“Is the climate system just too complex for useful prediction?”

In Science, Princeton meteorologist Isaac Held makes a provocative case against the wait-and-see advocates of climate complexity, focusing on the potential for “emergent simplicity”: 

“More fundamentally, an emphasis on complexity in the climate system must be balanced by recognition of emergent simplicity. The seasonal cycle provides a useful counterpoint. An individual year’s temperature record is a consequence of chaotic weather superposed on a relatively simple and smooth underlying cycle.”

And Judith Curry has a thoughtful-but-skeptical response:

“First, I don’t think the seasonal cycle works very well as an argument for external forcing… Second, it is not at all clear to me that natural internal variability and forced variability are easily separable in a linear way.  Third, a truly complex system cannot be understood as a linear superposition of individual elements (discussed in my Uncertainty Monster paper). Fourth, the climate response to the relatively small greenhouse forcing may well be linear, but this linear response may be swamped by the natural internal variability… To me, this is the heart of the scientific debate on climate change, and why the hiatus (and how long it will last) is so important.”