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Michael Hauber

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Comparing modelled and observed warming rates
« on: November 24, 2014, 04:19:24 AM »
GISS warming rate from 1980 to now:  0.155 degrees/decade.
CMIP Multi-model mean warming rate for RCP8.5 from 1980 to end of 2014:  0.233 degrees/decade.

Over the last 35 years models have overestimated the warming rate by 50%.  The multi-model mean anomaly vs 1950-1980 average for 2014 is 0.89.  Monthly values for GISS for 2014 range from 0.43 to 0.78.  Despite all the 'Its breaking records even in a neutral year' rhetoric, temperatures are still cooler than the multi-model mean.

A common non-scientific response is to assume that if the warming rate is slower than modeled over 35 years it must be slower than modeled for any foreseeable future. 

Another non-scientific response is to pretend the fact does not exist, while at the same time pointing to a few recent discoveries of why climate sensitivity might be 'higher' than something else and assume this 'higher' means the multi-model mean.

The correct scientific response is to start looking for reasons why there is a difference.  If co2 causes less warming then presumably someone will find a factor that the models have overlooked, plug it into the models and say 'look the models now match reality'.  But that hasn't happened (so far).  What has happened is that various confounding factors have been found to have contributed some cooling over recent years, which should be considered when trying to make the model vs reality comparison.  Looking at the variety of different factors I sometimes wonder whether combined they could push the warming rate up by enough to get significantly above the multi-model mean.  But no one has done any such calculation that I am aware of.  And if they did, would that mean we simply conclude that Co2 causes more warming than modeled?  Or do we then search for further confounding factors that may have caused some additional warming over the last 35 years?
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crandles

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Re: Comparing modelled and observed warming rates
« Reply #1 on: November 24, 2014, 12:35:47 PM »
Looking at the variety of different factors I sometimes wonder whether combined they could push the warming rate up by enough to get significantly above the multi-model mean.  But no one has done any such calculation that I am aware of.  And if they did, would that mean we simply conclude that Co2 causes more warming than modeled?  Or do we then search for further confounding factors that may have caused some additional warming over the last 35 years?

Are there good enough uncertainty bounds on estimates of each of the variety of different factors? Actually do you believe each central estimate for each of the variety of factors or do you suspect that the researchers may have pushed things to try to explain as much of the discrepancy as possible? Even if they have only pushed things a little, the direction of the remaining error might be wrong.

Even if you disagree with the possibility of the central estimate of the effect being exaggerated by the scientists proposing such an explanation, I expect carefully constructed uncertainty bounds for each factor when 'added' would result in a very wide range so you couldn't be sure which way the remaining error(s) go.

I have no expertise on this, but would point to
http://scienceblogs.com/stoat/2014/09/26/betting-on-sea-ice-with-crandles/#comment-51729
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Neven

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Re: Comparing modelled and observed warming rates
« Reply #2 on: November 26, 2014, 09:55:38 PM »
I know very little about this, but  GCMs are not like weather models in the sense that they predict the temp in any given year or sequence of years, right? In other words, they show that hiatuses can occur, but not when. How low can the 30-year average become because of a hiatus, according to the model mean?

It's obvious that since '98 La Niña has dominated the ENSO cycle, sun spots have been very low, PDO/AMO were negative, China and India have been spewing aerosols like crazy and Arctic amplification isn't measured correctly. Do all these things have an influence on the 30-year mean? If yes, how much? Will the difference become smaller once several or all of those factors flip again?
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Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #3 on: November 28, 2014, 12:10:38 AM »
Average nino 3.4 from July 1998 to Oct 2014 was -0.05.  So more La Nina than El Nino, but I wouldn't say dominated.  It would take 10 months at a nino3.4 value of +1 to push the average back up to 0.  I think SOI may come out a bit more in favour of La Nina though.

There was the period between 02 and 07 that was dominated by el nino, and the hiatus might be as much about temporary warmth between 02-07 as much as it may be about temporary cooling since 2008, which in my opinion is the real start of any pause.  The trend from 1980 to the end of 1998 was 0.160 deg/decade (so including the big spike for 1998), and the trend for GISS from 1980 to now has only gone down to 0.155.  So overall the period from 1998 hasn't really done anything to slow the post 1980 warming trend down. 

Perhaps the warmer years from 02-07 were the start of the warming rate due to Co2 starting to speed up, and the hiatus is other factors temporarily putting the brakes on this.  Or perhaps 02-07 was ahead of the trend due to other factors, and the 08-14 period is other factors swapping from warming to cooling and overall it balances out.
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Neven

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Re: Comparing modelled and observed warming rates
« Reply #4 on: November 28, 2014, 01:38:39 AM »
Quote
There was the period between 02 and 07 that was dominated by el nino, and the hiatus might be as much about temporary warmth between 02-07 as much as it may be about temporary cooling since 2008, which in my opinion is the real start of any pause.

I really don't know much about statistics (or nothing really), but does it matter for the trend whether a very cool year due to La Niña happens at the end of a period, or in the middle of it?

Quote
Despite all the 'Its breaking records even in a neutral year' rhetoric, temperatures are still cooler than the multi-model mean.

I don't know about rhetoric - I'm not a rhetorician  ;) - but it has to mean something when an ENSO neutral year beats a Super El Niño year, even if they are 16 years apart. What happens to the average trend if 2014 is followed by another atmospheric temperature record-breaking 2015 (due to El Niño, if it comes about)? Will that shift those back-to-back La Niñas from a couple of years ago to a less prominent statistical influence?

