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# Posted 8:27 PM by Ariel David Adesnik

ANOTHER FORAY INTO CLIMATE SCIENCE: As always, my role is the amateur plunging into a pool of expertise. On Thursday, George Will quoted Mark Steyn to the effect,

If you're 29, there has been no global warming for your entire adult life. If you're graduating high school, there has been no global warming since you entered first grade.

Kevin Drum ismissed Steyn's comment as a denialist talking point:

Global temps have been trending up for over a century, but in any particular year they can spike up and down quite a bit. In 1998 they spiked up far above the trend line and last year they spiked below the trend line. So 2008 was cooler than 1998.

Kevin provides the relevant graph to make his point.

I found the graph interesting for several reasons. First of all, it shows that global temperatures were falling from around 1940 through 1975. Then there were big jumps in the late 70s, late 80s and late 90s. Whatever's happening to our planet's temperatures, they certainly aren't holding steady.

Anyhow, Kevin's post (along with those of Ezra Klein and Ryan Avent) led Jim Manzi to defend Will and Steyn on the grounds that they are, at a minimum, technically correct, since average temperatures haven't risen over the past ten years, regardless of what's happened over the past thirty-five. Jim also raises some very interesting questions about how much data we actually need to know whether the globe is warming or not. He admits that ten years of stability doesn't mean much. But how many years of data do we actually need to come up with good answers about the existence/extent of global warming?

Finally, there's one last response from Kevin in which he takes Jim to task for saying that temperatures have been stable over the past decade, since they actually have risen (by one-fifth of a degree (Celsius) to be precise). Kevin's baseline year is 1999. Compared to 1998 (a hot year), it seems temperatures have actually fallen slightly. I think Kevin's argument would've been much more robust if he said that the average temperature for the past ten years was significantly higher than the average temperature for the decade before that.

So all I need to figure out is what the average temperature will be a decade from now.

Cross-posted at Conventional Folly

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Comments:

I think we are getting confused with all of the various arguments going around, but isn't the real question whether this warming is man-made? Whatever you think about the direction in the last decade, it is pretty obviously warmer than the decades of the last century - but why does that matter so much? World temperatures have gone up and done and up and done over the millenia. That's reality.

What matters (or should matter) is whether there is anything that needs to be done and anything that can be done - and unless this warming is man-made, the answer is probably, 'no.'

# posted by

Anonymous : 6:16 AM

The question is not "how much data," the question is "when do we get real science."

Real science being defined, in this case, as a model that can take data and make real, testable predictions on a lot of smaller indicators as well as the big one, which are then borne out. It would be nice, too, if such a model didn't have mysterious kludge factors in its calculations, and was consistent with physical law.

So far, we don't have one. Until then, from a scientific skeptic's point of view, global warming remains "not even wrong."

# posted by

Ray : 10:11 AM

What the 1998 vs. 1999 example shows is how much you can manipulate the trend through your choice of time frame.

One can also point out that the 1990's were not the hottest decade in the U.S., the 1930's were, with the inevitable response that the U.S. is not the planet, with the evitable but quite accurate response that the U.S. was one of the few places on the planet in the 1930's with decent temperature reporting.

We simply cannot make pronouncements about global temperatures in the 1930's because most of the planet wasn't keeping track. Which doesn't stop the alarmists from making pronouncements going much further back then that. They are willing to tell you the global temperature in 1850 to within a tenth of a degree even though 99% of the planet wasn't within 100 miles of a thermometer in 1850.

And so it goes.

The fact is, we have barely begun the data collection we need to do before drawing any drastic conclusions. There aren't even any known examples in the geologic record of "greenhouse gasses" causing a greenhouse effect. Yet this is a basic assumption.

# posted by

tim maguire : 12:34 PM