IPCC AR5: Unprecedented uncertainty

Since it is one of my core objectives with Energy Matters to place the veracity of climate science under the microscope I can hardly avoid commenting on the IPCC AR5 Summary for Policy Makers that was published on Friday 27th September. The IPCC (International Panel on Climate Change) is charged by The United Nations to advise the global community on the risks posed by Man made climate change, in particular the risk of global warming caused by the accumulation of carbon dioxide (CO2) in the atmosphere. Every several years the IPCC publish a mammoth report that only a few specialists read but as a prelude to this they publish an abridged Summary for Policy Makers that is widely read.

Download The Summary for Policy Makers here. AR5 is the 5th assessment report, AR4 was published in 2007.

Global warming has paused

This chart, lifted from IPCC AR5, shows how global surface temperatures have evolved in the last 150 years. The data comes from a large number of surface thermometer measurements. Warming has occurred in two stages, 1910 to 1945 and 1985 to 1998. Between these up legs are periods when temperatures have moved sideways or slowly down for a number of decades. Unfortunately for the IPCC and climate science in general (but fortunately for planet Earth) warming has paused since 1998 with 15 years of sideways fluctuating temperatures. This is unfortunate for the IPCC since none of the computer simulations that forecast future climate change, produced a decade ago, predicted this pause in warming. Clearly something is wrong, either with the models or, more likely, with the input data.

When confronted with data that does not fit a theory or model, good scientists should update that theory or model, and this in fact appears to have happened in AR5, partially at least. In essence, with warming proceeding more slowly than previously predicted, it seems that CO2 is a less potent warming agent than previously perceived, a point made by Otto et al (2013) [1].

AR5 deals with this on page 11:

The equilibrium climate sensitivity quantifies the response of the climate system to constant radiative forcing on multi-century time scales. It is defined as the change in global mean surface temperature at equilibrium that is caused by a doubling of the atmospheric CO2 concentration. Equilibrium climate sensitivity is likely in the range 1.5°C to 4.5°C (high confidence), extremely unlikely less than 1°C (high confidence), and very unlikely greater than 6°C (medium confidence)16. The lower temperature limit of the assessed likely range is thus less than the 2°C in the AR4, but the upper limit is the same. This assessment reflects improved understanding, the extended temperature record in the atmosphere and ocean, and new estimates of radiative forcing. {TFE6.1, Figure 1; Box 12.2}

The pause in warming has therefore led the IPCC to extend the range of possible climatic response to a doubling of CO2 downwards, the lower limit moving from 2˚C to 1.5˚C. This lower, lower limit, in fact moves us away from the danger zone and is to be welcomed. The range of uncertainty has gone up, the result of improved understanding, leaving policy makers with a hopelessly wide range of uncertainty to work with – everything from “nothing to worry about” to “catastrophic meltdown” remains in the policy scenario space.

Let’s put this into context. An equilibrium climate sensitivity of 1.5˚C would leave Earth a manageable 3˚C warmer after two doublings of CO2 to 1120 ppm. A sensitivity of 4.5˚C would leave Earth uninhabitable for many species at a toasty 9˚C warmer than today after two doublings.

Hockey sticks in disguise

For those not familiar with the hockey stick concept, it is founded upon the belief that many aspects of Earth’s recent climate, that is the past 100 to 10000 years, have remained relatively constant and that all recent changes in the Earth climate system are due to Man, mainly CO2 emissions. This may apply to atmospheric CO2 itself, surface temperatures, Arctic sea ice and many other phenomena. If history has been constant, then any recent change must be due to Man. The chart shows the now infamous Mann hockey stick from IPCC AR3 (2001). The black line shows proxy temperature data for the past 1000 years based largely on tree ring data with the modern thermometer record spliced on the end in red.

This extract from Figure SPM6 displays the current IPCC view of the natural world in mauve (left and centre panels) and the natural world as modified by Man in pink. The IPCC view that global temperatures should have been uniform for the last 100 years is, therefore, intact. In fact, if anything a gradual decline in temperatures over the past 50 years is modelled, something I have never understood. Whilst elsewhere in the report, the role of the Sun in influencing Earth’s climate is all but dismissed (see below) I am drawn to the fact that a grand solar maximum occurred around 1985 [2] and like many others I am left wondering to what extent a hyperactive Sun may explain in part late 20th Century warming. The IPCC view seems to be that natural changes in solar activity, cloud cover, volcanic eruptions, patterns of oceanic circulation, patterns of atmospheric circulation (e.g the North Atlantic Oscillation) and atmospheric convection rates are all more or less constant on the centennial time scale.  We are of course in the middle of an interglacial period where many of these variables may be expected to be in a state of flux. The chart above explicitly shows all late 20th Century warming due to Man whilst elsewhere in the report it is stated that “more than half” is due to Man (see Climate of confusion, below).

