Some observations about Connolly et al (2021) “How much has the sun influenced northern hemisphere temperature trends”
The Connolly et al paper can be found at:
From the Connolly paper:
“The main analysis and first draft of the manuscript were carried out by the first three authors
(RC, WS and MC).” Ie:
I’m not a climate scientist, so I can’t comment on the detailed science.
However, I will give a few general observations about the Connolly paper.
1. It deals with Northern hemisphere only – but, according to the wiki entry about Mike Lockwood (one of the scientists cited in the paper):
“Lockwood has stressed the distinction between global, regional and seasonal climate changes and is of the opinion that solar modulation of the winter, northern hemisphere jet stream might well result in … The biggest impact of such a decline in solar activity would be a higher occurrence frequency of relatively cold winters in the UK and across Europe, each of which would be accompanied by a relatively warm one elsewhere (for example in Greenland).”
2. The Lockwood paper referenced by Connolly doesn't support what he is saying.
As Lockwood says (in : Lockwood M. (2012) “Solar Influence on Global and Regional Climates” – one of the references in the Connolly paper):
“It [ie solar influence on climate] is also a field that in recent years has been corrupted by unwelcome political and financial influence as climate change sceptics have seized upon putative solar effects as an excuse for inaction on anthropogenic warming. In particular, figures and statistics with known errors, limitations and inaccuracies are repeatedly reproduced on the Internet and in the media (as discussed, for example, by Damon and Laut 2004), and publications are reported in a massively selective manner. None of this makes any difference to the scientific reality, or otherwise, of mechanisms connecting solar variability and Earth’s climate”
Connolly includes a part of this quote, apparently in support for his claims that someone other than climate change sceptics/deniers/delayists were the ones trying to corrupt IPCC processes. That is the opposite of what the Lockwood quote is clearly telling us. Reading the original Lockwood paper makes this even clearer. Perhaps Connolly didn’t realise what Lockwood was actually saying, and thought the quote would support his viewpoint?
More about Lockwood, from Laut (2009) “Climate Change: The Role of Flawed Science”:
“A few weeks ago, in Swedish Public Television, two of the world’s leading climatologists were asked about Svensmark and his solar theory. Now, scientific dispute has a long tradition for expressing disagreement in polite and neutral terms. Only in rare cases blunt words surface, as when Jon Egill Kristjánsson, professor at The University of Oslo concluded : “It should not be taken seriously – to put it plain and simple.” And Mike Lockwood of The Royal Society of London, who to begin with – years ago ‐ supported the theory, said “.. the change in the magnetic field since 1985 – it’s moved in the wrong direction”, which means that according to Svensmark’s ideas we should have experienced a global cooling since then. And he added: “I would love it to be right! I would absolutely love it to be right! Unfortunately, wanting something doesn’t change the scientific reality. One can’t use spin or rhetoric or anything to change the scientific reality.” “
3. There is some evidence that some of the works cited by Connolly lack some basic accuracy in charting data
Damon PE, Laut P (2004) “Pattern of strange errors plagues solar activity and terrestrial climate data”
heavily criticised the work of Eigil Friis-Christensen and Knud Lassen (work cited by Connolly)
Damon and Laut say:
“the sensational agreement with the recent global warming, which drew worldwide attention, has totally disappeared. Nevertheless, the authors and other researchers keep presenting the old misleading graph…
In 1991 Eigil Friis‐Christensen together with Knud Lassen, another Danish researcher, published an article in the scientific journal Science which attracted worldwide attention. It seemed to document a close agreement between data representing solar activity (solar cycle lengths), and terrestrial temperatures. The agreement was displayed on a graph which showed a solar and a terrestrial curve closely intertwined. What made the graph a sensation, was the fact, that the steep rise in temperature from about 1970, the ‘global warming’, was closely matched by a corresponding steep rise of the solar curve. This was seen by many as proof that global warming was caused by the sun. The graph has been reproduced extensively all over the world, both in the mass media and in scientific literature, and has helped to create a large community of believers, who claim that the sun is causing the global warming. Regrettably, it took some years before a careful analysis of the article revealed that the conspicuous steep rise of the solar curve actually had nothing to do with the behavior of the sun, but had been created (accidentally?) by a change of the mathematical procedure used to calculate the points creating the steep rise.”
