Sheldon Walker gets into a pickle picking pauses at WUWT

Sheldon Walker has written another two articles for Anthony Watts' blog WUWT (archived as Part 1 and Part 2). What Sheldon was trying to do was prove there was a Pause (with a capital P) in global surface warming recently. He didn't manage that, though he thinks he did. What I'm going to show is that in order to pick a Pause, Sheldon had to:

• carefully select a 13-year period for a linear trend (aka cherry-pick)
• avoid an interval just two years longer
• ignore a finding he started out with, that even 15 years is too short to be assured of a meaningful trend
• ignore another finding that non-overlapping trends suggest real differences
• accept that a Pause is not the same as a stop!

Global surface warming continues without pause contrary to denier claims

There's another new paper out in Nature Climate Change today that discusses the recent trends on global surface temperature. It's by a rash of notable authors: John C. Fyfe, Gerald A. Meehl, Matthew H. England, Michael E. Mann, Benjamin D. Santer, Gregory M. Flato, Ed Hawkins, Nathan P. Gillett, Shang-Ping Xie, Yu Kosaka, Neil C. Swart. Anthony Watts heralded the paper (archived here), which is unusual because he normally scoffs at the findings of most of these authors. He referred to an article in the Examiner newspaper, which claims that this paper contradicted "another study last June" that stated that the "the hiatus was just an artifact that “vanishes when biases in temperature data are corrected.”

Well it doesn't contradict it. Needless to say Anthony and the Examiner was comparing apples and oranges.

The new paper, Fyfe16, discussed the reality of the slowdown. There was no "hiatus" or stopping of global warming, contrary to Anthony Watts' headline. The rise in global surface temperatures slowed down earlier this century compared to the rate of rise from the mid-1970s to the late 1990s. As Jeff Tollefson of Nature wrote about the lead author: "Fyfe uses the term “slowdown” rather than “hiatus” and stresses that it does not in any way undermine global-warming theory."

ICYMI - there's no stopping the rise in surface temperature!

In case you missed it (ICYMI), a couple of new papers have been published recently, demonstrating that there has not been any "pause" or "hiatus" in surface temperature in recent years. Yes, the rate of increase wasn't as high as it has been in some other periods. However these papers demonstrate that there was nothing different from what can be expected from a warming trend with interannual variability imposed on it.

Change points of global temperature: Cahill, Rahmstorf and Parnell

If you're a fan of realclimate.org (the benchmark of world best practice in climate blogs), then you might remember the change point analysis written up there last December, by Stefan Rahmstorf. The article was called "Recent global warming trends: significant or paused or what?" This new work looks to be on the same topic written as a peer-reviewed paper in IOP Science: "Change points of global temperature". It's open access so you can read it at your leisure.

The perversity of deniers - and the "pause" that never was with Tom Peterson

Below is a TedX talk from Dr Tom Peterson on "What is Science: How it Differs from Art, Law and Quackery":

Tom quoted Stephen Jay Gould, Harvard geologist, from the video (which provided the title for this article):

Science does not deal in certainty, so "fact" can only mean a proposition affirmed to such a high degree it would be perverse to withhold one's provisional assent.

What follows is copied from a comment posted here at HotWhopper, from Tom Peterson of NOAA, co-author of the new paper in Science, and President of the WMO Commission for Climatology. The email exchange is about a subject of much recent discussion - the new Science paper, which I described here (with lots of links at the bottom for further reading).

Tom has subsequently confirmed the email exchange and kindly gave me permission to repost his comment as a blog article. Apart from remarking on Anthony's conspiracy ideation, there's not really anything more I need add. The exchange speaks for itself - and speaks volumes.

Email exchange between Anthony Watts and Tom Peterson

Dear Sou et al.,

I thought you might find an email exchange I had yesterday with Anthony Watts interesting. 16 hours ago I received this email from Anthony Watts:

More global warming denial from Anthony Watts at WUWT

The denial continues at Anthony Watts' blog WUWT. He's written a few words all by himself, for a change (archived here). (In the past four or five months, Anthony Watts has written almost nothing. He's handed his blog over to his readers to post their nonsense instead of writing his own nonsense. )

Source: Skeptical Science

Today Anthony is denying something that's plain - that the world is warming and climate change is happening. He was writing about a new paper in the journal Nature Climate Change, and he topped and tailed it with some words that he wrote all by himself - in what comes across as frustrated denial that the ice age still hasn't cometh.