The Sun

There is high confidence that changes in total solar irradiance have not contributed to the increase in global mean surface temperature over the period 1986 to 2008, based on direct satellite measurements of total solar irradiance. There is medium confidence that the 11-year cycle of solar variability influences decadal climate fluctuations in some regions. No robust association between changes in cosmic rays and cloudiness has been identified. {7.4, 10.3, Box 10.2}

In this statement the IPCC continues to resist attributing any significant role for solar variability in modulating Earth’s climate. One has to accept that variations in irradiance (i.e. total heat and light output) are too small over the 22 year measurement period to be significant. And no one seriously believes that changes in solar output over the 11 year cycle has a lasting global impact. By focussing on these two variables the IPCC miss the main point, which is a quite extraordinary omission.

Those who argue for a larger role for The Sun focus on poorly understood multi-decadal to centennial variability in the geomagnetic (not radiative) flux emanating from The Sun more commonly known as the Solar wind. The geomagnetic flux from The Sun does indeed protect Earth from cosmic rays but as IPCC points out a link between cosmic ray flux and cloudiness remains unproven. As already mentioned, The Sun peaked in a grand solar maximum in 1985 [2] but has since become uncommonly quiet and may well be heading for a grand solar minimum in the decades that lie ahead.

The chart shows the “11 year” solar cycle as expressed by sunspot activity. Note how the current cycle is puny compared with the previous 5 cycles. In the past, weak sunspot cycles that correlate with reduced geomagnetic flux, have been associated with extreme cold winter conditions in Europe, similar though more severe than experienced in the winter of 2009 and the spring of 2013.

In a paper published by a group working at the world renowned UK met office Hadley Centre, Ineson et al 2011 [3] report on larger than expected variance in the spectral output from The Sun linked to the decline towards solar minimum (i.e. a larger than expected drop in ultra violet emission) and using computer simulation of these conditions were able to reproduce the anomalous cold weather experienced by Europe in the winter of 2009.

The average of recent winters (2008/9, 2009/10 and 2010/11) shows cold conditions over northern Europe and the United States and mild conditions over Canada and the Mediterranean associated with anomalously low and even record low values of the NAO. This period also had easterly anomalies in the lower stratosphere. Given our modelling result, these cold winters were probably exacerbated by the recent prolonged and anomalously low solar minimum.

The possible dependency of climate on solar spectral variance supports work by Lean [4] and I anticipate that by the time AR6 is published spectral variance linked to atmospheric circulation and variance in cloud cover will be a leading contender to explain at least half of global temperature variance.

The Medieval warm period

Continental-scale surface temperature reconstructions show, with high confidence, multi- decadal periods during the Medieval Climate Anomaly (year 950 to 1250) that were in some regions as warm as in the late 20th century. These regional warm periods did not occur as coherently across regions as the warming in the late 20th century (high confidence). {5.5}

In this statement, the IPCC at least acknowledge the Medieval warm period that was written out of history by the original Mann hockey stick. Their treatment of the Medieval Warm Period is the same as The Little Ice Age that followed, neither of which are regarded as global events. There may be a grain of truth in this analysis if a change in global atmospheric circulation pattern results in some areas warming whilst others cool leaving a muted response on global average temperature, but climate may have changed everywhere.

Regarding the Medieval Warm Period as an anomaly betrays a strange prejudice in IPCC since over the past 2000 years, Earth has experienced the Roman Warm Period, the Medieval Warm Period and the Modern Warm Period. The warm periods are separated by the Dark Ages and Little Ice Age cool periods. Using IPCC terminology, all natural climate change is anomalous. Bond et al, (2001) [5] potentially recognise 10 such warm periods in the last 10,000 years. There is nothing anomalous about cyclic natural climate change during the Holocene.

