scientific consensus on climate change
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.
Nearly all actively publishing climate scientists say humans are causing climate change. Surveys of the scientific literature are another way to measure scientific consensus. A 2019 review of scientific papers found the consensus on the cause of climate change to be at 100%, and a 2021 study concluded that over 99% of scientific papers agree on the human cause of climate change. The small percentage of papers that disagreed with the consensus often contain errors or cannot be replicated.As stated by the Intergovernmental Panel on Climate Change (IPCC), the largest contributor to global warming is the increase in atmospheric carbon dioxide (CO2) since 1750, particularly from fossil fuel combustion, cement production, and land use changes such as deforestation.: 10–11   The IPCC's Fifth Assessment Report (AR5) stated already in 2013:

Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely (95–100%) that human influence has been the dominant cause of the observed warming since the mid-20th century
The evidence for global warming due to human influence has been recognized by the national science academies of all the major industrialized countries. In the scientific literature, there is a very 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. A few organizations with members in extractive industries hold non-committal positions, and some have tried to persuade the public that climate change is not happening, or if the climate is changing it is not because of human influence, attempting to sow doubt in the scientific consensus (see climate change denial).

Consensus points
The current scientific consensus is that:

Earth's climate has warmed significantly since the late 1800s.
Human activities (primarily greenhouse gas emissions) are the primary cause.
Continuing emissions will increase the likelihood and severity of global effects.
People and nations can act individually and collectively to  slow the pace of global warming, while also preparing for unavoidable climate change and its consequences.Changes in global temperature are usually expressed in terms of temperature anomalies: "In climate change studies, temperature anomalies are more important than absolute temperature. A temperature anomaly is the difference from an average, or baseline, temperature. The baseline temperature is typically computed by averaging 30 or more years of temperature data."Several studies of the consensus have been undertaken. Among the most cited is a 2013 study of nearly 12,000 abstracts of peer-reviewed papers on climate science published since 1990, of which just over 4,000 papers expressed an opinion on the cause of recent global warming. Of these, 97% agree, explicitly or implicitly, that global warming is happening and is human-caused. It is "extremely likely" that this warming arises from "human activities, especially emissions of greenhouse gases" in the atmosphere. Natural change alone would have had a slight cooling effect rather than a warming effect.This scientific opinion is expressed in synthesis reports, by scientific bodies of national or international standing, and by surveys of opinion among climate scientists. Individual scientists, universities, and laboratories contribute to the overall scientific opinion via their peer-reviewed publications, and the areas of collective agreement and relative certainty are summarised in these respected reports and surveys.

Assessment reports by IPCC
Synthesis reports are assessments of scientific literature that compile the results of a range of stand-alone studies in order to achieve a broad level of understanding, or to describe the state of knowledge of a given subject.

IPCC Sixth Assessment Report in 2021 to 2023
IPCC Fifth Assessment Report in 2014
The conclusions are summarized below:
"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia."
"Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years."
Human influence on the climate system is clear. It is extremely likely (95–100% probability) that human influence was the dominant cause of global warming between 1951 and 2010.
"Increasing magnitudes of [global] warming increase the likelihood of severe, pervasive, and irreversible impacts."
"A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability."
"The overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change"
Without new policies to mitigate climate change, projections suggest an increase in global mean temperature in 2100 of 3.7 to 4.8 °C, relative to pre-industrial levels (median values; the range is 2.5 to 7.8 °C including climate uncertainty).
The current trajectory of global greenhouse gas emissions is not consistent with limiting global warming to below 1.5 or 2 °C, relative to pre-industrial levels. Pledges made as part of the Cancún Agreements are broadly consistent with cost-effective scenarios that give a "likely" chance (66–100% probability) of limiting global warming (in 2100) to below 3 °C, relative to pre-industrial levels.

IPCC Fourth Assessment Report in 2007
In February 2007, the IPCC released a summary of the Fourth Assessment Report. According to this summary, the Fourth Assessment Report found that human actions are "very likely" the cause of global warming, meaning a 90% or greater probability. Global warming in this case was indicated by an increase of 0.75 degrees in average global temperatures over the last 100 years.The IPCC Fourth Assessment Report stated that:

Warming of the climate system is unequivocal, as evidenced by increases in global average air and ocean temperatures, the widespread melting of snow and ice, and rising global average sea level.
Most of the global warming since the mid-20th century is very likely due to human activities.Benefits and costs of climate change for [human] society will vary widely by location and scale. Some of the effects in temperate and polar regions will be positive, and others elsewhere will be negative. Overall, net effects are more likely to be strongly negative with larger or more rapid warming.
The range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time.
The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g. flooding, drought, wildfire, insects, ocean acidification), and other global change drivers (e.g. land-use change, pollution, fragmentation of natural systems, over-exploitation of resources).

Other key reports
U.S. Global Change Research Program
Thirteen federal agencies, led by the National Oceanic and Atmospheric Administration (NOAA), worked together under the auspices of the United States Global Change Research Program (USGCRP) to prepare the country's Fourth National Climate Assessment, published in two volumes as described below.
The Climate Science Special Report: Fourth National Climate Assessment, Volume I (October 2017) provided the following summary: 

This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.

Background
Formerly: Climate Change Science ProgramThe U.S. Global Change Research Program reported in June 2009 that:

Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities.
The 2009 report, which is about the effects that climate change is having in the United States, also said:

Climate-related changes have already been observed globally and in the United States. These include increases in air and water temperatures, reduced frost days, increased frequency and intensity of heavy downpours, a rise in sea level, and reduced snow cover, glaciers, permafrost, and sea ice. A longer ice-free period on lakes and rivers, lengthening of the growing season, and increased water vapor in the atmosphere have also been observed. Over the past 30 years, temperatures have risen faster in winter than in any other season, with average winter temperatures in the Midwest and northern Great Plains increasing more than 7 °F (3.9 °C). Some of the changes have been faster than previous assessments had suggested.

Arctic Climate Impact Assessment
In 2004, the intergovernmental Arctic Council and the non-governmental International Arctic Science Committee released the synthesis report of the Arctic Climate Impact Assessment:
Climate conditions in the past provide evidence that rising atmospheric carbon dioxide levels are associated with rising global temperatures. Human activities, primarily the burning of fossil fuels (coal, oil, and natural gas), and secondarily the clearing of land, have increased the concentration of carbon dioxide, methane, and other heat-trapping ("greenhouse") gases in the atmosphere. ... There is international scientific consensus that most of the warming observed over the last 50 years is attributable to human activities.

Statements by scientific organizations of national or international standing
This is a list of scientific bodies of national or international standing, that have issued formal statements of opinion, classifies those organizations according to whether they concur with the IPCC view, are non-committal, or dissent from it. The California Governor's Office website lists nearly 200 worldwide scientific organizations hold the position that climate change has been caused by human action.