Sorry for being so stupid and unscientific about this. I'm somewhat impressed by the 'Its breaking records even in a neutral year' rhetoric.  :)
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Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #5 on: November 28, 2014, 02:33:09 AM »
The trend is like a seesaw - the further away from the middle you go the more difference a warmer or cooler than average year makes to the calculation.

And personally I don't like putting emphasis on any individual year's results.  My problem is that I don't know what the 'rhetoric' behind the current temperatures is meant to imply.  No one really says anything specific like 'it proves warming rate must be x', probably because most realise that as just one data point can't prove all that much.  I'm suspicious people are trying to imply more warming than is reasonable.  Put this suspicion down to me being cranky and to bad experiences in the past in the climate wars.  But it does fit in well with the idea that warming is still continuing and that arguing global warming has 'stopped' as opposed to 'paused' is a nonsense.

The most reasonable expectation in my mind is that 2015 should be dramatically warmer than 2014, as el nino warming doesn't impact much until early in the second year.  However I am mindful of 2002 when temperatures increased quite significantly ahead of the 2002/2003 el nino but did not go up any further in 2003.  On the other hand the temperature increase since the end of the 2010/11 la nina has been quite weak and suggests a lot more warming potential in the current ENSO cycle.  The temperature spike for an El Nino is usually quite rapid through December and January with November typically normal, and January typically the peak before a slow decline (the pattern is much more consistent in UAH which I've analysed the most - evidently ENSO influence is amplified above the surface and UAH is influenced strongly by what goes on in the atmosphere above the surface).  I will be watching global temperatures with great interest over the next couple months.....
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bassman

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Re: Comparing modelled and observed warming rates
« Reply #6 on: November 28, 2014, 04:31:42 AM »
Michael,  I have been following surface temps a lot over the last couple of years.  A couple of things I would like to say.  I don't think I have come across a single blog posting, comment, tweet or news story suggesting climate models should be adjusted to the warmer side in response to 2014 temperature anomalies.   2014 is still a strong sign of AGW, considering all the neg natural forcings at play (volcanic activity especially). People say its a neutral year but most people don't notice that the first couple months were influenced by slightly neg ENSO conditions.  It is the PDO, 0-2000 ocean temps that I am also paying close attention to rather than just surface temps.  See link below.

https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/basin_data.html

It's hard to see right now how surface temps don't start to really pick up over the next decade.  Maybe I'm being bold but I don't think surface temps will ever be as low as 2012 again.  One key sign will be a snapping back of DEC-FEB temps in the NH to higher values again.  Hope that helps.

Neven

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Re: Comparing modelled and observed warming rates
« Reply #7 on: November 28, 2014, 09:36:45 AM »
My problem is that I don't know what the 'rhetoric' behind the current temperatures is meant to imply.  (...) But it does fit in well with the idea that warming is still continuing and that arguing global warming has 'stopped' as opposed to 'paused' is a nonsense.

Well, I for one 'use' the rhetoric to counter the global warming has stopped/paused meme, because it hasn't stopped or paused, it slowed down (which is no surprise given all those factors that influence it negatively). And I'm talking about atmospheric global temp, of course, not total accumulated energy in atmosphere + oceans.
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Laurent

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Re: Comparing modelled and observed warming rates
« Reply #8 on: November 28, 2014, 09:39:59 AM »
Great stuff, thanks.

I want to know what is the latest increase in bomb/seconde. I take this file (yearly heat content from 0 to 2000m) :
http://data.nodc.noaa.gov/woa/DATA_ANALYSIS/3M_HEAT_CONTENT/DATA/basin/yearly/h22-w0-2000m.dat

Substract  2013 - 2012 : 18.650-16.187 = 2,463 10y22 joule
Per day : /360 = 6,841666667×10¹⁹
per hour : /24 = 2,850694444×10¹⁸
pers seconde : /60 = 4,751157407×10¹⁶
per Hiroshima bomb : /63.10y12 = 754

754 bomb/seconde ouahou, tell me there is a mistake somewhere ?

Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #9 on: November 28, 2014, 10:41:17 AM »
Divide by 60 again for minutes.
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Laurent

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Re: Comparing modelled and observed warming rates
« Reply #10 on: November 28, 2014, 11:09:16 AM »
Of  course, thanks !
754 / 60  = 12,5 Bombs/seconde  !!!

Laurent

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Re: Comparing modelled and observed warming rates
« Reply #11 on: December 30, 2014, 07:54:56 PM »

Csnavywx

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Re: Comparing modelled and observed warming rates
« Reply #12 on: December 31, 2014, 04:51:49 PM »
http://www.nature.com/ngeo/journal/v7/n9/abs/ngeo2228.html

Removing the effect of ENSO produces trends very close to the central estimate.


Also, I will find the papers, but there were some modeling studies done using ENSO and PAC observations over the last ~15 years and with initial conditions prior to the "hiatus", with the models forced to fit to those cycles and allowed to run normally in other regions. When this occurred, they very accurately hindcasted the slower warming rate, lending credence to their predictions.

The true lynchpin then, is decadal natural variability and how/if it will be affected by AGW in the future.

Let's not also forget that CH4 levels leveled off for quite a few years in the 00's, and we still aren't sure why. This undoubtedly helped put a braking action on radiative forcing. This trend has reversed in the past 3-4 years.