Sea level and interglacials

It is interesting to note that the IPCC concede that the last interglacial period that lasted for 13,000 years (129,000 to 116,000 years ago) was significantly warmer than present at high latitudes (i.e. far north and far south), that the Greenland and Antarctic ice sheets were smaller than present, giving rise to sea levels at least 5 m higher than today.

There is very high confidence that maximum global mean sea level during the last interglacial period (129,000 to 116,000 years ago) was, for several thousand years, at least 5 m higher than present and high confidence that it did not exceed 10 m above present. During the last interglacial period, the Greenland ice sheet very likely contributed between 1.4 and 4.3 m to the higher global mean sea level, implying with medium confidence an additional contribution from the Antarctic ice sheet. This change in sea level occurred in the context of different orbital forcing and with high-latitude surface temperature, averaged over several thousand years, at least 2°C warmer than present (high confidence). {5.3, 5.6}

Presumably at this time the scale of permafrost melt would be far more advanced than today, releasing billions of tonnes of CO2 and methane into the atmosphere. And yet, runaway warming did not take place. Rather, what happened next was Earth being plunged back into the most recently ended phase of glaciation.


Volcanic eruptions are one natural phenomena known to have a temporary cooling impact upon Earth’s climate. Large volcanic eruptions located in the tropics can send billions of tonnes of ash and sulphate aerosol high into the stratosphere (the upper atmosphere) where it reflects a portion of incoming sunlight with consequent cooling of the climate. Once the dust settles, things revert back to normal, normally within a few years. The IPCC do not include volcanic eruptions in their models saying:

Volcanic forcing is not included as its episodic nature makes is difficult to compare to other forcing mechanisms.

Earth scientists would normally deal with unpredictable episodic events like this on a stochastic basis, i.e. the frequency of large volcanic eruptions is known and a model may be sprinkled with these occasional events even though the timing is unknown. Omitting volcanoes from the models may give the impression of reluctance to include any forcing that may actually lead to cooling, albeit temporary.


Clouds are one of the most complex and fundamentally one of the most important components of Earth’s atmosphere. Clouds reflect incoming ultra violet radiation and have a cooling effect. At the same time they reduce the flux of outgoing infra red radiation from  the surface leading to a warming effect. Where I live in NE Scotland, sunny days are invariably warmer than cloudy days, except in the depths of winter anti cyclones where incoming solar radiation is at a minimum.

In the IPCC report, cloud or clouds are only mentioned on 3 pages (9, 11 and 14) and usually in the context of how Man made activities may influence cloud cover. NASA has in fact spent a great amount gathering data on variations in global cloud cover under the International Satellite Cloud Climatology Project (ISCCP) and the data shows that a significant portion of global temperature variance may be explained by cyclical change in global cloud cover [6]. It is extraordinary that AR5 does not mention this.

In addition to satellite data, a large number of countries, including the UK, have lengthy records of ground based sunshine measurements (an inverse proxy for cloud cover) that also show cyclical variance that can be matched to the satellite cloud record and temperature variance at surface [7]. The chart shows co-variance of sunshine and temperature in the UK based on data from 23 Met office stations.

Together with fellow climate blogger Dr Clive Best, I have spent several months this year analysing the impact of cloud cover on variance of the surface temperature record and we have two papers under review on this topic [6,7]. The conclusion of both studies is that Earth’s climate can be simply modelled using combined cloud cover and CO2 variance (with no feedbacks) pointing to an equilibrium climate sensitivity close to 1.3˚C. As already stated, by the time AR6 comes around, I anticipate that spectral variance in solar output linked to variance in atmospheric circulation and cloud cover will come to dominate the climate change debate. Europe, possibly freezing in extreme winters, with inadequate energy supplies, will focus minds.

A climate of confusion

Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system. {2––14} (page 10)


The observed reduction in surface warming trend over the period 1998––2012 as compared to the period 1951––2012, is due in roughly equal measure to a reduced trend in radiative forcing and a cooling contribution from internal variability, which includes a possible redistribution of heat within the ocean (medium confidence). The reduced trend in radiative forcing is primarily due to volcanic eruptions and the timing of the downward phase of the 11-year solar cycle. (page10)

This statement (above) makes no sense to me at all. Solar cycles are roughly 11 years long and so the 14 year period (1998-2012) encompasses a full cycle, and the trend is currently rising. It is therefore nonsense to try and attribute a reduction in radiation to a descending 11 year solar cycle.

