Man Based Global Warming....

I agree - aerosols seem to be pretty complex. Plus, when they fall out there are surface changes to albedo, particularly in polar areas.

As for the models and CO2, it is a valid point to consider. However, I have several issues with it:
1) Given that several key model inputs are not well understood or even lack basic empirical values (such as aerosols), my understanding is they become parametrized -- sort of like a plug value using a range of suspected values since a no real value is known. So if for instance, the net true effect of aerosols is warming, this would decrease the significance of CO2. Similarly, if the oceans are poorly modeled, the projections will be thrown off.
2) For CO2 to have a large effect on climate, it requires some positive feedback mechanism. Although I believe it has been largely attributed to water vapor, it's not clear to me we have truly discovered what this feedback mechanism is. In fact, there is some recent speculation that water vapor, may be a negative feedback. If we don't even know the sign of a key input like water vapor - well - you can understand my uneasiness with the models.
3) Recent decreases in global temperatures point to other factors - as yet unidentified - that are having a greater effect than increasing levels of atmospheric CO2. In fact, given the very quiet state of the sun, one has to question whether that is a factor. Up until this point, most climatologists have said no, the change is TSI is not significant enough to change climate to the degree temperatures went up late in the 20th Century or to the extent they have declined recently. However, just as with CO2, there is now speculation whether we really understand solar influence. Is TSI the right measure? As with CO2, are there other feedbacks that amplify the effect of changes in solar output (however measured).

Much is still unknown in these areas, and they are but just a few examples.

 

I agree with that. This is one reason I'm not quick to use modeled systems as the basis for conviction on the subject, however, I still feel they are the best we have to go on (not counting observational data and historic records) and since I am also for the reduction of fossil fuel combustion and deforestation it seems like curbing greenhouse gas emissions is not such a bad thing. I do not support global warming on that basis soley. I do feel the data supporting global warming, while not conclusive, is enough to move forward with our reduction plans in a general sense. I'm not going to give my opinion on all of the various methods proposed to do so, only that I feel it should be done for a number of reasons.

 

Yours is a well-thought and rational perspective. We may disagree somewhat on the means (AGW), but perhaps not the ends (fossil fuel reduction). Always good to connect with you F8L.

 

Likewise Tim.

 

Tim,

So it seems we (PC'ers) have finally gotten past the debate regarding how much humans have raised CO2 level in the atmosphere am I correct? We all agree humans have played a large part in adding CO2 to the atmosphere.

So then that leaves us with the debate regarding CO2 actual influence on climate change, that is to say, its sensitivity and the effects of aerosols. So should we start a new thread on that one and beat it to death and hopefully learn something in the process? Or do you feel we still need to cover more basic debates to clear things up for lurkers?

 

F8L...

Excellent post on the climate model synopsis!

As I've mentioned in previous posts, I routinely use numerical weather prediction (NWP) models which are very closely related to GCMs (see, e.g., IPCC, "The Physical Science Basis", Chapter 8, "Climate Models and Their Evaluations"). The parameterizations are what in my opinion cause the bulk of the uncertainly inherent in these models.

NWPs (and I assume GCMs) use "Precipitation and Cloud Schemes" and "Convective Parameterization Schemes" to parameterize sub-grid-scale processes. Each "parameterization scheme" has several different "schemes" which can be used, e.g., the CP scheme can use the "Kain-Fritch" scheme, the "Bets-Miller-Janic" scheme, or the "Arakawa-Schubert" scheme, just to name a few. Each has its strengths and weaknesses.

All of these "parameterization schemes" use past observations to estimate sub-grid-scale processes in the model under similar projected atmospheric conditions. In the first place, these parameterizations induce quite a bit of uncertainty with respect to what actually happens, e.g., NWP models often project typical diurnal air mass convection in the relatively short term, which never materializes, or vice-versa. In the relatively courser resolution GCMs, even significant organized convective events like MCSs (clusters of thunderstorms) could potentially be missed.

The models also are frequently plagued by "convective feedback" issues which are projections of unrealistically high precipitation "bulls eyes" resulting from presumably errors in the convective parameterization schemes. I am also highly skeptical that current schemes will work even as well as they do now in a presumptive warmed climate scenario.

Cloud projections seem to be even worse, based on my experience. Model guidance is virtually worthless with respect to the projected cloud cover (it actually tends to over-forecast cloud cover usually). Even the IPCC acknowledges that cloud projections (i.e., a negative feedback issue) are the largest source of uncertainty with the GCMs.

Furthermore, the model terrain is a very poor depiction of actual terrain features (there are also several vertical coordinate systems to depict terrain).

Even the model calculations themselves contain errors (e.g., differential equations are solved by "finite differences" in NWP models). All of these errors propagate with projection time.

