New University Of Exeter Study Finds Climate Models Skewed, Overhype CO2 …”Uncertainties Rigorously Concealed”!

University of Exeter: Role of natural climate factors is underestimated

By Dr. Sebastian Lüning and Prof. Fritz Vahrenholt
(German text translated/edited by P Gosselin)

One of the main criticisms of the IPCC climate assessment is the marginalization of natural climate drivers. Indrani Roy of the University of Exeter published a paper in Frontiers, promoting greater consideration of natural factors in modern climate change. Press release from the University of Exeter of 10 October 2018:

Role of “natural factors” on recent climate change underestimated, research shows

Pioneering new research has given a new perspective on the crucial role that ‘natural factors’ play in global warming. The study, by Dr Indrani Roy at the University of Exeter, suggests that the natural phenomena such as solar eleven-year cycles and strong volcanic explosions play important roles in recent climate change which has been ‘underestimated’.

All existing studies focus on the rise in Co2 in the atmosphere as being the main driver of global temperature rises. However, Dr Roy suggests that the role natural factors plays in climate change should be given more prominence. This study explores various possible areas where models miss important contributions due to these natural drivers. The research is published in leading journal Frontiers. Although CO2 has risen significantly since 1998, global temperature did not show any significant increase. Models however suggested a significant rise.

Dr Roy said: “So what factors are missing?  It is a puzzle of recent slowdown of global warming trend or Hiatus and this study addresses that issue.” For the study, Dr Roy looked specifically at data between 1976-96, which not only covered two full strong solar cycles and two explosive volcanic eruptions during active phases of those cycles, but which also matched a period of abrupt global warming. These data were compared with other periods.”

The research highlighted the important role that a dominant Central Pacific (CP) El Nino, and its associated water vapour feedback, played in global warming within the chosen period. Dr Roy suggests that the explosive volcanoes seen during this phase, which changed the sea level pressure around the North Atlantic, kick-started a ‘chain mechanism’ that played a crucial role. Dr Roy added that the change in Indian Summer Monsoons and El Nino connection during that abrupt warming period, and a subsequent recovery thereafter, can also be explained by this ‘chain mechanism’.

Addressing on Abrupt Global Warming, Warming Trend Slowdown and Related Features in Recent Decades by Dr Indrani Roy is published in Frontiers in Earth Science (


“Uncertainties rigorously concealed from the public”

Image: Climate Etc.

Another criticism of the IPCC is that important remaining uncertainties are rigorously concealed from the public. Judith Curry has beautifully elaborated this point in a recent lecture.

Climate uncertainty monster: What’s the worst case?
On possibilities, known neglecteds, and the vicious positive feedback loop between scientific assessment and policy making that has created a climate Frankenstein. I have prepared a new talk that I presented yesterday at Rand Corp. My contact at Rand is Rob Lempert, of fame.  Very nice visit and interesting discussion. My complete presentation can be downloaded [Rand uncertainty].  This post focuses on the new material.

You’ll find the entire article with illustrations at Climate Etc.

12 responses to “New University Of Exeter Study Finds Climate Models Skewed, Overhype CO2 …”Uncertainties Rigorously Concealed”!”

  1. John F. Hultquist

    Has Indrani Roy of the University of Exeter been relieved of her position?

  2. Skeptik

    The main reason why the models overestimate the importance of CO2 as a driver of climate change is that nobody has, as yet, come up with an even vaguely plausible alternative or supplementary explanation for the temperature changes that we have actually seen. Such an additional explanation is badly needed.

    If CO2 were almost entirely responsible for the warming, we would expect to see a reasonable positive correlation between the rate of warming and the rate of increase in the log of the CO2 concentration. What we see, however, is the exact opposite. If we take the period from 1979 to 2017, we have twenty different periods each of twenty years over which we can calculate the correlation. For NOAA the correlation coefficient is =-0.16409; for GISS it is = -0.58774; for had|CRUT4 it is = – 0.68912; for Cowtan and Way it is =-0.34325; for RSS v 4.0 it is = – 0.50458; and for UAH v 6.0 it is = -0.86674.

    There will naturally be a temptation on the part of the convinced warmists to rubbish this 20/20 view of climate change on the grounds of the period(s) involved being too short. So, let us look at a rather longer period. If we take every period of 60 years from 1850 to 2017 using the CRU land filter on the Cowtan and Way series we find that the difference in the apparent sensitivity varies by a factor of more than 23. It should really be much the same throughout the period!

    This does not prove that Cow2 has NO effect, but it does indicate that it can only really be quite a small part of the overall story.

