A Brief Guide to the Scientific Consensus on Climate Change

This post, by Laurence Lewis, first appeared at DailyKos on February 19, 2012. Laurence Lewis retains copyright. Reproduced by permission and with thanks. Emphases added. -mt 

A brief guide to the scientific consensus on climate change

by Laurence Lewis

The most important issue humanity has ever faced isn’t even a part of the political conversation. On that front the politicians have failed.All of them.

The traditional media haven’t just failed, they are complicit in the deliberate cause of that failure. Which means it’s up to us. Just as the Occupy movement has changed the nature of the economic conversation in this country, we the people must change the nature of the political conversation in this country, and thus force the issue of climate change into public consciousness as not only urgent but of primary importance. It sounds like hyperbole, but on this task the future of life as we know it does in fact depend.President Obama and the Democrats are paradigmatically better than the Republicans on the issue of climate change, yet they to a dangerous degree understate and undervalue the criticality of the moment. But the Republicans deny the science of climate change altogether. Even worse, in their feign of acting reasonable the Republicans go so far as to pretend to care about the science of climate change, with the flatly false assertion that the science is controversial and unproven. The usually compliant and enabling traditional media usually support them in this lie. And worse.

This past week, one of the most insidious conspiracies to undermine public understanding of the facts about climate change finally was revealed. Some traditional media outlets responsibly reported the story, beginning with the British newspaper The Guardian; but it certainly hasn’t received the same attention given to the earlier false claim that the science of climate change has been fabricated— a story that itself received far more attention when it initially broke than when it was completely and thoroughly (pdf) and beyond all doubt debunked as not only systemic lies, but lies promoted through what appears to have been criminal activity.

None of this would be possible if people knew the scientific truth. The earlier concocted scandal would not have been taken seriously if people knew the scientific truth. The newly revealed legitimate scandal— which includes attempts to disinform children, and payments to scientists and bloggers who will deny the scientific consensus— was a direct assault on the scientific truth. And that is where we the people must start: the scientific truth. We must so embed in public consciousness the overwhelming scientific consensus on climate change that even such a well-funded disinformation industry, such incompetence and complicity from traditional media outlets, and what now has become boilerplate lunacy from Republicans cannot dissipate it. When people fully understand the scientific truth they will insist that politicians act. Republicans and other climate deniers will be dismissed with the disdain they deserve, and Democrats will, as they do often do, follow where the people lead. That is the great advantage of the Democrats. As with the Occupy movement, when the people are resolved and their message is clear, the Democrats do listen.

Most of what follows is well more than a year old. None of this is breaking news, although new reports about the impacts of climate change pour in almost daily. The scientific consensus has been well established, and that many in the traditional media and pretty much all prominent Republicans continue to deny it speaks not only to their blatant dishonesty, but given the strong terms used by the scientists, their reckless irresponsibility as well. What follows is a brief but scientifically comprehensive overview. Read it. Bookmark it. Send it to anyone who ever questions whether climate change really is happening, or whether there isn’t legitimate scientific debate about what really is happening. You don’t need to go into the details about carbon emissions or chemical processes or quantities of global ice loss or sea level elevations or ocean acidification or the potential feedback loop of tundra methane releases, although there is plenty of available information on all of them. But most people want to keep it clean and clear, and they just want to start by understanding whether or not this really is happening. What do the scientists say? Start with that. Let that sink in. Climate change is happening. The consequences are and will be devastating. Maybe we should do something about it.

In May of 2010, the Los Angeles Times reported:

In a sharp change from its cautious approach in the past, the National Academy of Sciences on Wednesday called for taxes on carbon emissions, a cap-and-trade program for such emissions or some other strong action to curb runaway global warming.Such actions, which would increase the cost of using coal and petroleum — at least in the immediate future — are necessary because “climate change is occurring, the Earth is warming … concentrations of carbon dioxide are increasing, and there are very clear fingerprints that link [those effects] to humans,” said Pamela A. Matson of Stanford University, who chaired one of five panels organized by the academy at the request of Congress to look at the science of climate change and how the nation should respond.

The three reports issued Wednesday, totaling more than 860 pages, provide the broad outlines for a U.S. response to the threat; two more reports are to come.

“This is the most comprehensive report ever on climate change,” said atmospheric scientist Ralph J. Cicerone, the president of the academy. They outline “why the U.S. should act now to reduce greenhouse gas emissions and why we should have a national strategy to adapt to the inevitable.”