It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. {10.3––10.6, 10.9} (page 12)


It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period. {10.3} (page 12)

The two statements above appear on the same page leaving any reader confused. Is all warming due to Man? Or is more than half of warming due to Man? It is claimed that “The best estimate of the human-induced contribution to warming is similar to the observed warming”, however, no best estimate is given in the report with climate sensitivity left floating aimlessly between 1.5˚C and 4.5˚C per doubling of CO2.


It should be abundantly clear to anyone reading this post that the IPCC has become confused. The consensus that only ever existed in name is broken. This is a good thing for science and society.

[1] Otto, A. et al. Energy budget constraints on climate response. Nature Geoscience 6, 415–416 (2013).
[2] Lockwood, M and Frohlich, C. Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature. Proc. R. Soc. A doi:10.1098/rspa.2007.1880
[3] Ineson et al. Solar forcing of winter climate variability in the Northern Hemisphere. Nature Geoscience 2011
[4] Lean, J. Evolution of the sun’s spectral irradiance since the Maunder minimum. Geophys. Res. Lett. 27, 2425–2428 (2000).
[5] Bond et al. Persistent Solar Influence on North Atlantic Climate During the Holocene. Science 294, 2130 (2001)
[6] Best, C. & Mearns, E. W. Effect of Cloud Radiative Forcing on Climate between 1983 and 2008 (under review)
[7] Mearns, E. W. & Best, C. Strong coherence between cloud cover and surface temperature variance in the UK (under review)

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28 Responses to IPCC AR5: Unprecedented uncertainty

  1. Hi Euan,

    Thanks for notifying me about your post. Looks good. The pause is good news in many ways.


    • euan mearns says:

      Hi Dave, thanks for testing the comments which seem to be working. It is of course good news that warming has paused, let’s hope it continues for a few decades. E

  2. Anthony Hanwell says:

    All new critics of the “consensus” are to be welcomed! The weight of CAGW info in the MSM needs all the counter it can get!

  3. G. Watkins says:

    Good post, clear and well written. Look forward to reading more. Best of luck.

  4. pesadia says:

    euan mearns
    Good luck with your new venture. If this article is typical of what we might
    expect, I will be a regular caller.

    It seems to me that the IPCC is more certain that there is less of a problem.

  5. Clive Best says:

    Euan, I have just attended the first day of the Royal Society meeting “Next Steps in Climate Change”. Some quick observations.

    Some good serious scientists. However there is a clear underlying IPCC branded message that they feel (perhaps under pressure?) needs to be portrayed to politicians. The overall review of the SPM by Thomas Stocker was I suspect a talk he had given to policy makers. There was much talk about how to control the communication with the public. He diminished the importance of the recent pause and stated that it would need to last for 3 decades before it meant anything at all.

    The hiatus in global warming itself was addressed by Joachem Marotzke in a very low key talk. IPCC confirms that there has indeed been a pause in warming that is independent of cherry picking the start date whether it be 1998 or 2000 or 1996. Therefore ha accepts that it is not a artifact of el Nino.

    Are models able to reproduce the hiatus ? Should they be even expected to do so ? All models essentially fail to explain the hiatus despite including natural variation. 111/114 simulations are predict too high trends. Detailed study of temperature data he claims show that the hiatus is concentrated in winter moths in the northern hemisphere. Gavin Schmidt propsed that sot emissions and aerosols from China may be to blame. Joachem

    The consensus explanation for the hiatus is that it is half natural – solar cycle, aerosols & volcanoes, and half unknown. So in other words there is the basic assumption that the models are right and that if only nature didn’t occasionally screw things up for them the predictions would be just fine. But anyway this is irrelevant as the pause will soon stop and warming will soon advance according to model predictions. I suspect and some floor comments noted that perhaps the hiatus could last another 10 years due to PDO.


    • euan mearns says:

      Hi Clive, thanks for your update on The Royal Society meeting.

      The consensus explanation for the hiatus is that it is half natural – solar cycle, aerosols & volcanoes, and half unknown.

      My own take is this. With the possibility of a deep solar minimum ahead of us, it is possible that we should now be in a shallow cooling trend that is being moderated by the possible excess GHG in the atmosphere.


  6. Great to see another blog with quality articles.

    If only we had had you when we started SCEF, then things might have been very different.

