0.3% consensus,
not 97.1%
‘Quantifying the
consensus on global warming
in the literature’:
a comment
by
Christopher
Monckton of Brenchley
Science
and Public Policy Institute
5501 Merchants’
View Square, #209, Haymarket, VA 20169
Capsule
The latest paper apparently showing 97% endorsement of
a consensus that more than half of recent global warming was anthropogenic really
shows only 0.3% endorsement of that now-dwindling consensus.
Abstract
Cook et al. (2013) stated that abstracts of nearly
all papers expressing an opinion on climate change endorsed consensus, which,
however, traditionally has no scientific role; used three imprecise definitions
of consensus interchangeably; analyzed abstracts only; excluded 67% expressing
no opinion; omitted some key results; misstated others; and thus concluded that
97.1% endorsed the hypothesis as defined in their introduction, namely that the
“scientific consensus that human activity is very likely causing most of the
current GW (anthropogenic global warming, or AGW)”. The authors’ own data file
categorized 64 abstracts, or only 0.5% of the sample, as endorsing the
consensus hypothesis as thus defined. Inspection shows only 41 of the 64, or
0.3% of the entire sample, actually endorsed their hypothesis. Criteria for
peer review of papers quantifying scientific consensus are discussed.
Though Cook et al. (2013) reviewed abstracts of 11,944
papers on climate change and concluded that 97.1% of those expressing an
opinion supported consensus, the philosophy of science allows no role for
head-count. Aristotle, in his Sophistical
Refutations, (c. 350 B.C.E.), identified the argument from consensus as one
of the dozen commonest logical fallacies in human discourse.
Al-Haytham, the
astronomer and philosopher of science in 11th-century Iraq who is
recognized as the father of the scientific method, wrote that “the seeker after
truth” – his phrase for the scientist – does not place his faith in any mere
consensus, however venerable. Instead, he checks. “The road to the truth,” said
al-Haytham, “is long and hard, but that is the road we must follow.”
In 1860 T.H.
Huxley said: “The improver of natural knowledge absolutely refuses to
acknowledge authority, as such. For him, skepticism is the highest of duties:
blind faith the one unpardonable sin.”
Albert Einstein,
when told that 100 Nazi scientists had published a book rejecting his theory of
special relativity, responded that a single paper would have sufficed to refute
his hypothesis. His own single paper of 1905 on the electrodynamics of moving
objects had demonstrated why Newton’s
laws, till then universally accepted as true, incompletely described the motion
of celestial objects.
Popper (1934)
formalized the scientific method as an iterative algorithm starting with a
general problem (GP0), to address which a scientist proposed a
falsifiable hypothesis or tentative theory (TT0). Thereupon others
would either demonstrate during the error-elimination phase (EE0)
that the hypothesis was false, in which event it was rejected, or, more rarely,
demonstrate that it was true.
By far the
commonest outcome, however, especially in the physical sciences, is that error
elimination will fall short of demonstrating the hypothesis but will fail to
disprove it, in which event it gains some credibility. The statement of the
general problem may then be modified accordingly (GP1), and a new
tentative theory (TT1) may later be advanced to address the modified
problem; and so on. Pedetemptim, and
if necessary ad infinitum, science
iteratively converges upon the truth (Fig. 1). Consensus adds no value to this
process.
In the
scientific method, then, there is no place for mere consensus. A hypothesis
that is demonstrated – such as Pythagoras’ theorem – needs no consensus, for it
is objectively true. A hypothesis that is disproven needs no consensus, for it
is objectively false. A hypothesis that is neither demonstrated nor disproven
gains credibility, and not because a dozen or even 12,000 papers endorse it but
because – and to the extent that – it has not been demonstrated to be false.
Science is not a belief system. A priori,
then, head-counts are inappropriate tests of scientific results.
Problems in
defining the climate consensus
Al-Haytham’s
scientific method required observing nature, stating a problem precisely,
formulating a hypothesis to address it, testing the hypothesis, analyzing the
results, drawing conclusions, and publishing the findings. It is essential to
the scientific method that a tentative theory be stated in rigorously precise
terms.
In particular, the definition of the hypothesis should be expressed
quantitatively. An imprecisely defined hypothesis, especially if it is not quantitative,
may be insufficiently rigorous to be testable. If it be untestable, then, stricto sensu, it is not of interest to
science. It is a mere curiosity. Yet Cook et al. do not confine themselves to a
single definition of the hypothesis to which their consensus is said to adhere.
Three definitions of climate consensus coexist in the
paper –
Definition (1): “the consensus position that humans
are causing global warming” (abstract);
Definition (2): the “scientific consensus that human
activity is very likely causing most of the current GW (anthropogenic global
warming, or AGW)” (introduction);
Definition (3): that our enhancement of the greenhouse
effect will be dangerous enough to be “catastrophic”; (implicit in the
introduction, in discussion of the need to raise awareness of scientific
consensus to justify a “climate policy”, and explicit in Table 2 of Cook et al., citing a paper opposing “the
catastrophic view of the greenhouse effect”).
President Obama was among those who thought Cook et al. had shown a consensus endorsing
definition (3). The following tweet was posted in his name:
“Ninety-seven percent of scientists agree: #climate
change is real, man-made and dangerous.”
[Emphasis added]
Definitions (1,
3) fall short of the criteria for definition of a Popper-falsifiable hypothesis,
and definition (2) could have been clearer. Not only do Cook et al. adopt the definitions
interchangeably, but each definition is imprecise and insufficiently quantified
to allow rigorous Popper-falsification. None of the definitions specifies the
period to which it applies, or how much global warming was observed over that
period, or whether the warming is continuing, or, if so, at what rate, or whether
that rate is considered dangerous, or what rate if any is considered dangerous.