4. Credibility and vested interests / potential conflicts of interest of referenced researchers
Not to put too fine a point on it, many of the references used by Connolly are works by ardent AGW deniers, and many have connections with AGW denial organisations.
A few examples, which popped up as I was fairly randomly following the references and reading around them:
Willie Soon (mentioned 149 times in the Connolly paper – more than anyone else)
According to wiki:
“Willie Wei-Hock Soon
Soon is a climate change denier, disputing the scientific understanding of climate change, and contends that most global warming is caused by solar variation rather than by human activity. He co-wrote a paper whose methodology was widely criticised by the scientific community. Climate scientists such as Gavin Schmidt of the Goddard Institute for Space Studies have refuted Soon's arguments, and the Smithsonian does not support his conclusions. He is nonetheless frequently cited by politicians opposed to climate-change legislation.
Soon co-authored The Maunder Minimum and the Variable Sun–Earth Connection with Steven H. Yaskell. The book treats historical and proxy records of climate change coinciding with the Maunder Minimum, a period from 1645 to about 1715 when sunspots became exceedingly rare.
From 2005 to 2015, Soon had received over $1.2 million from the fossil fuel industry, while failing to disclose that conflict of interest in most of his work”
“The Soon and Baliunas controversy involved the publication in 2003 of a review study written by aerospace engineer Willie Soon and astronomer Sallie Baliunas in the journal Climate Research, which was quickly taken up by the G.W. Bush administration as a basis for amending the first Environmental Protection Agency Report on the Environment.
The paper was strongly criticized by numerous scientists for its methodology and for its misuse of data from previously published studies, prompting concerns about the peer review process of the paper. The controversy resulted in the resignation of half of the editors of the journal and in the admission by its publisher Otto Kinne that the paper should not have been published as it was.”
Douglas Hoyt (mentioned 56 times in the Connolly paper)
“Douglas V. Hoyt is a retired solar physicist with Raytheon Corporation. Hoyt appears on Senator James Inhofe‘s list of 400+ “prominent” scientists who doubt global warming. He is listed as one of 49 who are currently retired. Inhofe’s most recent list contains over “650 international scientists.”
“In January 2018, more than 200 scientists endorsed an open letter calling on the American Museum of Natural History (AMNH) to remove climate change denier Rebekah Mercer from its board and to “end ties to anti-science propagandists and funders of climate science misinformation.” The New York Times reported that those among the AMNH letter calling for Mercer to step down were Michael E. Mann, director of the Earth System Science Center at Pennsylvania State University, and Katharine Hayhoe, director of the Climate Science Center at Texas Tech University.”
“Hoyt was among a group of climate change deniers who responded with their own open letter, calling for the AMNH “not to cave in to this pressure.” The letter was signed by numerous individuals with ties to groups funded by the Mercer Family Foundation such as Will Happer of the CO2 Coalition, Richard Lindzen, a fellow at the Cato Institute, Craig Idso, the chairman of the Center for the Study of Carbon Dioxide and Global Change. There are a number of signatories affiliated with the Heartland Institute, which has received over $5.78 million from the Mercer Family Foundation since 2008.”
Some of the other signatories to that letter are as follows, the work of whom is cited by Connolly in one paragraph on page 1 of his paper:
That is not an exhaustive list of overlaps – I’ve just cross-checked a small number of Connolly’s sources to the list of signatories to the AMNH letter.
According to desmog:
“The letter reads: “The Earth has supported abundant life many times in the geological past when there were much higher levels of carbon dioxide in the atmosphere. It is quite likely that future generations will benefit from the enrichment of Earth’s atmosphere with more carbon dioxide.”
“That statement itself is contradicted by every major scientific institution in the world and thousands of scientific studies over many decades.”
“Many of that letter’s signers are affiliated with groups funded by Mercer’s family foundation in recent years. There’s retired Professor Will Happer of the CO2 Coalition, Richard Lindzen, a fellow at the Cato Institute, Craig Idso, the chairman of the Center for the Study of Carbon Dioxide and Global Change.”
“In a footnote, the letter states: “The views represented in this letter are those of the individual signatories and not the institutions they are affiliated with. Institutions are listed simply for identification purposes.””
