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> As is widely published, 97+% of climate scientists agree that anthropogenic climate change is occurring. That "97%" claim is questionable. The usual source

by glenra 10y ago

> As is widely published, 97+% of climate scientists agree that anthropogenic climate change is occurring. That "97%" claim is questionable. The usual source on that number is this paper from 2009: http://onlinelibrary.wiley.com/doi/10.1029/2009EO030002/epdf http://onlinelibrary.wiley.com/doi/10.1029/2009EO030002/epdf A bunch of earth scientists were asked to take a web-based survey with a couple questions about climate. There was about a 30% response rate. Survey question #2 was: "Do you think human activity is a significant contributing factor in changing mean global temperatures"? 82% of survey participants answered yes to that question. Which, sure, sounds like a consensus, but it's not a rhetorically convincing level of consensus, so the researchers apparently kept slicing up the data until they could find something better-sounding. The salami slice that fit the bill turned out to be (quoting a Fig. 1 chart caption): "Climatologists who are active publishers on climate change", which is to say, folks who had multiple recent publications in climate journals and "more than 50% of their publications in the last 5 years had been on the subject of climate change." So basically the finding says among people who are able to get lots of papers published on climate change, THOSE guys share 97% agreement on the "humans are causing it" question. Out of 3146 scientists who responded, 77 were counted as "Climatologists who are active publishers on climate change". 75 out of those 77 answered "yes" to question 2, hence 97.1% agreement. But they also broke out just self-identified "climatologists". Eyeballing the chart, it looks to me like they have about 87% agreement on Question #2. TL;DR: Roughly 87% - not 97+% - of climate scientists agree that anthropogenic climate change is occurring. (Or at least, did so as of 2009).

ch4s3 10y ago
I don't have the citation handy, but there's been more consensus on Question #2 since 2009. Even assuming there wasn't, 87% agreement is pretty good evidence in favor of the idea.
- glenra 10y ago
  There's at least one other survey that did the same trick - turned ~80% agreement in a big group into 97% in a minuscule subsample. Additionally, John Cook - the guy who runs skepticalscience - did some studies claiming to find high agreement with "the consensus" among published papers about climate. But his paper were terrible, didn't show what he claimed they did, and were less relevant to your claim. Here's a blogpost going into some issues with the Cook studies and the claims made for them: http://daviddfriedman.blogspot.com/2014/02/a-climate-falsehood-you-can-check-for.html http://daviddfriedman.blogspot.com/2014/02/a-climate-falseho... The difference between disagreeing with 80%-ish and 97% is largely of rhetorical importance. For propaganda purposes it feels like the difference between "a respectable minority view" and "a lunatic fringe". Alas, scientists almost never agree on ANYTHING to the 97% level. So if you hear that level claimed, the best bet is that somebody either fudged with the question - watering it down to such a degree that all the "skeptics" also agree - or fudged with the sample pool, making the surveyed group so tiny and self-selected as to exclude lots of legitimate scientists in related fields.
- glenra 10y ago
  Forgot to mention: a key part of that question is the vagueness of the wording "significant contributing factor". "Significant" certainly includes "small but statistically significant" and also includes "a meaningful fraction (that still might be less than half)". Part of the IPCC "consensus view" on climate is the notion that human activity is responsible for more than half of recent warming. Thus it's quite possible - even likely - for someone to be skeptical of the consensus view and still answer "yes" to question 2. If question 2 were made more precise such that only people who agree with the consensus would answer yes, the level of agreement found - even among climatologists - would be much smaller even than 87%. (I'm guessing closer to 60%. Still probably a majority view in the field, still a "consensus", just not an overwhelming consensus.)

by glenra 10y ago

ch4s3 10y ago

I don't have the citation handy, but there's been more consensus on Question #2 since 2009. Even assuming there wasn't, 87% agreement is pretty good evidence in favor of the idea.

glenra 10y ago
There's at least one other survey that did the same trick - turned ~80% agreement in a big group into 97% in a minuscule subsample. Additionally, John Cook - the guy who runs skepticalscience - did some studies claiming to find high agreement with "the consensus" among published papers about climate. But his paper were terrible, didn't show what he claimed they did, and were less relevant to your claim. Here's a blogpost going into some issues with the Cook studies and the claims made for them: http://daviddfriedman.blogspot.com/2014/02/a-climate-falsehood-you-can-check-for.html http://daviddfriedman.blogspot.com/2014/02/a-climate-falseho... The difference between disagreeing with 80%-ish and 97% is largely of rhetorical importance. For propaganda purposes it feels like the difference between "a respectable minority view" and "a lunatic fringe". Alas, scientists almost never agree on ANYTHING to the 97% level. So if you hear that level claimed, the best bet is that somebody either fudged with the question - watering it down to such a degree that all the "skeptics" also agree - or fudged with the sample pool, making the surveyed group so tiny and self-selected as to exclude lots of legitimate scientists in related fields.
glenra 10y ago
Forgot to mention: a key part of that question is the vagueness of the wording "significant contributing factor". "Significant" certainly includes "small but statistically significant" and also includes "a meaningful fraction (that still might be less than half)". Part of the IPCC "consensus view" on climate is the notion that human activity is responsible for more than half of recent warming. Thus it's quite possible - even likely - for someone to be skeptical of the consensus view and still answer "yes" to question 2. If question 2 were made more precise such that only people who agree with the consensus would answer yes, the level of agreement found - even among climatologists - would be much smaller even than 87%. (I'm guessing closer to 60%. Still probably a majority view in the field, still a "consensus", just not an overwhelming consensus.)