions have not been increasing at a steady rate. The most important is CO2. A couple of years ago I tried to estimate from country data (filling in important gaps) how global CO2 emissions had increased. The increases per quarter century were
1900-1925 85%
1925-1950 60%
1950-1975 185%
1975-2000 45%
That meant global CO2 emissions increased more than 12 times (1100%) in 100 years. The conversion rate to retained CO2 seems to be roughly constant - 4Gt of carbon equivalent to increase CO2 levels by 1ppm. Furthermore, the C20th warming was nearly all in two phases. 1910-1945 and 1975-1998. Rather than temperature rise being related to CO2 emissions, it seems out of step. That would imply a combination of two things for the anthropogenic warming rate to be constant at 0.07–0.08 °C/decade. First is that CO2 has massively diminishing returns. Second is that CO2 emissions alone have a much smaller impact on the global average temperature changes (as reported in HADCRUT4), than this paper concludes.

Feb 9, 2013 at 3:48 PM | Unregistered CommenterManicBeancounter

I've been saying this for a year and even had paper on the subject turned down.

Feb 9, 2013 at 3:50 PM | Unregistered CommenterRon

Can somebody please remind me who first described the AMO?

Feb 9, 2013 at 3:59 PM | Unregistered CommenterPaul Butler

Paul Butler: "Can somebody please remind me who first described the AMO?"

From slide 23 of this presentation by Tung & Zhou:
Atlantic Multidecadal Oscillation -- A brief history
•Phrase coined by the Science writer Kerr (2000), who attributed the discovery to Delworth and Mann (2000).
•Schlesinger et al (2000) disputed the attribution, and claimed that the credit should go to Schlesinger and Ramankutty (1994), who found two cycles with period 65-70 years.
•Actually it should be Folland et al (1984), who found a worldwide temperature fluctuation of 0.6 K with power at 83 years for the period 1856-1981.
•In reply Kerr said two cycles did not constitute the discovery of an oscillation. Preferred “half a dozen or more” cycles
•Delworth and Mann studied a 330-year multi-proxy record and found 4.5 cycles of the AMO.
•It was not pointed out previously that the multi-proxy AMO does not agree with the instrumental AMO.

Feb 9, 2013 at 4:32 PM | Registered CommenterHaroldW

If, over the next fifteen years, temperatures continue to plateau, will there be claims of an overestimate by a factor of 4?

Can you imagine the head-in-hands dismay if temperatures actually begin to decline?

Feb 9, 2013 at 4:58 PM | Unregistered Commentertheduke

...and still there is no proof offered that CO2 has anything to do with the 16 year long non-rise in World temperature.

Feb 9, 2013 at 10:08 PM | Unregistered Commenternicholas tesdorf

Damn' facts getting in the way of a good story AGAIN....

Feb 10, 2013 at 10:50 AM | Unregistered CommenterDavid

Death by a thousand cuts.

Feb 10, 2013 at 11:37 AM | Unregistered CommenterDavid C

Bloke down the pub.: I wonder if the founders of the CET had a clue to what a debt we would owe them?

Richard Drake: Raise a glass to them next time you go down to the pub

A glass? For an incontrovertible neutral temperature record going back centuries?

I shall raise a jeroboam of bumbo or sack to them (if I can find one).

Feb 10, 2013 at 1:35 PM | Unregistered CommenterRick Bradford

Print out the GISS data.

Use the 5-year running mean to damp out the year-on-year variation.

Now look for the AMO peaks at 1880, 1945 and 2010, with troughs at 1912 and 1977.

There's a drop of 0.25 from the 1180 peak to the next trough. The corresponding drop after 1945 is 0.12.
The rise from the 1880 peak to the 1945 peak is 0.2. The rise from 1945 to 2010 is 0.52.

The clearest indication of the amplitude of the AMO is the rise from 1910 to 1945. That is about 0.5C, giving a variability of +/- 0.25C from the mid-range value.

Now look for the solar cycle. Candidate peaks are 1887, 1898, 1915, 1940, 1952, 1960, 1971, 1980, 1989, 2002. That's about 9 years per cycle, rather shorter than the 11 year average. The amplitude is around +/-0.1C.

The temperature change from 1910 to 2010 is from -0.4C to +0.6C , an increase of 1.0C, increaing at a lest squares rate of 0.1C/decade.

On the basis of the GISS data, Tung and Zhou are overestimating the effect of the AMO on the warming rate, and correct that there has been only a limited influence from variation in solar input.

The change from 1945 to 2013, both peak AMO and peak Solar cycle years and therefore cancelling out the effect of both cycles, is 0.52C in 67 years, giving a change due to CO2 + black carbon -aerosols of 0.078C per decade. They underestimate the effect of anthropogenic warming.

Feb 10, 2013 at 6:18 PM | Unregistered CommenterEntropic man


Grade 1 hand waving. So why isn't it warming then? And why hasn't it since Blair took office?

This is the question that warmists need to answer - if CO2 is the control knob (and you say anthropogenic warming effects are underestimated) and one third of the stuff we've ever put in the atmosphere hasn't had any impact at all, why not?

Feb 10, 2013 at 7:43 PM | Registered Commenterflaxdoctor

Say No To Fearmongers.

"Grade 1 hand waving. So why isn't it warming then?"

It's an old principle in science. Say it with numbers. You should try it, sometime.

Why isn't it warming? During the latter 20th century the Sun was, cycles excepted, a fairly constant energy source. Look at its low activity in recent years.

If the AMO and solar activity are both in decline you would expect a cooling trend. Instead the AMO and solar weakness are balanced by anthropogenic warming and temperatures appear constant.

Whether this will continue is as yet uncertain. The big jump in temperature shown by the UAH figures from Dr. Spencer for January may be a blip, or the start of a renewed warming trend.


Feb 10, 2013 at 8:18 PM | Unregistered CommenterEntropic man


I'm OK with scientific principles - it's what I get paid to do all day, after all. I'm questioning you about your claims - the IPCC say that variation in the sun's output have a negligible impact on warming, and I'm still looking for IPCC dogma regarding AMO trends (other than the immortal “What if climate change appears to be just mainly a multi-decadal natural fluctuation? They’ll kill us probably…”)

So in their infallibility it can't possibly be either of those, unless of course you're prepared to chuck the political consensus out and think for yourself.

I've read Spencer - and I've also read Bob Tisdale's comments on January - sea surface temperatures are substantially down and since the sea is a much better reservoir of heat energy than the atmosphere I'm not seeing any reason for warmist celebrations yet.

Yes, of course it's uncertain, but that's different from being 'settled'. And the reason I gave up on the warmists was because they tell so many public lies about certainty, when they know they're actually little better informed than mediaeval diviners playing with goat entrails and chicken bones. Here's dendrochronologist Dr. Ed Cook - "What we know for certain is that we know f***-all..."

I believe him - what gives you the insight he doesn't have? I chose to be a scientist because I want to discover the truth. I'm curious, I want to find things out. People who abuse science to lie, cheat, distort, bully, dismiss and otherwise oppress viscerally disgust me.

I used to trust them, but I read the Climategate emails for myself. I listened to them lying and faking 'investigations' and claiming messages were 'out of context' - nope, the context was all there to see. I know what they're capable of, and the fact that they've persuaded their 'peers' to pass anything for publication is no longer a valid measure of anything at all. If you haven't read these emails for yourself, then please do so. You sound like you're entering into discussions in good faith - but be warned - it might change your life. It did mine.

Feb 12, 2013 at 8:21 PM | Registered Commenterflaxdoctor

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