Additionally,
definitions (1) and (3) do not specify what fraction of warming was considered
anthropogenic, and definition (2) assigns no quantitative value to the term
“very likely”. Such imprecisions render the hypotheses unfalsifiable and hence beyond
the realm of legitimate scientific inquiry.
Definition (2) is akin to, but less precise than, that of the
Intergovernmental Panel on Climate Change (IPCC, 2007, p. 665):
“Greenhouse
gas forcing has very likely [90% confidence] caused most of the observed global warming over the last 50
years.”
Definition (3) is implicit in the opening words of Cook et al.:
“An accurate perception of the degree of scientific
consensus is an essential element to public support for climate policy (Ding et al., 2011). Communicating the
scientific consensus also increases people’s acceptance that climate change is
happening (Lewandowsky et al., 2012).”
The implication
is that the authors of all abstracts endorsing definitions (1) and (2) also
endorse the catastrophist definition (3). However, a hypothesis to the effect
that humans cause some warming, or even that most current global warming is
very likely to be anthropogenic, is not – and need not imply – a hypothesis
that current warming, if continued, might prove sufficiently damaging to justify
a climate policy. It is by this unwarranted extension that President Obama’s
Twitterer erroneously assumed that the survey indicated 97% endorsement of catastrophic
global warming.
The use of multiple imprecise and ill-quantified definitions of
climate consensus has some precedents in the literature. Cook et al. cite two instances:
“Surveys of climate scientists have found strong
agreement (97-98%) regarding AGW amongst publishing climate experts (Doran
& Zimmerman, 2009; Anderegg et al.,
2010).”
Doran and Zimmerman (2009)
The two authors
sent a 2-minute online survey to 10,257 earth scientists at universities and
government research agencies. Only 5% of the 3,146 respondents identified
themselves as climate scientists; 90% believed mean global temperatures had
generally risen compared with pre-1800s levels; and 82% believed human activity
was a significant contributing factor in changing mean global temperatures. Only
79 of the respondents listed climate science as their area of expertise and had
also published more than half of their recent peer-reviewed papers on climate
change. Of these, 98% believed human activity was a significant contributing
factor in changing mean global temperatures. However, the sample size was insufficient
to deliver a statistically reliable result, and the respondents were not asked
whether they believed the anthropogenic influence on temperature might become
sufficiently damaging to require a “climate policy”.
Anderegg et al. (2010)
From publication
and citation data, the authors selected 908 of 1372 climate researchers, defined
as people who had published at least 20 climate papers and had either signed
petitions opposing or supporting the IPCC’s positions or had co-authored IPCC
reports. Of these, 97-98% believed that “anthropogenic greenhouse gases have
been responsible for ‘most’ of the ‘unequivocal’ warming of the Earth's average
global temperature over the second half of the 20th century”. The definition of
the consensus in Anderegg et al. is
less imprecise than definition (2) in Cook et
al. Yet, like Cook et al., Anderegg
et al. did not seek to determine how
many researchers considered global warming to be actually or potentially
damaging enough to require a climate policy. Nevertheless, the two surveys are
often cited as demonstrating a near-unanimous scientific consensus in favor of
a climate policy, when in fact, like Cook et
al., neither survey had asked any question either about whether and to what
extent the anthropogenic component in recent warming might be dangerous or
about whether a “climate policy” should be adopted in attempted mitigation of
future warming.
In Cook et al., the definition of consensus
hypothesis that comes closest to those of the IPCC and of other head-count
papers is definition (2). Table 1 lists some of these definitions.
|
Source
|
Quantitative definition of
climate consensus
|
|
|
|
|
IPCC (2001),
Ch. 12 (attribution),
p. 699
|
“…
most of the observed warming over the last 50 years is likely to have been
due to the increase in greenhouse gas concentrations.”
|
|
Oreskes (2004)
|
As IPCC (2001), supra.
|
|
IPCC (2007),
Ch. 9 (attribution),
p.665
|
“Greenhouse
gas forcing has very likely [90% confidence] caused most of the observed global warming over the last
50 years.”
|
|
Schulte (2008)
|
As IPCC (2001), supra.
|
|
Doran & Zimmerman (2009)
|
“… human activity is a significant contributing factor
in changing mean global temperatures.”
|
|
Anderegg et al. (2010)
|
“… anthropogenic greenhouse gases have been
responsible for ‘most’ of the ‘unequivocal’ warming of the Earth's average
global temperature over the second half of the 20th century.”
|
|
Cook et al. (2013),
definition (2)
|
“…scientific consensus that human
activity is very likely causing most of the current GW (anthropogenic global
warming, or AGW).”
|
Table 1. Successive quantitative definitions of a climate consensus.
|
| |
|
|
|
|
|
Incomplete statement of the survey results
None of the seven “levels of endorsement” by which Cook et al. categorize their selected
abstracts provides evidence that any of the 11,944 abstracts encompasses the
catastrophist definition (3):
1
“Explicitly
states that humans are the primary cause of global warming”
2
“Explicit
endorsement without quantification”
3
“Implicit
endorsement”
4
“No
opinion, or uncertain”
5
“Implicit
rejection”
6
“Explicit
rejection without quantification”
7
“Explicit
rejection with quantification”
The
first endorsement level, “Explicitly states that humans are the primary cause
of global warming”, reflects definition (2) and is akin to the other
definitions in Table 1. The second and third levels, “Explicit endorsement
without quantification” and “Implicit endorsement”, reflect definition (1) in
that, like it, they are not quantitative. Yet the first
three levels of endorsement are treated as one in the results:
“To simplify the analysis, ratings
were consolidated into three groups: endorsements (including implicit and
explicit: categories 1-3) …”.