    1. Kenneth Richard

      The main reason why the models overestimate the importance of CO2 as a driver of climate change is that nobody has, as yet, come up with an even vaguely plausible alternative or supplementary explanation for the temperature changes that we have actually seen. Such an additional explanation is badly needed.

      Why do you believe there are no alternative-to-CO2 explanations for the temperature changes?

      Cloud cover changes alone can explain the radiation budget changes — and the Greenland ice sheet melt and Arctic sea ice decline — since the late 1970s. Simply put, during 1979-2011 per satellite observation, there was a positive imbalance in the radiation budget of +2.7 W m-2 (+2.3 W m-2 absorbed) due to the reduction in low cloud cover. This allowed more solar radiation to be absorbed by the oceans, and this extra heat was transmitted to the atmosphere. Here are just a small sampling of the papers demonstrating this.

      Herman et al., 2013
      “[T]here has been a global net decrease in 340 nm cloud plus aerosol reflectivity [1979-2011]. … Applying a 3.6% cloud reflectivity perturbation to the shortwave energy balance partitioning given by Trenberth et al. (2009) corresponds to an increase of 2.7 W m−2 of solar energy reaching the Earth’s surface and an increase of 1.4% or 2.3 W m−2 absorbed by the surface.”

      Goode and Palle´, 2007
      “The decrease in the Earth’s reflectance [cloud cover] from 1984 to 2000 suggested by Fig. 4, translates into … an additional global shortwave forcing of 6.8 Wm2. To put that in perspective, the latest IPCC report (IPCC, 2001) argues for a 2.4 Wm2 increase in CO2 longwave forcing since 1850. The temporal variations in the albedo are closely associated with changes in the cloud cover.”

      McLean, 2014
      The reduction in total cloud cover of 6.8% [between 1984 – 2009] means that 5.4 Wm−2 (6.8% of 79) is no longer being reflected but acts instead as an extra forcing into the atmosphere … To put this [5.4 Wm-2 of solar radiative forcing via cloud cover reduction between 1984-2009] into context, the IPCC Fifth Assessment Report…states that the total anthropogenic radiative forcing for 2011 relative to 1750 is 2.29 Wm−2 for all greenhouse gases and for carbon dioxide alone is 1.68 Wm−2. The increase in radiative forcing caused by the reduction in total cloud cover over 10 years is therefore more than double the IPCC’s estimated radiative forcing for all greenhouse gases and more than three times greater than the forcing by carbon dioxide alone [from 1750 to present]. … According to the energy balance described by Trenberth et al. (2009), the reduction in total cloud cover accounts for the increase in temperature since 1987, leaving little, if any, of the temperature change to be attributed to other forcings.”

      Kay et al., 2008
      “Reduced cloudiness and enhanced downwelling radiation are associated with the unprecedented 2007 Arctic sea ice loss. Over the Western Arctic Ocean, total summertime cloud cover estimated from spaceborne radar and lidar data decreased by 16% from 2006 to 2007. The clearer skies led to downwelling shortwave (longwave) radiative fluxes increases of +32 Wm−2 (−4 Wm−2) from 2006 to 2007. Over three months, simple calculations show that these radiation differences alone could enhance surface ice melt by 0.3 m, or warm the surface ocean by 2.4 K, which enhances basal ice melt. Increased air temperatures and decreased relative humidity associated with an anti‐cyclonic atmospheric circulation pattern explain the reduced cloudiness. Longer‐term observations show that the 2007 cloudiness is anomalous in the recent past, but is not unprecedented. Thus, in a warmer world with thinner ice, natural summertime circulation and cloud variability is an increasingly important control on sea ice extent minima.”

      Hofer et al., 2017
      Decreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet … We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone.

      1. Mike Haseler (Scottish Sceptic)

        “The decrease in the Earth’s reflectance”

        I refer you to my previous comment re the smog/cloud produced due to pollutants (probably SO2).

        For a graphic see:

        1. Kenneth Richard

          The SO2 increases and decreases are predominantly due to fluctuations in volcanism. Humans contribute to aerosol optical depth negligibly. This has been recognized for decades, tracing back to the global cooling scare of the 1970s when it was thought – and then dismissed – that humans were causing the 1940s to 1970s cooling trend. Both clouds and volcanism contribute to decadal-scale temperature fluctuations. Cloud cover changes are more influential than volcanic activity changes (Stanhill et al., 2014; Mateos et al., 2014), and both completely dominate over anthropogenic aerosol emissions when it comes to influencing climate changes.