Global warming will continue in line with long term projections

The paper is by scientists Matthew H. England, Jules B. Kajtar & Nicola Maher of the ARC Centre of Excellence for Climate System Science at the University of New South Wales. What they did was examine about 200 climate model projections, separating those that showed the sort of slowdown of the past few years from those that didn't.

Not so fast, with that so-called hiatus...

Update: Patrick Brown, the lead author, has just written an article about his paper, at realclimate.org. He is answering some questions in the comments.

Sou 14 May 2015

---

Anthony Watts (archived here) has posted a press release about a new paper in Nature's open access journal, Scientific Reports.  The research was led by Patrick T. Brown, a PhD student Duke University. What the scientists did was compare recent and projected climate change with that which has occurred over the past 1,000 years - mostly in the northern hemisphere (which is where there is most data). They looked at the recent global temperatures and compared them with projections of climate models - and drew what I see as overly-confident conclusions.

I feel a bit stretched on this subject, and am happy to be shown if I'm wrong about this.

A short pause: Bob Tisdale thinks climate models are weather forecasts of the Northern Hemisphere

There's a new paper out in Science mag, which is another one looking at the so-called hiatus. This time it's from a different angle. The researchers, Byron A. Steinman, Michael E. Mann and Sonya K. Miller, were exploring climate models and observations in relation to natural variation. They studied surface temperature variations in the northern hemisphere over the past 150 years.

A temporary respite before more heat kicks in

The abstract sums up the research. The study suggests the supposed pause is merely a coincidence of two features of natural oceanic fluctuations - a peak in the Atlantic Multidecadal Oscillation (AMO) and a strongly negative-trending Pacific Multidecadal Oscillation (PMO). That it is the combined effect of these (in other words, natural variability) that partly offset the ongoing greenhouse warming.

The paper suggests that it may not be long before we get a lot hotter.

Why did the water in the kettle boil? Because it got hot!

WUWT has been really, really quiet since the fiasco with Tim Ball's latest conspiracy blurb and the response. Usually there are anything from three to eight articles a day. There have only been three articles in the past three days, including the fiasco article.

There's one by Willis Eschenbach about a buoy and temperatures. It's too trivial to archive. There's another by "Bob Tisdale", about an article on Ed Hawkins' blog by Geert Jan van Oldenborgh. "Bob's" article isn't worth reading, either, though if you want to do so it's archived here. The article on Ed Hawkin's blog is worth reading.

Dr. van Oldenborgh's article is explaining how there is more energy being stored on earth than is coming in from the sun. He writes how most of it is being accumulated in the ocean.

"Bob" on the other hand doesn't want his readers to hear about that. He's gone off on some tropospheric tangent. He's also gone down the route that deniers go down, foolishly writing:

As we can see, yes, the oceans to depths of 2000 meters (about 1.25 miles) have warmed according to the NODC data, but note the warming rate. It is only +0.03 deg C/decade. That’s read 3 one-hundredths of a deg C per decade, which is a very tiny warming rate. It would be even tinier if we had data for the oceans from the surface to the ocean floor.

"Bob" doesn't mention the enormous heat capacity of the ocean. Just tosses around words like "miniscule" to describe ocean warming, which demonstrates his ignorance or his deceit. Or a mix of the two. Globally, the oceans are now probably as hot as they've been at least since the beginning of civilisation - and it won't stop as long as we insist on turning up the heat. The oceans absorb more than 90% of the extra energy that's being built up in the system. It won't take much for the surface to get quite a bit warmer. Here's a chart I did a while back on the ocean heat content:

Data Source: NOAA

You might recall that scientists have figured out that the oceans in the southern hemisphere have been warming faster - which doesn't show in the above.

There are some interesting charts in Dr. van Oldenborgh's article. He's plotted anomalies of surface temperatures against CO2, putting in the years. Go over and have a look. And while you're there you might think of something worthwhile to add to the comments, to let them know it's not just deniers reading the article :)

"Bob's" circular thinking

"Bob" is getting his excuses lined up for the next bout of global warming, writing:

Global surface temperatures in 2014 are very likely to be at record high levels in 2014. We are going to see that framed in many ways in months to come. However, we understand the reason for those record high levels to be the unusual warming of the eastern North Pacific. 

That's a bit like claiming that the water in the kettle boiled because it got hotter. It didn't boil because you put it on the stove and lit the gas.

