Talking about Climate Change: Publishing your Probability Density and Reasoning

Image by melancholic optimist via Flickr

"Phil" from "Statistical Modeling, Causal Inference, and Social Science" blog, I believe Phillip Price [ http://eetd.lbl.gov/ie/apt/staff/PricePN.html http://www.creekcats.com/pnprice/Job.html ].

As I say in my comments "Thank you for publishing your probability density for climate sensitivity, and the precise reasoning behind it. This is, practically, the _only_ way to communicate one's considered beliefs for this subject - if one is truly interested in communicating and not just indulging in motivated obscurantism or the art of controversy."

How helpful to have someone state their probability density and reasons behind it. It communicates so much.

Phillip Price: Say a little prior for me: more on climate change:

"Four out of the last 15 posts on this blog have been related to climate change, which is probably a higher ratio than Andrew would like. But lots of people keep responding to them, so the principle 'give the people what they want' suggests that another one won't hurt too much. So, here it is. If you haven't read the other posts, take a look at Andrew's thoughts about forming scientific attitudes, and my thoughts on Climategate and my suggestions for characterizing beliefs. And definitely read the comments on those, too, many of which are excellent.

I want to get a graphic 'above the fold', so here's the plot I'll be talking about.
...

Finally, we get to the graphic. Each of these probability distributions is supposed to summarize the belief of a different person. In blue, we have an 'anthropogenic climate change denier.' This is someone who just doesn't believe that doubling of atmospheric CO2 could have any substantial impact on the global mean temperature. I don't know if any such people think the effect could be negative, but maybe they do; if they don't, then just move all of that negative probability into the low positive range somewhere. At any rate, these people are convinced that there is just the right amount of negative feedback to cancel out the known effect of CO2 and the expected effect of water vapor.
...
But I think the hypothetical 'skeptic' curve puts way too much probability on very low values --- not as bad as the 'denier', but still, this is someone who is unjustifiably convinced that negative feedbacks will come close to counteracting the effects of CO2.

(By the way, none of the lines are supposed to go below zero, or even go to zero, at 6C, but the drawing software I used has done some funny stuff there and it doesn't seem worth fixing. Oh, and each of the curves is intended to have the same integral -- unity -- but since this is just a by-hand sketch, they probably don't).

Above, I've opened my soul, as it were, to discuss why I believe what I believe. Part of my belief, actually a substantial part, is informed by a very simple physical model that I believe is useful in spite of its simplicity, that shifts my prior well away from 0 as a reasonable estimate of climate sensitivity. What if you don't have the physics background to evaluate such a model for yourself? Then, you're more or less forced to choose who you care to believe: deniers, skeptics, 'experts,' journalists, bloggers, friends...

In a comment on Andrew's entry about forming attitudes on scientific issues I said this:

When it comes to anthropogenic climate change, if someone wants to allocate some probability to the chance that the skeptics have it right, I think that's a very reasonable thing to do. Make it 90% mainstream, 10% skeptics, or even 75% mainstream, 25% skeptics if you are are heavily inclined towards the skeptical camp. But there are people out there who are 90-10 the other way! If you are an expert climate modeler and you think your colleagues have the science wrong, that's one thing. If you're just some schmoe who only knows what he reads in the papers, and you choose to assign a 90% or 95% probability to the conclusions of the small band of skeptics...where does that come from? Do you really think the experts in a field get it wrong 90% or 95% of the time?

I think I'll leave it there.

"

My comments:

Thank you for publishing your probability density for climate sensitivity, and the precise reasoning behind it. This is, practically, the _only_ way to communicate one's considered beliefs for this subject - if one is truly interested in communicating and not just indulging in motivated obscurantism or the art of controversy.

I wish I had the chops to draw one myself. I don't, so I rely on the experts currently publishing articles. I find it hysterical to shriek about the corrupting influence of funding - I am not holding my breath waiting for the appearance of researchers comprised solely of incorruptible energy, freed of the need for money because they draw sustenance from the empty ether. Oh, please. All humans have their self-serving motivations, and reasonable people deal it with accordingly and with due measure. And, scientists never claimed to not be human.

Image via Wikipedia

I wish I had the chops to draw the _other_ curve with regards to carbon dioxide - loss of tonnage of fished protein/nutrition due to ocean acidification. Global temperature and ocean acidification both have a large expected impact on human civilization.

> The Kyoto Treaty was a large scale effort...

Surely the intervention can only earn the description of "large" if *some* authority judges it probable to effect the desired change. Otherwise, I could call the Dubai Towers a "large scale effort" to bridge the span to the surface of the moon.

It can be honestly asserted that no large scale efforts have been made to reduce greenhouse gas emissions.