How do we really know humans are causing global warming?*

*But however you answer my question, don’t cite no U.N. report!

So I’m sure that you, like me, are constantly getting e-mails or blog posts that sound like this:

I have been doing enormous amounts of research in this global warming (caused by man) theories and have concluded that there is not ONE shred of evidence to back it up. Can you PROVE to me that global warming is being caused by mankind?

Hmm. Not one shred of evidence? “PROVE” — in all caps, too! You know this is pointless, but still, it’s the day after your daughter’s first birthday, and you’re feeling in good spirits about humanity [she was very well behaved — didn’t grab any other kids and only needed to be sung to once to calm her down when people tried to make her eat cake she didn’t want (a good sign, I think, that she’s not going to be a sugar addict)], so you decide to reply something like:

This one is easy. Either you believe in science — i.e. we went to the moon, you go to the doctor, you have IT equipment you rely on — or you don’t. If you don’t, I can’t “prove” anything to anybody. If you do, then the IPCC reports — which are nothing more than a literature review by the top scientists in the world, commissioned by and summarized for policymakers, signed off by every friggin’ govt in the world — are as much proof as a human being could possibly want.

[Note to fellow parents — emails edited because I know some young people read this blog.]

So then you get a reply like this:

Sorry Joe but your email back to me is not proof of evidence. As for the IPCC report, I don’t buy into what they say. That is not proof. And yes, I very much believe in science which is why I don’t believe in humans have caused global warming. But my question is simple, what scientific proof can you show me, and I am not talking about some report from the UN, that humans are causing the Earth’s temperature to rise. Also, what is the right temperature for the Earth to be at?

The email goes on to ask for IPCC credentials since, “I have a list of 400 scientists, what they do and why the don’t believe in global warming as being caused by man.”

Oh, one of those. Once you realize the emailer hasn’t even bothered to read some of your recent posts, you send a reply that you think/hope will end things:

If you don’t buy into the IPCC, we have nothing to talk about. You might as well not buy into what the American Medical Association or the National Academy of Sciences says. Why take medicine? Why floss? Why get on an airplane? The IPCC report is a summary of the scientific evidence. Simple as that…. If you are talking about the well-debunked Inhofe 400, I guess you haven’t been reading this or other sites.

In retrospect, “laughable” is better than “well-debunked,” but then we all come up with better things to say after the fact. All one can do is press on and rewrite history on your blog….

Anyway, you turn out to be quite wrong about the effect of your email [duh!], and get this reply:

Your emails are proving my point. You have not even attempted to offer proof of global warming as caused by mankind. As for the IPCC report, I read it. It does NOT offer conclusive proof that man is causing theEarth’s temp to rise. I will make this even easier for you, just name ONE piece of evidence toprove global warming as caused by man. Just one! As for James Inhofe, he has provided people with enormous amounts of evidence to debunk global warming as caused by man.

Now you’ve done it, or is that, now I’ve done it. Either way, you/I certainly don’t want some random global warming doubter posting some where that “Climate Progress” — or, even better, the “Center for American Progress” refuses to “name ONE piece of evidence” to support its views [notwithstanding the IPCC, which I guess everybody knows doesn’t count]. Plus, I’m starting to think, hmm, maybe it would be useful to direct some readers to the literature on “attribution” [read, maybe you can turn this otherwise wasted time into a blog post]. So you/I reply:

Sigh. You want some shreds of evidence global warming is caused by mankind, but the IPCC is off limits. Interesting but easy challenge. Let’s start here — It’s a few years old now, but it is the best other review of recent science by the leading experts:

“Detecting and Attributing External Influences on the Climate System: A Review of Recent Advances” [It’s actually by “The International ad hoc Detection and Attribution Group.”]

I assume you have a subscription to Science. This is a good study. “Penetration of Human-Induced Warming into the World’s Oceans.”

Then there is: “Contribution of anthropogenic and natural forcing to recent tropospheric height changes.

Here’s NOAA: “The Detection and Attribution of Climate Change.

I am personally fond of this often-cited paper by NASA.

[Note to most people — The real place to start is “Understanding and Attributing Climate Change,” by Hegerl and Zwiers et al. but for reasons the first half of this post make clear, I can’t do that here.]

But, of course, being the kind of person you are, you can’t leave it at that:

I have more below at the end. But if you won’t believe the 2500 top climate scientists in the world citing hundreds of the latest studies, why would I believe for one second you would believe any studies I cite.

You hide behind the word “conclusive” — please define that word. As you seem to define it, there is no “conclusive” proof that cigarette smoking causes cancer or even that the sun will come up tomorrow.

Inhofe has no evidence. He has opinions backed up by the misinterpretation of a handful of studies that can’t explain what has actually been happening in the past 50 years. Not that it matters AT ALL to the science, but Al Gore does live what he preaches.

Anyway, if you’re serious about wanting to review the science and don’t trust the IPCC to do it, then you should probably read the following [the bibliography of Hegerl and Zwiers et al.]:

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I have read many of these, but, unlike you, I trust the IPCC’s ability to analyze them for me. Let me know when you’re done.

Anyway, if nothing else, perhaps this will discourage people from emailing me….

UPDATE: I just realized that the bibliography was cut off after the d’s. Oh well. Let’s see if the emailer notices….