AbruptSLR

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Re: Comparing modelled and observed warming rates
« Reply #13 on: December 31, 2014, 06:37:53 PM »
The following are two reposted Replies from the Antarctic folder's "Forcing" thread (see link below), and there are many other posts there on this topic:

http://forum.arctic-sea-ice.net/index.php/topic,41.msg36230/topicseen.html#msg36230

First Repost: The following reference and the associated extract and attached image indicate that mean global temperature would have increased, during the recent hiatus period, at the rate projected by CMIP5 if not for the variable factors cited below (eg ENSO, volcanoes and incorrect mean global temperature measurements):

Markus Huber & Reto Knutti, (2014), "Natural variability, radiative forcing and climate response in the recent hiatus reconciled", Nature Geoscience, Volume: 7, Pages: 651–656, doi:10.1038/ngeo2228

http://www.nature.com/ngeo/journal/v7/n9/full/ngeo2228.html


Abstract: "Global mean surface warming over the past 15 years or so has been less than in earlier decades and than simulated by most climate models. Natural variability, a reduced radiative forcing, a smaller warming response to atmospheric carbon dioxide concentrations and coverage bias in the observations have been identified as potential causes. However, the explanations of the so-called ‘warming hiatus’ remain fragmented and the implications for long-term temperature projections are unclear. Here we estimate the contribution of internal variability associated with the El Niño/Southern Oscillation (ENSO) using segments of unforced climate model control simulations that match the observed climate variability. We find that ENSO variability analogous to that between 1997 or 1998 and 2012 leads to a cooling trend of about −0.06 °C. In addition, updated solar and stratospheric aerosol forcings from observations explain a cooling trend of similar magnitude (−0.07 °C). Accounting for these adjusted trends we show that a climate model of reduced complexity with a transient climate response of about 1.8 °C is consistent with the temperature record of the past 15 years, as is the ensemble mean of the models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We conclude that there is little evidence for a systematic overestimation of the temperature response to increasing atmospheric CO2 concentrations in the CMIP5 ensemble."

Second Repost: The linked reference shows that a team of researchers from the US National Center for Atmospheric Research (NCAR) and the Centre for Australian Weather and Climate Research (CAWCR) demonstrated that, in certain conditions, current climate models can simulate the pause/hiatus.  This implies that as we leave the pause/hiatus period (that occurred due to natural variability, see the attached figure), that we are moving into a period of accelerated global warming:

Meehl, Gerald A., Haiyan Teng, and Julie M. Arblaster, “Climate model simulations of the observed early-2000s hiatus of global warming,” Nature Climate Change (2014), doi:10.1038/nclimate2357

http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2357.html

Abstract: "The slowdown in the rate of global warming in the early 2000s is not evident in the multi-model ensemble average of traditional climate change projection simulations. However, a number of individual ensemble members from that set of models successfully simulate the early-2000s hiatus when naturally-occurring climate variability involving the Interdecadal Pacific Oscillation (IPO) coincided, by chance, with the observed negative phase of the IPO that contributed to the early-2000s hiatus. If the recent methodology of initialized decadal climate prediction could have been applied in the mid-1990s using the Coupled Model Intercomparison Project Phase 5 multi-models, both the negative phase of the IPO in the early 2000s as well as the hiatus could have been simulated, with the multi-model average performing better than most of the individual models. The loss of predictive skill for six initial years before the mid-1990s points to the need for consistent hindcast skill to establish reliability of an operational decadal climate prediction system."
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Csnavywx

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Re: Comparing modelled and observed warming rates
« Reply #14 on: January 06, 2015, 06:40:23 PM »
You can't really use Nino 3.4 trends to accurately portray the effects of ENSO on global temperature trends. Part of the reason is due to the small size of the area and the nature of ENSO events themselves. We have had a couple of El Nino events which were more central and western based over the past 10-12 years which skew the trend numbers too warm if you're just using 3.4. Using 1-4 would be better, and using a system like Rahmstorf did to isolate ENSO/Tropical pacific effects from the rest of the globe is even better:

http://iopscience.iop.org/1748-9326/6/4/044022

Tamino did a good post on this a few years back and it is still relevant today:

http://tamino.wordpress.com/2011/12/06/the-real-global-warming-signal/

wili

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Re: Comparing modelled and observed warming rates
« Reply #15 on: January 15, 2015, 04:46:55 PM »
https://www.skepticalscience.com/kevin_cowtan_agu_fall_2014.html

This is a wide ranging discussion on media, policy and other things. But the part most relevant to this thread seemed to me to be this passage:

Quote
The two sea surface temperature series are shown in figure 4. When we use ERSSTv4 instead of HadSST3, two things happen:

    Recent temperature trends increase still further, because ERSSTv4 includes the correction for the transition from engine room intake to buoy observations. Using ERSSTv4 the 'hiatus' is a fairly insignificant affair.
    The climate sensitivity drops, due to warmer sea surface temperatures in the 19th century in ERSSTv4.

Why are the ERSSTv4 sea surface temperatures higher in the 19th century? The differences arise from a correction applied to early sea surface temperature observations. Early readings were taken by lifting water to the deck of a ship in a bucket, and measuring its temperature. The water cools during the process, leading to a bias which varies according to a number of factors, including the height of the ship's deck. ERSSTv4 does not show the expected decline in bucket correction with the lower ship deck heights in the 19th century.

The bucket correction is large, so this could be a big effect, and yet I have never seen a climate paper discussing the impact of 19th century ship design on estimates of climate sensitivity.
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crandles

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Re: Comparing modelled and observed warming rates
« Reply #16 on: January 15, 2015, 06:07:09 PM »
Wili re your comment there, perhaps it might have been
http://www.realclimate.org/index.php/archives/2008/06/of-buckets-and-blogs/

or maybe
The recent IPCC report had a thorough description of these issues (section 3.B.3) fully acknowledging that these corrections are a work in progress.

