Hi Michael...

I sort of followed Tara over here from scienceblogs, and I'm just using my initials (so they may match somebody else). I just spent an hour or so reading most of the thread at Netweather that you linked to at Gold, and I'm going to start off by answering their question here: Why do you (I) not trust the experts?

I'm an amateur, knowing just enough to be dangerous, but since '97 I've never been able to get a straight answer from anybody to the apparent objections I've seen to the science of "global warming".

1. The climate is an extremely complex non-linear system, and like any non-linear system a small perturbation has just as much chance of having a major effect as a large one. There are, however, many orders of magnitude more small perturbations. Given this, why can we expect to accurately model the effect of one "forcing" perturbation? Most descriptions I've seen have built-in the assumptions of linear systems.

2. Does the "Greenhouse" model really work? IR absorption from any molecule with >2 atoms is in narrow bands, if the absorption is close to 100% below the tropopause (as with CO2 and water) how does increasing the amount of it make a difference? What is the effect of an increase of, say, methane, where the amount is small enough that part of the radiation in its absorption band normally gets through? How is the amount of heat absorbed balanced by the amount re-radiated?

3. Assuming there is some added heat retention, wouldn't it cause added evaporation, leading to more cloud cover and a higher net albedo? I would assume a naive 50% chance the effect would be a net cooling? Why do the models all show a warming? Could it be an intuitive bias on the modelers' parts?

4. Why is it generally assumed that dumping more CO2 into the air would cause the level to go up significantly? The primary remover of CO2 is the enzyme RuBisCo (ribulose 1,5-bisphosphate carboxilase), which is operating way over on the tail end of its activity curve and should thus have an exponential response to more substrate. Right? Other explanations could include clear-cutting of forests or planting with well-irrigated crops.

5. Given the importance of aerosols in determining cloud behavior, shouldn't we expect them to be more important in impacting overall weather than greenhouse gases?

I distrust the whole affair because these are questions that many scientists in related fields should be asking the experts, and I've never found good answers on-line. I would expect CO2 to be the last thing to worry about, but when I ask I get specious answers such as that it's the easiest thing to attack.

In fact, forcing a reduction of net CO2 emission will be one of the hardest things to accomplish, and won't happen without reversing a four-century trend (increasing per capita energy usage) in western civilization. Frankly, I suspect a hidden agenda having nothing to do with climate.

As for "going for the gold", no offense but that's a specious argument. Most real scientists will feel much more rewarded by the money spent on their research projects than their salaries.

I should note that I finally found some answers to a some of my questions in 3D Radiative Transfer in Cloudy Atmospheres by Marshak and Davis. On page 489 I found some absorption graphs (reprinted from Thomas and Stamnes) that showed a single important spike for CO2 with distinctly slanted edges (thus an effect from more CO2). I also found, on page 10, a bar graph of the effects on a "well-known British climate model" to an imposed doubling of CO2. The actual effect of CO2 added up to about 0.8 degrees C. Adding in feedback from water vapor got us up to perhaps 1.8 degrees. Ice albedo feedback yields 2.5. Feedback from clouds varied between 2 and 5 degrees.

Hopefully this will start the discussion off!

AK,
HAH! Just what I thought! Your hard questions have elicited zero response because it is exactly these kinds of questions that show how faulty the "consensus" is. I wouldn't hold my breath waiting. In the mean time just open your checkbook and pony up to the Al Gore trough.
MW

Sorry, I missed the comment earlier. (The process of blogging through PBS still has some kinks to be worked out.)

These are very good questions, and I appreciate the honest way they are posed.

However, I note that they are about climate change, not about climate. This is very much affected by the way the press reports what we do, and as a consequence effects what people think we do.

1. The climate is an extremely complex non-linear system, and like any non-linear system a small perturbation has just as much chance of having a major effect as a large one. There are, however, many orders of magnitude more small perturbations. Given this, why can we expect to accurately model the effect of one "forcing" perturbation? Most descriptions I've seen have built-in the assumptions of linear systems.

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Actually, there is nothing much that can be said about "any" nonlinear system. However, it is generally accepted that weather is chaotic. This is not the same as saying that climate is chaotic. If you're familiar with popularizations of chaos theory, you'll have seen the two-lobed trajectory diagrams of the Lorenz system (which actually is a simple weather model). Predicting where the dot is on the two lobes is very difficult on the dynamic time scale of the system, which is why weather prediction has nearly zero skill beyond two weeks. (Usually the skill is high for about 5 days, which is what gets in the paper.) The climate of the Lorenz system is the SHAPE of the two lobes. If you change the parameters of the system, the shape of the lobes changes, but that change is not chaotic.

At a less abstract level, I cannot tell you if you will have a white Christmas (a three month weather preditction) but if you're in the US I'm willing to bet it will be colder than next July 4 (an eight month climate prediction).
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2. Does the "Greenhouse" model really work? IR absorption from any molecule with >2 atoms is in narrow bands, if the absorption is close to 100% below the tropopause (as with CO2 and water) how does increasing the amount of it make a difference? What is the effect of an increase of, say, methane, where the amount is small enough that part of the radiation in its absorption band normally gets through? How is the amount of heat absorbed balanced by the amount re-radiated?

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A common misconception is that the infrared only can get absorbed once. That isn't true. Consider the surface of Venus, which is hotter than Mercury.