Results of
an inspection of the Cook et al. data
file
It is not
possible to discern either from the paper or from the supplementary information
what fraction of all abstracts endorse definition (2). A file of raw data was
supplied, though it was only posted online some weeks after publication. This
comma-delimited text file was dowloaded and the abstracts allocated by Cook et al. to each level of endorsement were
counted. Results are given in Table 2:
|
E.Level
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
Total
|
|
|
Explicit
support
+quant
|
Explicit
support
–quant
|
Implicit
support
–quant
|
No
opinion
/uncert
|
Implicit
rejectn.
–quant
|
Explicit
rejectn.
–quant
|
Explicit
rejectn.
+quant
|
|
|
|
|
|
|
|
|
|
|
|
|
Papers
|
64
|
922
|
2910
|
7970
|
54
|
15
|
9
|
11,944
|
|
% all
|
0.5%
|
7.7%
|
24.4%
|
66.7%
|
0.5%
|
0.1%
|
0.1%
|
100%
|
|
% opin
|
1.6%
|
23.0%
|
72.5%
|
|
1.3%
|
0.4%
|
0.2%
|
99%
|
Table 2.
Abstracts in the seven levels of endorsement specified in Cook et al. (2013). Only 64 abstracts,
according to the authors’ data file, explicitly endorsed definition (2), the
quantitative hypothesis. NB: “+quant” indicates “with quantification”; “–quant”
indicates “without quantification”; “% all” indicates the percentage of all 11,944
abstracts that fell in each level of endorsement; “% opin” indicates the
percentages of all 4014 abstracts, excluding the 7930 that expressed no opinion
but including the 40 that expressed uncertainty (1% of all papers). These 40
are not shown separately in the datafile or in the table. Therefore, the
percentages of papers expressing an opinion sum to 99%, not 100%.
Definition (1): The
count confirmed the authors’ count that 3896 of the 11,944 abstracts (i.e.,
32.6%) fell in their endorsement levels 1-3, indicating that fewer than
one-third of all abstracts indicate implicit or explicit support even for the limited
definition (1) hypothesis that humans cause some warming. It was only by
excluding those 7930 endorsement-level-4 abstracts that expressed no opinion
(but retaining the 40 level-4 abstracts expressing uncertainty) that Cook et al. were able to conclude that 97.1%
endorsed consensus.
Definition (2):
The count, in line with an earlier result published by Friends of Science in
Canada, showed only 64 papers, or just 0.5% of the sample, explicitly endorsing
the quantitative hypothesis to the effect that humans are the primary cause of
current warming. This value was
independently verified by a separate inspection of the data file to identify
occurrences of the search term “,1” at the end of each data record using the
search facility in Microsoft Notepad, whereupon 64 such occurrences were indeed
found. However, of the 64 abstracts to which Cook et al. assigned an endorsement level of 1 (“explicit endorsement
with quantification”: Annex 1), 23 do not in fact endorse definition (2). Only
41 papers (0.3% of the sample: Annex 2) endorse definition (2).
The conclusion of Cook et
al., as expressed in their abstract, is as follows:
“Among [4014] abstracts
expressing a position on AGW, 97.1% endorsed the conssensus position that
humans are causing global warming.”
A 97% consensus is
also asserted in the closing words of the paper:
“Among [4014] papers expressing
a position on AGW, an overwhelming percentage (97.2% based on self-ratings,
97.1% based on abstract ratings) endorses the scientific consensus on AGW.”
In
the introduction. Cook et al. define
“AGW” as the “scientific consensus that human activity
is very likely causing most of the current GW (anthropogenic global warming, or
AGW)”. However, the authors’ own analysis shows that only 0.5% of all 11,944
abstracts, and 1.6% of the 4014 abstracts expressing a position, endorsed “AGW”
as they had defined it. Taking into account that more than one-third of the 64
abstracts do not in fact endorse the quantitative hypothesis in Cook et al., the true percentages endorsing
that hypothesis are 0.3% and 1.0% respectively.
Evidence
that the climate consensus is declining
Oreskes (2004) published
an essay in Science alleging that not
one of 928 abstracts she had reviewed had disagreed with the consensus as
defined in IPCC (2001): “Most of the observed warming over the last 50 years is
likely to have been due to the increase in greenhouse gas concentrations”. Her adopted
definition of consensus, then, was similar to but more precise than definition
(2) in Cook et al. It, too, falls well
short of stating that manmade warming may prove catastrophic.
Her essay concluded
that three-quarters of her sample endorsed the “consensus” either explicitly
or, by evaluating impacts or proposing mitigation, implicitly. A quarter took
no view. None, she said, disagreed with the consensus as defined in IPCC (2001).
Yet the fact that a paper evaluates impacts or proposes mitigation does not
necessarily imply that the authors endorse the notion that more than half of
the past 50 years’ global warming was anthropogenic.
Schulte (2008)
reviewed 539 papers published in the three years following the period studied
by Oreskes, using the same search term and the same IPCC definition of
consensus. He found that “the proportion of papers that now explicitly or
implicitly endorse the consensus has fallen from 75% to 45%.” Only 2% of the
papers reviewed “offer new field data or observations directly relevant to the
question whether anthropogenic warming has prevailed over natural variability
in the past half-century”. Only one paper mentioned the possibility of
catastrophic climate change, but without providing any evidence for it. No
paper provided quantitative evidence for the consensus hypothesis. Schulte
concluded: “There appears to be little basis in the peer-reviewed literature
for the degree of alarm on the issue of man-made climate change which is being
expressed in the media and by politicians.”
The 75%
consensus reported by Oreskes in 2004 exceeds the 45% found by Schulte in 2008,
which in turn exceeds the 0.5-1.6% (0.3-1.0% after correction) found but not reported
by Cook et al. in 2013.
Accordingly, the
undisclosed results in Cook et al. indicate
either that earlier head-count papers had not (as Cook et al. in their published results had not) drawn any distinction
between quantified and unquantified consensus, or that over the past decade the
consensus has dwindled.