While this discusses buckets, it isn't a discussion of 19th Century ship height or design. Also if "practices varied enormously among ships and fleets and over time" then it probably isn't as simple as cooling increasing with deck height.

wili

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Re: Comparing modelled and observed warming rates
« Reply #17 on: January 15, 2015, 10:05:42 PM »
Thanks, crandles. That was probably it.
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #18 on: January 16, 2015, 11:33:00 PM »
Note that my observation in the original post is based on the temperature trend from 1980 to now.  Which is a different issue to the 'pause'.  The cooler years after 2008 will of course contribute to the pause and a reduced trend from 1980.  However warmer years from 2002 to 2006 have increased the trend from 1980 to now at the same time as they have contributed to a reduction in trends such as from 1998 or from 2002.

For instance GISS trend 1980 to end of 2001 is 0.154 deg/decade
From 1980 to end of 2006 is 0.180 deg/decade
From 1980 to now is  0.155 deg/decade.

From these figures its quite possible that the pause is a transition from a warm natural variation from 1998 to 2006 to a cool natural variation from 2007 to 2013.  Overall these variations cancel out - note that the trend from 1980 to 2001 is almost exactly the trend from 1980 to now (although arguably the trend should have increased instead of staying the same.  Anyone motivated enough to check the models? I'm feeling lazy...)  So an explanation for the pause is not an explanation for the slower trend from 1980 to now.
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Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #19 on: January 28, 2015, 01:39:24 AM »
I got around to looking at CMIP projections vs actual GISS trends for before the pause.

First, the pause is commonly pegged as starting in 1998.  So running trends from 1980 to the end of 1997:

GISS:  0.120/decade
CMIP:  0.124/decade

Pretty spot on - perhaps the 'pause' is the only difference between actual and modelled?

But 1980-1997 is a much shorter time period and is dominated by two key volcanic eruptions.  Also a better understanding of the 'pause' in my opinion would start the pause in 2007.  The years 1998-2006 were ahead of the trend, and it is the comparison of these warm years to the cooler (compared to the trend) years from 2007 to 2014 that gives a 16 year trend with very little warming.  To illustrate this consider the trends to the end of 2006:

GISS:  0.179
CMIP:  0.226

Note how the years 1998-2006 increase the GISS trend by nearly 50%.  The first half the pause wasn't much of a pause was it?  Note also that the addition of these nine years increases the CMIP trend by 82%, whereas adding the next 8 years up to 2014 only increases it by 3%, which I believe reflects a possible issue with the modelling of the Pinatubo and Chicon volcanic eruptions.

Another thought is to push the start date from 1980 to 1975.  Tamino has previously stated that a break point analysis suggests that about 1975 is the start of the modern warming trend.

1975 to end 1997:

CMIP 0.136
GISS 0.161

warming faster than the model, and again the question mark around the volcano.

1975 to end 2006:

CMIP 0.207
GISS 0.188

this is about the fastest warming trend in GISS I can find.  Close to but not quite equal to the model warming rate.  This would be my choice as the best date range to do a comparison of pre-pause actual warming rate vs model warming rate.

1975 to end 2014

CMIP: 0.219
GISS: 0.166

And this is what the warming rate looks like after the 'pause', going back to 1975 instead of 1980.
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Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #20 on: January 28, 2015, 11:40:17 PM »
And why not look at 1900-2014 as well:

CMIP: 0.079
GISS: 0.082

Here the models are pretty much spot on, (slightly behind the observed warming rate).  I don't fully trust the data prior to about 1980, but that might make the real figure higher as easily as it could make it lower.
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Steven

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Re: Comparing modelled and observed warming rates
« Reply #21 on: January 29, 2015, 08:02:18 PM »
...which I believe reflects a possible issue with the modelling of the Pinatubo and Chicon volcanic eruptions.

Schmidt et al. 2014 suggests that the cooling effect (in the early 1990s) of the Pinatubo eruption was overestimated in the CMIP5 model runs.  The following quote is from the caption of Figure 1a in that paper:

Quote
The latest reconstructions of optical depth for volcanic aerosols 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.

wili

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Re: Comparing modelled and observed warming rates
« Reply #22 on: March 10, 2015, 05:48:08 PM »
Romm covering predicted acceleration in the rate of warming: http://thinkprogress.org/climate/2015/03/10/3631632/climate-change-rate/



Global rates of decadal temperature change over 40-year periods. Results are shown for: central climate assumptions (thick solid line), range due to uncertainty in aerosol forcing (grey shading), and range due to uncertainty in climate sensitivity (blue shading). The outer bounding cases are shown as dotted lines. The thin solid black line shows the historical rate of change using the HADCRU4 observational data. The vertical dashed line indicates 2014. Via PNNL.

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Re: Comparing modelled and observed warming rates
« Reply #23 on: March 10, 2015, 08:03:19 PM »
It is obvious that the GCMs are significantly understating the negative forcing effects of tropospheric sulfates as well as regional deposition rates on the pacific decadal oscillation, resulting in the recent negative phase.
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Re: Comparing modelled and observed warming rates
« Reply #24 on: June 10, 2015, 07:08:17 AM »
The Real Climate article on the NOAA update has nice charts comparing temperature history to both the CMIP5 (ran 2013ish) and CMIP3 (ran 2000ish) model runs:




For the CMIP5 runs they include an adjusted projection in dotted lines which takes into account the cooling effect of volcanic and solar effects.