Concurring
Academies of science (general science)
Since 2001, 34 national science academies, three regional academies, and both the international InterAcademy Council and International Council of Academies of Engineering and Technological Sciences have made formal declarations confirming human induced global warming and urging nations to reduce emissions of greenhouse gases. The 34 national science academy statements include 33 who have signed joint science academy statements and one individual declaration by the Polish Academy of Sciences in 2007.

Joint national science academy statements
2001 Following the publication of the IPCC Third Assessment Report, seventeen national science academies issued a joint statement, entitled "The Science of Climate Change", explicitly acknowledging the IPCC position as representing the scientific consensus on climate change science. The statement, printed in an editorial in the journal Science on 18 May 2001, was signed by the science academies of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, Turkey, and the United Kingdom.
2005 The national science academies of the G8 nations, plus Brazil, China and India, three of the largest emitters of greenhouse gases in the developing world, signed a statement on the global response to climate change. The statement stresses that the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action, and explicitly endorsed the IPCC consensus. The eleven signatories were the science academies of Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, the United Kingdom, and the United States.
2007 In preparation for the 33rd G8 summit, the national science academies of the G8+5 nations issued a declaration referencing the position of the 2005 joint science academies' statement, and acknowledging the confirmation of their previous conclusion by recent research. Following the IPCC Fourth Assessment Report, the declaration states, "It is unequivocal that the climate is changing, and it is very likely that this is predominantly caused by the increasing human interference with the atmosphere. These changes will transform the environmental conditions on Earth unless counter-measures are taken." The thirteen signatories were the national science academies of Brazil, Canada, China, France, Germany, Italy, India, Japan, Mexico, Russia, South Africa, the United Kingdom, and the United States.
2007 In preparation for the 33rd G8 summit, the Network of African Science Academies submitted a joint "statement on sustainability, energy efficiency, and climate change": A consensus, based on current evidence, now exists within the global scientific community that human activities are the main source of climate change and that the burning of fossil fuels is largely responsible for driving this change. The IPCC should be congratulated for the contribution it has made to public understanding of the nexus that exists between energy, climate and sustainability. 
2008 In preparation for the 34th G8 summit, the national science academies of the G8+5 nations issued a declaration reiterating the position of the 2005 joint science academies' statement, and reaffirming "that climate change is happening and that anthropogenic warming is influencing many physical and biological systems". Among other actions, the declaration urges all nations to "[t]ake appropriate economic and policy measures to accelerate transition to a low carbon society and to encourage and effect changes in individual and national behaviour". The thirteen signatories were the same national science academies that issued the 2007 joint statement.
2009 In advance of the UNFCCC negotiations to be held in Copenhagen in December 2009, the national science academies of the G8+5 nations issued a joint statement declaring, "Climate change and sustainable energy supply are crucial challenges for the future of humanity. It is essential that world leaders agree on the emission reductions needed to combat negative consequences of anthropogenic climate change". The statement references the IPCC's Fourth Assessment of 2007, and asserts that "climate change is happening even faster than previously estimated; global CO2 emissions since 2000 have been higher than even the highest predictions, Arctic sea ice has been melting at rates much faster than predicted, and the rise in the sea level has become more rapid". The thirteen signatories were the same national science academies that issued the 2007 and 2008 joint statements.

Polish Academy of Sciences
In December 2007, the General Assembly of the Polish Academy of Sciences (Polska Akademia Nauk), which has not been a signatory to joint national science academy statements issued a declaration endorsing the IPCC conclusions, and stating:
it is the duty of Polish science and the national government to, in a thoughtful, organized and active manner, become involved in realisation of these ideas.
Problems of global warming, climate change, and their various negative impacts on human life and on the functioning of entire societies are one of the most dramatic challenges of modern times.

PAS General Assembly calls on the national scientific communities and the national government to actively support Polish participation in this important endeavor.

Additional national science academy and society statements
American Association for the Advancement of Science as the world's largest general scientific society, adopted an official statement on climate change in 2006: The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society. ... The pace of change and the evidence of harm have increased markedly over the last five years. The time to control greenhouse gas emissions is now.
Federation of Australian Scientific and Technological Societies in 2008 published FASTS Statement on Climate Change which states: Global climate change is real and measurable. ... To reduce the global net economic, environmental and social losses in the face of these impacts, the policy objective must remain squarely focused on returning greenhouse gas concentrations to near pre-industrial levels through the reduction of emissions. The spatial and temporal fingerprint of warming can be traced to increasing greenhouse gas concentrations in the atmosphere, which are a direct result of burning fossil fuels, broad-scale deforestation and other human activity.
United States National Research Council through its Committee on the Science of Climate Change in 2001, published Climate Change Science: An Analysis of Some Key Questions. This report explicitly endorses the IPCC view of attribution of recent climate change as representing the view of the scientific community: The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability. Human-induced warming and associated sea level rises are expected to continue through the 21st century. ... The IPCC's conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue.
Royal Society of New Zealand having signed onto the first joint science academy statement in 2001, released a separate statement in 2008 in order to clear up "the controversy over climate change and its causes, and possible confusion among the public": The globe is warming because of increasing greenhouse gas emissions. Measurements show that greenhouse gas concentrations in the atmosphere are well above levels seen for many thousands of years. Further global climate changes are predicted, with impacts expected to become more costly as time progresses. Reducing future impacts of climate change will require substantial reductions of greenhouse gas emissions.
The Royal Society of the United Kingdom has not changed its concurring stance reflected in its participation in joint national science academies' statements on anthropogenic global warming. According to the Telegraph, "The most prestigious group of scientists in the country was forced to act after fellows complained that doubts over man made global warming were not being communicated to the public". In May 2010, it announced that it "is presently drafting a new public facing document on climate change, to provide an updated status report on the science in an easily accessible form, also addressing the levels of certainty of key components." The society says that it is three years since the last such document was published and that, after an extensive process of debate and review, the new document was printed in September 2010. It summarises the current scientific evidence and highlights the areas where the science is well established, where there is still some debate, and where substantial uncertainties remain. The society has stated that "this is not the same as saying that the climate science itself is in error – no Fellows have expressed such a view to the RS".  The introduction includes this statement: There is strong evidence that the warming of the Earth over the last half-century has been caused largely by human activity, such as the burning of fossil fuels and changes in land use, including agriculture and deforestation.

