Having just returned from another New Orleans meeting – this time, a NASA A-Train satellite constellation symposium — I thought I would check the latest sea surface temperatures from our AMSR-E instrument.

The following image shows data updated through yesterday (October 27). Needless to say, there is no end in sight to the cooling. (Click on image for the full-size version).

Since these SST measurements are mostly unaffected by cloud cover like the traditional infrared measurements are, I consider this to be the most accurate high-time resolution SST record available…albeit only since mid-2002, when the Aqua satellite was launched.

I won’t make any predictions about whether SSTs will go as low as the 2007-08 La Nina event. I’ll leave that to others.

(edited for clarity at 2:45 p.m.)

There was a very clever paper published in Science this past week by Lacis, Schmidt, Rind, and Ruedy that uses the GISS climate model (ModelE) in an attempt to prove that carbon dioxide is the main driver of the climate system.

This paper admits that its goal is to counter the oft-quoted claim that water vapor is the main greenhouse gas in our atmosphere. (They provide a 1991 Lindzen reference as an example of that claim).

Through a series of computations and arguments, the authors claim that is actually the CO2, not water vapor, that sustains the warmth of our climate system.

I suspect this paper will result in as many opinions in the skeptic community as there are skeptics giving opinions. But unless one is very careful in reading this paper and knows exactly what the authors are talking about, it is easy to get distracted by superfluous details and miss the main point.

For instance, their table comparing the atmospheres of the Earth, Venus, and Mars does nothing to refute the importance of water vapor to the Earth’s average temperature. While they show that the atmosphere of Mars is very thin, they fail to point out the Martian atmosphere actually has more CO2 than our atmosphere does.

I do not have a problem with the authors’ calculations or their climate model experiment per se. There is not much new here, and their model run produces about what I would expect. It is an interesting exercise that has value by itself.

It is instead their line of reasoning I object to — what they claim their model results mean in terms of causation– in their obvious attempt to relegate the role of water vapor in the atmosphere to that of a passive component that merely responds to the warming effect of CO2…the real driver (they claim) of the climate system.

OUR ASSUMPTIONS DETERMINE OUR CONCLUSIONS

From what I can tell reading the paper, their claim is that, since our primary greenhouse gas water vapor (and clouds, which constitute a portion of the greenhouse effect) respond quickly to temperature change, vapor and clouds should only be considered “feedbacks” upon temperature change — not “forcings” that cause the average surface temperature of the atmosphere to be what it is in the first place.

Though not obvious, this claim is central to the tenet of the paper, and is an example of the cause-versus-effect issue I repeatedly refer to in the past when discussing some of the most fundamental errors made in the scientific ‘consensus’ on climate change.

It is a subtle attempt to remove water vapor from the discussion of “control” over the climate system — by definition. Only those of us who know enough of the details of forcing-feedback theory within the context of climate change theory will likely realize this, through.

Just because water vapor responds quickly to temperature change does not mean that there are no long-term water vapor changes (or cloud changes) — not due to temperature — that cause climate change. Asserting so is a non sequitur, and just leads to circular reasoning.

I am not claiming the authors are being deceptive. I think I understand why so many scientists go down this path of reasoning. They view the climate system as a self-contained, self-controlled complex of physically intertwined processes that would forever remain unchanged until some “external” influence (forcing) enters the picture and alters the rules by which the climate system operates.

Of course, increasing CO2 is the currently fashionable forcing in this climatological worldview.

But I cannot overemphasize the central important of this paradigm (or construct) of climate change theory to the eventual conclusions the climate researcher will inevitably make.

If one assumes from the outset that the climate system can only vary through changes imposed external to the normal operation of the climate system, one then removes natural, internal climate cycles from the list of potential causes of global warming. And natural changes in water vapor (or more likely, clouds) are one potential source of internally-driven change. There are influences on cloud and water vapor other than temperature which in turn help to determine the average temperature state of the climate system.

After assuming clouds and water vapor are no more than feedbacks upon temperature, the Lacis et al. paper then uses a climate model experiment to ‘prove’ their paradigm that CO2 drives climate — by forcing the model with a CO2 change, resulting in a large temperature response!

Well, DUH. If they had forced the model with a water vapor change, it would have done the same thing. Or a cloud change. But they had already assumed water vapor and clouds cannot be climate drivers.

Specifically, they ran a climate model experiment in which they instantaneously removed all of the atmospheric greenhouse gases except water vapor, and they got rapid cooling “plunging the climate into an icebound Earth state”. The result after 7 years of model integration time is shown in the next image.

