The Scientific Consensus on Climate Change

There is an overwhelming level of scientific consensus on human-caused climate change. Over 95% of actively publishing climate scientists agree that the earth is warming and that human activity is the cause. In spite of this agreement, only about 50% the general public think that scientists have reached a consensus on human-caused climate change. Two sources of the discrepancy are the unbalanced portrayal of the situation in the media, and the Manufactured Doubt Industry.
organizations convinced by ACC

The Science

When "scientific consensus" is referred to in relation to climate change, it's referring to the following points:

  • The earth is getting warmer
  • The warming is mostly due to human activity
  • If greenhouse gas (GHG) emissions continue, the warming will accelerate

The Consensus

Numerous survey studies have been done, and the results are overwhelmingly in favor of scientific consensus that the earth is warming and human activity is the cause. Surveys done by reputable organizations find that around 97% of climate scientists agree with the statements above. The following are results from a few of these surveys, plus a resolution from a very distinguished group of scientists.

Expert Credibility in Climate Change (NAS)

This study compiled a list of 1,372 climate scientists, and then looked at those who are "actively publishing" in the science of climate. They categorized the scientists as either "convinced" or "unconvinced" by the evidence. The results were that 97% of actively publishing climate scientists are convinced by the evidence of anthropogenic climate change. They also found that those scientists that were unconvinced had significantly fewer publications (in any science) than those that were convinced. This suggests that the (vocal) "unconvinced" group actually has done a lot less research. (Read this study in full.)

Examining the Scientific Consensus on Climate Change (AGU)

This study was done in order to address the broader question of public opinion versus scientific opinion. It asked two questions, one about whether temperature is increasing, and one about whether or not human activity is contributing to any change. Here are the results:

Question #1: When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?

    About 90% of all the scientists and 97% of the climate scientists said temperatures had risen.

Question #2: Do you think human activity is a significant contributing factor in changing mean global temperatures?

    About 82% of all the scientists and 97% climate scientists agreed that human activity is a significant contributing factor.

The anonymous poll sought the opinion of the most complete list of earth scientists they could find, contacting more than 10,200 experts at universities and government labs around the world listed in the 2007 edition of the American Geological Institute's Directory of Geoscience Departments. The 2-minute, two-question poll had 3146 responses (30.7% of those polled). Approximately 90% of the scientists who responded were from the U.S., and about 90% held a Ph.D. degree. Of these scientists, 5% were climate scientists who published more than 50% of all their peer-reviewed publications in the past five years on the subject of climate change. The authors noted that the survey included participants with well-documented dissenting opinions on global warming theory. More results from this study, including responses from the general public, are shown below in Figure 1. (Read this study in full.)

public and scientific opinion on climate change
Figure 1. Response distribution to the question, "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Source)

More on the consensus surveys in a blog post by Dr. Jeff Masters.

Nobel Laureates

In May 2011, seventeen Nobel laureates gathered in Stockholm and published a memorandum supporting the science of anthropogenic climate change, and calling for "fundamental transformation and innovation in all spheres and at all scales in order to stop and reverse" it. Here's a piece of what they say:

    Science makes clear that we are transgressing planetary boundaries that have kept civilization safe for the past 10,000 years. [...] We can no longer exclude the possibility that our collective actions will trigger tipping points, risking abrupt and irreversible consequences for human communities and ecological systems. We cannot continue on our current path. The time for procrastination is over. We cannot afford the luxury of denial.

More on the Nobel laureates' call to action from RealClimate.

The Oregon Petition: Manufacturing Doubt

Since 1999, the "Oregon Institute of Science and Medicine" has been circulating a petition opposing the consensus on climate change and the efforts to mitigate it. The petition's purpose is to argue that there is no consensus on climate change. The petition website currently lists 31,000 signatures, although the credentials of those signing it are unknown, and the authenticity is disputed. The following is an excerpt from Dr. Jeff Masters' blog, "The Manufactured Doubt Industry and the Hacked Email Controversy."

organizations convinced by ACC

In 1988, the fossil fuel industry realized it had a serious problem. The summer of 1988 had shattered century-old records for heat and drought in the U.S., and NASA's Dr. James Hansen, one of the foremost climate scientists in the world, testified before Congress that human-caused global warming was partially to blame. A swelling number of scientific studies were warning of the threat posed by human-cause climate change, and that consumption of fossil fuels needed to slow down.