Has there
been any ‘current’ warming?
 |
| Figure 2. No global warming for 12 years 6 months, according to the HadCRUt4 dataset. |
Cook
et al.’s definition (1) is that
“humans are causing global warming”.
Definition (2) is that humans are the chief cause of “the current warming”.
Though the least-squares linear-regression trend on the monthly HadCRUt4
dataset (Morice et al., 2012) shows surface
warming over the half-century 1956-2005 at a rate equivalent to 1.2 Cº/century,
trends on the same dataset over shorter periods show no warming exceeding the
upper bound of the published measurement uncertainties for more than 17 years,
no warming at all over the 12 years 6 months November 2000 to May 2013 (Fig.
2), and cooling at 0.5 Cº/century over the decade May 2003-April 2013.
In
the usual sense of the word “current”, then, global warming is not currently
occurring, rendering definitions (1) and (2) untestable: for no scientist could
legitimately endorse a consensus to the effect that global warming is currently
occurring when, currently, it is not.
Discussion
The defects
identified in the surveys of climate consensus by Cook et al. and by the authors of some of the papers they cite follow a
pattern to whose existence peer-reviewers should be alert. First, any argument
from consensus on a question such as the extent to which anthropogenic global
warming may prove dangerous is defective a
priori and ought really to be rejected without further review.
Secondly, no
survey of opinion for or against a consensus hypothesis ought to be regarded as
scientific where it is not made clear which hypothesis is under test, or where
the hypothesis under test is not clearly and precisely formulated. A fortiori, a survey paper that exhibits
multiple definitions of the consensus hypothesis and fails to state clearly the
identity and definition of the hypothesis on the basis of which the survey was
actually conducted should surely be rejected.
Thirdly, the
consensus hypothesis under test ought to be expressed in quantitative terms.
Mere qualitative definitions of any scientific hypothesis run the risk of
appearing more political than scientific in their formulation, and papers based
on such definitions may also prove more political than scientific in their effect.
Fourthly, if
several “levels of endorsement” are specified, then the number of abstracts,
papers, or scientists considered to have supported each level of endorsement ought
to be explicitly stated in the paper under review. Cook et al. specified three levels of endorsement that supported the
notion of anthropogenic warming (however defined); yet, on the stated ground of
simplifying the analysis, the number of papers allocated to each of the three
levels of endorsement – a key result on any view – was not stated. The analysis
would indeed have been simpler if one endorsement level supporting one
definition of climate consensus had been adopted.
Conclusion
The
non-disclosure in Cook et al. of the
number of abstracts supporting each specified level of endorsement had the
effect of not making available the fact that only 41 papers – 0.3% of all 11,944
abstracts or 1.0% of the 4014 expressing an opinion, and not 97.1% – had been
found to endorse the quantitative hypothesis, stated in the introduction to Cook
et al. and akin to similar
definitions in the literature, that “human activity is very likely causing most
of the current GW (anthropogenic global warming, or AGW)”.
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Annex 1
The 41
papers endorsing the quantitative consensus
Relevant
extracts from those 41 of 64 abstracts listed by Cook et al. as endorsing their quantitative definition of the consensus
hypothesis that actually endorse it are below. The remaining 23, in Annex 2, do
not endorse it.
The data entries have been edited for clarity,
particularly by including a space after each delimiting comma; decapitalizing
abstract titles; abbreviating and italicizing journal names; removing a “|”
mark that appeared after each author’s name; capitalizing all authors’
initials; and correcting some typographical errors.
1: 1992, Implications for
global warming of intercycle solar irradiance variations, Nature, Schlesinger M.E.; Ramankutty N, 2, 1
“… we find that since the nineteenth century,
greenhouse gases, not solar irradiance variations, have been the dominant
contributor to the observed temperature changes.”
4: 1994, Greenhouse
statistics – Time-series analysis 2, Theor.
& Appl. Climatol., Tol RSJ, 4, 1
“… the hypothesis that the anthropogenically
enhanced greenhouse effect is not responsible for the observed global warming
during the last century is rejected with a 99% confidence, is reconfirmed.”
6: 1997, Assessments of the
global anthropogenic greenhouse and sulfate signal using different types of
simplified climate models, Theor. &
Appl. Climatol., Schonwiese CD; Denhard M; Grieser J; Walter A, 2, 1
“Our statistical assessments, based on the
1866–1994 period, lead to a GHG signal of 0.8–1.3 K and a combined GHG-SU
signal of 0.5–0.8 K detectable in observations. This is close to GCM
simulations and clearly larger than the volcanic, solar and ENSO (El
Niño/southern oscillation) signals also considered.”
11: 2000, Recent warming in a
500-year palaeotemperature record from varved sediments; Upper Soper Lake;
Baffin Island; Canada, Holocene,
Hughen KA; Overpeck JT; Anderson RF, 5, 1
“Comparisons of Upper Soper Lake and Arctic average
palaeotemperature to proxy-records of hypothesized forcing mechanisms suggest
that the recent warming trend is mostly due to anthropogenic emissions of
atmospheric greenhouse gases.”
14: 2002, Global Warming
2001, J. de Physique IV, Berger A, 4,
1
“In its Third Assessment
Report, the Intergovernmental Panel on Climate Change (IPCC) states clearly
that "an increasing body of observations give a collective picture of a
warming world and other changes in the climate system" and that "there
is new and stronger evidence that most of the warming observed over the last
50 years is attributable to human activities".
16: 2003, Do models
underestimate the solar contribution to recent climate change?, J. Clim., Stott PA; Jones GS; Mitchell
JFB, 4, 1
“… the results
confirm previous analyses showing that greenhouse gas increases explain most of
the global warming observed in the second half of the twentieth century.”