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Re: Comparing modelled and observed warming rates
« Reply #25 on: June 15, 2015, 07:19:15 PM »
Recent papers that show PMO and AMO impacts on recent decades with increasing uncertainty regarding the impacts of anthropogenic aerosols during this period:

Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures
Byron A. Steinman,1 * Michael E. Mann, 2 Sonya K. Miller2
http://www.les-crises.fr/wp-content/uploads/2015/04/SteinmanEtAlScience15.pdf
24 June 2014; accepted 26 January 2015
10.1126/science.1257856

Quote
Our findings (the AIE experiments, especially) suggest that natural internal variability has had a modest influence on Atlantic SST over the past half century and that multidecadal climate variability attributed to Atlantic SST changes (such as variations in tropical storm frequency and strength and Sahel and Midwestern North American drought) (48–51) was largely driven by external forcing (as concluded in other recent work) (52). Our results also highlight the  substantial uncertainties associated with the role of anthropogenic aerosol forcing in recent decades because the greatest discrepancies using the three different ensembles occur during that time period.

Impact of aerosol radiative effects on 2000–2010 surface temperatures
A. Gettelman · D. T. Shindell · J. F. Lamarque
http://www.cgd.ucar.edu/staff/andrew/papers/gettelman2015aerorecent.pdf
DOI 10.1007/s00382-014-2464-2
Clim Dyn
Received: 15 September 2014 / Accepted: 25 December 2014

Quote
It is possible that the aerosol forcing pattern may force modes of variability in the earth system, such as forcing in the North Atlantic that may alter the meridional overturning
circulation for example, which we do not capture in the slab ocean (CESM) or short coupled (ModelE2) simulations. We have considered the major effect of aerosols on clouds through sulfate, but other responses (e.g., from nitrate) that are neglected here are possible. Pattern correlations are suggestive that there is an aerosol imprint on the temperature response. With the internal variability and the strength of the aerosol-induced response in these two models it’s extremely difficult to detect the influence of aerosols over this time period.

Influence of aerosols in multidecadal SST variability simulations over the North Pacific
Boo et. al
First published: 23 January 2015Full publication history
DOI: 10.1002/2014JD021933
http://onlinelibrary.wiley.com/doi/10.1002/2014JD021933/full

Quote
In summary, in this study we find that aerosol processes play an important role in explaining simulated multidecadal SST variability between the 1920s and 1990s, over the North Pacific. The simulated change from warm to cool conditions represents many characteristics of the observed temporal and spatial SST response, although the simulated amplitude of change is larger and occurs somewhat earlier. Prior to this period, both the historical experiments, with and without aerosol changes, show forced SST variability linked to the eruption of Krakatoa, and the results are of a larger magnitude than those of the observed. Unlike in the Atlantic [Booth et al., 2012], the anthropogenic aerosol effects start to play a role after the 1920s.
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Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #26 on: June 16, 2015, 08:01:41 AM »
Some further interesting quotes from those papers:

Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures
Byron A. Steinman,1 * Michael E. Mann, 2 Sonya K. Miller2

Quote
Using this method, the AMO and PMO are found to explain a large proportion of internal variability in Northern Hemisphere mean temperatures.

(which they call the NMO)
Quote
Our analysis shows the NMO to be decreasing at the end of the series...That observation
is consistent with recent findings that the anomalous slowing of warming over the past decade
is tied to subsurface heat burial in the tropical Pacific....Our analysis attributes this trend to internal variability as a consequence of the failure of the CMIP5 models to identify a recent forced trend of this nature. However, there is paleoclimate evidence suggesting that a La Niña – like response might arise from positive radiative forcing (47), and the possibility remains that state-of-the-art climate models fail to capture such a dynamical response to anthropogenic radiative forcing

I'm not really sure what they are getting at when they talk about the uncertainties with anthropogenic aerosol forcing.  Their analysis does seem to be arguing that the recent slowdown is a result of natural variability rather than aerosols, and they discuss the possibility that the recent natural variability may be due to a positive radiative forcing, and of course aerosols are a negative radiative forcing.  This does seem speculative, so this doesn't rule out the possibility that the NMO may actually be driven by aerosol changes.



Impact of aerosol radiative effects on 2000–2010 surface temperatures
A. Gettelman · D. T. Shindell · J. F. Lamarque

Quote
Pattern correlations indicate significant correlations between observed decadal surface temperature changes and simulated surface temperature changes from recent sulfate aerosol forcing in an equilibrium framework.  Sulfate ACI might be a contributor to the spatial patterns
of recent temperature forcing, but not to the global mean ‘hiatus’ itself.

This paper argues that aerosols did not contribute to the 'hiatus'.



Influence of aerosols in multidecadal SST variability simulations over the North Pacific
Boo et. al

Quote
This study uses seven historical simulations of the HadGEM2-AO for Coupled Model Intercomparison Project phase 5 (CMIP5) contribution

Quote
The simulated change from warm to cool conditions represents many characteristics of the observed temporal and spatial SST response, although the simulated amplitude of change is larger and occurs somewhat earlier. Prior to this period, both the historical experiments, with and without aerosol changes, show forced SST variability linked to the eruption of Krakatoa, and the results are of a larger magnitude than those of the observed.

The simulated response to aerosols appears to be stronger than what is observed, implying a lower amount of aerosol cooling, and therefore a lower amount of warming if and when the aerosols are removed in the future.
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jai mitchell

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Re: Comparing modelled and observed warming rates
« Reply #27 on: June 16, 2015, 08:11:08 PM »

This paper argues that aerosols did not contribute to the 'hiatus'.