5. The science
As for the science. The gist of the actual scientific claims in the Connolly paper appears to be that “It’s the sun, rather than humans, that is causing global warming”
Which is debunked in quite some detail here:
A key quote from Skepticalscience:
“… neither direct nor indirect solar influences can explain a significant amount of the global warming over the past century, and certainly not over the past 30 years. As Ray Pierrehumbert said about solar warming, “That’s a coffin with so many nails in it already that the hard part is finding a place to hammer in a new one.””
The Ray Pierrehumbert article this is quoted from can be found here:
The argument presented by Connolly is a bit more subtle than the gist I describe above, in that he suggests that the uncertainties around the variability in the sun’s energy output mean that it can’t be ruled out that it might be the sun.
It’s not surprising that AGW deniers are attacking using uncertainties in the science of solar output. There are precedents, eg Patrick Frank’s theory of propagating errors in temperature measurements and forecasts, and the Tobacco industry’s attacking controls on smoking through making claims about uncertainties in the science connecting smoking and cancer.
6. Claims of political and financial influence (in more detail)
“Lockwood (2012) argues that “The field of Sun-climate relations [...] in recent years has been corrupted by unwelcome political and financial influence as climate change sceptics have seized upon putative solar effects as an excuse for inaction on anthropogenic warming””
That reference is (in full):
Lockwood M. (2012) “Solar Influence on Global and Regional Climates”
“The literature relevant to how solar variability influences climate is vast—but much has been based on inadequate statistics and non-robust procedures. The common pitfalls are outlined in this review. The best estimates of the solar influence on the global mean air surface temperature show relatively small effects, compared with the response to anthropogenic changes (and broadly in line with their respective radiative forcings).”
He also says:
“However, the situation is more interesting when one looks at regional and season variations around the global means.”
And this perhaps explains why Connolly has decided to focus his paper on Northern Hemisphere trends rather than global trends.
Lockwood also goes on to say:
“It is also a field that in recent years has been corrupted by unwelcome political and financial influence as climate change sceptics have seized upon putative solar effects as an excuse for inaction on anthropogenic warming. In particular, figures and statistics with known errors, limitations and inaccuracies are repeatedly reproduced on the Internet and in the media (as discussed, for example, by Damon and Laut 2004), and publications are reported in a massively selective manner. None of this makes any difference to the scientific reality, or otherwise, of mechanisms connecting solar variability and Earth’s climate; however, it does make evaluation of the evidence much more difficult. Recent reviews have been presented by Reid (2000), Rind (2002), Haigh (2003, 2007), Beer (2006), Foukal et al. (2006), de Jager (2008), Gray et al. (2010) and Lockwood (2004, 2010, 2012).”
From the wiki entry about Mike Lockwood:
Positions on solar influence on global and regional climate
In 2007, Lockwood co-authored a paper about solar data from the past 40 years. He was partly inspired to conduct the study after seeing the Great Global Warming Swindle, which contends that the Sun is the primary cause of recent climate change. He found that between 1985 and 1987 all the solar factors that could affect climate performed an "U-turn in every possible way". Lockwood told the New Scientist that he seriously doubted that solar influences were a big factor compared to anthropogenic influences: to explain the lack of global cooling since 1987 would require a very long response time to any solar forcing which is not found in detected responses to volcanic forcing.
However, Lockwood has stressed the distinction between global, regional and seasonal climate changes and is of the opinion that solar modulation of the winter, northern hemisphere jet stream might well result in Europe experiencing a higher fraction of cold winters. From past variations of the Sun deduced from cosmogenic isotopes he concludes that a slide into a new Maunder Minimum is possible over the next 50–100 years. The biggest impact of such a decline in solar activity would be a higher occurrence frequency of relatively cold winters in the UK and across Europe, each of which would be accompanied by a relatively warm one elsewhere (for example in Greenland).
In 2012, Lockwood said the field of Sun-climate relations had been "corrupted by unwelcome political and financial influence as climate change sceptics have seized upon putative solar effects as an excuse for inaction on anthropogenic warming"
Connolly claims that the IPCC has been “suppressing dissenting views on any issues where there is still scientific disagreement”.
I decided to trace through some of the references provided by Connolly in relation to this claim. While not representing a comprehensive tracing of all relevant references (time, and the reader’s attention and patience, being limited) I thought this might provide a useful indicator of the general quality of the referencing used by Connolly. I also thought it might shed some light on the credibility of the sources cited by him.