          Neely et al., 2013

          “We employ model runs that include the increases in anthropogenic sulfur dioxide (SO2) over Asia and the moderate volcanic explosive injections of SO2 observed from 2000 to 2010. Comparison of the model results to observations reveals that moderate volcanic eruptions, rather than anthropogenic influences, are the primary source of the observed increases in stratospheric aerosol.”

          Höpfner et al., 2013

          The increase in the stratospheric aerosol concentration observed in the past years is caused mainly by sulfur dioxide from a number of volcano eruptions. Variation of the concentration is mainly due to volcanoes. Lower stratospheric variability of SO2 could mainly be explained by volcanic activity and no hint for a strong anthropogenic influence has been found.”

          Hoyt et al., 1979

          “Conclusions: The trends in [anthropogenic] atmospheric transmission at the three locations examined in this paper are very small, perhaps nonexistent, and generally not statistically significant. If the trends in atmospheric transmission and hence anthropogenic aerosols are small near their presumed sources, then the global increase in aerosols must be very small indeed. Consequently, the effects of anthropogenic aerosols on climate is probably negligible.”

          “There now appear to be two schools of thought concerning anthropogenic aerosols. One school argues that their increase has caused much of the observed cooling of the Northern Hemisphere since 1940. Some proponents of this viewpoint are Bryson and Dittberner (1976) and Budyko (1969). The other school of thought contends that there is no evidence for an increase in anthropogenic aerosols on a global scale and hence they are unlikely to be important climatically. Proponents of this viewpoint include Ellsaesser (1975), Dyer (1974) and Landsberg (1975). The results of this paper support the views of the latter. A recent study by Jones and Jiusto (1980) also indicates the impact of urban areas on climate is undetectable in most cases.”

          Griggs, 1973,1975

          “The scientific community (e.g., SCEP1 and SMIC2 ) has become increasingly aware in recent years of the importance of atmospheric aerosols and their optical properties in possible climate modification. The aerosols in the atmosphere consist of man-made and natural particles, and it is the man-made contribution due to combustion added to the natural (dust, sea spray, forest fires, and volcanic dust) background that is generally considered to be important in determining climatic changes. However, the man-made contribution on a global scale is quite small; estimates range from a negligible amount to about 6% of the natural background. … McCormick and Ludwig presented evidence of a worldwide buildup of atmospheric aerosols which could increase the earth albedo resulting in a cooling of the earth-atmosphere system. This effect would counteract the postulated increase of temperature in the lower atmosphere due to the greenhouse effect of the increased CO2 emissions by human activities. In fact, there has been a decrease in the mean annual air temperature since about 1945 at mid latitudes, suggesting that the aerosol pollution effect is greater than that of the CO2 increase”

          Cobb, 1973

          “It has been estimated (Squires, 1966; Selezneva, 1966; Hidy and Brock, 1970; Robinson and Robbins, 1970) that the anthropogenic component of the global particulate burden of the atmosphere amounts to 5-12%; not, it would seem a very alarming figure. … Ellis and Pueschel (1971), in a report based on solar radiation data at Mauna Loa for the period 1958-70, conclude that human activities have not affected the atmospheric turbidity on a global scale. They also conclude that the 1963 eruption of Mount Agung, a natural phenomena, produced stratospheric aerosols which persisted for 7 years.”

          Mitchell, 1970

          “The secular increase of global atmospheric particulate loading by human activity is estimated, and compared with a construction of the secular variability of stratospheric dust loading derived from data on volcanic activity since 1850. It is concluded that the total human-derived particulate load is at present comparable to the average stratospheric dust load from volcanic eruptions, but that the variations of human-derived loading are an order of magnitude less than those of volcanic dust loading. For reasonable estimates of the thermal cooling effect of dust load increases, it is inferred that secular cooling due to human-derived particulate loading is currently of the order of 0.05°C per decade. Although changes of total atmospheric dust loading may possibly be sufficient to account for the observed 0.3°C-cooling of the earth since 1940, the human-derived contribution to these loading changes is inferred to have played a very minor role in the temperature decline.”

