How do we know there’s a scientific consensus on climate change? Pundits and the press tell us so. And how do the pundits and the press know? Until recently, they typically pointed to the number 2500 – that’s the number of scientists associated with the United Nations Intergovernmental Panel on Climate Change. Those 2500, the pundits and the press believed, had endorsed the IPCC position.
To their embarrassment, most of the pundits and press discovered that they were mistaken – those 2500 scientists hadn’t endorsed the IPCC’s conclusions, they had merely reviewed some part or other of the IPCC’s mammoth studies. To add to their embarrassment, many of those reviewers from within the IPCC establishment actually disagreed with the IPCC’s conclusions, sometimes vehemently.
The upshot? The punditry looked for and recently found an alternate number to tout — “97% of the world’s climate scientists” accept the consensus, articles in the Washington Post and elsewhere have begun to claim.
This number will prove a new embarrassment to the pundits and press who use it. The number stems from a 2009 online survey of 10,257 earth scientists, conducted by two researchers at the University of Illinois. The survey results must have deeply disappointed the researchers – in the end, they chose to highlight the views of a subgroup of just 77 scientists, 75 of whom thought humans contributed to climate change. The ratio 75/77 produces the 97% figure that pundits now tout.
The two researchers started by altogether excluding from their survey the thousands of scientists most likely to think that the Sun, or planetary movements, might have something to do with climate on Earth – out were the solar scientists, space scientists, cosmologists, physicists, meteorologists and astronomers. That left the 10,257 scientists in disciplines like geology, oceanography, paleontology, and geochemistry that were somehow deemed more worthy of being included in the consensus. The two researchers also decided that scientific accomplishment should not be a factor in who could answer – those surveyed were determined by their place of employment (an academic or a governmental institution). Neither was academic qualification a factor – about 1,000 of those surveyed did not have a PhD, some didn’t even have a master’s diploma.
To encourage a high participation among these remaining disciplines, the two researchers decided on a quickie survey that would take less than two minutes to complete, and would be done online, saving the respondents the hassle of mailing a reply. Nevertheless, most didn’t consider the quickie survey worthy of response –just 3146, or 30.7%, answered the two questions on the survey:
1. When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?
2. Do you think human activity is a significant contributing factor in changing mean global temperatures?
The questions were actually non-questions. From my discussions with literally hundreds of skeptical scientists over the past few years, I know of none who claims that the planet hasn’t warmed since the 1700s, and almost none who think that humans haven’t contributed in some way to the recent warming – quite apart from carbon dioxide emissions, few would doubt that the creation of cities and the clearing of forests for agricultural lands have affected the climate. When pressed for a figure, global warming skeptics might say that human are responsible for 10% or 15% of the warming; some skeptics place the upper bound of man’s contribution at 35%. The skeptics only deny that humans played a dominant role in Earth’s warming.
Surprisingly, just 90% of those who responded to the first question believed that temperatures had risen – I would have expected a figure closer to 100%, since Earth was in the Little Ice Age in the centuries immediately preceding 1800. But perhaps some of the responders interpreted the question to include the past 1000 years, when Earth was in the Medieval Warm Period, generally thought to be warmer than today.
As for the second question, 82% of the earth scientists replied that that human activity had significantly contributed to the warming. Here the vagueness of the question comes into play. Since skeptics believe that human activity been a contributing factor, their answer would have turned on whether they consider a 10% or 15% or 35% increase to be a significant contributing factor. Some would, some wouldn’t.
In any case, the two researchers must have feared that an 82% figure would fall short of a convincing consensus – almost one in five wasn’t blaming humans for global warming — so they looked for subsets that would yield a higher percentage. They found it – almost — in those whose recent published peer-reviewed research fell primarily in the climate change field. But the percentage still fell short of the researchers’ ideal. So they made another cut, allowing only the research conducted by those earth scientists who identified themselves as climate scientists.
Once all these cuts were made, 75 out of 77 scientists of unknown qualifications were left endorsing the global warming orthodoxy. The two researchers were then satisfied with their findings
. Are you?
Lawrence Solomon is executive director of Energy Probe and the author of The Deniers.