The purpose of this post was not to show that Aerosols are being attributed as the cause of the false hiatus.  It was to show that recent modelling efforts has shown that the false hiatus was shown to be a northern hemisphere event related to internal variability and that the role of aerosols on this period may be significant but the models are unable to wean out the values. (the steinman paper)

Then to show that highest level of modelling of aerosols is not yet able to determine the impact on the internal variability but temperature patterns in the northern hemisphere suggest there may be significant correlation.  (Gettelman paper, which is excellent btw  ;D

from that paper, read it again:

Quote
Pattern correlations are lower in the full coupled simulations with ModelE2. Aerosols may be contributing to the regional pattern of forcing, but do not appear be the dominant factor leading to the ‘hiatus’ in warming (if it exists). It is possible that the aerosol forcing pattern may
force modes of variability in the earth system, such as forcing in the North Atlantic that may alter the meridional overturning circulation for example, which we do not capture in the slab ocean (CESM) or short coupled (ModelE2) simulations. We have considered the major effect of aerosols
on clouds through sulfate, but other responses (e.g., from nitrate) that are neglected here are possible. Pattern correlations are suggestive that there is an aerosol imprint on the
temperature response. With the internal variability and the strength of the aerosol-induced response in these two models it’s extremely difficult to detect the influence of aerosols
over this time period


Influence of aerosols in multidecadal SST variability simulations over the North Pacific
Boo et. al

Quote
The simulated response to aerosols appears to be stronger than what is observed, implying a lower amount of aerosol cooling, and therefore a lower amount of warming if and when the aerosols are removed in the future.

I am assuming you are referring to figure 3 of the paper, if so, then your reading of the values is incorrect.  The variability of SST is high but the ensemble spread covers that variability.  Toward the later half of the century the values correlate very well.

again, the study looked only at SST and the correlation to anthropogenic aerosols in the northern hemisphere.  This paper shows quite clearly that there is correlation in the northern hemisphere to SST and implicates an impact that is theorized in the previous 2 papers that there may be an additional forcing mechanism resulting from anthropogenic aerosol effects on sea surface temperature decadel and mulit-decadel oscillations.
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TheWeatherMan

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Re: Comparing modelled and observed warming rates
« Reply #28 on: June 16, 2015, 10:22:25 PM »
I think the recent PDO spike will lead to more nino events which will build system inertia and carry us very close to or over CIMP5 modeled values.

Our closed system has a fair amount of inertia (sort of like a pot of boiling water).  It takes several years for a series of ninos to really spike the global temperatures and vice versa.  The year 1999 and 2000 are a perfect example.  The effect of the 1998 nino was proven to carry on nearly 3-4 years after the peak MEI occured.  It takes several years for all that heat to flush out of the system.

The opposite is also true, which I believe is a large chunk of our current "hiatus."  We've been ENSO negative (below 0 ONI) for a whopping 75% of the time between 2008-2014.  It will take several years for natural heat to build back into the system and really expose the anthropogenic signal if this is truly a phase shift.

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Re: Comparing modelled and observed warming rates
« Reply #29 on: June 17, 2015, 11:25:10 AM »

The purpose of this post was not to show that Aerosols are being attributed as the cause of the false hiatus.  It was to show that recent modelling efforts has shown that the false hiatus was shown to be a northern hemisphere event related to internal variability and that the role of aerosols on this period may be significant but the models are unable to wean out the values. (the steinman paper)

The topic of this thread is comparing modelled and observed warming rates.  Are you are claiming that aerosols have a greater impact on global temperatures than the models currently include despite the fact that statements from all three papers contradict this assertion?  Or are only pointing out that aerosols have an influence on modes of regional variability such as PDO and AMO without influencing global temperatures (beyond what is currently included in the models)?  That is an interesting issue, but has nothing to do with the topic at hand.

If the hiatus is false, why are you posting papers that claim to explain what caused it?

If the hiatus is real then the global warming rate will go up when the hiatus is over.  If the hiatus is false then there can't be any increase in warming rate due to the hiatus being over.

from that paper, read it again:

I'd already read the bit talking about aerosols having a regional influence.  Did you read the bit two sentences later about the aerosols having no influence at the global scale?

I am assuming you are referring to figure 3 of the paper, if so, then your reading of the values is incorrect.  The variability of SST is high but the ensemble spread covers that variability.  Toward the later half of the century the values correlate very well.
No I refer to the sentence I quoted directly from that paper which states that the modelled impact of aerosols was higher than the observed impact of the aerosols.
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jai mitchell

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Re: Comparing modelled and observed warming rates
« Reply #30 on: June 17, 2015, 05:06:13 PM »
Aerosols are driving the PDO

The "pause" is false.

The papers show that there is a pattern of localized aerosol deposition in the troposphere that indicates a potential driver for (what was previously considered to be) natural variability in the AMO and the PDO, both of which are primary forces leading to a lack of increase in temperatures that the climate models expected over the last decade.


No I refer to the sentence I quoted directly from that paper which states that the modelled impact of aerosols was higher than the observed impact of the aerosols.

If you bothered to read the actual paper you would see that there was increased impact in both the cooling and subsequent warming of the Krakatoa event on SST, that you have not only misunderstood the statement that you quoted but you also then applied it to the overall results of the paper which yields a very different conclusion than the paper's authors.

Oh, I forgot! That is what you always do, every time!
« Last Edit: June 17, 2015, 05:23:54 PM by jai mitchell »
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Re: Comparing modelled and observed warming rates
« Reply #31 on: June 18, 2015, 03:12:41 AM »
If you bothered to read the actual paper you would see that there was increased impact in both the cooling and subsequent warming of the Krakatoa event on SST, that you have not only misunderstood the statement that you quoted but you also then applied it to the overall results of the paper which yields a very different conclusion than the paper's authors.

Oh, I forgot! That is what you always do, every time!

