They don't need to know, but if we were talking about something less politicized by the fossil fuel industry, we'd think they were idiots for not deferring to the generally accepted science and instead saying "I don't know."

Like, say they were doing a show on the big bang. That's a pretty non-controversial thing, but we obviously don't know what happened back then. Still, we sure don't see a whole lot of big bang skeptics around (and probably a lot of us here would think they were being willfully ignorant or coy to say "well, I don't know, I wasn't there"). Big bang skepticism isn't an unofficial part of a major political party, either. What's the difference here, I wonder.

>Big bang skepticism isn't an unofficial part of a major political party, either.

Isn't it?

https://en.wikipedia.org/wiki/Christian_right

It shouldn't be. It was a Catholic priest who came up with the idea.

Yes, we're sure about CO2 being one of the causes. As is widely published, 97+% of climate scientists agree that anthropogenic climate change is occurring. The consensus is that average temps are rising, and that weather is becoming more extreme.

The only really valid criticism there seem to be that he flies around in a private jet, which seem pretty contrary to his beliefs. Who cares that he advocates for "green" policies that he'd stand to benefit from? If he truly believes in these initiatives, why would he invest in them himself? Do you question SV investors who advocate for better stem education or net neutrality?

> 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

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).

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.

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-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.

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.)

But the thing is we DO know: global temperatures are increasing due to increased levels of greenhouse gases, the dominant cause of which is human fossil fuel consumption. This is ironclad fact. Virtually all of the scientific literature supports it.