Coyote Blog

I am skeptical of some but not all global warming claims, but must admit that even as a skeptic, I find this argument by James Lewis uncompelling:

Now imagine that all
the variables about global climate are known with less than 100 percent
certainty. Let's be wildly and unrealistically optimistic and say that
climate scientists know each variable to 99 percent certainty! (No such
thing, of course). And let's optimistically suppose there are only one-hundred x's, y's, and z's
--- all the variables that can change the climate: like the amount of
cloud cover over Antarctica, the changing ocean currents in the South
Pacific, Mount Helena venting, sun spots, Chinese factories burning
more coal every year, evaporation of ocean water (the biggest
"greenhouse" gas), the wobbles of earth orbit around the sun, and yes,
the multifarious fartings of billions of living creatures on the face of the earth, minus,
of course, all the trillions of plants and algae that gobble up all the
CO2, nitrogen-containing molecules, and sulfur-smelling exhalations
spewed out by all of us animals. Got that? It all goes into our best
math model.

So
in the best case, the smartest climatologist in the world will know 100
variables, each one to an accuracy of 99 percent. Want to know what the
probability of our spiffiest math model would be, if that perfect world existed?  Have you ever multiplied (99/100) by itself 100 times? According to the Google calculator, it equals a little more than 36.6 percent.

The Bottom line: our best imaginable model has a total probability of one out of three. How many billions of dollars in Kyoto money are we going to spend on that chance?

Yes, there is a point to be made that climate is really complicated.  However, I can still make correct and valid directional predictions without knowing the exact state of every variable.  For example, I can say with some certainty that, at least here in Arizona, that the temperature at 4PM is going to be higher than the temperature at 4AM, and probably by many degrees.  I can make this statement despite having no idea what the temperature at either time actually is.

I think one can say that the hypothesis is pretty strong that man-made CO2 is increasing atmospheric CO2 concentrations which in turn is causing some warming.  Where Mr. Lewis probably has a point is on the issue of positive and negative feedbacks.  Most of the warming in the estimates in productions like "An Inconvenient Truth"  relies not on just CO2-driven warming, but warming from a variety of feedback processes.  These feedbacks are really really complicated and not well understood.  I discuss this issue of feedbacks both here and here and here.

(HT Maggies Farm)