International science academies
African Academy of Sciences in 2007 was a signatory to the "statement on sustainability, energy efficiency, and climate change". This joint statement of African science academies, was organized through the Network of African Science Academies. Its stated goal was "to convey information and spur action on the occasion of the G8 Summit in Heiligendamm, Germany, in June 2007": A consensus, based on current evidence, now exists within the global scientific community that human activities are the main source of climate change and that the burning of fossil fuels is largely responsible for driving this change.
European Academy of Sciences and Arts in 2007 issued a formal declaration on climate change titled Let's Be Honest: Human activity is most likely responsible for climate warming. Most of the climatic warming over the last 50 years is likely to have been caused by increased concentrations of greenhouse gases in the atmosphere. Documented long-term climate changes include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones. The above development potentially has dramatic consequences for mankind's future.
European Science Foundation in a 2007 position paper states: There is now convincing evidence that since the industrial revolution, human activities, resulting in increasing concentrations of greenhouse gases have become a major agent of climate change ... On-going and increased efforts to mitigate climate change through reduction in greenhouse gases are therefore crucial.
InterAcademy Council As the representative of the world's scientific and engineering academies, the InterAcademy Council issued a report in 2007 titled Lighting the Way: Toward a Sustainable Energy Future. Current patterns of energy resources and energy usage are proving detrimental to the long-term welfare of humanity. The integrity of essential natural systems is already at risk from climate change caused by the atmospheric emissions of greenhouse gases. Concerted efforts should be mounted for improving energy efficiency and reducing the carbon intensity of the world economy.
International Council of Academies of Engineering and Technological Sciences (CAETS) in 2007, issued a Statement on Environment and Sustainable Growth: As reported by the Intergovernmental Panel on Climate Change (IPCC), most of the observed global warming since the mid-20th century is very likely due to human-produced emission of greenhouse gases and this warming will continue unabated if present anthropogenic emissions continue or, worse, expand without control. CAETS, therefore, endorses the many recent calls to decrease and control greenhouse gas emissions to an acceptable level as quickly as possible.

Physical and chemical sciences
American Chemical Society
American Institute of Physics
American Physical Society
Australian Institute of Physics
European Physical Society

Earth sciences
American Geophysical Union
The American Geophysical Union (AGU) adopted a statement on Climate Change and Greenhouse Gases in 1998. A new statement, adopted by the society in 2003, revised in 2007, and revised and expanded in 2013, affirms that rising levels of greenhouse gases have caused and will continue to cause the global surface temperature to be warmer:

Human activities are changing Earth's climate. At the global level, atmospheric concentrations of carbon dioxide and other heat-trapping greenhouse gases have increased sharply since the Industrial Revolution. Fossil fuel burning dominates this increase. Human-caused increases in greenhouse gases are responsible for most of the observed global average surface warming of roughly 0.8 °C (1.5 °F) over the past 140 years. Because natural processes cannot quickly remove some of these gases (notably carbon dioxide) from the atmosphere, our past, present, and future emissions will influence the climate system for millennia.
While important scientific uncertainties remain as to which particular impacts will be experienced where, no uncertainties are known that could make the impacts of climate change inconsequential. Furthermore, surprise outcomes, such as the unexpectedly rapid loss of Arctic summer sea ice, may entail even more dramatic changes than anticipated.

American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
In May 2011, the American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and Soil Science Society of America (SSSA) issued a joint position statement on climate change as it relates to agriculture:
A comprehensive body of scientific evidence indicates beyond reasonable doubt that global climate change is now occurring and that its manifestations threaten the stability of societies as well as natural and managed ecosystems. Increases in ambient temperatures and changes in related processes are directly linked to rising anthropogenic greenhouse gas (GHG) concentrations in the atmosphere.
Unless the emissions of GHGs are curbed significantly, their concentrations will continue to rise, leading to changes in temperature, precipitation, and other climate variables that will undoubtedly affect agriculture around the world.

Climate change has the potential to increase weather variability as well as gradually increase global temperatures. Both of these impacts have the potential to negatively impact the adaptability and resilience of the world's food production capacity; current research indicates climate change is already reducing the productivity of vulnerable cropping systems.

European Federation of Geologists
In 2008, the European Federation of Geologists (EFG) issued the position paper Carbon Capture and geological Storage:
The EFG recognizes the work of the IPCC and other organizations, and subscribes to the major findings that climate change is happening, is predominantly caused by anthropogenic emissions of CO2, and poses a significant threat to human civilization.
It is clear that major efforts are necessary to quickly and strongly reduce CO2 emissions. The EFG strongly advocates renewable and sustainable energy production, including geothermal energy, as well as the need for increasing energy efficiency.

CCS [Carbon Capture and geological Storage] should also be regarded as a bridging technology, facilitating the move towards a carbon free economy.

European Geosciences Union
In 2005, the Divisions of Atmospheric and Climate Sciences of the European Geosciences Union (EGU) issued a position statement in support of the Joint national science academy statements on global response to climate change. The statement refers to the Intergovernmental Panel on Climate Change (IPCC), as "the main representative of the global scientific community", and asserts that the IPCC:
represents the state-of-the-art of climate science supported by the major science academies around the world and by the vast majority of science researchers and investigators as documented by the peer-reviewed scientific literature.
Additionally, in 2008, the EGU issued a position statement on ocean acidification which states, "Ocean acidification is already occurring today and will continue to intensify, closely tracking atmospheric CO2 increase. Given the potential threat to marine ecosystems and its ensuing impact on human society and economy, especially as it acts in conjunction with anthropogenic global warming, there is an urgent need for immediate action." The statement then advocates for strategies "to limit future release of CO2 to the atmosphere and/or enhance removal of excess CO2 from the atmosphere". And, in 2018 the EGU issued a statement concurring with the findings of the Special Report on Global Warming of 1.5 °C, with Jonathan Bamber, president of the organisation, noting: "EGU concurs with, and supports, the findings of the SR15 that action to curb the most dangerous consequences of human-induced climate change is urgent, of the utmost importance and the window of opportunity extremely limited."

Geological Society of America
In 2006, the Geological Society of America adopted a position statement on global climate change. It amended this position on 20 April 2010, with more explicit comments on need for CO2 reduction:
Decades of scientific research have shown that climate can change from both natural and anthropogenic causes. The Geological Society of America (GSA) concurs with assessments by the National Academies of Science (2005), the National Research Council (2006), and the Intergovernmental Panel on Climate Change (IPCC, 2007) that global climate has warmed and that human activities (mainly greenhouse‐gas emissions) account for most of the warming since the middle 1900s. If current trends continue, the projected increase in global temperature by the end of the twenty first century will result in large impacts on humans and other species. Addressing the challenges posed by climate change will require a combination of adaptation to the changes that are likely to occur and global reductions of CO2 emissions from anthropogenic sources.

