Vox Populi

Readers here tend to be pretty knowledgeable about climate science, and about science in general. Perhaps we should remember that many people — including some among the strongest supporters of action to reduce greenhouse gas emissions — are not so knowledgeable.

For instance, I recently found out about a post on DailyKOS about the “Global Online Climate Change Brainstorm – November 14.” I just found out about it this morning.

It’s a great idea for different groups to collaborate on a common goal and to brainstorm about how to further the cause. But one thing about the DailyKOS post troubled me. Namely, this:

Why are we doing this?

• The world is warming. Satellite records show that in the past two decades, the process of warming has sped up. 2010 is on track to be the warmest year on record.

• Without drastic action, we risk temperature rises of 6°C or more by the end of this century. This would be a catastrophe.

Let me express skepticism about these claims.

First, about “the process of warming has sped up.” I’m not aware that satellite records show that warming has accelerated in the past two decades. In fact I’m quite confident that they don’t. As regular readers know, I’ve studied temperature time series in detail, both from satellites and from ground-based observations, and I have the “skillz” to do that. Global temperature over the last three-and-a-half decades, according to surface temperature and satellite records, is indistinguishable from a linear increase plus autocorrelated noise.

Maybe when they say “sped up” they’re comparing the modern warming rate to that prior to 1975. But that doesn’t make a lot of sense to me — and they certainly didn’t make that clear. The simple interpretation of the claim is that warming is proceeding faster now than it was just two decades ago. Trouble is, there’s no evidence of that.

Now consider “2010 is on track to be the warmest year on record.” That’s true — if one uses the GISS surface temperature data set. In fact, for GISS data this year will almost certainly be the hottest on record. But there are other data sets. I think GISS is the best available, but according to HadCRU this will probably not be the hottest year on record — close, but no cigar. More troubling is that the “on track to be” comment follows mention of the satellite record, and I doubt that either of the most popular satellite data sets (RSS or UAH) will set the record this year. They might, but it’s unlikely given the switch to la Nina-type conditions. Perhaps I’m being too critical, but I think at least some qualification (like “according to NASA”) should have been mentioned.

As for “… we risk temperature rises of 6°C or more by the end of this century,” we do. But — it’s disputable whether 21st-century temperature increase is likely to be that large. The probable range of climate sensitivity is 2 to 4.5 deg.C/doubling of CO2, and we may well exceed doubling CO2 this century but we may not. And even if we do, the thermal inertia of the climate system means we won’t realize the full warming due to greenhouse gases until decades after the increase. So there’s a good chance that warming this century will be less than 6 deg.C, it may well be only half that. But the statement offers no caveat, no qualifier. And exaggerating the likely warming is hardly necessary; only half the indicated warming, a “mere” 3 deg.C, can be disaster enough.

I’m sure the post wants people to know just how dangerous the coming climate changes are. But there’s plenty to worry about within the limits of actual expectation. How about heat waves like this last July in Moscow becoming a once-every-ten-or-fifteen-years event? How about sea level rise of “only” a meter? Or that increased drought that worries BPL (and others) so much?

On blogs like this, we tend to “make speeches for each other.” But the masses of people are untouched. Their politics, and their science, are confined to bread and rent.

Perhaps we need to initiate some serious, well crafted outreach. Let’s get real, hard scientific information out there, to the voting public and to the advocates of saving the earth and human civilization, in a way they can understand — both technically and viscerally. And I don’t mean using phrases like “indistinguishable from a linear increase plus autocorrelated noise.” That just makes people roll their eyes and get bored. We need to express our message in a way that’s accessible, crystal-clear, and 100% unimpeachable.

Perhaps it’s much more valuable, and much more necessary, to educate “Joe the Plumber” than it is to show Anthony Watts the error of his ways.

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