In my opinion, the reliability of GCMs has been overstated based on my experience, especially projections over decadal time scales. I'm not so much a AGW skeptic as I am a climate model skeptic.

 

I also meant to mention that I conducted an 18-month study of NWP model guidance temperature projections for several forecast points in the Southern Appalachian region about 5 years ago. The purpose of the study was to quantify how much, if any, increase in temperature forecast accuracy (over GFS model forecast guidance) could be achieved by using various ensemble forecasting techniques. It was not to explicitly verify the GFS forecast guidance.

However, the results showed that the GFS guidance had an absolute forecast error of over 7 degrees F at all sites for day 7, and it was not unusual for the absolute error to be 10 degrees or more. Granted, this is a sub-climate time scale and sub-global spacial scale (mesoscale) study, and some of the absolute error could be attributed to timing errors of various synoptic features, but there were bias errors of about 2 degrees F at day 7 for all sites (both negative and positive bias errors, depending on the site). Errors in the mesoscale eventually induce errors in the synoptic scale which eventually induce errors in the global scale, especially when considering the projection time of the climate models (several decades out). That gives plenty of time for error propagation!

This is another reason why I personally take climate model temperature projections (and precipitation projections for that matter) with a large grain of salt.

 

Thank you for your posts. You are not alone:

NEW ON THE SEPP WEB

"... those that advocate the idea that the response of the real climate to radiative forcing is adequately represented in climate models have an obligation to prove that they have not overlooked a single nonlinear, possibly chaotic feedback mechanism that Nature itself employs..."

 

Gentlemen and scholars all.... :hug: phththththth...

 

How about condescending just one more time and explaining to me (hurler of hyperbole) exactly where 'we all agree humans have played a large part in adding CO2 to the atmosphere.' I realize this might be somewhat misleading in that you say ‘adding’. But let us keep in mind the more relevant overall picture.

From NASA:

Current estimates of human-produced carbon dioxide emissions into the atmosphere are based on inventories and estimates of where fossil fuels are burned and where other carbon dioxide-producing human activities are occurring. However, the availability and precision of this information is not uniform around the world, not even from within developed countries like the United States.

From Wiki:

Carbon dioxide in the Earth's atmosphere - Wikipedia, the free encyclopedia

Carbon dioxide is released to the atmosphere by a variety of natural sources, and over 95 % of total CO2 emissions would occur even if humans were not present on Earth.

Here are the figures as they relate to the ‘greenhouse effect’. Man’s role seems rather smaller than larger.

http://www.geocraft.com/WVFossils/greenhouse_data.html

 

Compared to the total of CO2? Of course it is a small amount. We all know that but as was stated earlier, adding more CO2 and achieving a "tipping" point or bifurcation point if you prefer bigger words, can indeed produce large results. When you overwhelm a system it will usually rearrange itself to accomodate the added input which can completely change the system ogranization and energy distribution. This could be rather catastrophic where climate is concerned due to the sensitivity of human systems (infrastructurte, economy, health etc.)

It is not hard to calculate the total amount of fossil fuel emissions produced in the 20th century. We have documentation stating how much has been drilled, exported, sold, and in most cases burned. That is simple math. We can also compare current carbon 14, 13, and 12 ratios in the atmosphere with those in ice cores, tree rings, and coral. Fossil fuels are depleted in carbon 14 after having been stored underground for millions of years (carbon 14 half life is 5,730 ± 40 years). We can analyze carbon isotope ratios (in oceans and the atmosphere) and see that carbon 14 has been reduced as well as carbon 13 while carbon 12 figures have increased which is what one would expect when 7+Gt's of fossil fuel-derived CO2 has been added to the earths systems. There are calibration curves to compensate for the effects of carbon 14 half-life in the oceans, dendrochronology (thanks to the Pinus longaeva!), corals, cave deposits etc.. Futhermore, approx. 50%-55% of these emissions are retained in the atmosphere with the rest being added to the global carbon cycle (hydrosphere and biosphere). For more on this look into the Suess Effect.

With regards to anthropogenic additions being small compared to the total of non-anthropogenic CO2 totals just keep in mind.... A bathtub in equilibrium but filled to the brim can still overflow with the addition of small inputs....... If that visualization doesn't work for you think back to chemistry class and titrations and how just a tiny drop of titrant added just before the "endpoint" can have drastic results.

If you find me condesending then I'd have to say I honestly don't care. You obviously enjoy being antagonistic so I have no problem being disrespectful in light of such attitudes.

 

So, you're saying that because we don't know with absolute precision what the exact effects will be at a particular future time, we should continue digging up poisons and spreading them around as fast as possible?

We know we are doing great harm, yet the rate of damage continues to accelerate.