Geological Society of London
In November 2010, the Geological Society of London issued the position statement Climate change: evidence from the geological record:
The last century has seen a rapidly growing global population and much more intensive use of resources, leading to greatly increased emissions of gases, such as carbon dioxide and methane, from the burning of fossil fuels (oil, gas and coal), and from agriculture, cement production and deforestation. Evidence from the geological record is consistent with the physics that shows that adding large amounts of carbon dioxide to the atmosphere warms the world and may lead to: higher sea levels and flooding of low-lying coasts; greatly changed patterns of rainfall; increased acidity of the oceans; and decreased oxygen levels in seawater.
There is now widespread concern that the Earth's climate will warm further, not only because of the lingering effects of the added carbon already in the system, but also because of further additions as human population continues to grow. Life on Earth has survived large climate changes in the past, but extinctions and major redistribution of species have been associated with many of them. When the human population was small and nomadic, a rise in sea level of a few metres would have had very little effect on Homo sapiens. With the current and growing global population, much of which is concentrated in coastal cities, such a rise in sea level would have a drastic effect on our complex society, especially if the climate were to change as suddenly as it has at times in the past. Equally, it seems likely that as warming continues some areas may experience less precipitation leading to drought. With both rising seas and increasing drought, pressure for human migration could result on a large scale.

International Union of Geodesy and Geophysics
In July 2007, the International Union of Geodesy and Geophysics (IUGG) adopted a resolution titled "The Urgency of Addressing Climate Change". In it, the IUGG concurs with the "comprehensive and widely accepted and endorsed scientific assessments carried out by the Intergovernmental Panel on Climate Change and regional and national bodies, which have firmly established, on the basis of scientific evidence, that human activities are the primary cause of recent climate change". They state further that the "continuing reliance on combustion of fossil fuels as the world's primary source of energy will lead to much higher atmospheric concentrations of greenhouse gases, which will, in turn, cause significant increases in surface temperature, sea level, ocean acidification, and their related consequences to the environment and society".

National Association of Geoscience Teachers
In July 2009, the National Association of Geoscience Teachers (NAGT) adopted a position statement on climate change in which they assert that "Earth's climate is changing [and] "that present warming trends are largely the result of human activities":
NAGT strongly supports and will work to promote education in the science of climate change, the causes and effects of current global warming, and the immediate need for policies and actions that reduce the emission of greenhouse gases.

Meteorology and oceanography
American Meteorological Society
The American Meteorological Society (AMS) statement adopted by their council in 2012 concluded:
There is unequivocal evidence that Earth's lower atmosphere, ocean, and land surface are warming; sea level is rising; and snow cover, mountain glaciers, and Arctic sea ice are shrinking. The dominant cause of the warming since the 1950s is human activities. This scientific finding is based on a large and persuasive body of research. The observed warming will be irreversible for many years into the future, and even larger temperature increases will occur as greenhouse gases continue to accumulate in the atmosphere. Avoiding this future warming will require a large and rapid reduction in global greenhouse gas emissions. The ongoing warming will increase risks and stresses to human societies, economies, ecosystems, and wildlife through the 21st century and beyond, making it imperative that society respond to a changing climate. To inform decisions on adaptation and mitigation, it is critical that we improve our understanding of the global climate system and our ability to project future climate through continued and improved monitoring and research. This is especially true for smaller (seasonal and regional) scales and weather and climate extremes, and for important hydroclimatic variables such as precipitation and water availability.
Technological, economic, and policy choices in the near future will determine the extent of future impacts of climate change. Science-based decisions are seldom made in a context of absolute certainty. National and international policy discussions should include consideration of the best ways to both adapt to and mitigate climate change. Mitigation will reduce the amount of future climate change and the risk of impacts that are potentially large and dangerous. At the same time, some continued climate change is inevitable, and policy responses should include adaptation to climate change. Prudence dictates extreme care in accounting for our relationship with the only planet known to be capable of sustaining human life.
A 2016 survey found that two-thirds of AMS members think that all or most of climate change is caused by human activity.

Australian Meteorological and Oceanographic Society
The Australian Meteorological and Oceanographic Society has issued a Statement on Climate Change, wherein they conclude:
Global climate change and global warming are real and observable ... It is highly likely that those human activities that have increased the concentration of greenhouse gases in the atmosphere have been largely responsible for the observed warming since 1950. The warming associated with increases in greenhouse gases originating from human activity is called the enhanced greenhouse effect. The atmospheric concentration of carbon dioxide has increased by more than 30% since the start of the industrial age and is higher now than at any time in at least the past 650,000 years. This increase is a direct result of burning fossil fuels, broad-scale deforestation and other human activity.

Canadian Foundation for Climate and Atmospheric Sciences
In November 2005, the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS) issued a letter to the Prime Minister of Canada stating that:
We concur with the climate science assessment of the Intergovernmental Panel on Climate Change (IPCC) in 2001 ... We endorse the conclusions of the IPCC assessment that 'There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities'. ... There is increasingly unambiguous evidence of changing climate in Canada and around the world. There will be increasing impacts of climate change on Canada's natural ecosystems and on our socio-economic activities. Advances in climate science since the 2001 IPCC Assessment have provided more evidence supporting the need for action and development of a strategy for adaptation to projected changes.

Canadian Meteorological and Oceanographic Society
In November 2009,  a letter to the Canadian Parliament by The Canadian Meteorological and Oceanographic Society states:
Rigorous international research, including work carried out and supported by the Government of Canada, reveals that greenhouse gases resulting from human activities contribute to the warming of the atmosphere and the oceans and constitute a serious risk to the health and safety of our society, as well as having an impact on all life.

Royal Meteorological Society (UK)
In February 2007, after the release of the IPCC's Fourth Assessment Report, the Royal Meteorological Society issued an endorsement of the report. In addition to referring to the IPCC as "[the] world's best climate scientists", they stated that climate change is happening as "the result of emissions since industrialization and we have already set in motion the next 50 years of global warming – what we do from now on will determine how worse it will get."

World Meteorological Organization
In its Statement at the Twelfth Session of the Conference of the Parties to the U.N. Framework Convention on Climate Change presented on 15 November 2006, the World Meteorological Organization (WMO) confirms the need to "prevent dangerous anthropogenic interference with the climate system". The WMO concurs that "scientific assessments have increasingly reaffirmed that human activities are indeed changing the composition of the atmosphere, in particular through the burning of fossil fuels for energy production and transportation". The WMO concurs that "the present atmospheric concentration of CO2 was never exceeded over the past 420,000 years"; and that the IPCC "assessments provide the most authoritative, up-to-date scientific advice".

American Quaternary Association
The American Quaternary Association (AMQUA) has stated:
Few credible scientists now doubt that humans have influenced the documented rise in global temperatures since the Industrial Revolution. The first government-led U.S. Climate Change Science Program synthesis and assessment report supports the growing body of evidence that warming of the atmosphere, especially over the past 50 years, is directly impacted by human activity.