Such a result is not unexpected for the GISS model. But while this is indeed an interesting theoretical exercise, we must be very careful about what we deduce from it about the central question we are ultimately interested in: “How much will the climate system warm from humanity adding carbon dioxide to it?” We can’t lose sight of why we are discussing all of this in the first place.

As I have already pointed out, the authors have predetermined what they would find. They assert water vapor (as well as cloud cover) is a passive follower of a climate system driven by CO2. They run a model experiment that then “proves” what they already assumed at the outset.

But we also need to recognize that their experiment is misleading in other ways, too.

First, the instantaneous removal of 100% of the greenhouse gases in the atmosphere except for water vapor causes about 8 times the radiative forcing (over 30 Watts per sq. meter) as does a 100% increase in CO2 (2XCO2, causing less than 4 Watts per sq. meter), something that will not occur until late this century — if ever.

This is the so-called ‘logarithmic effect’…adding more and more CO2 has a progressively weaker radiative forcing response.

Currently, we are about 40% of the way to that doubling. Thus, their experiment involves 20 times (!) the radiative forcing we are now experiencing (theoretically, at least) from over a century of carbon dioxide emissions.

So are we to assume that this dramatic theoretical example should influence our views of the causes and future path of global warming, when their no-CO2 experiment involves ~20 times the radiative forcing of what has occurred to date from adding more CO2 to the atmosphere?

Furthermore, the cloud feedbacks in their climate model are positive, which further amplifies the model’s temperature response to forcing. As readers here are aware, our research suggests that cloud feedbacks in the real climate system might be so strongly negative that they could more than negate any positive water vapor feedback.

In fact, this is where the authors have made a logical stumble. Everyone agrees that the net effect of clouds is to cool the climate system on average. But the climate models suggest that the cloud feedback response to the addition of CO2 to our current climate system will be just the opposite, with cloud changes acting to amplify the warming.

What the authors didn’t realize is that when they decided to relegate the role of clouds in the average state of the climate system to one of “feedback”, their model’s positive cloud feedback actually contradicts the known negative “feedback” effect of clouds on the climate’s normal state.

Oops.

(In retrospect, I suppose they could claim that cloud feedbacks switched from negative at the low temperatures of an icebound Earth, to being positive at the higher temperatures of the real climate system. But that might mess up Jim Hansen’s claim of strongly positive feedbacks during the Ice Ages).

CONCLUSION
Taken together, the series of computations and claims made by Lacis et al. might lead the casual reader to think, “Wow, carbon dioxide really does have a strong effect on the Earth’s climate system!” And, in my view, it does. But the paper really tells us nothing new about (1) how much warming we can expect from adding more CO2 to the atmosphere, or (2) how much of recent warming was caused by CO2.

The paper implies that it presents new understanding, but all it does is get more explicit about the conceptual hoops one must jump through in order to claim that CO2 is the main driver of the climate system. From that standpoint alone, I find the paper quite revealing.

Unfortunately, what I present here is just a blog posting. It would take another peer-reviewed paper that follows an alternative path, to effectively counter the Lacis paper, and show that it merely concludes what it assumes at the outset. I am only outlining here what I see as the main issues.

Of course, the chance of editors at Science allowing such a response paper to get published is virtually zero. The editors at Science choose which scientists will be asked to provide peer review, and they already know who they can count on to reject a skeptic’s paper.

Many of us have already been there, done that.

Since I just provided the September 2010 global tropospheric temperature update, I decided it was time to update the global SST data record from the AMSR-E instrument flying on Aqua.

The following plot, updated through yesterday (October 4, 2010) shows that both the global average SST, and the Nino3.4 region average from the tropical E. Pacific, continue to cool.

(click on the plot for the full-size, undistorted version. Note that the global values have been multiplied by 10 for easier intercomparison with Nino3.4)

Past experience (and radiative-convective equilibrium) dictates that the global tropospheric temperature, still riding high at +0.60 deg. C for September, must cool in response to the cool ocean conditions.