17: 2003, Modern global
climate change, Science, Karl TR;
Trenberth KE, 2, 1
“Modern climate change is dominated by human influences, which are now
large enough to exceed the bounds of natural variability. The main source of
global climate change is human-induced changes in atmospheric composition.”
19: 2004, Numerical
simulation of global temperature change during the 20th century with the
IAP/LASG GOALS model, Advances In Atmos.
Sci., Ma XY; Guo YF; Shi GY; Yu YQ, 2, 1
“The global warming during the 20th century is
caused mainly by increasing greenhouse gas concentration especially since the
late 1980s.”
20: 2004, Soot climate
forcing via snow and ice albedos, PNAS,
Hansen J; Nazarenko L, 4, 1
“… soot contributions to climate change do not alter the conclusion that
anthropogenic greenhouse gases have been the main cause of recent global
warming and will be the predominant climate forcing in the future.”
22: 2005, Mid-late Holocene
monsoon climate retrieved from seasonal Sr/Ca and δ18O records of porites lutea corals at Leizhou Peninsula; northern coast of South
China Sea, Global & Planetary Change,
Yu KF; Zhao JX; Wei GJ; Cheng XR; Wang PX, 5, 1
“… the increase in
the concentration of anthropogenic greenhouse gases played a dominant role in
recent global warming, …”
23: 2006, Assessment of 20th-century
regional surface temperature trends using the GFDL CM2 coupled models, J. Clim., Knutson TR; Delworth TL; Dixon
KW; Held IM; Lu J; Ramaswamy V; Schwarzkopf MD; Stenchikov G; Stouffer RJ, 4, 1
“The simulations
support previous findings that twentieth-century global warming has resulted
from a combination of natural and anthropogenic forcing, with anthropogenic
forcing being the dominant cause of the pronounced late-twentieth-century
warming.”
25: 2006, Phenomenological
solar contribution to the 1900-2000 global surface warming, GRL, Scafetta N; West BJ, 4, 1
“We estimate that the sun contributed as much
as 45–50% of the 1900–2000 global warming, and 25–35% of the 1980–2000 global
warming. These results, while confirming that anthropogenic-added climate
forcing might have progressively played a dominant role in climate change
during the last century, also suggest that the solar impact on climate change
during the same period is significantly stronger than what some theoretical
models have predicted.”
27: 2006, Study on CO2
recovery system from flue gas by honeycomb type adsorbent I – results of tests
and simulation), Kagaku Kogaku Ronbunshu,
Matsukuma Y; Matsushita Y; Kakigami H; Inoue G; Minemoto M; Yasutake A; Oka N,
3, 1
“Carbon dioxide (CO2) included in
the exhaust gas from heat power plants is the chief cause of global warming.”
29: 2007, A model for the CO2
capture potential, Int. J. GHG Control,
Stanyeland A, 3, 1
“Global warming is
a result of increasing anthropogenic CO2
emissions, and the consequences will be dramatic climate changes if no action
is taken.”
30: 2007, Avoiding
self-organized extinction: toward a co-evolutionary economics of
sustainability, Int. J. Sustain. Devel.
& World Ecol., Gowdy J, 2, 1
“There is a a near-universal consensus that
global warming is human-caused and that its effects are now accelerating.”
31: 2007, CO2
emissions from road transport and selected parts in the Kosice City, Acta Montanistica Slovaca, Carach V;
Muller G; Janoskova K, 4, 1
“Nowadays it is clear that the climatic
unstability is mostly caused by human activities.”
32: 2007, Global climate
change and children's health, Pediatrics,
Shannon MW; Best D; Binns HJ; Forman JA; Johnson CL; Karr CJ; Kim JJ; Mazur LJ;
Roberts JR; Shea KM, 2, 1
There is a broad scientific consensus that the global
climate is warming, the process is accelerating, and that human activities are
very likely (>90% probability) the main cause.”
33: 2007, Global warming is
driven by anthropogenic emissions: a time series analysis approach, Phys. Rev. Lett., Verdes PF, 2, 1
“Here we show, using two independent driving force reconstruction
techniques, that the combined effect of greenhouse gases and aerosol emissions
has been the main external driver of global climate during the past decades.”
35: 2008, Carbonation of
alkaline paper mill waste to reduce co2 greenhouse gas emissions into the
atmosphere, Appl. Geochem.,
Perez-Lopez R; Montes-Hernandez G; Nieto JM; Renard F; Charlet L, 3, 1
“The global warming
of Earth’s near-surface, air and oceans in
recent decades is a direct consequence of anthropogenic emission of greenhouse
gases into the atmosphere such as CO2,
CH4, N2O
and CFCs. The CO2 emissions
contribute approximately 60% to this climate change.”
36: 2008, Climate policy
architectures for the post-Kyoto world, Environment,
Aldy JE; Stavins RN, 3, 1
“The Intergovernmental Panel on Climate Change
has determined earlier that most of the increase in global average temperatures
is very likely due to the adverse increase in anthropogenic greenhouse gas
concentrations.”
37: 2008, Cycle analysis of
low and high H2 utilization SOFCS/gas turbine combined cycle for CO2
recovery, Electronics & Comms. in
Japan, Taniuchi T; Sunakawa D; Nagahama M; Araki T; Onda K; Kato T, 3, 1
“Global warming is mainly caused by CO2 emission from thermal power plants, which burn
fossil fuel with air.”
38: 2008, Energy sources and
global climate change: the Brazilian case, Energy
Sources A, Simoes AF; La Rovere EL, 3, 1
“Fossil fuels consumption is the primary cause of global
warming.”
41: 2008, Leaf carbon assimilation
in a water-limited world, Plant Biosys.,
Loreto F; Centritto M, 2, 1
“Over the past 150 years the amount of CO2
in the atmosphere has been increasing, largely as a result of land-use change
and anthropogenic emissions from the burning of fossil fuels.”