From the WUWT comments

There aren't a lot of comments. I'll just pick out two as typical:

Neillusion is very sure what is not causing this very rapid rise in temperatures;

November 29, 2014 at 5:32 am
It is a change, a change from warming to ‘no change’ in temp that has three possible future trends, to start warming again, to stay even, or to start cooling. Until it is known why it warmed in the first place (and was cooling before that), no-one knows which of the three futures it’s gonna be. The only thing I’m personally sure of is that the ‘why’ has nothing to do with CO2

david smith, for some inexplicable reason, thinks that we here will be annoyed about what he thinks is virtually undetectable warming, that has been detected:

November 29, 2014 at 5:02 am
Thank you Bob. Informative as always.
The essential message from this post is (quite correctly) that we have absolutely nothing to worry about, the ocean ‘warming’ is virtually undetectable, and the models have been useless.
They’ll be annoyed over at Hot Whopper. 

Smaller volcanic eruptions helped slow warming, but deniers at WUWT don't believe it

There was a paper that came out last week that you might have heard about. It was by David Ridley from MIT and a team of others, including some very high profile scientists. What they did was investigate the impact of volcanoes over the past few years. They found that the cooling effect of volcanoes since 2000 could be from 0.05°C up to as much as 0.12 °C, which would be quite a bit more than previously thought.

The Sarychev Peak Volcano, on Matua Island, erupted on June 12, 2009.
Credit: NASA via AGU

There have been other recent studies looking at the impact of volcanoes, including by some of the co-authors of this paper. I've written previously about the article by Gavin Schmidt, Drew Shindell and Kostas Tsigaridis,  in a special edition of Nature Geoscience, "Focus on recent slowdown in global warming". That issue also had an article on volcanoes, two of whose co-authors were also co-authors on the Ridley paper.

This new work was different.

What this team did was look particularly at the impact of volcanic aerosols in the stratosphere below 15 km. From satellite observations, scientists know that above 15 km, volcanic eruptions that are smallish in size can perturb incoming solar radiation. David Ridley found that below 15 km in the stratosphere, there has also been a measurable impact by volcanoes.

Don't count on hiatus, volcanoes won't help us

If you thought that global warming was bad enough now, just wait.

I was following up an article at WUWT (archived here), where deniers seem to have discovered for the first time that sulphate aerosols have a cooling effect. I thought they'd have known that by now, but no. More on that below.

In doing so, I found a new paper at GRL, which is a bit of a worry. The paper is "Drivers of decadal hiatus periods in the 20th and 21st Centuries" by Nicola Maher, Alexander Sen Gupta and Matthew H. England from the University of New South Wales.

The scientists figure that there won't be too many hiatus in surface temperatures after 2030, even if there's a large volcanic eruption. It's just going to get a lot hotter, and a lot hotter still if we don't cut CO2 emissions.

Here is the abstract:

The latest generation of climate model simulations are used to investigate the occurrence of hiatus periods in global surface air temperature in the past and under two future warming scenarios. Hiatus periods are identified in three categories, (i) those due to volcanic eruptions, (ii) those associated with negative phases of the Interdecadal Pacific Oscillation (IPO) and (iii) those affected by anthropogenically released aerosols in the mid 20th Century. The likelihood of future hiatus periods is found to be sensitive to the rate of change of anthropogenic forcing. Under high rates of greenhouse gas emissions there is little chance of a hiatus decade occurring beyond 2030, even in the event of a large volcanic eruption.

We further demonstrate that most non-volcanic hiatuses across CMIP5 models are associated with enhanced cooling in the equatorial Pacific linked to the transition to a negative IPO phase.

If you're around much after 2030, best plan ahead. You can look forward to unrelenting warming with maybe a little relief every now and again (relatively speaking) from negative IPO phases or a big volcanic eruption. Below is a figure from the supporting information, which shows the projected effect of volcanoes on the surface air temperature based on the Access 1-0 climate model. Barely a blip, even if there were an equivalent of Krakatau.

SAT (surface air temperature) for the RCP4.5 (blue) and RCP8.5 (red) future scenarios in the ACCESS1-0 model. The effect of two different sized volcanic eruptions, Santa Maria size (dashed lines) and Krakatau sized (dotted lines) if they occurred in 2032 and 2087 are shown. b) Artificial annual radiative forcing from two volcanic eruptions in 2032 and 2087, Santa Maria (dashed black) and Krakatau (purple) sized.
Source: Maher14 Supporting Information

This finding is consistent with the work that was done over the past couple of years by Feulner and Rahmstorf in 2010 and by Meehl et al in 2013, on the effect of a grand solar minimum. Both papers found that there'd be minimal impact on global warming.