One such reference was Hoppe, I., & Rodder, S. (2019) “Speaking with one voice for climate science--climate researchers' opinion on the consensus policy of the IPCC”
There is no mention in that paper of “suppressing” anyone. However, they do say:
“.. the literature review shows that many analysts from the social sciences are critical of the consensus policy while eminent climate scientists as well as some social scientists focus on the communicative and political advantages of scientific consensus.”
And they also give some general criticisms of consensus:
The reference to Geden is
Geden, O. (2015). “Policy: Climate advisers must maintain integrity”
“Climate scientists and economists who counsel policy-makers are being pressured to extend their models and options for delivering mitigation later”
Ie advisers to the IPCC are being pressured by delayists (not by AGW proponants)
“policy-makers are delighted to hear that despite 20 years of mounting emissions, the 2 °C target is still theoretically within reach. They ignore the fine print of the IPCC reports, to climate scientists’ increasing dismay. That said, there are positive signs of researchers holding their ground. For example, the Working Group III contribution to the fifth IPCC report, which assesses mitigation options, rejected the task assigned to it by the UNFCCC: that of evaluating the adequacy of a 2 °C target compared to one of 1.5 °C. The IPCC turned the question straight back to policymakers, saying that target-setting is too dependent on ethical and value judgements. This principled stance could pave the way for a weaker climate objective. By saying that science is incapable of judging levels of risk avoidance or intergenerational fairness, the IPCC might dilute its influence in the global target-setting process. But if scientific advisers were to refrain from demanding exact stabilization targets, the UNFCCC would no longer be able to justify a global political agreement with a simple ‘science says so.”
“The scientific community must defend its independence from outside interference - from government administrations and nongovernmental organizations attempting to woo scientists to back their ‘just’ causes, and from climate-change deniers.”
“Everyday politics is therefore dominated not by evidence-based policy-making but by
attempts at ‘policy-based evidence-making’.”
“Climate-policy advisers should align their expectations with those in other public-policy domains such as development, health, foreign and security policy: scientific evidence is just one of many factors affecting political decisions, such as voter preferences, available funds, competing interests and sheer pragmatics. The best that scientists can hope for is ‘evidence-informed policy-making… Their task is to analyse critically the risks and benefits of political efforts and contribute empirically sound — and sometimes unwelcome — perspectives to the global climate-policy discourse”
I think what these quotes are saying is that the IPCC was being put under (political) pressure to consider a 2 degree target as more pragmatic than a 1.5 degree one (ie a form of “delayist” intent versus sticking to a 1.5 degrees target). They resisted that pressure.
As a footnote to the above, in 2018 the IPCC issued a report highlighting the extra damage caused by 2 degrees of warming versus only 1.5 degrees of warming, thereby indicating that they continued to resist, very effectively, the political pressure noted by Geden.
As a further footnote, nowhere in Geden (2015) is there any mention of the deliberations of the IPCC on the relative proportions of human activities versus other factors impacting global warming.
So, the article cited by Hoppe as evidence that the IPCC , “by focussing on anthropogenic influence and excluding other reasons for climatic change, was said to compromise scientific integrity” in fact demonstrates evidence of the opposite. When faced with political pressure (no doubt supported by AGW deniers and delayists) to water-down the climate challenge and consider accepting 2 degrees as a target instead of 1.5 degrees, they stuck to their scientific guns.
Hopper and Rodder go on to say they did a poll and found that there was a strong level of agreement with the scientific consensus process/policy of the IPCC, especially among climate scientists, although they noted that climate scientists are more supportive of the IPCC’s consensus approach than scientists who do not primarily focus their work on climate.
The Curry reference in Hoppe et al is to:
Curry, J. A. (2013). ‘Kill the IPCC: after decades and billions spent, the climate body
still fails to prove humans behind warming’. Financial Post. URL:
“Scientists with a perspective that is not consistent with the consensus are at best marginalised (difficult to obtain funding and get papers published by ‘gatekeeping’ journal editors) or at worst ostracised by labels of ‘denier’ or ‘heretic.” [Curry, 2013).
The quote is from a newspaper article, and there are no further references or pieces of evidence provided to support the above statement.
So, in this example of following references to their source, we find that Connolly’s claim that “many researchers argue that scientific results that might potentially interfere with political goals are unwelcome” is, at best, anecdotal in this instance, and at worst, a twisting and reversal of what the evidence (such as was referenced) reveals about what pressure was brought to bear and by whom.
In his conclusions, Connolly says:
“… recent attempts to force an apparent scientific consensus (including the IPCC reports) on these scientific debates are premature and ultimately unhelpful for scientific progress.”
However, as shown by the previous results of my tracing through the references provided, apparently in support of that claim, the references largely support the opposite view that political pressures brought to bear on the IPCC were most likely from AGW deniers or delayists, rather than (as clearly suggested by Connolly), by other groups or individuals. The references I traced also do not provide evidence of the IPCCs scientific integrity having been “corrupted” as Connolly claims.
“We argue that the Sun/climate debate is one of these issues where the IPCC’s “consensus” statements were prematurely achieved through the suppression of dissenting scientific opinions.”
“we believe that it is timely to convey to the rest of the scientific community the existence of several unresolved problems, as well as establish those points where there is general agreement.”
“… we have agreed not to take the “consensus-driven” approach of the IPCC.”
Therefore, presumably, the paper is a collection of diverse views, which might or might not agree with each other on important matters affecting whether they do or don’t disprove the characteristics and extent of AGW.
The paper then goes on to talk about Northern hemisphere temp changes and TSI (Total Solar irradiance)
TSI and CMIP6
CMIP6 is explained in detail here:
TSI is described here:
Carbon Brief do say that:
“There is still some debate around how much solar output changed in the past, with some reconstructions suggesting more variation than others.”
But they also say:
Dr Gavin Schmidt, director of NASA Goddard Institute of Space Studies, tells Carbon Brief that it would take around a seven watts per metre squared change in TSI to result in 1C warming, meaning that the observed rise in solar activity between 1880 and 1980 would result in only 0.1C warming.
There are indirect effects that need to be accounted for as well. Increases in solar UV output increase the formation of ozone, which is itself a greenhouse gas. This could at most double solar’s contribution to warming, taking it to 0.2C.
This shows that solar has only had a small impact of global temperatures over the last century or so, says Schmidt:
“Just as for the other drivers of change (such as deforestation, air pollution and greenhouse gases) we can calculate the fingerprint for these variations in time throughout the climate system from the surface to the mesosphere [in the upper atmosphere]. When we match that up with what we have observed over time though, the solar contribution is small –- close to zero over the last 50 years, and perhaps as large as 10% since the late 19th century.”
“We urge researchers who are genuinely interested in trying to answer the question posed by the title of this paper to consider a wide range of TSI estimates and not just ones that agree with the researchers’ prior beliefs or expectation … uncertainties involved in estimating how solar activity has varied over recent decades, let alone centuries, have not been satisfactorily addressed.”
But he doesn’t seem to present any solid evidence that any researchers are “just [considering ranges of TSI estimates] that agree with the researchers’ prior beliefs or expectation.”
Connolly claims urbanisation bias is an unresolved issue, because:
“it is only in the estimates [ie when calculating and estimating temperature trends since the
19th century or earlier] that consider both urban and rural station records in which the recent warming period appears particularly unusual. This suggests to us that urbanization bias does remain a significant problem for current temperature trend estimates.”
He cites the work of McKitrick.
However, the “Urban Heat Island” effect is rebutted here:
Connolly’s paper might have set out with the aim of being a collection of diverse views, in order to “emphasize where dissenting scientific opinions exist as well as where there is scientific agreement.” He might have succeeded in the former, but with very little of the latter.
In any case, his paper does not make any positive contribution to advancing scientific knowledge on important matters affecting the characteristics and extent of AGW.
Instead, it comes across as a veritable gish gallop of scientific views – a scattergun approach, including views from numerous AGW deniers among the many cited references.
This brief foray into his work reminds me of the works of Bjorn Lomborg, many of which have been reviewed by experts and found to be suffering from similar deficiencies to those I’ve just outlined here in relation to Connolly’s paper. See more in my previous blog post about Lomborg.
This has not been a full scientific review or rebuttal of the Connolly paper. I’ll leave that to the many interested parties with appropriate climate science expertise.
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