42: 2008, On avoiding dangerous anthropogenic
interference with the climate system: formidable challenges ahead, PNAS, Ramanathan V; Feng Y, 2, 1
IPCC models suggest that ≈25% (0.6°C) of the committed warming has been
realized as of now.
43: 2008, The potential of
water power in the fight against global warming in the US, Energy Policy, Kosnik L, 3, 1
“The leading cause
of climate change today is the burning of fossil fuels related to energy
production.”
45: 2009, Climate changes and
the actions of the European Union for environmental protection, Metalurgia Int., Brezoi AG; Tharin M, 4,
1
“According to the meetings of the experts … the
human origin of present-day climate changes is estimated at 90%.”
47: 2010, A novel formulation
of carbon emissions costs for optimal design configuration of system
transmission planning, Renewable Energy,
Sadegheih A, 3, 1
“Global warming,
which is mainly caused by the emissions of Green House Gases (GHGs), is said to
be a serious part of these environmental problems.”
48: 2010, Analysis of the
global warming dynamics from temperature time series, Ecol. Modelling, Viola FM; Paiva SLD; Savi MA, 4, 1
“Global warming is
the observed increase of the average temperature of the Earth. The primary
cause of this phenomenon is the release of the greenhouse gases by burning of
fossil fuels, land cleaning, agriculture, among others, leading to the increase
of the so-called greenhouse effect.”
50: 2010, Conceptual design
and simulation analysis of thermal behaviors of TGR blast furnace and oxygen
blast furnace, Science China – Technol.,
Zhang H; Li HQ; Tang Q; Bao WJ, 3, 1
“Extensive use of carbon based fuel is the main
inducement for global warming and more extreme weather.”
51: 2010, Consumption-based
accounting of CO2 emissions, PNAS,
Davis SJ; Caldeira K, 4, 1
“CO2 emissions from the burning of fossil fuels are the
primary cause of global warming.”
52: 2010, Dynamic competition
under cap and trade programs, Infor,
Jeev K; Campos-Nanez E, 3, 1
“Greenhouse gases (GHG), like carbon dioxide (CO2), which are
released in the atmosphere due to anthropogenic activities like power
production, are now accepted as the main culprits for global warming.”
53: 2010, Short-term effects
of controlling fossil-fuel soot; biofuel soot and gases; and methane on climate;
arctic ice; air pollution; and health, JGR
Atmos., Jacobson MZ, 3, 1
“… net global warming (0.7–0.8 K) is due mostly
to gross pollutant warming from fossil-fuel greenhouse gases (2–2.4 K), …”
56: 2011, Early onset of
significant local warming in low latitude countries, Env. Res. Lett., Mahlstein I; Knutti R; Solomon S; Portmann RW, 2,
1
“… most of the global warming of the past
half-century can very likely be attributed to human influence.”
57: 2011, Earth's energy
imbalance and implications, Atmos. Chem.
& Phys., Hansen J; Sato M; Kharecha P; Von Schuckmann K, 4, 1
“The inferred planetary energy imbalance, 0.58 ± 0.15 W m−2
during the 6-yr period 2005–2010, confirms the dominant role of the human-made
greenhouse effect in driving global climate change.”
58: 2011, Emergent dynamics
of the climate-economy system in the anthropocene, Philos. Trans. Royal Soc. A, Kellie-Smith O; Cox PM, 4, 1
59: 2011, Insights on global
warming, Aiche J., Seinfeld JH, 4, 1
“The global temperature increase over the last
century and a half (∼ 0.8°C), and
the last three decades in particular, is well outside of that which can be
attributed to natural climate fluctuations. The increase of atmospheric CO2 over this period has been conclusively
demonstrated to be a result largely of fossil fuel burning. … That the Earth
has warmed and that GHGs are responsible is unequivocal.”
60: 2011, isolation and
application of SOx- and NOx-resistant microalgae in
biofixation of CO2 from thermo-electricity plants, Energy Conversion And Management,
Radmann EM; Camerini FV; Santos TD; Costa JAV, 3, 1
“Microalgae have
been studied for their potential use in foodstuffs, agriculture, in the
treatment of wastewater and, in particular, in the reduction of atmospheric
carbon dioxide, the main cause of global warming.”
61: 2011,On the time-varying
trend in global-mean surface temperature, Clim.
Dynam.,Wu ZH; Huang NE; Wallace JM; Smoliak BV; Chen XY, 4, 1
“… we estimate that up to one third of the late
twentieth century warming could have been a consequence of natural
variability.”
62: 2011, Performance of
amine-multilayered solid sorbents for CO2 removal: effect of
fabrication variables, Int. J. GHG Control,
Jiang BB; Kish V; Fauth D; Gray ML; Pennline HW; Li BY, 3, 1
“The emission of
fossil fuel carbon dioxide (CO2) to the atmosphere
is implicated as the predominant cause of global climate change.”
63: 2011, Sensitivity of the
attribution of near surface temperature warming to the choice of observational
dataset, GRL, Jones GS; Stott PA, 4,
1
“Our results show that the dominant contributor
to global warming over the last 50 years of the 20th century is that due to
greenhouse gases.”
64: 2011, The relative
contribution of waste heat from power plants to global warming, Energy, Zevenhoven R; Beyene A, 4, 1
“Evidence on global
climate change, being caused primarily by rising levels of greenhouse gases in
the atmosphere, is perceived as fairly conclusive.”
Annex 2
The 23
papers not endorsing the quantitative consensus
Relevant
extracts from those 23 of the 64 abstracts listed by Cook et al. as endorsing their quantitative definition of the consensus
hypothesis that do not endorse it are below, with reasons why they do not
endorse it. The remaining 41 abstracts, in Annex 1, endorse it.