International Union for Quaternary Research
The statement on climate change issued by the International Union for Quaternary Research (INQUA) reiterates the conclusions of the IPCC, and urges all nations to take prompt action in line with the UNFCCC principles:
Human activities are now causing atmospheric concentrations of greenhouse gases—including carbon dioxide, methane, tropospheric ozone, and nitrous oxide—to rise well above pre-industrial levels ... Increases in greenhouse gases are causing temperatures to rise ... The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action ... Minimizing the amount of this carbon dioxide reaching the atmosphere presents a huge challenge but must be a global priority.

Biology and life sciences
Life science organizations have outlined the dangers climate change pose to wildlife.

American Association of Wildlife Veterinarians
American Institute of Biological Sciences. In October 2009, the leaders of 18 US scientific societies and organizations sent an open letter to the United States Senate reaffirming the scientific consensus that climate change is occurring and is primarily caused by human activities.  The American Institute of Biological Sciences (AIBS) adopted this letter as their official position statement. The letter goes on to warn of predicted impacts on the United States such as sea level rise and increases in extreme weather events, water scarcity, heat waves, wildfires, and the disturbance of biological systems.  It then advocates for a dramatic reduction in emissions of greenhouse gases.
American Society for Microbiology
Australian Coral Reef Society
Institute of Biology (UK)
Society of American Foresters issued two position statements pertaining to climate change in which they cite the IPCC and the UNFCCC.
The Wildlife Society (international)

Human health
A number of health organizations have warned about the numerous negative health effects of global warming:

American Academy of Pediatrics
American College of Preventive Medicine
American Medical Association
American Public Health Association
Australian Medical Association in 2004 and in 2008
World Federation of Public Health Associations
World Health Organization

The Bulletin of the Atomic Scientists and "Doomsday clock"
In 1945, Albert Einstein and other scientists who created atomic weapons used in the atomic bombings of Hiroshima and Nagasaki founded the "Bulletin of the Atomic Scientists" and created the "Doomsday Clock". The goal of the clock is to convey threats to humanity and the planet, and to create public awareness that will lead to solutions. In the beginning, the Doomsday Clock focused on the dangers of nuclear war, but in the 21st century, it has begun to deal with other issues like climate change and disinformation on the internet.
On 23 January 2020 the organization moved the doomsday clock to 100 seconds before midnight, closer than ever. It explained that it did it because of three factors:

Increasing danger of nuclear war,
Increasing danger from climate change, and
Increasing danger from disinformation in the internet regarding the issues in points 1 and 2 and other "disruptive technologies".The organization praised the climate movement of young people and called to citizens and governments to act to take greater action on climate change.

Miscellaneous
A number of other national scientific societies have also endorsed the opinion of the IPCC:

American Astronomical Society
American Statistical Association
Canadian Council of Professional Engineers  
The Institution of Engineers Australia
International Association for Great Lakes Research
Institute of Professional Engineers New Zealand
World Federation of Engineering Organizations (WFEO)

Non-committal
The last national or international scientific body to drop dissent was the American Association of Petroleum Geologists, which in 2007 updated its statement to its current non-committal position. Some other organizations, primarily those focusing on geology, also hold non-committal positions.

American Association of Petroleum Geologists
As of June 2007, the American Association of Petroleum Geologists (AAPG) Position Statement on climate change stated:
the AAPG membership is divided on the degree of influence that anthropogenic CO2 has on recent and potential global temperature increases ... Certain climate simulation models predict that the warming trend will continue, as reported through NAS, AGU, AAAS and AMS. AAPG respects these scientific opinions but wants to add that the current climate warming projections could fall within well-documented natural variations in past climate and observed temperature data. These data do not necessarily support the maximum case scenarios forecast in some models.
Prior to the adoption of this statement, the AAPG was the only major scientific organization that rejected the finding of significant human influence on recent climate, according to a statement by the Council of the American Quaternary Association. Explaining the plan for a revision, AAPG president Lee Billingsly wrote in March 2007:
Members have threatened to not renew their memberships ... if AAPG does not alter its position on global climate change ... And I have been told of members who already have resigned in previous years because of our current global climate change position ... The current policy statement is not supported by a significant number of our members and prospective members.
AAPG President John Lorenz announced the "sunsetting" of AAPG's Global Climate Change Committee in January 2010.  The AAPG Executive Committee determined:
Climate change is peripheral at best to our science ... AAPG does not have credibility in that field ... and as a group we have no particular knowledge of global atmospheric geophysics.

American Institute of Professional Geologists (AIPG)
The official position statement from AIPG on the Environment states that "combustion of fossil fuel include and the generation of GHGs [greenhouse gases] including carbon dioxide (CO2) and methane (CH4).  Emissions of GHGs are perceived by some to be one of the largest, global environmental concerns related to energy production due to potential effects on the global energy system and possibly global climate. Fossil fuel use is the primary source of the increased atmospheric concentration of GHGs since industrialization".In March 2010, AIPG's Executive Director issued a statement regarding polarization of opinions on climate change within the membership and announced that the AIPG Executive had made a decision to cease publication of articles and opinion pieces concerning climate change in AIPG's news journal, The Professional Geologist.

Opposing
Since 2007, when the American Association of Petroleum Geologists released a revised statement, no longer does any national or international scientific body reject the findings of human-induced effects on climate change.

Surveys of scientists and scientific literature
Various surveys have been conducted to evaluate scientific opinion on global warming. They have concluded that almost all climate scientists support the idea of anthropogenic climate change.A 2012 analysis of published research on global warming and climate change between 1991 and 2012 found that of the 13,950 articles in peer-reviewed journals, only 24 rejected anthropogenic global warming. A follow-up analysis looking at 2,258 peer-reviewed climate articles with 9,136 authors published between November 2012 and December 2013 revealed that only one of the 9,136 authors rejected anthropogenic global warming. His 2015 paper on the topic, covering 24,210 articles published by 69,406 authors during 2013 and 2014 found only five articles by four authors rejecting anthropogenic global warming. Over 99.99% of climate scientists did not reject AGW in their peer-reviewed research.A 2013 study, published in the peer-reviewed journal Environmental Research Letters analyzed 11,944 abstracts from papers published in the peer-reviewed scientific literature between 1991 and 2011, identified by searching the ISI Web of Science citation index engine for the text strings "global climate change" or "global warming". The authors found that 3974 of the abstracts expressed a position on anthropogenic global warming, and that 97% of those endorsed the consensus that humans are causing global warming. The authors found that of the 11,944 abstracts, 3896 endorsed that consensus, 7930 took no position on it, 78 rejected the consensus, and 40 expressed uncertainties about it. This study was criticised in 2016 by Richard Tol, but strongly defended by a companion paper in the same volume.James Lawrence Powell reported in 2017 that using rejection as the criterion of consensus, five surveys of the peer-reviewed literature from 1991 to 2015, including several of those above, combine to 54,195 articles with an average consensus of 99.94%.
In November 2019, his survey of over 11,600 peer-reviewed articles published in the first seven months of 2019 showed that the consensus had reached 100%.A survey conducted in 2021 found that of a random selection of 3,000 papers examined from 88,125 peer-reviewed studies related to climate that were published since 2012, only 4 were sceptical about man-made climate change.Depending on expertise, a 2021 survey of 2780 Earth scientist showed that between 91% and 100% agreed human activity is causing climate change. Among climate scientists, 98.7% agreed, a number that grows to 100% when only the climate scientists with high level of expertise are counted (20+ papers published).