          Mitchell, 1971

          “Turning to the presumed effect of such large-scale background aerosol increases, a number of authors have called attention to the coincidence between these increases and a systematic decline of worldwide average temperature in the past two or three decades, and have considered the possibility of a causal connection between the two phenomena (McCormick and Ludwig, 1967; Bryson, 1968; Budyko, 1969; Bryson and Wendland, 1970; Mitchell, 1970). … With particular regard to the recent cooling trend of worldwide climate, the attribution of this cooling (or any significant part of it) to secular increases in atmospheric particles from human activities now appears unlikely, not merely on quantitative grounds (see Mitchell, 1970) but on qualitative grounds as well. Indeed, long-term increases of particulate pollution of the atmosphere by man may serve to augment, rather than oppose, other warming effects of human activities, such as the increasing carbon dioxide content and direct thermal pollution of the atmosphere. In that event the observed climatic cooling of the past quarter century emerges more persuasively than ever as a natural geophysical phenomenon, with man the innocent bystander.”

          Bryson and Goodman, 1980

          Volcanic Activity and Climate Changes
          “Since the measured values of direct solar radiation decreased about 5 percent during the 1945 to 1975, the surface mean temperature should have decreased 6 to 10 K during this time if only the solar constant varied. This is clearly much larger than the 0.3 K or so [of cooling] that was observed. … From 1945 to 1970, the annual eruption numbers roughly doubled from 16 to 18 per year to 37 to 40 per year. During the same interval, the aerosol optical depth also roughly doubled. This is in good agreement with the observations of Hammer, who reported a doubling in the amount of nonorganic impurities deposited on the Greenland Ice Sheet between times of low and high volcanic activity based on ice core analysis for the past 300 years.”

          Ellsaesser , 1974

          “Has man, through increasing emissions of particulates, changed the climate?
          It is estimated that man now contributes 13.6% of the 3.5 x 109 tons of primary and secondary particulates presently emitted to the atmosphere annually. … [W]hile an anthropogenic upward trend in airborne particulates existed in the past, it was halted and may even have been reversed over the past few decades.”

          1. Yonason

            “The SO2 increases and decreases are predominantly due to fluctuations in volcanism. Humans contribute to aerosol optical depth negligibly.” – Kenneth Richard

            Yes, as we learn from this NOVA special:

            NARRATOR: The satellite identifies the gas as sulfur dioxide, SO2, the primary cause of acid rain. And Nyiragongo is producing more than any place in the world, up to 50,000 tons per day. That’s more than the amount produced by all power plants, factories and cars in the United States. And the high concentration of SO2 is another clue for forecasting the next eruption.

            Also consider: “The [Ambrym Volcano] lava lakes below us generate more poisonous sulphur dioxide gas than any other volcano on earth.”
            (Great video shot with volcano expert John Seach, if you can find it)

            And those are just two of many

          2. Yonason

            That was supposed to be the Yasur volcano, not Ambrym. Sorry.

            (both are in the Vanuatu area.

    2. Adrian

      “nobody has, as yet, come up with an even vaguely plausible alternative or supplementary explanation for the temperature changes that we have actually seen”

      That is false. Lorenz already came up with a very plausible alternative. It’s called ‘spontaneous climatic variation’. Look it up.

      Anyway, even if your claim would be true, it’s a fallacy and real sciences avoid fallacies, do not embrace them. It’s called an appeal to ignorance.

    3. Mike Haseler (Scottish Sceptic)

      “as yet, come up with an even vaguely plausible alternative or supplementary explanation for the temperature changes that we have actually seen. Such an additional explanation is badly needed.”

      Please refer to my previous comment

  3. Bitter&twisted

    Interesting. Exeter has previously been a hotbed of climate alarmism.
    Maybe, just maybe we are seeing signs of a slow pivot away.
    The start of a “plausible deniability” campaign to get these parasites off the hook?

  4. Mike Haseler (Scottish Sceptic)

    In the 1970s we had a peak of smog causing pollution. Smog or cloud reflects sunlight and cools the earth. It is therefore not very surprising that in the 1970s we also have a “global cooling” scare primarily focussed on temperature falls in places like the US with highest levels of pollution/smog

    In 1970s we saw global introduction of clean air acts.

    From 1970 to around 2000 we saw a massive cleaning up of the atmosphere and … global warming. This was predominantly focusses in “hot spots” down wind from 1970s SO2 producing areas.

    Then as nations like China started emitting pollutants and clean up efforts came to an end, from 2000 onwards we’ve not seen much trend in air pollution … and similarly we’ve not seen much trend in global temperatures.

    My belief, is that if this 1970-2000 warming from reducing pollution is accounted for, what we are left with is predominantly things like solar cycle forcing, ocean currents. If these dominant determinants of the climate are then accounted for … we might just be able to detect a small contribution from changing CO2.

  5. “Weekly Climate and Energy News Roundup #338 | Watts Up With That?

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