Effects of reduction in anthropogenic sulphate aerosols quantified

There are some similarities with the article referred to at WUWT except that was about human interference by way of first dirtying the air and then cleaning it up, rather than aerosols from volcanoes. The paper was also in GRL and was by Pierre Nabat, Samuel Somot, Marc Mallet, Arturo Sanchez-Lorenzo and Martin Wild. What they found was that reduced sulphate aerosols resulted in 23% of the warming and 81% of the brightening in Europe between 1980 and 2012.

The interesting thing was that this seemed to come as a surprise to Anthony Watts and his crew. His rather odd headline was: "The law of unintended climate consequences at work – study says 23% of warming in Europe since 1980 due to clean air laws". Seems like he didn't know that sulphate aerosols are a cooling force. It was almost as if he'd rather have dirty air than global warming.

The other odd thing was the following paragraph, which was probably directly copied from the denier website where Anthony got his article:

Note: Sulfur dioxide is an actual air pollutant, unlike harmless, essential, & beneficial carbon dioxide, despite the widespread scaremongering propaganda labelling CO2 as “carbon pollution”

Well, it's not really odd given that WUWT rejects science. Still, you more commonly read that sort of nonsense in the comments rather than in the main article, unless the main article is by ratbags like Tim Ball or Christopher Monckton.

From the WUWT comments

DS doesn't know about CO2 or aerosol forcing or solar radation and says:

July 25, 2014 at 11:18 am
But…but…but… I was told (obsessively, I might add) that the sun had nothing to do with Temps!
How can less pollution leading to more sun lead to higher temps if the sun has nothing to do with temps?

philjourdan has a very strange view of the world (and the paper) and says:

July 25, 2014 at 11:42 am
So now they want dirty (real) air! It is not enough to just starve all the poor and freeze them. They have to pollute the planet to save it. 

I don't know what is going through Joe Public's mind when he says:

July 25, 2014 at 11:50 am
Let’s not forget that in the UK (at least) the Clean Air Act led directly to the replacement of millions of domestic coal fires with much-more efficient gas fires.
That ensured far less CO2 & ‘waste’ heat being dumped into the atmosphere.
The net change was probably not proportional across Europe, but did the report’s writers factor that into their model? 

Kelvin Vaughan gets it right, especially for places where there are no clean air regulations enforced, when he says:

July 25, 2014 at 12:06 pm
So shutting down all the coal fired power stations will lead to more warming.

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Nicola Maher, Alexander Sen Gupta and Matthew H. England, (2014) "Drivers of decadal hiatus periods in the 20th and 21st Centuries", Geophys. Res. Lett. doi: 10.1002/2014GL060527

Meehl, Gerald A., Julie M. Arblaster, and Daniel R. Marsh. "Could a future “Grand Solar Minimum” like the Maunder Minimum stop global warming?." Geophysical Research Letters 40, no. 9 (2013): 1789-1793.  DOI: 10.1002/grl.50361

Feulner, Georg, and Stefan Rahmstorf. "On the effect of a new grand minimum of solar activity on the future climate on Earth." Geophysical Research Letters 37, no. 5 (2010).  doi:10.1029/2010GL042710, 2010

Pierre Nabat, Samuel Somot, Marc Mallet, Arturo Sanchez-Lorenzo and Martin Wild (2014). "Contribution of anthropogenic sulfate aerosols to the changing Euro-Mediterranean climate since 1980." Geophys. Res. Lett. doi: 10.1002/2014GL060798

Gavin Schmidt & Co have been reconciling climate models and surface temperature observations

Gavin A. Schmidt, Drew T. Shindell & Kostas Tsigaridis have a new article in Nature Geoscience (open access).  What they've done is estimate the impact of actual measures of solar, volcanoes and ENSO on a CMIP5 ensemble.  They found that this reduced the recent difference between models and observations a whole lot.

What they found in particular was the the models most likely overestimated the cooling from the Pinatubo eruption in the 1990s, making the models too cool and, when observed solar radiation, volcanic eruptions and ENSO were factored, in the models are pretty close to observations.

Here is the figure from the paper. Click to enlarge it.