Surveys prior to 2010
In 2004, the geologist and historian of science Naomi Oreskes summarized a study of the scientific literature on climate change. She analyzed 928 abstracts of papers from refereed scientific journals between 1993 and 2003 and concluded that there is a scientific consensus on the reality of anthropogenic climate change.
Oreskes divided the abstracts into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Seventy-five per cent of the abstracts were placed in the first three categories (either explicitly or implicitly accepting the consensus view); 25% dealt with methods or paleoclimate, thus taking no position on current anthropogenic climate change. None of the abstracts disagreed with the consensus position, which the author found to be "remarkable". According to the report, "authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point."
In 2007, Harris Interactive surveyed 489 randomly selected members of either the American Meteorological Society or the American Geophysical Union for the Statistical Assessment Service (STATS) at George Mason University. 97% of the scientists surveyed agreed that global temperatures had increased during the past 100 years; 84% said they personally believed human-induced warming was occurring, and 74% agreed that "currently available scientific evidence" substantiated its occurrence. Catastrophic effects in 50–100 years would likely be observed according to 41%, while 44% thought the effects would be moderate and about 13 percent saw relatively little danger. 5% said they thought human activity did not contribute to greenhouse warming.Dennis Bray and Hans von Storch conducted a survey in August 2008 of 2058 climate scientists from 34 countries. A total of 373 responses were received giving an overall response rate of 18.2%. No paper on climate change consensus based on this survey has been published yet (February 2010), but one on another subject has been published based on the survey. To the question "How convinced are you that climate change, whether natural or anthropogenic, is occurring now?", 67.1% said they very much agreed, 26.7% agreed to some large extent, 6.2% said to they agreed to some small extent (2–4), none said they did not agree at all. To the question "How convinced are you that most of recent or near future climate change is, or will be, a result of anthropogenic causes?" the responses were 34.6% very much agree, 48.9% agreeing to a large extent, 15.1% to a small extent, and 1.35% not agreeing at all.
A poll performed by Peter Doran and Maggie Kendall Zimmerman at University of Illinois at Chicago received replies from 3,146 of the 10,257 polled Earth scientists. Results were analyzed globally and by specialization. 76 out of 79 climatologists who "listed climate science as their area of expertise and who also have published more than 50% of their recent peer-reviewed papers on the subject of climate change" believed that mean global temperatures had risen compared to pre-1800s levels. Seventy-five of 77 believed that human activity is a significant factor in changing mean global temperatures. Among all respondents, 90% agreed that temperatures have risen compared to pre-1800 levels, and 82% agreed that humans significantly influence the global temperature. Economic geologists and meteorologists were among the biggest doubters, with only 47 percent and 64 percent, respectively, believing in significant human involvement. The authors summarised the findings:
It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes.
A 2010 paper in the Proceedings of the National Academy of Sciences analyzed "1,372 climate researchers and their publication and citation data to show that (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". Judith Curry has said "This is a completely unconvincing analysis", whereas Naomi Oreskes said that the paper shows "the vast majority of working [climate] research scientists are in agreement [on climate change]... Those who don't agree, are, unfortunately—and this is hard to say without sounding elitist—mostly either not actually climate researchers or not very productive researchers." Jim Prall, one of the coauthors of the study, acknowledged "it would be helpful to have lukewarm [as] a third category."

Existence of a scientific consensus
A question that frequently arose in popular discussion was whether there is a scientific consensus on climate change.  Several scientific organizations have explicitly used the term "consensus" in their statements:

American Association for the Advancement of Science, 2006: "The conclusions in this statement reflect the scientific consensus represented by, for example, the Intergovernmental Panel on Climate Change, and the Joint National Academies' statement."
US National Academy of Sciences: "In the judgment of most climate scientists, Earth's warming in recent decades has been caused primarily by human activities that have increased the amount of greenhouse gases in the atmosphere. ... On climate change, [the National Academies' reports] have assessed consensus findings on the science ..."
Joint Science Academies' statement, 2005: "We recognise the international scientific consensus of the Intergovernmental Panel on Climate Change (IPCC)."
Joint Science Academies' statement, 2001: "The work of the Intergovernmental Panel on Climate Change (IPCC) represents the consensus of the international scientific community on climate change science. We recognise IPCC as the world's most reliable source of information on climate change and its causes, and we endorse its method of achieving this consensus."
American Meteorological Society, 2003: "The nature of science is such that there is rarely total agreement among scientists. Individual scientific statements and papers—the validity of some of which has yet to be assessed adequately—can be exploited in the policy debate and can leave the impression that the scientific community is sharply divided on issues where there is, in reality, a strong scientific consensus ... IPCC assessment reports are prepared at approximately five-year intervals by a large international group of experts who represent the broad range of expertise and perspectives relevant to the issues. The reports strive to reflect a consensus evaluation of the results of the full body of peer-reviewed research ... They provide an analysis of what is known and not known, the degree of consensus, and some indication of the degree of confidence that can be placed on the various statements and conclusions."
Network of African Science Academies: "A consensus, based on current evidence, now exists within the global scientific community that human activities are the main source of climate change and that the burning of fossil fuels is largely responsible for driving this change."
International Union for Quaternary Research, 2008: "INQUA recognizes the international scientific consensus of the Intergovernmental Panel on Climate Change (IPCC)."
Australian Coral Reef Society, 2006: "There is almost total consensus among experts that the earth's climate is changing as a result of the build-up of greenhouse gases ... There is broad scientific consensus that coral reefs are heavily affected by the activities of man and there are significant global influences that can make reefs more vulnerable such as global warming ..."

