It is time to stop quivering in our boots in pointless fear of the future and just roll up our sleeves and build it.
- Ray Pierrehumbert

Sunday, June 26, 2011

Good Question

Yet another graph of the "you ain't seen nothin' yet" variety from our friends Martin and Stefan, one which presumably some skeptic has already attacked using a linear extrapolation.

A crucial key to more-or-less genuinely skeptical misunderstanding of climate science is revealed in this question at Kloor's from kdk33:
The most difficult, almost intractable, aspect of the technical debate (IMVHO), is the time constant argument (both MT and Bart have offered this to me recently), Basically, the idea that GHG added today lock in warming for coming decades (the system has large time constants or lag times).

So, rabid deniers like myself ask to see the scary SLR data or the extreme weather data or the runaway temperature data and the scary just ain’t there. But the MTs and Barts will say the the scary is yet to come; we must act now, hurry, if we wait for confirming scary data it will be too late.

I, rabid denier, think MT and Bart sound like carnivel seers. MT and Bart, convinced their predictions are firmly grounded in science, think I’m a knuckle draggin’ republican who believes in god and other right wing fairy tales.

Their predictions AIUI are based in part on computer models and in part on their understanding of various climate forcings and responses. One the one hand, I’m forgiving if computer models don’t get all the details right – I think they are useful, even necessary, learning tools. OTOH, I do think they are (very much) abused…

So, my question to MT and Bart and other similarly minded folks (my questions are usually ignored, indicating my position on the CaS pecking order, but nevertheless) is this: What data can you show us, what evidence can you offer, to better convince people that your projections are likely to be right.
I object to the religion-baiting but otherwise it is a perceptive question

I think a really good answer will require some work. Please don't let me get away with forgetting. I think it is worthwhile, at least, agreeing that this is a sticking point.

But if anyone cares to venture a quick answer, please give it a try.


James Annan said...

But qualitatively, this is trivial. The ocean is deep and mixes on the century/millennium time scale. Hence high heat capacity.

Quantitatively is hardly any more difficult if the questioner is prepare to accept some fairly reasonable numerical estimates. This doesn't rely on fancy complex theories, just conservation of energy.

Michael Tobis said...

I believe this error is key to the confusion among the more fair-minded skeptics. It is one thing to get some to avoid this error in the phase of neutral inquiry.

But how to explain the nature of the error to a member of a community that is stuck on it?

The ocean heat capacity is one part of it. Aerosol masking of the temperature perturbation is another. And the long time constants of glacial ice is another.

So there are at least three major factors at work.

I don't believe the concept that in general, systems may have widely varying time constants is commonly even comprehended, never mind understood.

John Cook said...

The evidence for what the future will look like comes from the past. The last time global temperature was 1 to 2 degrees warmer than now (around 120,000 years ago), sea levels were 6 to 9 metres higher than now. The last time CO2 levels were around 350 to 400 parts per million (around 3 million years ago), sea levels were 25 metres higher than current levels. These figures don't come from models - they come from empirical measurements of Earth's past. I find much greater cause for concern from the empirical past than from climate models.

Grypo said...

A good understanding of the aerosol problem is probably step one. People need to understand the full GW potential on small timescales is masked by reflection properties of particles. They also need to understand that the accumulation of CO2 and the resulting forcing will overpower that masking, even if we accelerate the use of aerosols. This, of course, if the person were just looking to doubt, will get you into issues of the reliability of aerosol numbers. But the concept that everything we experience is only partial, and soon won't be, should be a good lead in to the discussion of CO2 sink, air fraction, then on to ocean heat capacity, glacial time constants, etc. Unfortunately, you may have to even start out with an explanation of the imbalance and equilibrium. People are very mixed up on what is important and what isn't.

Hank Roberts said...

Remember how the argument is, er, framed, as you try to explain this -- you're talking to people who start from the Watts level (you know how to find this topic)


Yes, none of those are relevant comparisons to climatology. But that's how he sets up the problem.

Hank Roberts said...

Watts mentioned Kukla (Time 1975 on cooling), but omitted Kukla's update:

Aaron said...

Take a freezer that needs defrosting. turn it off and leave the door open (on a summer day). Then measure the amount of ice and water that comes out of the freezer as it warms.

At first there is only a trickle of water, and you think it will take all day to defrost that freezer, but soon chunks of ice are falling off the coils and bouncing across the floor.

The defrost that you thought would take 8 hours, only takes 3 hours.

Melting ice is a very non-linear process. Pretty soon big ice starts breaking up into little pieces and falling to the floor (or into the ocean). This is the nature of ice. It is how icicles fall off the eves of buildings in the spring. There is nothing linear about icicles falling off buildings.

In a warming world, ice from Greenland and Antarctica that falls into the ocean raises sea level. However, you say, "That can not happen, that ice is solid!" (Just like the icicles on the eves of your house in the spring?)

When you opened the freezer door to defrost the freezer, did you expect so much of the ice to come off as pieces?

Think of the Earth as a very big freezer, that has had the door left open for a century (AGW) and now, ice is about to start falling into the oceans in -- chunks. When the process starts, (i.e., the ice approaches 0C), it will proceed as fast as icicles fall off your house or ice falls out of the coils of your defrosting freezer (as scaled for size).

The fact that moulins are forming on the big ice sheets tells us that the ice is approaching 0C.

Some will argue that icicles and defrosting freezers can not be scaled up. However, in the spring of 2005, I stepped out onto a ice field the size of a football field that I had climbed on every one of the previous 20 years, and had it slide out from under my feet, over a cliff, and into the valley below. The whole thing took 10 minutes. Yes, even big ice behaves abruptly.

Michael Tobis said...

Aaron, a nice answer, but Holy Cow! Did you write anything up anywhere about that ice sheet event? Got pictures?

Steve Bloom said...

That ice behaves like this (and I'm familar with many examples from my childhood growing up in the upper Midwest; Montreal is much the same) is basically a function of the time it takes to warm the ice to the melting point, yes? River and lake ice breakups are common larger-scale examples, although not so spectacular as Aaron's.

Michael Tobis said...

Yes. I think it's not surprising that geologists tend to come from the western states, and meteorologists from the plains states.

But it also seems to me that climatologists tend to come from icy climates, where the annual cycle can be regarded as a deep mystery, rather than as minor perturbations from normalcy, and where the many moods of ice and water are apparent on a daily basis.

Nobody knows how Greenland will fail; given a sufficiently sharp warming it may be quite strange. We have a pretty good idea how West Antarctica will fail, and it seems to be going about doing just that.

Michael Tobis said...

Here's an interesting way to get it wrong.