And the press release from the National Academies:

The compelling case that climate change is occurring and is caused in large part by human activities is based on a strong, credible body of evidence, says Advancing the Science of Climate Change, one of the new reports.  While noting that there is always more to learn and that the scientific process is never “closed,” the report emphasizes that multiple lines of evidence support scientific understanding of climate change.  The core phenomenon, scientific questions, and hypotheses have been examined thoroughly and have stood firm in the face of serious debate and careful evaluation of alternative explanations.”Climate change is occurring, is caused largely by human activities, and poses significant risks for — and in many cases is already affecting — a broad range of human and natural systems,” the report concludes.  It calls for a new era of climate change science where an emphasis is placed on “fundamental, use-inspired” research, which not only improves understanding of the causes and consequences of climate change but also is useful to decision makers at the local, regional, national, and international levels acting to limit and adapt to climate change.  Seven cross-cutting research themes are identified to support this more comprehensive and integrative scientific enterprise.

The 2009 State of the Climate report released today draws on data for 10 key climate indicators that all point to the same finding: the scientific evidence that our world is warming is unmistakable. More than 300 scientists from 160 research groups in 48 countries contributed to the report, which confirms that the past decade was the warmest on record and that the Earth has been growing warmer over the last 50 years.

The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society.

The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years.Earth-orbiting satellites and other technological advances have enabled scientists to see the big picture, collecting many different types of information about our planet and its climate on a global scale. Studying these climate data collected over many years reveal the signals of a changing climate.

Certain facts about Earth’s climate are not in dispute:

  • The heat-trapping nature of carbon dioxide and other gases was demonstrated in the mid-19th century.2 Their ability to affect the transfer of infrared energy through the atmosphere is the scientific basis of many JPL-designed instruments, such as AIRS. Increased levels of greenhouse gases must cause the Earth to warm in response.
  • Ice cores drawn from Greenland, Antarctica, and tropical mountain glaciers show that the Earth’s climate responds to changes in solar output, in the Earth’s orbit, and in greenhouse gas levels. They also show that in the past, large changes in climate have happened very quickly, geologically-speaking: in tens of years, not in millions or even thousands.

The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.

The Earth’s climate is now clearly out of balance and is warming. Many components of the climate system-including the temperatures of the atmosphere, land and ocean, the extent of sea ice and mountain glaciers, the sea level, the distribution of precipitation, and the length of seasons-are now changing at rates and in patterns that are not natural and are best explained by the increased atmospheric abundances of greenhouse gases and aerosols generated by human activity during the 20th century. Global average surface temperatures increased on average by about 0.6¡C over the period 1956-2006. As of 2006, eleven of the previous twelve years were warmer than any others since 1850. The observed rapid retreat of Arctic sea ice is expected to continue and lead to the disappearance of summertime ice within this century. Evidence from most oceans and all continents except Antarctica shows warming attributable to human activities.

Careful and comprehensive scientific assessments have clearly demonstrated that the Earth’s climate system is changing rapidly in response to growing atmospheric burdens of greenhouse gases and absorbing aerosol particles (IPCC, 2007). There is very little room for doubt that observed climate trends are due to human activities. The threats are serious and action is urgently needed to mitigate the risks of climate change.

Indeed, strong observational evidence and results from modeling studies indicate that, at least over the last 50 years, human activities are a major contributor to climate change.Direct human impact is through changes in the concentration of certain trace gases such as carbon dioxide, chlorofluorocarbons, methane, nitrous oxide, ozone, and water vapor, known collectively as greenhouse gases.

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 twentyfirst 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.

  • Joint statement by the American Association for the Advancement of Science, American Chemical Society, American Geophysical Union, American Institute of Biological Sciences, American Meteorological Society, American Society of Agronomy, American Society of Plant Biologists, American Statistical Association, Association of Ecosystem Research Centers, Botanical Society of America, Crop Science Society of America, Ecological Society of America, Natural Science Collections Alliance, Organization of Biological Field Stations, Society for Industrial and Applied Mathematics, Society of Systematic Biologists, Soil Science Society of America, University Corporation for Atmospheric Research:

Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science. Moreover, there is strong evidence that ongoing climate change will have broad impacts on society, including the global economy and on the environment.

  • Joint statement (pdf) by the Science Academies of the G8+5 (Canada, France, Germany, Italy, Japan, Russia, United Kingdom, United States, Brazil, China, India, Mexico and South Africa):

The IPCC 2007 Fourth Assessment of climate change science concluded that large reductions in the emissions of greenhouse gases, principally CO2, are needed soon to slow the increase of atmospheric concentrations, and avoid reaching unacceptable levels.However, 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. Feedbacks in the climate system might lead to much more rapid climate changes.

The need for urgent action to address climate change is now indisputable. For example, limiting global warming to 2°C would require a very rapid worldwide implementation of all currently available low carbon technologies. The G8+5 should lead the transition to an energy efficient and low carbon world economy, and foster innovation and research and development for both mitigation and adaptation technologies. Capitalizing on new technologies will require a major scientific effort and policy initiatives to accelerate adoption of new technologies. The need to find solutions to climate change presents a huge but as yet unrealized opportunity for the creation of new jobs and for the stimulation of new and emerging markets. The role of innovation in delivering energy efficiency and a low carbon world should become a major part of the efforts to rebuild the global economy.