Surveys of scientists' views on climate change
Surveys of scientists' views on climate change – with a focus on human-caused or anthropogenic global warming (AGW) – have been undertaken since the 1990s. A 2016 paper (which was co-authored by Naomi Oreskes, Peter Doran, William Anderegg, Bart Verheggen, Ed Maibach, J. Stuart Carlton and John Cook, and which was based on a half a dozen independent studies by the authors) concluded that "the finding of 97% consensus [that humans are causing recent global warming] in published climate research is robust and consistent with other surveys of climate scientists and peer-reviewed studies." A 2019 study found scientific consensus to be at 100%, and a 2021 study found that consensus exceeded 99%.

2020s
Myers et al., 2021
Krista Myers led a paper which surveyed 2780 Earth scientists. Depending on expertise, between 91% (all scientists) to 100% (climate scientists with high levels of expertise, 20+ papers published) agreed human activity is causing climate change. Among the total group of climate scientists, 98.7% agreed. The agreement was lowest among scientists who chose Economic Geology as one of their fields of research (84%).

Lynas et al., 2021
In 2021, Mark Lynas et al assessed studies published between 2012 and 2020. They found over 80,000 studies. They analysed a random subset of 3000. Four of these were skeptical of the human cause of climate change, 845 were endorsing the human cause perspective at different levels, and 1869 were indifferent to the question. The authors estimated the proportion of papers not skeptical of the human cause as 99.85% (95% confidence limit 99.62%–99.96%). Excluding papers which took no position on the human cause led to an estimate of the proportion of consensus papers as 99.53% (95% confidence limit 98.80%–99.87%). They confirmed their numbers by explicitly looking for alternative hypotheses in the entire dataset, which resulted in 28 papers.

2010s
Powell, 2019
In 2019, James L. Powell, a former member of the National Science Board, analysed titles of peer-reviewed studies published in the first seven months of 2019 and found not a single study disagreed with the consensus view. When the titles implied uncertainty about the cause of climate change, the abstracts or the article in its entirety were examined. The total amount of articles found via Web of Science was 11,602.

Verheggen et al., 2014
In 2014, Bart Verheggen of the Netherlands Environmental Assessment Agency surveyed 1,868 climate scientists. They found that, consistent with other research, the level of agreement on anthropogenic causation correlated with expertise - 90% of those surveyed with more than 10 peer-reviewed papers related to climate (just under half of survey respondents) explicitly agreed that greenhouse gases were the main cause of global warming. They included researchers on mitigation and adaptation in their surveys in addition to physical climate scientists, leading to a slightly lower level of consensus compared to previous studies.

Powell, 2013
James L. Powell analyzed published research on global warming and climate change between 1991 and 2012 and found that of the 13,950 articles in peer-reviewed journals, only 24  (<0.2%) rejected anthropogenic global warming. This was a follow-up to an analysis looking at 2,258 peer-reviewed articles published between November 2012 and December 2013 revealed that only one of the 9,136 authors rejected anthropogenic global warming.

John Cook et al., 2013
Cook et al. examined 11,944 abstracts from the peer-reviewed scientific literature from 1991 to 2011 that matched the topics 'global climate change' or 'global warming'. They found that, while 66.4% of them expressed no position on anthropogenic global warming (AGW), of those that did, 97.1% endorsed the consensus position that humans are contributing to global warming. They also invited authors to rate their own papers and found that, while 35.5% rated their paper as expressing no position on AGW, 97.2% of the rest endorsed the consensus. In both cases the percentage of endorsements among papers expressing a position was marginally increasing over time. They concluded that the number of papers actually rejecting the consensus on AGW is a vanishingly small proportion of the published research.In their discussion of the results, the authors said that the large proportion of abstracts that state no position on AGW is as expected in a consensus situation, as anticipated in a chapter published in 2007, adding that "the fundamental science of AGW is no longer controversial among the publishing science community and the remaining debate in the field has moved on to other topics."A 2016 study entitled Learning from mistakes in climate research examined the quality of the 3% of peer-reviewed papers discovered by this work to reject the consensus view. They discovered that "replication reveals a number of methodological flaws, and a pattern of common mistakes emerges that is not visible when looking at single isolated cases".

Farnsworth and Lichter, 2011
In an October 2011 paper published in the International Journal of Public Opinion Research, researchers from George Mason University analyzed the results of a survey of 998 scientists working in academia, government, and industry. The scientists polled were members of the American Geophysical Union (AGU) or the American Meteorological Society (AMS) and listed in the 23rd edition of American Men and Women of Science, a biographical reference work on leading American scientists, and 489 returned completed questionnaires. Of those who replied, 97% agreed that global temperatures have risen over the past century. 84% agreed that "human-induced greenhouse warming is now occurring," 5% disagreed, and 12% didn't know.When asked what they regard as "the likely effects of global climate change in the next 50 to 100 years," on a scale of 1 to 10, from Trivial to Catastrophic:
13% of respondents replied 1 to 3 (trivial/mild), 44% replied 4 to 7 (moderate), 41% replied 8 to 10 (severe/catastrophic), and 2% didn't know.

Anderegg, Prall, Harold, and Schneider, 2010
Anderegg et al., in a 2010 paper in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), reviewed publication and citation data for 1,372 climate researchers, based on authorship of scientific assessment reports and membership on multisignatory statements about anthropogenic climate change. The number of climate-relevant publications authored or coauthored by each researcher was used to define their 'expertise', and the number of citations for each of the researcher's four highest-cited papers was used to define their 'prominence'. Removing researchers who had authored fewer than 20 climate publications reduced the database to 908 researchers but did not materially alter the results. The authors of the paper say that their database of researchers "is not comprehensive nor designed to be representative of the entire climate science community," but say that since they drew the researchers from the most high-profile reports and public statements, it is likely that it represents the "strongest and most credentialed" researchers both 'convinced by the evidence' (CE) and 'unconvinced by the evidence' (UE) on the tenets of anthropogenic climate change.Anderegg et al. drew the following two conclusions:

(i) 97–98% of the climate researchers most actively publishing in the field surveyed here 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.

2000s
Doran and Kendall Zimmerman, 2009
This paper is based on the Zimmerman 2008 MS thesis; the full methods are in the MS thesis. A web-based poll performed by Peter Doran and Maggie Kendall Zimmerman of the Earth and Environmental Sciences department, University of Illinois at Chicago. They received replies from 3,146 of the 10,257 polled Earth scientists. The survey was designed to take less than two minutes to complete. Results were analyzed globally and by specialization. Among all respondents, 90% agreed that temperatures had generally risen compared to pre-1800 levels, and 82% agreed that humans significantly influence the global temperature. 76 out of the 79 respondents who "listed climate science as their area of expertise, and who also have published more than 50% of their recent peer-reviewed papers on the subject of climate change", thought that mean global temperatures had risen compared to pre-1800s levels. Of those 79 scientists, 75 out of the 77 (97.4%) answered that human activity was a significant factor in changing mean global temperatures. The remaining two were not asked, because in question one they responded that temperatures had remained relatively constant. Economic geologists and meteorologists were among the biggest doubters, with only 47 percent and 64 percent respectively thinking that human activity was a significant contributing factor. In summary, Doran and Zimmerman wrote:

It seems that the debate on the authenticity of global warming and the role played by human activity is largely nonexistent among those who understand the nuances and scientific basis of long-term climate processes.