  7. DMA says:

    You write “Let’s put this into context. An equilibrium climate sensitivity of 1.5˚C would leave Earth a manageable 3˚C warmer after two doublings of CO2 to 1120 ppm. A sensitivity of 4.5˚C would leave Earth uninhabitable for many species at a toasty 9˚C warmer than today after two doubling.”
    I thought the sensitivity to doubling was a logarithmic curve so the first doubling to 560 PPM would have the 1.5C to 4.5C effect but the next would be a small portion of that. Am I misunderstanding this or is your statement a slip?
    I find all this very interesting but don’t have much formal science to analyze it all and find myself agreeing with the arguments that seem to come from the most levelheaded and dispassionate messages. I see that here and hope you do well.

    • euan mearns says:

      Hi DMA, the logarithmic relationship is between CO2 and temperature and not sensitivity and temperature – see chart. For the first doubling we need to increase CO2 by 280ppm leading to X˚C increase. To get 2X˚C we then need to increase CO2 by a further 560ppm. This is why climate sensitivity is such an important variable to understand. It is now split into two parts. The first part is the immediate warming response to CO2 alone called the “transient climate response” and the second part is the assumed feed backs which over time lead to an “equilibrium climate sensitivity”. Climate feedbacks are a very tricky quantity to manage. They are in effect theoretical and unproven. The IPCC sees only positive feedbacks, for example, higher temperature leads to more water vapour leads to even higher temperature and less sea ice leads to oceans absorbing more heat leads to even less sea ice etc. The trouble with this is that if the climate system is dominated by only positive feedbacks it would quickly run out of control – this is what a certain faction is concerned about. In reality we know our climate system is in fact robust suggesting that if positive feedbacks play a role then they are balanced by negative feedbacks. The most obvious negative feedback is convection that is in fact the dominant process for the removal of heat from the surface to the top of the troposphere (circa 30,000 to 50,000 ft). So imagine if it gets a bit warmer we get more convection and more movement of warm air upwards where it then cools by radiative heat loss. Crucially, radiative heat loss at the top of the troposphere by passes all the water vapour that is held in the troposphere. Hope this is accurate and makes some sense.

    • euan mearns says:

      And the chart and a link to a good article by Cive Best that explains Radiative Forcing of CO2:


  8. Luís says:

    Hi there Euan. I’m glad to see you too will keep on writing.

    In this post you touch several weak points of the man induced climate change theory with some sharp remarks. But by far the most important weakness is that the Earth lacks the fossil fuel resource to ever lead to a doubling of atmospheric CO2 concentrations over the pre-industrial estimate.

    • Euan Mearns says:

      Hi Luis, welcome to Energy Matters! You are referring to work you and I did back in 2008.

      IEA WEO 2008 – Fossil Fuel Ultimates and CO2 Emissions Scenarios

      I am less sure now about the conclusion of that work. The inventevness and tenacity of Man at getting at low grade fossil fuel resources like shale oil and gas means that a revision is in order. Also, China seems to be able to overcome all barriers when it comes to increasing coal production.

  9. John Cooke says:

    Excellent – good luck with this. I hope it remains a place for clear, level headed discussion of the science and how to do it properly. I’m a retired physicist and am unimpressed by a lot of the stuff I read on the web put out by the climate science community and their followers. Look forward to reading more good stuff here!

  10. Peter Shaw says:

    Just a small quibble:
    While the relevant UN Resolution (UNGA43/53) mentions “human activities” (twice), it is phrased more generally; eg “…all sources and causes of climate change”.
    See also 5, 6, & 10(b) therein.
    I had expected substantial discussion of CO2 as a limiting nutrient and the effect of longer temperate growing seasons, also the ocean’s natural contribution to CO2 increase.

  11. peter2108 says:

    The sign up process seems broken. No confirmatory email was received. I tried twice at least two hours apart.

    • Euan Mearns says:

      Hi Peter, thanks for the note. I just asked my wife to sign up and all worked OK. I’m advised by son Duncan that his confirmation email ended up in spam / junk email folder so you could perhaps check there. Pls let me know how you get on.

