2010-09-01 03:56:14Basic 97: Climate is chaotic and cannot be predicted.

One of the defining traits of a chaotic system is 'sensitive dependence to initial conditions'. This means that even very small changes in the state of the system can quickly and radically change the way that the system develops over time. Edward Lorenz's landmark 1963 paper demonstrated this behavior in a simulation of fluid turbulence, and ended hopes for long-term weather forecasting.

However, climate is not weather, and modeling is not forecasting.

Although it is generally not possible to predict a specific future state of a chaotic system (there is no telling what temperature it will be in Oregon on December 21 2012), it is still possible to make statistical claims about the behavior of of the system as a whole (it is very likely that Oregon's December 2012 temperatures will be colder than its July 2012 temperatures.) There are chaotic components to the climate system, such as El Nino and fluid turbulence, but they all have much less long-term influence than the greenhouse effect.  It's a little like an airplane flying through stormy weather: It may be buffeted around from moment to moment, but it can still move from one airport to another.

Nor do climate models generally produce weather forecasts. Models often run a simulation multiple times with different starting conditions, and the ensemble of results are examined for common properties. (One example: Easterling 2009) This is, incidentally, a technique used by mathematicians to study the Lorenz functions.

The chaotic nature of turbulence is no real obstacle to climate modeling, and it does not negate the existence or attribution of climate change.

2010-09-01 04:32:32

Lovely. Maybe some brief mention of physical constraints on boundaries would be good but at least a plurality of "normal" people are not  going to require that. I'm making so bold as to vote for this right now...
2010-09-01 06:17:02
Nicholas Berini

Loving the Oregon 2012 analogy.
2010-09-01 13:05:24


great piece - one possible additional thought is something that james hanson talked about, and that is that we know most about how the climate works through studying how it behaved in the past.

2010-09-01 19:39:32Top man!
Graham Wayne

God, you nailed that first time. Of course, there's something I'd like to see included, but I would say that, wouldn't I? (It's fractals, perhaps a more widely known example of sensitivity to input conditions).

Anyway, thumbs up...

2010-09-04 01:14:50Bump.

Can anybody see their way clear to pushing this over the top?
2010-09-04 03:55:56I don't get the airplane analogy


"It's a little like an airplane flying through stormy weather: It may be buffeted around from moment to moment, but it can still move from one airport to another."

WHAT's like an airplane flying through stormy weather? What do the airports correspond to?

I'm missing the simile.


Just another point:

If you predict that it will rain on Monday, Wednesday and Friday, but instead it rains on Tuesday, Thursday and Saturday, you will be 100% right on the climate and 0% correct on the weather.


2010-09-04 15:20:00
Michael Searcy


I like the current read, though I agree with Neal that the analogy might need a tweak.  I tend to think of a boulder running down a mountain.  You may not be able to predict at exactly what position it will come to rest, but you can confidently say it will be somewhere at the bottom.  I'm also reminded of the old "Plinko" game from "The Price is Right" television show.


Also, for what it's worth, I always thought this argument was completely backward. The danger lies not in our inability to predict the climate but in the loss of that ability.  Consciously or not, we predict the climate all the time.  All of human society is predicated on that predictability.  It dictates where we live, how we build our homes, what food we grow along with when and where, where we get our water, and on and on.  Events that disturb this predictability, even for short terms, like earthquakes, droughts, floods, etc. have massive impacts on society and carry huge costs associated with them.  The loss of this predictability on a global and long term scale carries unimaginable consequences.

2010-09-04 17:29:18Love it
Graham Wayne
Ah Michael, I will be stealing that fine argument...it's particularly apt, I find.
2010-09-07 23:04:01Basic 97: Chaos


"behavior of of the system as a whole"  too many ofs. third paragraph.


I am not totally clear on the airplane, but this is an excellent article: short, clear, convincing.



2010-09-07 23:17:30OK, go for it

2010-09-08 00:15:10Published
John Cook

Made just a few minor tweaks based on comments throughout this discussion thread