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.

Policy: The AIP supports a reduction of the green house gas emissions that are leading to increased global temperatures, and encourages research that works towards this goal.Reason: Research in Australia and overseas shows that an increase in global temperature will adversely affect the Earth’s climate patterns. The melting of the polar ice caps, combined with thermal expansion, will lead to rises in sea levels that may impact adversely on our coastal cities. The impact of these changes on biodiversity will fundamentally change the ecology of Earth.

Realizing, 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;

Stabilization of climate to avoid “dangerous anthropogenic interference with the climate system”, as called for in the UN Framework Convention on Climate Change, will require significant cutbacks in greenhouse gas emissions during the 21st century; and

Mitigation of and adaptation to climate change can be made more effective by reducing uncertainties regarding feedbacks and the associated mechanisms;


Nations collectively to begin to reduce sharply global atmospheric emissions of greenhouse gases and absorbing aerosols, with the goal of urgently halting their accumulation in the atmosphere and holding atmospheric levels at their lowest practicable value;

National and international agencies to adequately support comprehensive observation and research programs that can clarify the urgency and extent of needed mitigation and promote adaptation to the consequences of climate change;

Resource managers, planners, and leaders of public and private organizations to incorporate information on ongoing and projected changes in climate and its ramifications into their decision-making, with goals of limiting emissions, reducing the negative consequences of climate change, and enhancing adaptation, public well-being, safety, and economic vitality; and

Organizations around the world to join with IUGG and its member Associations to encourage scientists to communicate freely and widely with public and private decision-makers about the consequences and risks of on-going climate change and actions that can be taken to limit climate change and promote adaptation; and


To act with its member Associations to develop and implement an integrated communication and outreach plan to increase public understanding of the nature and implications of human-induced impacts on the Earth system, with the aim of reducing detrimental consequences.


  1. Over the last five years perhaps thousands of articles similar to this in tone and content, florid and full of accusations worthy of Glenn Beck, have appeared on the net. The hyper partisan language, the breathless "exposure" of Heartland, the unscientific attribution of current events obscures any actual facts within and diminishes the impact of the quoted paragraphs which follow.

  2. Just in case you mistake this for an unconstructive comment, let me start by saying that I completely agree that the overwhelming scientific consensus is that man-made global warming is happening and that that consensus is correct -- and also that global warming is a huge threat.

    All that seems obvious to me, and yet many people question it. How does one reach those people? Here is where I'm not so sure about your approach. I think most deniers are simply not impressed by all those pronouncements from learned bodies. Instead, they have in their minds a narrative that's something like this. Yes, the scientific consensus is that man-made global warming is happening. But that's because scientists are like sheep: they don't dare to contradict the consensus even when the consensus flies in the face of the evidence, and those few brave souls who do contradict it find that they can't publish their papers in good journals because the editors of those journals are of the sheep-like kind.

    For that reason I think you may be wrong to focus on what scientists say, important though that is. I think a more basic message is that carbon dioxide is a greenhouse gas, that concentrations have increased significantly, and that it would be very peculiar indeed if global warming were not the result. Or rather, the message should be in three parts: basic physics leads us to have a strong expectation that the carbon dioxide we've pumped into the atmosphere should cause global warming; the measurements that have been made bear this out; the scientific consensus about the previous two statements is overwhelming.

  3. Well, this article was originally from DailyKos, so the target audience was definitely not "most deniers" - or any of them at all. It was I believe a reminder to the politically active on the left, big Obama supporters, that this is an important issue. And in that regard it seemed pretty effective in its original context. Not sure why MT thought it belonged here too though - at the least the headline probably ought to have been edited a little for a new audience.

  4. I think you've accurately described the opinions of some, maybe many, deniers. I don't have a good answer to how to reach them - conspiracy theories are hermetically sealed because any evidence to the contrary is interpreted as evidence that the conspiracy is larger. The irony of course is that scientists are the least sheep-like people around. Perhaps part of the answer is more outreach all across science to just expose more non-scientists to what the pursuit of science is like and what the people who do it are like.

    Meanwhile, reminding people of the vast nature of the consensus of major scientific bodies may well be helpful for the less informed "doubters" even if it's pointless with the hard core deniers.

  5. Well, we do want to meander back to science and not get totally caught up in the soap opera, but I think asserting that there indeed is a consensus is a god place to start. Also this seemed a good contemporary roundup of the evidence, not for the climate crisis itself, but for the near-unanimity among scientists that there is one. This is at least a useful point for further reference.

  6. Pingback: A Brief Guide to the Scientific Consensus on Climate Change | Planet3.0 « Secularity

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