Methane is more effective on a per-molecule basis and is an important contributor the the anthropogenic greenhouse effect.

In the end (with a very small asterisk or two) energy escaping the earth balances energy arriving. The question is how many bounces it takes before it gets out. That dominates the surface temperature.

===

3. Assuming there is some added heat retention, wouldn't it cause added evaporation, leading to more cloud cover and a higher net albedo? I would assume a naive 50% chance the effect would be a net cooling? Why do the models all show a warming? Could it be an intuitive bias on the modelers' parts?

===
Added evaporation does not directly lead to more cloud cover. The very reason for the added evaporation is that the warmer atmosphere can hold more vapor. Also, added cloud cover does not directly lead to cooling. Clouds themselves have a greenhouse effect.

I will try to talk about the models in some detail in this series, so you can get a better grasp of what they are and how much or little the bias of the investigators can effect them. It's an interesting topic indeed.

That said, the only way to get at complicated feedbacks like these is through modeling. On the other hand, note that the initial perturbation is certainly in the direction of warming.

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4. Why is it generally assumed that dumping more CO2 into the air would cause the level to go up significantly? The primary remover of CO2 is the enzyme RuBisCo (ribulose 1,5-bisphosphate carboxilase), which is operating way over on the tail end of its activity curve and should thus have an exponential response to more substrate. Right? Other explanations could include clear-cutting of forests or planting with well-irrigated crops.

===

I don't know anything about RuBisCo, but if you are talking about exchanges with the biota, that is not really a major sink, because in most circumstances biota decay at essentially the same rate as they grow. The main sink on policy time scales is the deep ocean, and the main sink on geological timescales is limestone formation which is driven by plankton forming calcium carbonate.

There is, of course, much more to say about this, and I expect to do an article or two about the carbon cycle.

===

5. Given the importance of aerosols in determining cloud behavior, shouldn't we expect them to be more important in impacting overall weather than greenhouse gases?

===

Well, that used to be an open question. That was the basis for some people worrying about global cooling back in the 1970s. You just have to do the numbers. In the end, CO2's hand is stronger because its rtesidency time in the system is centuries, while aerosols only stay up for months.

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As for distrusting the whole business, I don't know what I or any of us can do beyond trying our best to be trustowrthy. I put as much time as I can into explaining what we are about, but that isn't my day job. There are expert communicators whose day job it is to encourage your distrust, and in response we have a few volunteers who know the science but we mostly aren't really trained communicators. So I'll keep trying.

What I hope to do here is to focus on what's known, on the context for our concern. I blog plenty about climate change on my own blog. On Correlations, I intend to try to focus on the agreed science and not the controversy. This will help readers get a better handle on the controversies as they encounter them.

Thanks Michael. I don't know whether I should go on with my questions here or wait for another article, so for the moment I'll just respond to your comment about trained communicators.

As I mentioned at another blog, with one exception, "[t]he problem with most GW opponents is that their science is about on a par with Intelligent Design." Even if their science made sense, I'd want to look at the peer-reviewed literature before I bought it. My questions are my own, even if they duplicate someone else's objections.

I'm looking forward to your articles, and I hope you aren't required to tie each one to some news event. I'm especially interested in the perspective(s) the modelers themselves use in understanding non-linear systems and the interaction between weather and climate. OTOH, I don't want to drag things to a technical level beyond the target readership here. Please let me know when/if I am.

Thanks.

AK, I think it makes sense for the comments to go a bit deeper than the articles. If it gets deeper than I can handle from time or expertise I'll try to refer you to some literature.

I am hoping to talk about what we know about climate. One of the big problems is that lots of people are going on about climate change without knowing much about climate. I am hoping to use this opportunity to pull together a primer of sorts, along the lines that Isaac Asimov might do if he were still with us.

I am sure some of the questions will be about climate change, not just climate, just the same. The way you read about us in the press, it seems like "global warming" is all we do, but that just isn't so.

If comments are ridiculously confrontational or just rehashed nonsense from the denial industry, I won't take them up. The answers are out there for anyone who takes the time to look. If, like yours, they seem to arise from independent thought, I'll do my best under the time constraints I have.

Thanks Michael. Your answer to number 2 cleared up my issues on the subject, I just submitted a long post at your "Trust and Expertise" thread.

It's hard to separate questions about climate from questions about change, since the models involve predicting an ever-changing system. Let me try with oscillations:

I see many mentions of oscillations in the literature (ENSO, Madden-Julian, etc.) Do these generally emerge from the models as negative feedback effects (like a pendulum), or multiple intermittent positive feedbacks taking turns in a sort of "round robin"?

I've been researching "tipping points", including the RC paper, and I can't tell whether the usual definition would include any amplifying effect (e.g. a 1 degree average temp change here creates a 30% rainfall increase there), or just major temperature effects a global level. Given the difficulty computational models have with them, if smaller feedback cycles existed in the real climate, would the models be able to distinguish them from noise?

For instance, if a particular year is "ripe" for one or more "pineapple expresses" would the models have to treat the number and severity as an average? Or a random perturbation coming up from the weather scale? I don't know whether the number/severity has an amplifying effect on/via the winter North American snowpack, but for purposes of illustration suppose it did, how would the models handle it?

Or am I off-base thinking such conditions are possible in the weather/climate interaction?

Thanks for any enlightenment on the subject.

AK

AK, I detect confusion about the difference between weather models and climate models. Stay tuned.