As directly quoted from the last paragraph of the paper:

Quote
In summary, in this study we find that aerosol processes play an important role in explaining simulated multidecadal SST variability between the 1920s and 1990s, over the North Pacific.  The simulated change from warm to cool conditions represents many characteristics of the observed temporal and spatial SST response, although the simulated amplitude of change is larger and occurs somewhat earlier. Prior to this period, both the historical experiments, with and without aerosol changes, show forced SST variability linked to the eruption of Krakatoa, and the results are of a larger magnitude than those of the observed.

In summary: This is the key conclusion of the author

explaining simulated multicecadal SST variability:  Not observed, but simulated.  The paper finds that the impact of aerosols on variability is in the models.  The models used in this paper are CMIP5.

simulated amplitude of change is larger:  And the variability in the the models is larger than what is observed. So it cannot explain any of the difference between observed and modelled temperature trends, which would require a larger effect in the observations than in the models.
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jai mitchell

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Re: Comparing modelled and observed warming rates
« Reply #32 on: June 18, 2015, 08:24:50 PM »
In your quote when they say, "prior to that period" they mean pre-1920.

here is the graphic of the variability of the runs pre-1920 and after.




Your quoted statement doesn't mean what you say it will mean but even so, your very basis of comparison is a falsehood since you 

  • don't show what the modeled values are hence making the comparison a false one
  • pan over the longer-range implications of the study wrt the Aleutian Low and climate impacts all over the world (e.g. the California drought)
  • use a tactic of misdirection since the SST values are not at issue what is at issue is the FACT that the fingerprint of aerosol driving SST variability is being determined.  This is the whole point , that the long-term negative PDO in the pacific over the last 15 years has largely been driven by south east asian aerosols.


By using a tactic of misdirection and then a type of gish gallop (where you assert that the pre-1920 model results indicate that the paper's results are supposed to be about the VALUE of SST change not the DRIVER of SST multidecadel variability)  you have taken considerable amounts of time and effort away from my day so that I can correct your falsehoods.

So, you use the proved tactics of misdirection and gish galloping as a way to skew the conversation away from the very basic results that I laid out, because?

Quote
you are here to simply disrupt discussions, using practiced disruption techniques taken from the denialist community.  No wonder ASLR left.

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Re: Comparing modelled and observed warming rates
« Reply #33 on: June 18, 2015, 10:25:05 PM »
since we are talking about model rus vs. observations........

any chance this is where the "missing heat" went?

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Re: Comparing modelled and observed warming rates
« Reply #34 on: June 19, 2015, 04:47:21 AM »

  • don't show what the modeled values are hence making the comparison a false one
  • pan over the longer-range implications of the study wrt the Aleutian Low and climate impacts all over the world (e.g. the California drought)
  • use a tactic of misdirection since the SST values are not at issue what is at issue is the FACT that the fingerprint of aerosol driving SST variability is being determined.  This is the whole point , that the long-term negative PDO in the pacific over the last 15 years has largely been driven by south east asian aerosols.



1)  I didn't make the comparison.  The authors of the paper made the comparison and I quoted them.  It is you that are using the tactic of misdirection.
2) This has nothing to do with a comparison of modelled and observed global temperature trends.  It is you that are using the tactic of misdirection.
3) The fact that there is a relationship between aerosols and SST is not relevant to explaining a difference between modelled and global temperature trends.  It can only be relevant if this relationship is stronger than what is included in the models.  The modelled relationship between aerosols and North Pacific SST variability is stronger than what is observed.  Therefore this is not evidence that the relationship between aerosols and global temperature is stronger than what is included in the models.
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Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #35 on: June 19, 2015, 05:06:08 AM »
since we are talking about model rus vs. observations........

any chance this is where the "missing heat" went?

I'm pretty sure the total raw heat energy required to melt that amount of ice is nowhere near enough to explain the difference in global temperature.  However it wouldn't surprise me if the same factor was contributing to both differences, and that potentially in the future this factor could reverse and we wind up in a world that is warmer than the models predict, but has more Arctic sea ice than predicted.

It is also worth noting that this comparison is not with the CMIP5 models used for the latest IPCC assessment report.   From memory I think its CMIP3.  A comparison of CMIP5 modelled Arctic ice vers observations can be found from the 4th page of Hezel et al
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AbruptSLR

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Re: Comparing modelled and observed warming rates
« Reply #36 on: July 10, 2015, 04:34:00 PM »
The linked research promises more accurate projections of CO₂ induced global warming:

Oleg L. Polyansky, Katarzyna Bielska, Mélanie Ghysels, Lorenzo Lodi, Nikolai F. Zobov, Joseph T. Hodges, and Jonathan Tennyson (15 June 2015), "High-Accuracy CO 2 Line Intensities Determined from Theory and Experiment", Phys. Rev. Lett. 114, 243001.


http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.114.243001

Abstract: "Atmospheric CO 2 concentrations are being closely monitored by remote sensing experiments which rely on knowing line intensities with an uncertainty of 0.5% or better. Most available laboratory measurements have uncertainties much larger than this. We report a joint experimental and theoretical study providing rotation-vibration line intensities with the required accuracy. The ab initio calculations are extendible to all atmospherically important bands of CO 2 and to its isotologues. As such, they will form the basis for detailed CO 2 spectroscopic line lists for future studies."