  12. So I can get my theoildrum fix here.Thanks!

  13. Will Mackin says:

    My impression was that there is more heat being absorbed in the ocean to depth than was built into the models. http://www.realclimate.org/index.php/archives/2013/09/what-ocean-heating-reveals-about-global-warming/

    • euanmearns says:

      Will, the hunt for missing heat is only relevant for equilibrium climate sensitivity >> 2˚C where theoretical feedbacks give rise to much of the heat that is deemed to be missing. With the new lower extension of the range to 1.5˚C the missing heat will most likely never have existed.

  14. peter2108 says:

    Leif Svalgaard (http://www.leif.org/research/) comments on WUWT from time to time to insist that there never was a grand solar maximum in the last part of the c20. As I recall he attributes the appearence of such a maximum to chnages in the way sunspots were counted. He is in fact organising a major effort to correct the record. If he is right it would be another example where the supposed data of climate science runs like quicksilver through the fingers.

    In fact what agreed data is there beyond the Mauna Loa CO2 readings? Everything else seems to be controversial. The philosopher Karl Popper said that should agreement on the data disappear then science became impossible.

    • euanmearns says:

      Peter, glad you got signed up OK. There may have been a problem with the site host the day you tried – everything was running slow.

      Regarding data, there is much to agree on. For example I would not refute the general accuracy of the thermometer temperature record, the Mauna Loa CO2, shrinking Arctic Sea Ice and shrinking glaciers. When you get into the historic and proxy records things become much more complex. For example I would place as much emphasis on records of Alpine glacier growth during the 18thC as documented by Jean Grove in her book “The Little Ice Age” as I would to the documentation of their subsequent retreat.

    • euanmearns says:

      Regarding The Sun. NASA have recorded a dramatic drop in the intensity of the solar wind in recent decades and the cosmogenic isotope record (14C and 10Be) bears witness to cyclic changes in solar geomagnetic activity. The current solar cycle as recorded by sun spot activity is much weaker than the previous 5 cycles, so I don’t see good reason to question the findings of Lockwood and Frohlich, who incidentally were arguing that changes in late 20thC solar activity could not account for warming. I feel they should perhaps have allowed for some time lags in their analysis.

      • peter2108 says:

        Well people do fight over the temperature record! Anthony Watts says it runs too hot because many weather stations have become surrounded by heat trapping urban development (UHI – urban heat islands). The Sun – yes it is now weak. Leif S. was saying that it had not been especially strong.

        Anyway I am looking forward to following this site especially your paper with Dr Best which I hope we will be able to access in due course!

        PS If I make too long a comment the ‘Post Comment’ button disapperars. This is an issue with the CSS stylesheet used in the WordPress template probably. Could be a valuable feature 🙂

  15. Euan,

    “Clearly something is wrong, either with the models or, more likely, with the input data.” This statement needs to be corroborated.

    Also, would be interested to see you focus on Ocean Acidification in one of your future posts.

    – Jelte.

    • Euan Mearns says:

      Jelte, with a range of official scientific opinion that goes from 1.5˚ to 4.5˚C for ECS, it is quite clear that not all of the models that produce this range of outcomes can be correct. Models that do not dynamically take into account changes in convection rates, for example, stemming from dT or a change in atmospheric circulation, for example a switch in the NAO, have no chance of being correct. Likewise, models need to be able to accommodate natural changes in ocean circulation, and since these are not understood and cannot be forecast, then the modelling community have their work cut out.

      Regarding ocean acidification, there is a helpful chart in AR5 that puts this in context. I may visit this topic some time, but next on my list of climate topics is sea ice variations and the cloud variations.

  16. Euan,
    Thanks for your reply. You wrote in your post, “Clearly something is wrong, either with the models or, more likely, with the input data.” To me, and I suspect to others as well, that reads like you are suggesting the input data used is inaccurate or otherwise flawed.
    In your reply to my question, on the other hand, you point out some of the many features that current generation GCM’s are lacking. These are problems with the models themselves, however – not with the ‘input data’. What input data GCM’s do and don’t take is a feature of the models themselves.
    Perhaps what you meant was that important variables are currently being ignored by the models? That is undoubtedly true, although there may well also be issues with the current climate system response being *more* dynamic (and ‘further from equilibrium’) than captured by current models. As in the public confusion around oil reserves vs. flow rates in the ‘Peak Oil issue’, there exists a lack of appreciation for the importance of CO2 *fluxes* to the atmosphere, as opposed to absolute amounts.
    – Jelte

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