Naturally, the fossil fuel industry fought back. They launched a massive PR campaign that continues to this day, led by the same think tanks that worked to discredit the ozone depletion theory. The George C. Marshall Institute, the Competitive Enterprise Institute, Heartland Institute, and Dr. Fred Singer's SEPP (Science and Environmental Policy Project) have all been key players in both fights, and there are numerous other think tanks involved. Many of the same experts who had worked hard to discredit the science of the well-established link between cigarette smoke and cancer, the danger the CFCs posed to the ozone layer, and the dangers to health posed by a whole host of toxic chemicals, were now hard at work to discredit the peer-reviewed science supporting human-caused climate change.

As is the case with any Manufactured Doubt campaign, a respected scientist was needed to lead the battle. One such scientist was Dr. Frederick Seitz, a physicist who, in the 1960s, chaired the organization many feel to be the most prestigious science organization in the world—the National Academy of Sciences. Seitz took a position as a paid consultant for R.J. Reynolds tobacco company beginning in 1978, so was well-versed in the art of Manufactured Doubt. According to the book Climate Cover-up, over a 10-year period Seitz was responsible for handing out $45 million in tobacco company money to researchers who overwhelmingly failed to link tobacco to anything the least bit negative. Seitz received over $900,000 in compensation for his efforts. He later became a founder of the George C. Marshall Institute, and used his old National Academy of Sciences affiliation to lend credibility to his attacks on global warming science until his death in 2008.

It was Seitz who launched the "Oregon Petition", which contains the signatures of more than 34,000 scientists saying global warming is probably natural and not a crisis. The petition is a regular feature of the Manufactured Doubt campaign against human-caused global warming. The petition lists the "Oregon Institute of Science and Medicine" as its parent organization. According to Climate Cover-up, the Institute is a farm shed situated a couple of miles outside of Cave Junction, OR (population 17,000). The Institute lists seven faculty members, two of whom are dead, and has no ongoing research and no students.

The history of the Manufactured Doubt industry provides clear lessons in evaluating the validity of their attacks on the published peer-reviewed climate change science. One should trust that the think tanks and allied "skeptic" bloggers such as Steve McIntyre of Climate Audit and Anthony Watts of Watts Up With That will give information designed to protect the profits of the fossil fuel industry. Yes, there are respected scientists with impressive credentials that these think tanks use to voice their views, but these scientists have given up their objectivity and are now working as lobbyists. I don't like to call them skeptics, because all good scientists should be skeptics. Rather, the think tank scientists are contrarians, bent on discrediting an accepted body of published scientific research for the benefit of the richest and most powerful corporations in history. Virtually none of the "sound science" they are pushing would ever get published in a serious peer-reviewed scientific journal, and indeed the contrarians are not scientific researchers. They are lobbyists. (Continue reading this blog.)

More on the Oregon Petition from SkepticalScience and RealClimate.

Climate Change and the Media

According to a poll done by (WPO) after the 2010 election, 45% of voting Americans think that most scientists do not agree that climate change is occurring. WPO goes on further to estimate that this percentage has actually increased over the past ten years. A recent Pew study found that an overwhelming majority of Americans like science, have a positive regard for scientists, and think that science "contributes a lot to society's well-being." So if there's obvious consensus among scientists, why is that information not making it to the public?

Never Rarely Once a week 2-3 times a week Almost every day
Fox News 30 37 45 36 60
CNN 51 40 39 25 25
MSNBC 49 34 35 35 20
Network TV news broadcasts 59 37 41 36 35
Public Broadcasting (NPR or PBS) 49 41 36 21 13
Newspapers & news magazines (in print or online) 48 43 41 24 40
Table 1. Of people who responded that they agree with the statement "most scientists believe that global warming is not occurring," 60% watch Fox News almost every day. (Source)

The average American learns about climate science from the media, and which media source you choose could influence your understanding of the facts (Table 1). Unfortunately, when the media covers climate change science, it usually frames the science as a debate in order to present "balanced" news to the viewers. But the debate among climate scientists has long been over. Pitting a climate scientist and a climate "contrarian" (who's usually not a scientist at all) against one another makes it appear this is a 50/50 struggle between fact and fiction, when in reality, 97% of climate scientists agree that global temperatures are rising and human activity is to blame. Whereas in political discourse the method of giving two opposing sides equal coverage is valid, in science there is an objective truth. To present science as a subjective debate is misleading.

Position Statements By Other Major Scientific Institutes

The following is a list of climate change position papers put out by the major governmental scientific institutes of the world that deal with the atmosphere, ocean, and climate. All of these organizations agree that significant human-caused climate change is occurring:

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