Figure 1: Updated external influences on climate and their impact on the CMIP5 model runs.
a, The latest reconstructions of optical depth for volcanic aerosols9, 10 from the Mount Pinatubo eruption in 1991 suggest that the cooling effect of the eruption (1991–1993) was overestimated in the CMIP5 runs, making the simulated temperatures too cool. From about 1998 onwards, however, the cooling effects of solar activity (red), human-made tropospheric aerosols (green) and volcanic eruptions (pink) were all underestimated. WMGHG, well-mixed greenhouse gases.
b, Global mean surface temperature anomalies, with respect to 1980–1999, in the CMIP5 ensemble (mean: solid blue line; pale blue shading: 5–95% spread of simulations) on average exceeded two independent reconstructions from observations (GISTEMP Land–Ocean Temperature Index (LOTI)6, solid red; HadCRUT4 with spatial infilling7, dashed red) from about 1998. Adjusting for the phase of ENSO by regressing the observed temperature against the ENSO index11 adds interannual variability to the CMIP5 ensemble mean (dashed blue), and adjusting for updated external influences as in a further reduces the discrepancy between model and data from 1998 (black). The adjusted ensemble spread (dashed grey) clearly shows the decadal impact of the updated drivers. As an aside, we note that although it is convenient to use the CMIP5 ensemble to assess expected spreads in possible trends, the ensemble is not a true probabilistic sample.

It's going to get hotter

The authors conclude the following, which won't come as news (or welcome news) to HotWhopper readers (my bold):

We conclude that use of the latest information on external influences on the climate system and adjusting for internal variability associated with ENSO can almost completely reconcile the trends in global mean surface temperature in CMIP5 models and observations. Nevertheless, attributing climate trends over relatively short periods, such as 10 to 15 years, will always be problematic, and it is inherently unsatisfying to find model–data agreement only with the benefit of hindsight. We see no indication, however, that transient climate response is systematically overestimated in the CMIP5 climate models as has been speculated, or that decadal variability across the ensemble of models is systematically underestimated, although at least some individual models probably fall short in this respect.

Most importantly, our analysis implies that significant warming trends are likely to resume, because the dominant long-term warming effect of well-mixed greenhouse gases continues to rise. Asian pollution levels are likely to stabilize and perhaps decrease, although lower solar activity may persist and volcanic eruptions are unpredictable. ENSO will eventually move back into a positive phase and the simultaneous coincidence of multiple cooling effects will cease. Further warming is very likely to be the result. 

Anthony Watts hasn't picked up on this paper yet, but I expect he will sooner or later.

For the record, this is a link to the March 2014 special issue of Nature Geoscience "Recent slowdown in global warming".

Gavin A. Schmidt, Drew T. Shindell & Kostas Tsigaridis, Reconciling warming trends, Nature Geoscience 7, 158–160 (2014) doi:10.1038/ngeo2105 Published online 27 February 2014

A miscellaneous collation: fires, ice and cycles...

There is little to report from denier bloggers this past couple of days. (In Anthony Watts' latest, he's running a competition to see who is the most offensive - "alarmists" or "fake sceptics" - archived here.)

In any case, I've been suffering what I can only describe as heat fatigue (not quite the same as heat exhaustion).  Thankfully a cool change came through yesterday afternoon.  (Last night I slept for nearly 12 hours straight.)

Bushfires rage in Australia

Firefighters who were busy battling blazes across south eastern Australia weren't so fortunate and wouldn't have got much sleep.  They were too busy fighting major fires on the outskirts of Melbourne, in the Latrobe Valley, in far east Gippsland and the southern Flinders Ranges in South Australia as well as elsewhere.  Twenty homes were thought to have been destroyed in Victoria yesterday.

It's been another hot summer down here, with more than our share of days over 40 degrees in south-eastern Australia and up north too.  The fires have been bad, but not as bad as other years.  Below is a comparison of mid-January last year with fires across Australia today:

Some of the people commenting at WUWT seem to think that the world is heading for an ice age, because it's the most snow the USA has seen in 20 years or something.  However there's no hint down under of any ice age cometh-ing.

Feel free to treat this as an open thread and comment about anything at all relating to climate.  Here are a couple of articles to get you going.

How Greenland's ice sheets are melting

First from ScienceDaily.com: Greenland ice sheets are melting from above and below - more measurements are sorely needed. An excerpt:

The paper describes the mechanisms causing the melting of the ice sheet, particularly at its margin, where the glaciers extend into the ocean. This so-called "submarine melting" has increased as the ocean and atmosphere have warmed over the past two decades.

"What a lot of research around Greenland and the fjords has shown is that if the North Atlantic Ocean warms, then these warm waters will rapidly reach the fjords and hence the margins of Greenland's glaciers," says Straneo.

But scientists today know that the situation is more complex than just "a warmer ocean melts ice."

