Global Warming Debunked! Or…not.
The headline on Forbes.com, highlighted on the Drudgereport, is just too juicy: “New NASA Data,” it says, “Blow Gaping Hole in Global Warming Alarmism.”
As many of the scientists I know say in response to an eyebrow-raising claim, “Important… if true.”
It's the “if” part that's problematic here. First, the Forbes headline is way more sensational than anything Dr. Roy Spencer actually says in his new paper. As Climate Central chief scientist Phil Duffy says:
The paper itself is far less aggressive in its claims than the Forbes article is. The paper's abstract, for example concludes:
“It is concluded that atmospheric feedback diagnosis of the climate system remains an unsolved problem, due primarily to the inability to distinguish between radiative forcing and radiative feedback in satellite radiative budget observations”
This is hardly a sweeping claim!
But his underlying theory (both here and in earlier papers; this isn't a new idea on his part) are almost universally doubted by other climate scientists. Spencer, himself a bona fide climate scientist, albeit one whose views often lie outside the consensus, basically says that changes in cloud cover are a major cause of climate change.
Just about everyone else in the field, by contrast, considers clouds to be a feedback mechanism in the climate system. That means that warming alters the rate and type of clouds that form, and those in turn affect temperature — most scientists think they drive it up further, although some think not by much, and they could actually exert a small net cooling. The warming comes first; the clouds respond.
Things like changes in the Sun's brightness, by contrast are a forcing mechanism — they push on the climate system from outside, and make it warm up or cool down. (Greenhouse gases like carbon dioxide, or CO2, can be both. Add more to the atmosphere by burning fossil fuels, and the planet warms. But if the planet warms for any reason, more CO2 enters the atmosphere from natural sources. So CO2, unlike clouds, is both a forcing and a feedback.) All of this is Climate Science 101 (maybe the spring semester).
Now Spencer is saying that data from NASA's Terra satellite supports his controversial claim. This already shows the Forbes headline to be somewhat misleading: it's not that NASA data are blowing a hole in anything. It's that Spencer's interpretation of NASA data are blowing… something, somewhere.
But that interpretation depends on a climate model created by Spencer, and a number of climate scientists, having read the paper, are not impressed. Andrew Dessler, for example, from Texas A&M University, says in an email to me that
Overall, the argument made in all of these papers… is extremely weak. What they do is show some data, then they show a very simple model with some free parameters that they tweak until they fit the data. They then conclude that their model is right. However, if the underlying model is wrong, then the agreement between the model and data proves nothing.
The underlying model, Dessler thinks, is not just wrong — it's badly, badly wrong (I wrote about some of Dessler's work in TIME last year on behalf of Climate Central).
If Spencer were right, then clouds would be a major cause of El Niño cycles — which we know is not correct. Talk to any expert [on those cycles] and tell them that clouds cause [them] and they'll laugh at you.
You can see more in an email exchange between Dessler and Spencer that took place a number of months ago.
Kevin Trenberth of the National Center for Atmospheric Research, was a little more blunt. He emailed me to say, in part:
I find the whole discussion [in Spencer's new paper] to be out of touch with reality… Nearly all of the variations in water vapor and clouds, except for those affected by aerosol[s], are a response to the weather and climate variations; they are NOT a forcing. This is a major error that continues in Spencer's work…
Even if you define the extremely carefully thought out projections in global temperatures and other climate factors put together by hundreds of responsible scientists (now being updated to include new research) as “alarmist,” which is more than a little absurd, and even if the new paper by Spencer and his collaborator William Braswell bolsters their argument slightly — which is debatable — it would still take an awful lot more than this to blow a hole in anything, no matter what some headlines say.