 

Thank you for the disrespect.

Your examples, including the present 'visualizations' and the prior example pointing out that water freezes when temperature drops another tiny fraction to a point certain are unconvincing straw man arguments.

What I previously pointed out and you chose to ignore is that we have absolutely no proof that a similar thing will occur if CO2 reaches an as yet unknown, perhaps non-existant 'tipping point'. It is no doubt possible to model such an occurance, but it will, because of the inadequacies of models, remain irrelevant in the real world. We still do not know how to include all the possibilities affecting climate into the models. The models are as subject to GIGO as any other programs.

 

So the precautionary principle means nothing to you I assume. Enough proof exists to warrant caution. To ignore the signs and data just because the proof is not 100% accurate is pure folly IMO and irresponsible. What is to be gained? We save some money that was spent on research? What else would have spent it on? War? subsidizing CEO paychecks? Paying vagrants to not work? If I think a dog may attack me I am not going to stand there and wait till he sinks his teeth into me just to be 100% certain....

Your opinion leads to business continuing as usual and that is bad news for EVERYONE whether they know it or not.

 

It's not possible to draw that conclusion from my remarks, Ranger.

#1 CO2 is not a poison and not a pollutant. You breathe it out with every breath. Plants thrive on it. It's essential for life on earth.

#2 I'm saying there is imprecision all over the so-called science from which the conclusion is drawn that mankind's small contribution to the atmosphere will result in irreversable cataclysm for earth.

#3 We should not destroy economies and/or spend enormous sums based on inconclusive evidence.

#4 I am not saying that man cannot find great benefit from other, cleaner sources of energy. In fact I am in favor of developing nuclear, solar and wind resources in a free market situation. The workable and economically feasible soution to energy problems will naturally result.

#5 I am against the federal government spending tax-payer funds to promote one idea over another. But we'll no doubt see it soon as the present U.S. administration will (through the EPA) label CO2 a pollutant and force businesses (and at the end of the line, consumers) to spend big money in a wide variety of ways. Brace yourself. Prepare for the price of energy to rise spectacularly. We're not supposed to discuss politics here (even though it is the prime mover in this whole debate) so I'll leave it at that.

 

As am I, for the most part. Without coming to any premature conclusions, does your comment mean to say anything about current subsidies for the oil industry?

 

There are powerful secondary issues that get ignored and those are the ones I pay attention to. They are not at all involved in AGW, but are very much involved in reasons to justify changing the coal and oil economy.
1) Coal burning just flat dumps a lot of mercury and other heavy metals into the air, water, and soil around us. Then there is all the coal ash that gets dumped...where?
2) CO2 increases does have measurable effects on the ocean pH. What does this mean. Not known, but assuming no effect is the same as assuming too much of an effect. It's just not AGW that has a potentional impact globally.
3) Continued extraction of oil in shale and tar sands requires immense amount of water that ends up quite polluted.
4) Where does most of the oil profits go? Do these profits get spent on a better world than if they were spent on renewable energy?

AGW panic and extremism-I'm tired of it as much as anyone. Free markets always come up with the best answer....well certainly not for ANY unregulated fishing grounds.

 

As usual Wxman, you bring a lot to the discussion. Although I obviously don't have the same pedigree as you (nor do I pretend to), as a lay-person I would say I have some of the same general reservations about the models. Namely, the unknowns simply seem too great and as you note, they propagate error over time.

I definitely believe CO2 has some effect on climate, but am highly skeptical the models can project it. And based on existing temperature data vs. CO2 trends, am not convinced CO2 has had much effect on the climate of the past 60 or 70 years.

 

Not sure if that is a compliment or a sarcastic insult, but I'll take it as the former.

 

Well from what I have read it seems fairly uncontroversial that much (most?) of the rise in CO2 over the past 75+ years is due to man's contribution.

So yes, climate sensitivity and effects of aerosols are big factors in predicting temperature. A discussion would be interesting.

I would also suggest further discussion of temperature trends of the past 100+ years.
- There was obviously a rapid rise in temperatures up to about 1940 that did not correlate with rapidly rising levels of CO2.
- Likewise, from around 1940 to the '80s temperatures fell as CO2 rose rapidly.
- Then CO2 and temperatures rose in apparent lock-step from ~ 1980 to around 2002. However, as I noted before, if one looks at that last period closely, it is quite apparent that some sort of "step change" in temperature took place around 1998 that accounted for roughly 3/4 of that temperature increase over that ~ 20 year span. What is the mechanism by which CO2 cause such a temperature "step"?
- And again, from around 2002 onward temperatures have been flat to declining despite a continued rapid rise in CO2.

These are some pretty large discrepancies that I would need explained before I could rationally conclude that CO2 is a primary driver of global climate.