The data entries have been edited for clarity,
particularly by including a space after each delimiting comma; decapitalizing
abstract titles; abbreviating and italicizing journal names; removing a “|”
mark that appeared after each author’s name; capitalizing all authors’
initials; and correcting some typographical errors.
2: 1992, Past; present and
future levels of greenhouse gases in the atmosphere and model projections of
related climatic changes, J. Experim.
Botany, Roeckner E, 2, 1
“The more recent increase in greenhouse
gases since pre-industrial times can be related to human activities.”
Reason for rejection: The increase “can be related to
human activities”, but the abstract falls short of saying that most of the
increase is attributable to human activities.
3: 1993, How sensitive is the
world’s climate?, Research & Explor.,
Hansen J; Lacis A; Ruedy R; Sato M; Wilson H, 4, 1
“Observed global warming of approximately 0.5 C° in the past 140 years is
consistent with anthropogenic greenhouse gases being the dominant climate forcing
in that period.”
Reason for rejection: “… is consistent with” is not the
same thing as “is likely to have been”.
5: 1995, Climate response to
increasing levels of greenhouse gases and sulfate aerosols, Nature, Mitchell JFB; Johns TC; Gregory
JM; Tett SFB, 4, 1
“CLIMATE
models suggest that increases in greenhouse-gas concentrations in the
atmosphere should have produced a larger global mean warming than has been
observed in recent decades, unless the climate is less sensitive than is
predicted by the present generation of coupled general circulation models.”
Reason for rejection: The abstract qualifies its first
statement by saying that the climate may be less sensitive than models predict.
7: 1998, A Bayesian statistical
analysis of the enhanced greenhouse effect, Clim.
Change, Tol RSJ; De Vos AF, 4, 1
“… there is a robust statistical relationship
between the records of the global mean surface air temperature and the
atmospheric concentration of carbon dioxide over the period 1870–1991. As such,
the enhanced greenhouse effect is a plausible explanation for the observed
global warming.”
Reason for rejection: The greenhouse effect is a
“plausible explanation”, but it is not definite, and there is no
quantification.
8: 1999, CFC and halon
replacements in the environment, J.
Fluor. Chem., McCulloch A, 3, 1
“Substitute
fluorocarbons may have direct environmental impact, for example as greenhouse
gases … The growth in hydrofluorocarbons (HFCs) amounts to about 10% of the
fall in CFCs. It is likely that the impact of new fluorocarbons on climate
change will be a very small fraction of the total impact, which comes mainly
from the accumulation of carbon dioxide in the atmosphere.”
Reason for rejection: The “total impact” mentioned in
the abstract is the impact of Man, not that of Man and nature combined. Man’s
impact does come mainly from the accumulation of CO2 in the air, but that falls
short of saying that Man’s impact has caused more than half of recent warming.
9: 2000, Causes of climate
change over the past 1000 years, Science,
Crowley TJ, 5, 1
“The combination of a unique level of temperature increase in the late
20th century and improved constraints on the role of natural variability
provides further evidence that the greenhouse effect has already established
itself above the level of natural variability in the climate system.”
Reason for rejection: The greenhouse effect may (or may
not) have added to the warming that may have arisen from natural variability,
but there is no quantification of how much it has added to natural warming.
10: 2000, Radiative forcings
and global warming potentials of 39 greenhouse gases, JGR Atmos., Jain AK; Briegleb BP; Minschwaner K; Wuebbles DJ, 4, 1
“Our total radiative forcing due to increase in
major greenhouse gas concentrations for the period 1765–1992 is 2.32 Wm−2, only 2% higher than other recent estimates;
however, the differences for individual gases are as large as 23%.”
Reason for rejection: Stating the magnitude of a
radiative forcing falls short of stating the magnitude of the warming the
forcing may be thought to have engendered.
12: 2000, Response of the
NCAR climate system model to increased co2 and the role of physical processes, J. Clim., Meehl GA; Collins WD; Boville
BA; Kiehl JT; Wigley TML; Arblaster JM, 4, 1
“Another process that
contributes to climate response to increasing CO2 is sea-ice
changes, which are estimated to enhance global warming by roughly 20% in the
CSM and 37% in the DOE model. Sea-ice retreat with increasing CO2 in
the CSM is less than in the DOE model in spite of identical sea-ice
formulations.”
Reason for rejection: The fact that global warming in the
future may be enhanced by sea-ice retreat tells us nothing about whether global
warming in the past has chiefly been manmade.
13: 2001, Strong radiative
heating due to the mixing state of black carbon in atmospheric aerosols, Nature, Jacobson MZ, 4, 1
“The magnitude of the direct
radiative forcing from black carbon itself exceeds that due to CH4,
suggesting that black carbon may be the second most important component of
global warming after CO2 in terms of direct forcing.”
Reason for rejection: The abstract is talking of the
manmade component, not including the natural component. So there is no
quantification of the relative magnitudes of the two: nor is any period
specified.
15: 2002, Modeling future
climate changes: certainties and uncertainties, Houille Blanche Revue Internationale de l’Eau, Le Treut H, 4, 1
“Present projections indicate, in all cases, a
significant change, with a global surface warming in 2100 between 2 C° and 6 C°.”
Reason for rejection: Projections are one thing;
observations another. The fact that global warming is projected tells us nothing
about what fraction of it in the observed past is attributable to Man.
18: 2003, Utilization of
carbon dioxide as soft oxidant in the dehydrogenation of ethylbenzene over
supported vanadium-antimony oxide catalystst, Green Chemistry, Chang JS; Vislovskiy VP; Park MS; Hong DY; Yoo JS;
Park SE, 3, 1
“This work shows that carbon dioxide, which is
a main contributor to the global warming effect, could be utilized as a
selective oxidant in the oxidative dehydrogenation of ethylbenzene over
alumina-supported vanadium oxide catalysts.”