See also:
http://www.climatenewsnetwork.net/quantum-leap-taken-in-measuring-greenhouse-effect/
Extract: "British scientists have devised a new way to observe the greenhouse world, enabling researchers to measure with exquisite accuracy how atmospheric carbon dioxide builds up, migrates, evolves and absorbs radiation.
The technique will allow more accurate predictions about how much the Earth is likely to warm over the next few decades as a result of the inexorable rise in atmospheric CO2 – from car exhausts, power station chimneys and burning forests – that drives global warming and climate change.
More than a century has elapsed since the Swedish Nobel laureate Svante Arrhenius first predicted the greenhouse effect, but scientists have until now only been able to establish the way CO2 absorbs light, with accuracies of about 5% at best.
But Oleg Polyanksy and Jonathan Tennyson, professors in the Department of Physics and Astronomy at University College London, and colleagues report in the journal Physical Review Letters that they can exploit the laws of quantum mechanics to narrow the uncertainty to 0.3%.
The consequence is that a range of dedicated satellite missions – among them Japan’s Greenhouse Gas Observing Satellite (GOSAT), the US space agency NASA’s Orbiting Carbon Observatory-2 (OCO-2) and potential European Space Agency missions such as CarbonSat − will not just be able to identify industrial sources of CO2 and map their spread, but watch the gas in action, slowly warming the planet by as much as 5°C by 2100."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Michael Hauber

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Re: Comparing modelled and observed warming rates
« Reply #37 on: July 31, 2015, 01:27:29 AM »
Climate models (CMIP5) with updated forcings (yes, unheard of, but somehow people failed to predict volcanic eruptions...) are fully in line with the observations (and do _NOT_ overpredict temperature rise), and they do have ECS between 2.1 and 4.5K.
http://onlinelibrary.wiley.com/doi/10.1029/2012GL051607/full


As I've posted above models seem to overpredict temperature rise slightly (but well within a reasonable bound for expected error).  I'm not sure how the referenced paper is relevant to comparing model to observed trends, as the abstract states an estimate for equilbrium climate sensitivity and not for transient sensitivity, and when I quickly scan the paper I don't seem to see anything like a model-observation comparison.
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Re: Comparing modelled and observed warming rates
« Reply #38 on: July 31, 2015, 07:13:22 AM »
Plinius has posted a link to a paper on another thread that is quite relevant here me thinks.

It is this new paper from Kevin Cowtan  in GRL (he was the one who used kringing [whatever that is  :-\] to fill the data-gap in the arctic regions in the Hadcrut4 dataset, if I remember correctly).

If I understand it right, the paper shows that until now, the comparison between measured and modeled temperatures was done wrong. Simply put: We did not compare apples with apples. If we do (and that seems to be quite difficult), 38%  of the difference between observed and modeled temperatures is gone (period 1975 -2014) . Add the historical ENSO values and the volcanic forcing - and the gap disappears completely. Or what do you think?

See also the post from Tamino on the paper.

PS: Here is a blog post from Kevin Cowtan himself on the paper, very interesting read (see also the image at the end which has the following explanation: "Figure 5: Comparison of models to observations using the IPCC method and the correct method. Thin lines are annual mean temperatures, thick lines are the trends on the period since 1975. (The data in this case are not global, but restricted to where HadCRUT4 has coverage.)").

And here is a post from Sou about the paper.

Abstract :
Quote
The level of agreement between climate model simulations and observed surface temperature change is a topic of scientific and policy concern. While the Earth system continues to accumulate energy due to anthropogenic and other radiative forcings, estimates of recent surface temperature evolution fall at the lower end of climate model projections. Global mean temperatures from climate model simulations are typically calculated using surface air temperatures, while the corresponding observations are based on a blend of air and sea surface temperatures. This work quantifies a systematic bias in model-observation comparisons arising from differential warming rates between sea surface temperatures and surface air temperatures over oceans. A further bias arises from the treatment of temperatures in regions where the sea ice boundary has changed. Applying the methodology of the HadCRUT4 record to climate model temperature fields accounts for 38% of the discrepancy in trend between models and observations over the period 1975-2014.
« Last Edit: July 31, 2015, 07:46:55 AM by S.Pansa »

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Re: Comparing modelled and observed warming rates
« Reply #39 on: August 03, 2015, 02:02:40 PM »
There's a questions and answers session today on reddit.com/r/science featuring the authors of the recent paper:
"Robust comparison of climate models with observations using blended land air and ocean sea surface temperatures"

The authors taking part are

Zeke Hausfather
Ed Hawkins
Peter Jacobs
Michael Mann
Robert Way
and perhaps some others if they have time

Here's there intro

Hello there, /r/Science[1] !
We* are a group of researchers who just published a paper[2] showing previous comparisons of global temperatures change from observations and climate models were comparing slightly different things, causing them to appear to disagree far more than they actually do.
The lead author Kevin Cowtan has a backgrounder on the paper here[3] and data and code posted here[4] . Coauthor /u/ed_hawkins [5] also did a background post on his blog here[6] .
Basically, the observational temperature record consists of land surface measurements which are taken at 2m off the ground, and sea surface temperature measurements which are taken from, well, the surface waters of the sea. However, most climate model data used in comparisons to observations samples the air temperature at 2m over land and ocean. The actual sea surface temperature warms at a slightly lower rate than the air above it in climate models, so this apples to oranges comaprison makes it look like the models are running too hot compared to observations than they actually are. This gets further complicated when dealing with the way the temperature at the sea ice-ocean boundaries are treated, as these change over time. All of this is detailed in greater length in Kevin's backgrounder and of course in the paper itself.
The upshot of our paper is that climate models and observations are in better agreement than some recent comparisons have made it seem, and we are basically warming inline with model expectations when we also consider differences in the modeled and realized forcings and internal climate variability (e.g. Schmidt et al. 2014[7] ).
You can read some other summaries of this project here[8] , here[9] , and here[10]


Here's the link https://www.reddit.com/r/science/comments/3flzb4/science_ama_series_climate_models_are_more/
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel