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This is a list of scientists who have made statements that conflict with the scientific consensus on global warming as summarized by the Intergovernmental Panel on Climate Change and endorsed by other scientific bodies. A minority of them are climatologists.
Scientific consensus on climate change is the consensus of climate scientists regarding the degree to which global warming is occurring, its likely causes, and its probable consequences. Currently, there is a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports.
Global warming is the long-term rise in the average temperature of the Earth's climate system. It is a major aspect of climate change, and has been demonstrated by direct temperature measurements and by measurements of various effects of the warming. The terms global warming and climate change are often used interchangeably. However, speaking more accurately, global warming denotes the mainly human-caused increase in global surface temperatures and its projected continuation, but climate change includes both global warming and its effects, such as changes in precipitation. While there have been prehistoric periods of global warming, many observed changes since the mid-20th century have been unprecedented over decades to millennia.
The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations that is dedicated to providing the world with an objective, scientific view of climate change, its natural, political, and economic impacts and risks, and possible response options.
Nearly all publishing climate scientists (97–98% [1] ) support the consensus on anthropogenic climate change. [3] [4] The scientific consensus is that the global average surface temperature has risen over the past century. Scientific opinion on climate change was summarized in the 2001 Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). The main conclusions on global warming at that time were as follows:
Human impact on the environment or anthropogenic impact on the environment includes changes to biophysical environments and ecosystems, biodiversity, and natural resources caused directly or indirectly by humans, including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Modifying the environment to fit the needs of society is causing severe effects, which become worse as the problem of human overpopulation continues. Some human activities that cause damage to the environment on a global scale include human reproduction, overconsumption, overexploitation, pollution, and deforestation, to name but a few. Some of the problems, including global warming and biodiversity loss pose an existential risk to the human race, and overpopulation causes those problems.
The IPCC Third Assessment Report (TAR), Climate Change 2001, is an assessment of available scientific and socio-economic information on climate change by the IPCC. The IPCC was established in 1988 by the United Nations Environment Programme (UNEP) and the UN's World Meteorological Organization (WMO) "... to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation." The Third Assessment Report is the third of a series of assessments; it has been superseded by the IPCC Fourth Assessment Report (AR4), released in 2007.
These findings are recognized by the national science academies of all the major industrialized nations; [9] the consensus has strengthened over time [10] and is now virtually unanimous. [11] The level of consensus correlates with expertise in climate science. [12]
There have been several efforts to compile lists of dissenting scientists, including a 2008 US senate minority report, [13] the Oregon Petition, [14] and a 2007 list by the Heartland Institute, [15] all three of which have been criticized on a number of grounds. [16] [17] [18]
The Global Warming Petition Project, also known as the Oregon Petition, is a petition urging the United States government to reject the global warming Kyoto Protocol of 1997 and similar policies. Some consider it to be a political petition designed for disinforming and confusing the public about the scientific results and the consensus of climate change research.
For the purpose of this list, a "scientist" is defined as an individual who has published at least one peer-reviewed research article in the broad field of natural sciences, although not necessarily in a field relevant to climatology. Since the publication of the IPCC Third Assessment Report, each has made a clear statement in his or her own words (as opposed to the name being found on a petition, etc.) disagreeing with one or more of the report's three main conclusions, and each has been described in reliable sources as a climate skeptic, denier, or in disagreement with any of the three main conclusions. Their views on climate change are usually described in more detail in their biographical articles. Few of the statements in the references for this list are part of the peer-reviewed scientific literature; most are from other sources such as interviews, opinion pieces, online essays and presentations.
Nota bene : Only individuals who have their own Wikipedia article may be included in the list.
Nota bene is a Latin phrase which first appeared in English writing c. 1711. Often abbreviated as NB, n.b., or with the ligature , the phrase is Latin for "note well" and comes from the Latin roots notāre and bene ("well"). It is in the singular imperative mood, instructing one individual to note well the matter at hand, i.e., to take notice of or pay special attention to it. In Modern English, it is used, particularly in legal papers, to draw the attention of the reader to a certain (side) aspect or detail of the subject on hand. While NB is also often used in academic writing, note is a common substitute.
These scientists have said that it is not possible to project global climate accurately enough to justify the ranges projected for temperature and sea-level rise over the 21st century. They may not conclude specifically that the current IPCC projections are either too high or too low, but that the projections are likely to be inaccurate due to inadequacies of current global climate modeling.
These scientists have said that the observed warming is more likely to be attributable to natural causes, rather than to human activities. Their views on climate change are usually described in more detail in their biographical articles.
These scientists have said that no principal cause can be ascribed to the observed rising temperatures, whether man-made or natural.
These scientists have said that projected rising temperatures will be of little impact or a net positive for society or the environment.
These scientists published material indicating their opposition to the mainstream scientific assessment of global warming prior to their deaths.
Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent global warming and related climate changes on Earth. The effort has focused on changes observed during the period of instrumental temperature record, particularly in the last 50 years. This is the period when human activity has grown fastest and observations of the atmosphere above the surface have become available. According to the Intergovernmental Panel on Climate Change (IPCC), it is "extremely likely" that human influence was the dominant cause of global warming between 1951 and 2010. The best estimate is that observed warming since 1951 has been entirely human caused.
Siegfried Fred Singer is an Austrian-born American physicist and emeritus professor of environmental science at the University of Virginia. Singer trained as an atmospheric physicist and is known for his work in space research, atmospheric pollution, rocket and satellite technology, his questioning of the link between UV-B and melanoma rates, and that between chlorofluoro compounds and stratospheric ozone loss, his public downplaying of the health risks of passive smoking, and as an advocate for climate change denial. He is the author or editor of several books including Global Effects of Environmental Pollution (1970), The Ocean in Human Affairs (1989), Global Climate Change (1989), The Greenhouse Debate Continued (1992), and Hot Talk, Cold Science (1997). He has also co-authored Unstoppable Global Warming: Every 1,500 Years (2007) with Dennis Avery, and Climate Change Reconsidered (2009) with Craig Idso.
The global warming controversy concerns the public debate over whether global warming is occurring, how much has occurred in modern times, what has caused it, what its effects will be, whether any action can or should be taken to curb it, and if so what that action should be. In the scientific literature, there is a strong consensus that global surface temperatures have increased in recent decades and that the trend is caused by human-induced emissions of greenhouse gases. No scientific body of national or international standing disagrees with this view, though a few organizations with members in extractive industries hold non-committal positions, and some have attempted to convince the public that climate change isn't happening, or if the climate is changing it isn't because of human influence, attempting to sow doubt in the scientific consensus.
Patrick J. ("Pat") Michaels is an American climatologist. Michaels was a senior fellow in environmental studies at the Cato Institute until Spring 2019. Until 2007 he was research professor of environmental sciences at the University of Virginia, where he had worked from 1980.
Sallie Louise Baliunas is a retired astrophysicist. She formerly worked at the Harvard-Smithsonian Center for Astrophysics and at one point was the Deputy Director of the Mount Wilson Observatory.
The Center for the Study of Carbon Dioxide and Global Change is a 501(c)(3) non-profit organization based in Tempe, Arizona. The Center produces a weekly online science newsletter called CO2Science.
Craig D. Idso is the founder, former president and current chairman of the board of the Center for the Study of Carbon Dioxide and Global Change. He is the brother of Keith E. Idso and son of Sherwood B. Idso.
Sherwood B. Idso is the president of the Center for the Study of Carbon Dioxide and Global Change, a 501(c)(3) nonprofit that disputes the consensus scientific opinion on climate change. Previously he was a Research Physicist with the U.S. Department of Agriculture's Agricultural Research Service at the U.S. Water Conservation Laboratory in Phoenix, Arizona, where he worked since June 1967. He was also closely associated with Arizona State University over most of this period, serving as an Adjunct Professor in the Departments of Geology, Geography, and Botany and Microbiology. His two sons, Craig and Keith, are, respectively, the founder and vice president of the Center for the Study of Carbon Dioxide and Global Change.
Gilbert Norman Plass was a Canadian physicist who in the 1950s made predictions about the increase in global atmospheric carbon dioxide levels in the 20th century and its effect on the average temperature of the planet that closely match measurements reported half a century later.
The Great Global Warming Swindle is a polemical documentary film that suggests that the scientific opinion on climate change is influenced by funding and political factors, and questions whether scientific consensus on global warming exists. The program was formally criticised by Ofcom, the UK broadcasting regulatory agency, which upheld complaints of misrepresentation made by David King.
Climate change denial, or global warming denial is denial, dismissal, or unwarranted doubt that contradicts the scientific consensus on climate change, including the extent to which it is caused by humans, its impacts on nature and human society, or the potential of adaptation to global warming by human actions. Many who deny, dismiss, or hold unwarranted doubt about the scientific consensus on anthropogenic global warming self-label as "climate change skeptics", which several scientists have noted is an inaccurate description. Climate change denial can also be implicit, when individuals or social groups accept the science but fail to come to terms with it or to translate their acceptance into action. Several social science studies have analyzed these positions as forms of denialism, pseudoscience, or propaganda.
The New Zealand Climate Science Coalition was a group of individuals who set up a climate change denial organisation in New Zealand with the aim of "refuting what it believes were unfounded claims about anthropogenic global warming". The Coalition came to prominence in 2010 when it challenged the methodology and accuracy of NIWA's historical temperature records in court. The Coalition lost the case, could not afford to pay costs awarded against it and was forced into liquidation. There is an unrelated website called the New Zealand Climate Science Coalition which is an American blog also written by climate change deniers. The American website links to a different URL to the original URL associated with the New Zealand website which no longer exists.
A greenhouse gas is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). The atmospheres of Venus, Mars and Titan also contain greenhouse gases.
William Happer is an American physicist who has specialized in the study of atomic physics, optics and spectroscopy. He is the Cyrus Fogg Brackett Professor of Physics, Emeritus, at Princeton University, and a long-term member of the JASON advisory group, where he pioneered the development of adaptive optics. From 1991 to 1993, Happer served as director of the Department of Energy's Office of Science as part of the George H.W. Bush administration. He was dismissed from the Department of Energy in 1993 by the Clinton Administration after disagreements on the ozone hole.
The history of the scientific discovery of climate change began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect first identified. In the late 19th century, scientists first argued that human emissions of greenhouse gases could change the climate. Many other theories of climate change were advanced, involving forces from volcanism to solar variation. Thomas Edison, pioneer of electrical technologies, voiced concern for climate change and support for renewable energy in the 1930s. In the 1960s, the warming effect of carbon dioxide gas became increasingly convincing. Some scientists also pointed out that human activities that generated atmospheric aerosols could have cooling effects as well.
The Nongovernmental International Panel on Climate Change (NIPCC) is a climate change denial advocacy organisation set up by S. Fred Singer's Science & Environmental Policy Project, and later supported by the Heartland Institute lobbying group, in opposition to the assessment reports of the Intergovernmental Panel on Climate Change (IPCC) on the issue of global warming.
(i) 97–98% of the climate researchers most actively publishing in the field support the tenets of ACC (Anthropogenic Climate Change) outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.
Both methods—abstract analysis and self-rating of authors—additionally demonstrate that scientific consensus on anthropogenic global warming (AGW) has been growing in the covered period (1991–2011).
There are good and straightforward scientific reasons to believe that the burning of fossil fuel and consequent increase in atmospheric carbon dioxide will lead to an increase in the average temperature of the world above that which would otherwise be the case. Whether the increase will be large enough to be noticeable is still an unanswered question.
I am here today to give you an example of the failed science that is used to convince uninformed people that burning fossil fuels has had and will continue to have harmful effects on the planet.
CO2 alone will never cause a warming of more than 2 degrees Celsius (3.6 degrees Fahrenheit) by the end of the century. Only with the help of supposed amplification effects, especially water vapor, do the computers arrive at a drastic temperature increase.
leading German green - former activist and Hamburg state environment senator Prof Fritz Vahrenholt. The evidence for man-made global warming is looking shakier by the day, Germany's answer to Jonathon Porritt or George Monbiot admitted. Far more likely a culprit is the sun.
The blind adherence to the harebrained idea that climate models can generate 'realistic' simulations of climate is the principal reason why I remain a climate skeptic.
[Many open questions] are not ″minor″ issues to be ″cleaned up″ by further research. Rather, they are deficiencies that erode confidence in the computer projections. [...They are] fundamental challenges to our understanding of human impacts on the climate, and they should not be dismissed with the mantra that 'climate science is settled.' While the past two decades have seen progress in climate science, the field is not yet mature enough to usefully answer the difficult and important questions being asked of it.
In conclusion, observational data do not support the sea level rise scenario. On the contrary, they seriously contradict it.
prominent skeptics...Nils-Axel Mörner
IPCC gör ingen egen forskning, utan söker som grupp stöd för en given hypotes - att koldioxiden har en avgörande betydelse för jordens framtida klimat. Detta är egentligen ogörligt, då ingen ännu har klarlagt klimatsystemets naturliga variationer. Enligt de vetenskapliga principer som växt fram under hundratals år tyder de senaste 20 årens observationer snarare på att hypotesen är falsk. (Own translation to English: The IPCC does not make its own research, but is a group searching for a given hypothesis – that carbon dioxide is crucial for the earth’s future climate. This is actually impossible since nobody has yet clarifed the climate system’s natural variability. According to the scientific principles that have developed over hundreds of years, the last 20 years of observations rather indicate that the hypothesis is false.)
It is claimed, on the basis of computer models, that this should lead to 1.1 – 6.4 C warming. What is rarely noted is that we are already three-quarters of the way into this in terms of radiative forcing, but we have only witnessed a 0.6 (+/-0.2) C rise, and there is no reason to suppose that all of this is due to humans.
Philip Stott, a professor in biogeography at the University of London and a climate change skeptic
[The IPCC AR4] estimate of equilibrium climate sensitivity is not easily reconciled with recent forcing estimates and observational data. There is increasing support for values of climate sensitivity around or below 2°C.
The IPCC and their supported scientists have worked to remove the pesky Medieval Warm Period, the Little Ice Age, and the period emailer Tom Wigley referred to as the "warm 1940s blip," and to pump up the recent warm cycle.
First, the computer models are very good at solving the equations of fluid dynamics but very bad at describing the real world. [...] Sixth, summing up the other five reasons, the climate of the earth is an immensely complicated system and nobody is close to understanding it.
But Lindzen, plainly, is different. He can’t be dismissed. Nor, of course, is he the only skeptic with serious scientific credentials. Judith Curry, the chair of the School of Earth and Atmospheric Sciences at Georgia Tech, William Happer, professor of physics at Princeton, John Christy, a climate scientist honored by NASA, now at the University of Alabama, and the famed physicist Freeman Dyson are among dozens of scientists who have gone on record questioning various aspects of the IPCC’s line on climate change. Lindzen, for his part, has said that scientists have called him privately to thank him for the work he’s doing
Claims that climate change is accelerating are bizarre. [...] The quality of the data is poor [...] The general support for warming is based not so much on the quality of the data, but rather on the fact that there was a little ice age from about the 15th to the 19th century.
A new temperature reconstruction for the past 2,000 years created by Craig Loehle of the National Council for Air and Stream Improvement indicates that, 1,000 years ago, globally averaged temperature was about 0.3 degrees Celsius warmer than the current temperature.
“I know that the models are not adequate,” Tsonis told Fox News. “There are a lot of climate models out there. They don’t agree with each other – and they don’t agree with reality.”
The findings of mathematicians Kyle L. Swanson and Anastasios Tsonis contradict the assumptions of many climate scientists... who say the planet is currently warming.
Natural variability of the climate system has been underestimated by IPCC and has, to now, dominated human influences.
William Kininmonth, a noted climate change sceptic(Subscription required.)
Natural climate changes occur unrelated to carbon dioxide contents.
Mr Plimer, a noted climate sceptic
There has always been and always will be climate change, but it has very little to do with human activity and has nothing at all to do with pollution of course.
global warming-skeptic Timothy Ball
We know that [the sun] was responsible for climate change in the past, and so is clearly going to play the lead role in present and future climate change. And interestingly... solar activity has recently begun a downward cycle.
Harris and [Ian] Clark are global warming "skeptics."Retrieved =8 April 2017.
There is no global warming due to human anthropogenic activities.CS1 maint: unfit url (link)
Canada's most vocal climate skeptics...University of Ottawa lecturer Tad Murty
The main driver of climate change, [Tim Patterson] believes, is a combination of solar changes (well-known cycles of the sun's intensity) as well as cosmic rays.
At this stage, two scenarios of potential human impact on climate appear feasible: (1) the standard IPCC model that advocates the leading role of greenhouse gases, particularly of CO
2, and (2) the alternative model that argues for celestial phenomena as the principal climate driver. The two scenarios are likely not even mutually exclusive, but a prioritization may result in different relative impact. Models and empirical observations are both indispensable tools of science, yet when discrepancies arise, observations should carry greater weight than theory. If so, the multitude of empirical observations favours celestial phenomena as the most important driver of terrestrial climate on most time scales, but time will be the final judge.
The case for anthropogenic climate change during the 20th century rests primarily on the fact that concentrations of carbon dioxide and other greenhouse gases increased and so did global temperatures. Attempts to show that certain details in the climatic record confirm the greenhouse forcing (e.g. Mitchell et al. 2001) have been less than conclusive. By contrast, the hypothesis that changes in cloudiness obedient to cosmic rays help to force climate change predicts a distinctive signal that is in fact very easily observed, as an exception that proves the rule.
Henrik Svensmark of the Danish National Space Institute is the main proponent of the hypothesis linking [comic rays] to global climate change
The story we hear from the IPCC is faulty in many respects
prominent, vigorous skeptic... Nir Shaviv
Based on my own observations of how the climate varies naturally, I am skeptical of the CO2 hypothesis (own translation from Norwegian)
Global warming results not from the emission of greenhouse gases [...], but from an unusually high level of solar radiation and [...] growth in its intensity.
A Russian astronomer named Khabibullo Abdusamatov from St Petersburg has predicted the next ice age will start between 2035 and 2045 due to a decline in solar activity
After a long time of studying climate variations, I have come to the conclusion that the space weather suggests that we are more likely heading towards a colder period than a warmer. (own translation from Swedish)
The IPCC's temperature curve (the so-called 'hockey stick' curve) must be in error [...] All measurements of solar luminosity and 14C isotopes show that there is at present an increasing solar radiation which gives a warmer climate
Tom Segalstad, a Norwegian geologist who says human-released CO2 would not have a large effect on the climate
[T]he recent warming trend in the surface temperature record cannot be caused by the increase of human-made greenhouse gases in the air.
prominent climate-change doubter, Sallie Baliunas, who was studying variations in solar radiation
[...]observed increases in carbon dioxide and other greenhouse gases make only a negligible contribution to climate warming.
Because the warming periods in these oscillations [of glaciers] occurred well before atmospheric CO
2 began to rise rapidly in the 1940s, they could not have been caused by increased atmospheric CO
2, and global warming since 1900 could well have happened without any effect of CO
2. If the cycles continue as in the past, the current warm cycle should end soon[...]
...global warming skeptic who argued that federal scientists have been manipulating climate data to inflate temperatures. The views of retired geology professor Don Easterbrook are considered in the minority.
[Global warming] probably has little to do with carbon dioxide, just like past warmings had little to do with carbon dioxide
About half of the warming during the 20th century occurred prior to the 1940s, and natural variability accounts for all or nearly all of the warming.
Professor David Legates of the University of Delaware, a former climatologist for the state, bluntly rejected leading climate change claims
There's no doubt the climate is changing; that's a given," he said. "But the question is: What's causing it. Is it mankind alone, which a lot of people say? Is it some mix of man and nature? Or is it nature? I would say nature is mostly responsible. There may be a role for man in there somewhere, but how much, I don't know.
we needn't worry about human use of hydrocarbons warming the Earth. We also needn't worry about environmental calamities, even if the current, natural warming trend continues: After all the Earth has been much warmer during the past 3,000 years without ill effects.
Robinson, a chemist and outspoken skeptic of human-caused global warming
Salby...suggests that its warmth which tends to produce more CO2, rather than vice versa - which, incidentally is the story of the past recoveries from ice ages.
Another dissenter, the American atmospheric physicist Murry Salby...
At least 60% of the warming of the Earth observed since 1970 appears to be induced by natural cycles which are present in the solar system. A climatic stabilization or cooling until 2030–2040 is forecast by the phenomenological model.
prominent, vigorous skeptic... Nicola Scafetta
The greenhouse effect is real. However, the effect is minute, insignificant, and very difficult to detect.
But, there are always skeptics. For one example among several, Fred Singer, retired University of Virginia professor of physics
there's increasingly strong evidence that previous research conclusions [...] may have been biased by underestimation of natural climate variations.
Willie Soon is a hero of the skeptical movement
I predict that [scientists will realise] most of the climate change we have observed is natural, and that mankind’s role is relatively minor
Internationally, sceptics look to climatologist Dr Roy Spencer
Taylor said he believes climate change is a combination of natural factor and human factors. "I don't deny that human activities affect climate change," he said. "But I believe up to now, natural variations have played a more important role than human activities.
:The increase in the CO
2 content of the atmosphere is an observed fact and mankind is most certainly responsible. In the long term, this increase will without doubt become harmful, but its exact role in the climate is less clear. Various parameters appear more important than CO
2. Consider the water cycle and formation of various types of clouds, and the complex effects of industrial or agricultural dust. Or fluctuations of the intensity of the solar radiation on annual and century scale, which seem better correlated with heating effects than the variations of CO
2 content.
France's foremost climate sceptic, Claude Allègre
it is not possible to exclude the idea that climate changes can be due to natural causes
climate change skeptics such as... Antonino Zichichi
The UN Intergovernmental Panel on Climate Change (IPPC) has determined that the earth's temperature has risen by about 0.7° C since 1901. According to Dr Brekke, this time period coincides not only with an increase in human-caused greenhouse gas emissions, but also with a higher level of solar activity, which makes it complicated to separate the effects of these two phenomena. [...] Dr Brekke has published more than 40 scientific articles on the sun and on the interaction between the sun and the earth. "We could be in for a surprise," he cautions. "It's possible that the sun plays an even more central role in global warming than we have suspected. Anyone who claims that the debate is over and the conclusions are firm has a fundamentally unscientific approach to one of the most momentous issues of our time."
Natural processes involving changes in the Sun could have at least as powerful an effect on global temperature as increased emissions of carbon dioxide (CO2)...
[T]he method of study adopted by the International Panel of Climate Change (IPCC) is fundamentally flawed, resulting in a baseless conclusion: Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. Contrary to this statement ..., there is so far no definitive evidence that 'most' of the present warming is due to the greenhouse effect. ... [The IPCC] should have recognized that the range of observed natural changes should not be ignored, and thus their conclusion should be very tentative. The term 'most' in their conclusion is baseless.
Dr Akasofu and Tokyo Institute of Technology geology professor Shigenori Maruyama are highly critical of the UN Intergovernmental Panel on Climate Change's acceptance that hazardous global warming results mainly from man-made gas emissions.
[I]t is very likely that the recent upward trend [in global surface temperature] is very real and that the upward signal is greater than any noise introduced from uncertainties in the record. However, the general error is most likely to be in the warming direction, with a maximum possible (though unlikely) value of 0.3 °C. ... At this moment in time we know only that: (1) Global surface temperatures have risen in recent decades. (2) Mid-tropospheric temperatures have warmed little over the same period. (3) This difference is not consistent with predictions from numerical climate models.Cite journal requires
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(help)...the data show a small underlying positive trend that is consistent with CO
2 climate forcing with no-feedback. [...] There is disagreement in regard to the validity of the global warming hypothesis that states that there are positive feedback processes leading to gains g that are larger than 1, perhaps as large as 3 or 4. However, recent studies suggest that the values of g is much smaller.
...I see neither the developing catastrophe nor the smoking gun proving that human activity is to blame for most of the warming we see. Rather, I see a reliance on climate models (useful but never "proof") and the coincidence that changes in carbon dioxide and global temperatures have loose similarity over time.
John Christy — a prominent climate-change skeptic
Carbon dioxide should not be considered as a dominant force behind the current warming...how much of the [temperature] increase can be ascribed to CO
2, to changes in solar activity, or to the natural variability of climate is uncertain
Petr Chylek of Los Alamos National Lab, a noted skeptic
The amount of climatic warming that has taken place in the past 150 years is poorly constrained, and its cause – human or natural – is unknown. There is no sound scientific basis for predicting future climate change with any degree of certainty. If the climate does warm, it is likely to be beneficial to humanity rather than harmful. In my opinion, it would be foolish to establish national energy policy on the basis of misinformation and irrational hysteria.
longtime warming skeptic David Deming
(3:59) They are making more strides in understanding el nino, but they cannot predict something like that one or two months in advance. And they are wanting me to believe a climate model projecting 50 years, 70 years in advance, enough said on that.
...there is no compelling reason to believe that the rise in temperature was caused by the rise in CO2. Furthermore, it is highly unlikely that future increases in the air's CO2 content will produce any global warming; for there are numerous problems with the popular hypothesis that links the two phenomena.
The rising CO
2 content of the air should boost global plant productivity dramatically, enabling humanity to increase food, fiber and timber production and thereby continue to feed, clothe, and provide shelter for their still-increasing numbers ... this atmospheric CO
2-derived blessing is as sure as death and taxes.
climate change skeptic Craig Idso
[W]arming has been shown to positively impact human health, while atmospheric CO
2 enrichment has been shown to enhance the health-promoting properties of the food we eat, as well as stimulate the production of more of it. ... [W]e have nothing to fear from increasing concentrations of atmospheric CO
2 and global warming.
Sherwood Idso, a longtime coal-sponsored global warming skeptic
Scientists know quite precisely how much the planet will warm in the foreseeable future, a modest three-quarters of a degree (Celsius), plus or minus a mere quarter-degree ... a modest warming is a likely benefit... human warming will be strongest and most obvious in very cold and dry air, such as in Siberia and northwestern North America in the dead of winter.
Patrick J. Michaels, a climate skeptic at the Cato Institute
the global warming argument, particularly with all the disastrous consequences that are being promulgated ... this is all a non-sustainable argument. In other words the facts will, in time, prove them to be wrong
It's absurd. Of course [temperature's] going up. It has gone up since the early 1800s, before the Industrial Revolution, because we're coming out of the Little Ice Age, not because we're putting more carbon dioxide into the air.
Reid Bryson "is referred to as a global warming skeptic."CS1 maint: BOT: original-url status unknown (link)
professor [Robert Carter], writing in the London Daily Telegraph, does not dispute the evidence that we're in an era of rising temperatures. Who does? But he suggests that man exhibits considerable hubris—insolence, even—if he imagines that he's responsible.
To support the argument that carbon dioxide is causing [global warming], the evidence would have to distinguish between human-caused and natural warming. This has not been done.
climate sceptic Chris de Freitas
I am of the opinion that [global warming] is one of the greatest hoaxes ever perpetrated on the American people.
Gray – who has gotten attention lately for calling global warming a hoax
there is no proven link between human activity and global warming
So we see that the scientific facts indicate that all the temperature changes observed in the last 100 years were largely natural changes and were not caused by carbon dioxide produced in human activities.