Reason for rejection: “A main contributor” is not the
same as “the main contributor”.
21: 2005, Is the Sonoran Desert
losing its cool?, Global Change Biol.,
Weiss JL; Overpeck JT, 2, 1
“Minimum temperature variability in the Sonoran
Desert does, however, correspond to global temperature variability attributed
to human-dominated global warming.”
Reason for rejection: A correspondence between regional
and global patterns of temperature variability attributed to Man is not the
same as an assertion that most recent warming is manmade.
24: 2006, Observational
constraints on past attributable warming and predictions of future global
warming, J. Clim., Stott PA; Mitchell
JFB; Allen MR; Delworth TL; Gregory JM; Meehl GA; Santer BD, 4, 1
“… the spatial and
temporal nature of observed twentieth-century temperature change constrains the
component of past warming attributable to anthropogenic greenhouse gases to be
significantly greater (at the 5% level) than the observed warming over the
twentieth century.”
Reason for rejection: A 5% confidence level is too low to
be reliable.
26: 2006, Positive feedback
between global warming and atmospheric CO2 concentration inferred
from past climate change, GRL,
Scheffer M; Brovkin V; Cox PM, 5, 1
“There is good evidence that higher global
temperatures will promote a rise of greenhouse gas levels, implying a positive
feedback which will increase the effect of anthropogenic emissions on global
temperatures. However, the magnitude of this effect predicted by the available
models remains highly uncertain, due to the accumulation of uncertainties in
the processes thought to be involved.”
Reason for rejection: The abstract tells us nothing of
what has happened. It merely predicts
what will happen.
28: 2006, Transient climate
simulations with the HADGEM1 climate model: causes of past warming and future
climate change, J. Clim., Stott PA;
Jones GS; Lowe JA; Thorne P; Durman C; Johns TC; Thelen JC, 4, 1
“The ability of climate
models to simulate large-scale temperature changes during the twentieth century
when they include both anthropogenic and natural forcings and their inability
to account for warming over the last 50 yr when they exclude increasing greenhouse
gas concentrations has been used as evidence for an anthropogenic influence on
global warming. … new simulations support previous work by showing that there
was a significant anthropogenic influence on near-surface temperature change
over the last century.”
Reason for rejection: “A significant anthropogenic
influence” does not necessarily mean “more than 50%”.
34: 2008, Banagrass vs.
eucalyptus wood as feedstocks for metallurgical biocarbon production, Indust. & Eng. Chem. Res., Yoshida
T; Turn SQ; Yost RS; Antal MJ, 3, 1
“Excessive emissions of
fossil CO2 are known to be a primary
cause of global climate change.”
Reason for rejection: “A primary cause” is not the same
as “the primary cause”.
39: 2008, Implications of
“peak oil” for atmospheric CO2 and climate, Global Biogeochem. Cycles, Kharecha PA; Hansen JE, 3, 1
“Unconstrained CO2 emission from fossil fuel burning has been the
dominant cause of observed anthropogenic global warming.”
Reason for rejection: The dominant cause of anthropogenic warming, but not
necessarily the dominant cause of all global
warming.
40: 2008, Industrialization;
fossil fuels; and the transformation of land use, J. Indust. Ecol., Erb KH; Gingrich S; Krausmann F; Haberl H, 4, 1
“Human-induced changes in global stocks and
flows of carbon are major drivers of global climate change.”
Reason for rejection: “Major drivers”, but not “the major
drivers”.
44: 2009, Climate change and
drying of agricultural products, Drying
Technol., Piacentini RD; Mujumdar AS, 3, 1
“Global warming is affecting the world and will
continue to affect humans and the ecosystem in the future.”
Reason for rejection: Global warming may or may not be
“affecting the world”, but there is nothing in the abstract to tell us that
more of it is anthropogenic than natural.
46: 2009, Cost-benefit
analysis of climate change dynamics: uncertainties and the value of
information, Clim. Change, Rabl A;
Van Der Zwaan B, 4, 1
“We analyze climate change in a cost–benefit
framework, using the emission and concentration profiles of Wigley et al.
(Nature 379(6562):240–243, 1996). They present
five scenarios that cover the period 1990–2300 and are designed to reach
stabilized concentration levels of 350, 450, 550, 650 and 750 ppmv,
respectively.”
Reason for rejection: The abstract concerns itself with
projections, and – other than referring to Wigley’s scenarios starting in 1900
– makes no reference to past warming at all, let alone saying that most of it
was manmade.
49: 2010, Assessing the
climatic benefits of black carbon mitigation, PNAS, Kopp RE; Mauzerall DL, 3, 1
“To limit mean global warming to 2 °C, a goal supported by more than 100
countries, it will likely be necessary to reduce emissions not only of
greenhouse gases but also of air pollutants with high radiative forcing (RF),
particularly black carbon (BC).”
Reason for rejection: The statement of a target for
future emissions is not equivalent to a statement that most recent warming was
caused by past emissions.
54: 2010, The Copenhagen
accord for limiting global warming: criteria; constraints; and available
avenues, PNAS, Ramanathan V; Xu YY,
3, 1
“At last, all the major emitters of greenhouse gases (GHGs) have agreed
under the Copenhagen Accord that global average temperature increase should be
kept below 2 °C.”
Reason for rejection: The adoption of a target for future
emissions is not equivalent to a statement that most recent warming was caused
by past emissions.
55: 2011, Coupled
climate-society modeling of a realistic scenario to achieve a sustainable
earth, J. Oceanog.,Ikeda M, 4, 1
“The surface air temperature (SAT) rises due to
the atmospheric carbon, which is partially absorbed by the terrestrial
ecosystem and the ocean. These absorption rates are reduced by the rising SAT.”
Reason for rejection: There is no statement here that the
surface air temperature rises solely or chiefly owing to the atmospheric CO2.
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