But given Mother Nature’s sense of humor, I’ve given up predicting when that might occur. 🙂

YR MON GLOBE NH SH TROPICS
2009 1 0.251 0.472 0.030 -0.068
2009 2 0.247 0.565 -0.071 -0.045
2009 3 0.191 0.324 0.058 -0.159
2009 4 0.162 0.315 0.008 0.012
2009 5 0.139 0.161 0.118 -0.059
2009 6 0.041 -0.021 0.103 0.105
2009 7 0.429 0.190 0.668 0.506
2009 8 0.242 0.236 0.248 0.406
2009 9 0.505 0.597 0.413 0.594
2009 10 0.362 0.332 0.393 0.383
2009 11 0.498 0.453 0.543 0.479
2009 12 0.284 0.358 0.211 0.506
2010 1 0.648 0.860 0.436 0.681
2010 2 0.603 0.720 0.486 0.791
2010 3 0.653 0.850 0.455 0.726
2010 4 0.501 0.799 0.203 0.633
2010 5 0.534 0.775 0.292 0.708
2010 6 0.436 0.550 0.323 0.476
2010 7 0.489 0.635 0.342 0.420
2010 8 0.511 0.674 0.347 0.364
2010 9 0.603 0.556 0.651 0.284

Despite cooling in the tropics, the global average lower tropospheric temperature anomaly has stubbornly refused to follow suit: +0.60 deg. C for September, 2010.

Since the daily global average sea surface temperature anomalies on our NASA Discover web page have now cooled to well below the 2002-2010 average, there remains a rather large discrepancy between these two measures. Without digging into the regional differences in the two datasets, I currently have no explanation for this.

For those following the race for warmest year in the satellite tropospheric temperature record (which began in 1979), 2010 is slowly approaching the record warm year of 1998. Here are the 1998 and 2010 averages for Julian Days 1 through 273:

1998 +0.590
2010 +0.553

[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT’s are individually calibrated in a laboratory before being installed in the instruments.]

I’ve been out of pocket for a while, partly because I have been preparing to provide expert testimony in a mock global warming trial.

The mock trial was the final event at the ABA Section of Environment, Energy, and Resources Law Summit held at the Sheraton New Orleans this past week. We had a good turnout, with approximately 200 attorneys there to watch the show.

The mock trial was patterned after the Comer vs. Murphy Oil lawsuit, in which the plaintiffs claim that the greenhouse gas emissions of energy companies in the U.S. made Hurricane Katrina worse.

I was the testifying expert for the evil, GHG-spewing industry side, while a PhD ecologist, Mark Laska, represented the IPCC “scientific consensus” side.

We were fortunate to have U.S. District Court Judge Eldon E. Fallon (of Vioxx and Chinese drywall litigation fame) presiding. Judge Fallon provided advice and insights as the mock trial progressed, not so much for the participants’ benefit, but for the audience of attorneys, some of whom anticipate being involved in future climate-related litigation.

I must confess, I had fun. Mike Freeman, of Balch & Bingham, LLP, the defense attorney on my side of the case, did an excellent job with his opening remarks and cross examination of Dr. Laska. Over the last few weeks, Mike quickly developed a good understanding of the key science shortcomings of global warming theory (as I see them, anyway), and was able to turn that knowledge into effective lines of questioning.

In fact, many of us ‘skeptical’ scientists have been waiting for years to see the science of global warming exposed in a trial setting. People like Al Gore can no longer hide behind claims of supposed scientific consensus and appeals to authority.

It’s time to put up, or shut up.

Even though this wasn’t the real thing, I was able to find out how an experienced trial lawyer (Allan Kanner) would handle such a case with his opening statement, direct examination of Dr. Laska, and cross-examination of me.

Without going into a blow-by-blow account of what transpired at the mock trial, I do want to briefly address what I now recognize will be a central problem with the expert testimony in any future climate-related litigation.

There will be no end to the amount of irrelevant climate science which can be used to hoodwink a jury

In our very brief academic exercise, it became immediately apparent to me that one tactic will be the attempt to claim the scientific high ground.

For example, Mr. Kanner and Dr. Laska spent an inordinate amount of time describing the scientific method. You know, forming hypotheses, testing those hypotheses with observational data, modifying the hypotheses accordingly, etc.

This totally irrelevant exercise was an apparent attempt to imply that our side does NOT employ the scientific method. At least I think that’s what they were attempting….it never was clear exactly why they went down this Mom-and-apple-pie road.

What is really ironic about this tactic is that it is the IPCC scientific consensus side that has abandoned a cornerstone of scientific investigation — exploring alternative hypotheses for global warming. As I have previously discussed ad nauseum, there has never been a serious research effort directed toward exploring the role of natural, internal climate cycles as a potential cause of most of the recent warming we have measured.

I have also noticed over the years that it is those who do not actually perform climate research who tend to clothe themselves in the scientific method as some sort of shiny coat of armor which they hope will make them impervious to criticism. Sheesh.

