by Judith Curry
I just spotted spotted an article on Reuters entitled “The Harry Potter Theory of Climate,” and I couldn’t resist doing a post on it.
The article is an interview with Mark Serreze, Director of the National Snow and Ice Data Center (NSIDC).
“Climate doesn’t change all by itself,” Serreze said. “It’s not like the Harry Potter theory of climate, where he flicks his magic wand and the climate suddenly changes. Climate only changes for a reason.”
He crossed off other possible drivers for climate change one by one.
“Could it be that the Sun is shining more brightly than it was? No, that doesn’t work. We’ve been monitoring energy coming from the Sun and apart from the 11-year sunspot cycle, there’s not much happening.
“Is it that the warming is coming from the oceans — the oceans are releasing heat into the atmosphere? … Well, if that were the case, we’d have to observe that the oceans are cooling … but oceans are not cooling, the oceans are warming like the atmosphere.
“We might be able to argue that it’s something we don’t understand, something like a cosmic ray flux modulated by the Sun … That’s pretty much of a cop-out, OK? Because you’re not really making an explanation, you’re making a supposition.”
The only factor that can explain the observed rise in global average temperature — 1.4 degrees F or .8 degrees C over the last century — is climate forcing due to heightened levels of greenhouse gases, Serreze said.
Ouch. On previous Climate Etc. threads on attribution of 20th century climate change, we have pretty much debunked each of these arguments. Serreze’s weak arguments do not necessarily mean that anthropogenic CO2 has not warmed the planet during the 20th century, it just means that he has made weak arguments. Now that I think about it, the Harry Potter theory might be good nomenclature for natural unforced variability; climate scientists seem to reject as magic warming that isn’t forced.
Serreze did make one statement that I find interesting:
“When we have autumns with low sea ice, these tend to be followed by negative Arctic Oscillation,” Serreze said. If this theory holds up, it could improve prospects for seasonal prediction of climate.
Makes sense, I will definitely take a look at that one, given my interest in seasonal predictability of weather regimes.
The Harry Potter article follows an article yesterday “Extreme winter weather linked to climate change,” which is mostly an interview with Jeff Masters and Mark Serreze. I much preferred the interpretation NOAA’s Climate Scene Investigation Team, which finds the heavy snows to result from the combination of La Nina and the negative Arctic Oscillation.
And while we are on the subject of the Arctic, I would like to point out a new paper in GRL entitled “Recovery Mechanisms of Arctic Sea Ice” Abstract:
We examine the recovery of Arctic sea ice from prescribed ice-free summer conditions in simulations of 21st century climate in an atmosphere–ocean general circulation model. We find that ice extent recovers typically within two years. The excess oceanic heat that had built up during the ice-free summer is rapidly returned to the atmosphere during the following autumn and winter, and then leaves the Arctic partly through increased longwave emission at the top of the atmosphere and partly through reduced atmospheric heat advection from lower latitudes. Oceanic heat transport does not contribute significantly to the loss of the excess heat. Our results suggest that anomalous loss of Arctic sea ice during a single summer is reversible, as the ice–albedo feedback is alleviated by large-scale recovery mechanisms. Hence, hysteretic threshold behavior (or a “tipping point”) is unlikely to occur during the decline of Arctic summer sea-ice cover in the 21st century.
This is consistent with sea ice simulations I did in the 1990’s with a stand alone sea ice model. It is pretty difficult to get the wintertime sea ice not to return, would need much more warming than say tripling CO2.
Upon reflection, the Harry Potter theory of climate science seems preferable to these recent statements by Serreze and Masters.