A warmer atmosphere is resulting in increased surface melting above the ice sheet, and this runoff too enhances submarine melting. Surface melt water falls through cracks in the glacier creating a freshwater river that rushes out into the ocean at the base of the glacier, sometimes 600 meters (1,800 feet) below sea level. This river mixes rapidly with the dense, salty seawater, contributing to the heat transfer from the ocean to the ice, resulting in even more submarine melting beneath the sea surface.

Accelerated trade winds over the Pacific

Matthew England from the University of New South Wales and colleagues have a paper in Nature Climate Change, which suggests that stronger than normal trade winds across the Pacific have meant that global surface temperatures haven't risen as much as they might have in recent years.  From the ABC News:

It was found the winds were churning the Pacific like a washing machine, bringing the deeper colder water to the surface and pushing the warmer water below.

"The phase we're in of accelerated trade winds particularly lasts a couple of decades," Professor England said.

"We're about 12 to 13 years in to the most accelerated part of the wind field. "It's important to point out there's a cycle we expect to reverse and when they do reverse back to their normal levels we'd expect global warming to kick in and start to rise."

Professor England rejects the argument from sceptics that the slowdown suggests global warming is not as bad as first thought and that the climate models are not working.

"We want the community to have confidence in the climate models," he said. "They are very good but in this instance the wind acceleration has been that strong and that much stronger than what the models projected."

Cycles in the South

For the cycle afficionados, David W. J. Thompson and Elizabeth A. Barnes have found periodic behaviour in large-scale Southern Hemisphere atmospheric circulation.  From the latest issue of Science (paywalled):

Periodic behavior in the climate system has important implications not only for weather prediction but also for understanding and interpreting the physical processes that drive climate variability.

Here we demonstrate that the large-scale Southern Hemisphere atmospheric circulation exhibits marked periodicity on time scales of approximately 20 to 30 days. The periodicity is tied to the Southern Hemisphere baroclinic annular mode and emerges in hemispheric-scale averages of the eddy fluxes of heat, the eddy kinetic energy, and precipitation. Observational and theoretical analyses suggest that the oscillation results from feedbacks between the extratropical baroclinicity, the wave fluxes of heat, and radiative damping.

The oscillation plays a potentially profound role in driving large-scale climate variability throughout much of the mid-latitude Southern Hemisphere.

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Fiammetta Straneo, Patrick Heimbach. North Atlantic warming and the retreat of Greenland's outlet glaciers. Nature, 2013; 504 (7478): 36 DOI: 10.1038/nature12854

Matthew H England et al. Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus. Nature Climate Change, February 9, 2014; doi:10.1038/nclimate2106

David W. J. Thompson and Elizabeth A. Barnes, Periodic Variability in the Large-Scale Southern Hemisphere Atmospheric Circulation; Science 7 February 2014: Vol. 343 no. 6171 pp. 641-645 DOI: 10.1126/science.1247660

About that "Hiatus" - IPCC climate models and recent observations

This week the fashion is shaping up to be a look at models vs observation.  Some deniers keep saying  the comparison of recent observed surface temperature anomalies with models is not covered in the new WG1 report but all that shows is that those deniers haven't read the WG1 report.  For example, Judith Curry writes (archived here):

What is wrong is the failure of the IPCC to note the failure of nearly all climate model simulations to reproduce a pause of 15+ years.

Once again, Judith Curry is wrong.  I believe she's wrong to call it a "pause of 15+ years", particularly as this starts close to the extremely hot year of 1998 after which the temperature dropped below the trend only to rise higher still later on.  The first decade of this century was the hottest in the instrumental record and 2010 was equal hottest year ever recorded (with 2005).  If I were to say there was a "hiatus" I'd say it started around 2005, which is hardly long enough to even call it a "pause".  The following animated chart illustrates why I say that and so does the chart further down in this article:

Data source: NASA

Regardless of when the "pause" started, Judith is definitely wrong to imply that the report doesn't address the difference between model average and observations in recent years.  (There is a difference between observations and model averages, but the observations are still within the range of modeled temperatures.)

The IPCC WG1 report does note that there is a difference - and at some length.  I started with the technical summary from page TS-26, which has a box labelled:

Box TS.3: Climate Models and the Hiatus in Global-Mean Surface Warming of the Past 15 years

Before getting too worked up about any discrepancy, I thought it worthwhile to look at how well models and observations lined up in the past.  This strikes me as being relevant because models don't claim to match observations closely on a year to year basis.  They are looking at longer periods of time - those relevant to climate change, not weather change.

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