Bray and von Storch, 2008
Dennis Bray and Hans von Storch, of the Institute for Coastal Research at the Helmholtz Research Centre in Germany, conducted an online survey in August 2008, of 2,059 climate scientists from 34 different countries, the third survey on this topic by these authors. A web link with a unique identifier was given to each respondent to eliminate multiple responses. A total of 375 responses were received giving an overall response rate of 18%. The climate change consensus results were published by Bray, and another paper has also been published based on the survey.The survey was composed of 76 questions split into a number of sections. There were sections on the demographics of the respondents, their assessment of the state of climate science, how good the science is, climate change impacts, adaptation and mitigation, their opinion of the IPCC, and how well climate science was being communicated to the public. Most of the answers were on a scale from 1 to 7 from 'not at all' to 'very much'.In the section on climate change impacts, questions 20 and 21 were relevant to scientific opinion on climate change.
Question 20, "How convinced are you that climate change, whether natural or anthropogenic, is occurring now?" Answers:  67.1% very much convinced (7), 26.7% to some large extent (5–6), 6.2% said to some small extent (2–4), none said not at all.
Question 21, "How convinced are you that most of recent or near future climate change is, or will be, a result of anthropogenic causes?" Answers:  34.6% very much convinced (7), 48.9% being convinced to a large extent (5–6), 15.1% to a small extent (2–4), and 1.35% not convinced at all (1).

STATS, 2007
In 2007, Harris Interactive surveyed 489 randomly selected members of either the American Meteorological Society or the American Geophysical Union for the Statistical Assessment Service (STATS) at George Mason University. The survey found 97% agreed that global temperatures have increased during the past 100 years; 84% say they personally believe human-induced warming is occurring, and 74% agree that "currently available scientific evidence" substantiates its occurrence. Only 5% believe that human activity does not contribute to greenhouse warming; 41% say they thought the effects of global warming would be near catastrophic over the next 50–100 years; 44% say said effects would be moderately dangerous; 13% saw relatively little danger; 56% say global climate change is a mature science; 39% say it is an emerging science.

Oreskes, 2004
A 2004 article by geologist and historian of science Naomi Oreskes summarized a study of the scientific literature on climate change. The essay concluded that there is a scientific consensus on the reality of anthropogenic climate change. The author analyzed 928 abstracts of papers from refereed scientific journals between 1993 and 2003, listed with the keywords "global climate change". Oreskes divided the abstracts into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. 75% of the abstracts were placed in the first three categories, thus either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, thus taking no position on current anthropogenic climate change; none of the abstracts disagreed with the consensus position, which the author found to be "remarkable". According to the report, "authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point."

Bray and von Storch, 2003
In 2003, Bray and von Storch conducted a survey of the perspectives of climate scientists on global climate change. The survey received 530 responses from 27 different countries. The 2003 survey has been strongly criticized on the grounds that it was performed on the web with no means to verify that the respondents were climate scientists or to prevent multiple submissions. The survey required entry of a username and password, but the username and password were circulated to a climate change denial mailing list and elsewhere on the internet. Bray and von Storch defended their results and accused climate change deniers of interpreting the results with bias. Bray's submission to Science on 22 December 2004 was rejected.One of the questions asked in the survey was "To what extent do you agree or disagree that climate change is mostly the result of anthropogenic causes?", with a value of 1 indicating strongly agree and a value of 7 indicating strongly disagree. The results showed a mean of 3.62, with 50 responses (9.4%) indicating "strongly agree" and 54 responses (9.7%) indicating "strongly disagree". The same survey indicates a 72% to 20% endorsement of the IPCC reports as accurate, and a 15% to 80% rejection of the thesis that "there is enough uncertainty about the phenomenon of global warming that there is no need for immediate policy decisions."

1990s
In 1996, Dennis Bray and Hans von Storch undertook a survey of climate scientists on attitudes towards global warming and related matters. The results were subsequently published in the Bulletin of the American Meteorological Society. The paper addressed the views of climate scientists, with a response rate of 40% from a mail survey questionnaire to 1000 scientists in Germany, the United States and Canada. Most of the scientists accepted that global warming was occurring and appropriate policy action should be taken, but there was wide disagreement about the likely effects on society and almost all agreed that the predictive ability of currently existing models was limited. On a scale of 1 (highest confidence) to 7 (lowest confidence) regarding belief in the ability to make "reasonable predictions" the mean was 4.8 and 5.2 for 10- and 100-year predictions, respectively. On the question of whether global warming is occurring or will occur, the mean response was 3.3, and for future prospects of warming the mean was 2.6.
A Gallup poll of 400 members of the American Geophysical Union and the American Meteorological Society along with an analysis of reporting on global warming by the Center for Media and Public Affairs, a report on which was issued in 1992. Accounts of the results of that survey differ in their interpretation and even in the basic statistical percentages:
Fairness and Accuracy in Reporting states that the report said that 67% of the scientists said that human-induced global warming was occurring, with 11% disagreeing and the rest undecided.
George Will reported "53 percent do not believe warming has occurred, and another 30 percent are uncertain." (Washington Post, 3 September 1992). In a correction Gallup stated: "Most scientists involved in research in this area believe that human-induced global warming is occurring now."
Stewart, T. R., Mumpower, J. L., and Reagan-Cirincione, P. (1992). Scientists' opinions about global climate change: Summary of the results of a survey. NAEP (National Association of Environmental Professionals) Newsletter, 17(2), 6–7.
In 1991, the Center for Science, Technology, and Media conducted a survey of 118 scientists regarding views on the climate change. Analysis by the authors of the respondents projections of warming and agreement with statements about warming resulted in them categorizing response in 3 "clusters":  13 (15%) expressing skepticism of the 1990 IPCC estimate, 39 (44%) expressing uncertainty with the IPCC estimate, and 37 (42%) agreeing with the IPCC estimate.
Global Environmental Change Report, 1990: GECR climate survey shows strong agreement on action, less so on warming. Global Environmental Change Report 2, No. 9, pp. 1–3

See also
References
Sources
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IPCC AR4 SYR (2007), Core Writing Team; Pachauri, R. K.; Reisinger, A. (eds.), Climate Change 2007: Synthesis Report (SYR), Contribution of Working Groups I, II and III to the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change, Geneva, Switzerland: IPCC, ISBN 978-92-9169-122-7.
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