During Mr. Kanner’s cross examination of me, he invoked the Tragedy of the Commons in an apparent attempt to get me to agree that, even though the defendants’ greenhouse gas emissions are a small portion of global emissions, the defendants are still just as responsible for climate change (and, presumably, the intensification of Hurricane Katrina) as everyone else is.

But I refused to accept the premise that there is even a ‘tragedy in the commons’ when it comes to global warming. In my view, none of the participants in the emission of greenhouse gases have caused a tragedy. If you’ve got a problem with Hurricane Katrina and what it did, take it up with Mother Nature.

After all, the vast majority of the most intense hurricanes to hit the U.S. occurred before 1970, and so occurred before the main period of “global warming”. Yes, Katrina was a tragedy. But a hurricane disaster has been predicted for New Orleans long before global warming ever became fashionable.

And as we now close out the 5th Atlantic hurricane season since Katrina, it looks like this will be the first 5 year period without a Cat 3 or stronger hurricane hitting the mainland since 1910-1914! What a difference five years can make to scientific ‘truth’.

In fact, if one surveys the recent literature, it is no longer obvious that warming has led to more intense hurricanes — let alone warming being the fault of mankind.

Mr. Kanner also alluded to the alleged cover-up of global warming science by executives in the petroleum or coal industry. I assume that we are supposed to equate any such behavior to the tobacco industry. Exactly how anyone could hush Al Gore or NASA’s James Hansen, I don’t know.

Every grade school student has heard of the 37 different ways we are all going to die from global warming. Has Exxon Mobil managed to cover up the 38th way we will die? Gasp!

But I do know that anything that energy industry executives did or didn’t do is totally irrelevant to the issue at hand: Have mankind’s greenhouse gas emissions caused any measurable change in the climate system or weather systems?

And I suppose this will be the Achilles’ heel of climate-related litigation: Causation. The case for mankind (versus Mother Nature) causing climate change is so weak, that only through scientific incompetence (or a jury’s bias against big business) should the plaintiffs prevail in these lawsuits.

To me, I don’t care whether another climate expert is the equivalent of Mother Theresa, or a member of the Nazi Party. All I care about is what they can demonstrate scientifically.

I don’t know much about legal issues or the law, so maybe my views are naive. But I do know that it will be essential for judges and lawyers to be able to separate the wheat from the chaff in expert testimony.

This is no small task, since most of the experts in this field are rather muddled in their own thinking on the subject anyway. Climate change science covers a wide range of complex and interrelated sub-disciplines, and the challenge will be to separate the 95% of the science that supports the theory of anthropogenic global warming from the 5% that can trump all the rest, potentially causing the IPCC’s house of cards to collapse.

Since it has been a while since I have addressed water vapor feedback, and I am now getting more questions about it, I thought this would be a good time to revisit the issue and my opinions on the subject.

Positive water vapor feedback is probably the most “certain” and important of the feedbacks in the climate system in the minds of mainstream climate researchers. Weak warming caused by more carbon dioxide will lead to more water vapor in the atmosphere, which will then amplify the weak warming through water vapor’s role as the atmosphere’s primary greenhouse gas.

Positive water vapor feedback makes sense intuitively. Warmer air masses, on average, contain more water vapor. Warmer air is associated with greater surface evaporation rates, which is the ultimate source of almost all atmospheric water vapor.

And since water vapor is the atmosphere’s main greenhouse gas, most scientists have reasonably inferred that climate warming will be enhanced by increasing water vapor amounts. After all, water vapor feedback is positive in all of the IPCC climate models, too.


But when one looks at the details objectively, it is not so obvious that water vapor feedback in the context of long-term climate change is positive. Remember, it’s not the difference between warmer tropical air masses and cooler high-latitude air masses that will determine water vapor feedback…its how those air masses will each change over time in response to more carbon dioxide. Anything that alters precipitation processes during that process can cause either positive or negative water vapor feedback.

Here are some of those details.

1) Evaporation versus Precipitation

The average amount of water vapor in the atmosphere represents a balance between two competing processes: (1) surface evaporation (the source), and (2) precipitation (the sink). While we know that evaporation increases with temperature, we don’t know very much about how the efficiency of precipitation systems changes with temperature.

The latter process is much more complex than surface evaporation (see Renno et al., 1994), and it is not at all clear that climate models behave realistically in this regard. In fact, the models just “punt” on this issue because our understanding of precipitation systems is just not good enough to put something explicit into the models.

Even cloud resolving models, which can grow individual clouds, have gross approximations and assumptions regarding the precipitation formation process.

2) Negative Water vapor Feedback Can Occur Even with a Water Vapor Increase
Most atmospheric water vapor resides in the lowest levels, in the ‘turbulent boundary layer’, while the water vapor content of the free troposphere is more closely tied to precipitation processes. But because the outgoing longwave radiation is so much more sensitive to small changes in upper-layer humidity especially at low humidities (e.g. see Spencer & Braswell, 1997), it is possible to have a net increase in total integrated water vapor, but negative water vapor feedback from a small decrease in free-tropospheric humidity. See #4 (below) for observational support for this possibility.

3) Cause Versus Effect
Just because we find that unusually warm years have more water vapor in both the boundary layer and free troposphere does not mean that the warming caused the moistening.

There are a variety of processes (e.g. tropospheric wind shear causing changes in precipitation efficiency) which can in turn alter the balance between evaporation and precipitation, which will then cause warming or cooling as a RESULT OF the humidity change – rather than the other way around.

This cause-versus-effect issue has been almost totally ignored in feedback studies, and is analogous to the situation when estimating cloud feedbacks, the subject of our most recent paper.

Similar to our cloud feedback paper, evidence of causation in the opposite direction is the de-correlation between temperature and humidity in the real world versus in climate models (e.g. Sun et al., 2001).

4) Evidence from Radiosondes
There is some evidence that free tropospheric vapor has decreased in recent decades (e.g. the Paltridge et al., 2009 analysis of the NCEP Reanalysis dataset) despite this being a period of surface warming and humidifying in the boundary layer. Miskolczi (2010) used the radiosonde data which provide the main input to the NCEP reanalysis to show that the resulting cooling effect of a decrease in vapor has approximately counterbalanced the warming influence of increasing CO2 over the same period of time, leading to a fairly constant infrared opacity (greenhouse effect).

Of course, water vapor measurements from radiosondes are notoriously unreliable, but one would think that if there was a spurious drying from a humidity sensor problem that it would show up at all altitudes, not just in the free troposphere. The fact that it switches sign right where the turbulent boundary layer pushes up against the free troposphere (around 850 mb, or 5,000 ft.) seems like too much of a coincidence.

5) The Missing “Hot Spot”
Most people don’t realize that the missing tropospheric “hot spot” in satellite temperature trends is potentially related to water vapor feedback. One of the most robust feedback relationships across the IPCC climate models is that those models with the strongest positive water vapor feedback have the strongest negative lapse rate feedback (which is what the “hot spot” would represent). So, the lack of this negative lapse rate feedback signature in the satellite temperature trends could be an indirect indication of little (or even negative) water vapor feedback in nature.

Conclusion
While it seems rather obvious intuitively that a warmer world will have more atmospheric water vapor, and thus positive water vapor feedback, I’ve just listed the first 5 reasons that come to my mind why this might not be the case.

I am not saying that’s what I necessarily believe. I will admit to having waffled on this issue over the years, but that’s because there is evidence on both sides of the debate.

At a minimum, I believe the water vapor feedback issue is more complicated than most mainstream researchers think it is.

In my previous post I argued, using commonly cited numbers, that the greenhouse effect enhancement of adding carbon dioxide to the atmosphere would be about 3% for a doubling of CO2 (“2XCO2”).

The 3% enhancement is based upon 2 commonly quoted numbers: (1) 33 deg. C global-average surface warming for the natural greenhouse effect, and (2) about 1 deg. C additional surface warming from 2XCO2, without feedbacks. (Interestingly, these numbers can only be computed from theory, which always requires a variety of assumptions.)

The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and the estimated surface temperature if there was no atmosphere.


I explained that the 3% statistic is the one we should be dealing with conceptually, rather than what some people seem to be interested in, which is what portion of the Earth’s greenhouse effect is due to CO2. I argued that the answer to that question, which has been recently addressed in a new paper by Schmidt et al., really tells us very little regarding the impact of adding more CO2 to the atmosphere.

But what many people don’t realize is that the 33 deg. C of surface warming is not actually a measure of the greenhouse warming – it represents the balance between TWO competing effects: a greenhouse warming effect of about 60 deg. C (the so-called “pure radiative equilibrium” case), and a convective cooling effect of about 30 deg. C. When these two are combined, we get the real-world observed “radiative-convective equilibrium” case.

This has been known since at least 1964 (Manabe and Strickler, 1964). It was also discussed in Dick Lindzen’s 1990 paper, Some Coolness Regarding Global Warming, which is when I became aware of its significance.

Why is this Important?

When global warming is discussed, the warming effect of greenhouse gases is obviously of prime interest. But it is seldom if ever mentioned that about 50% of the surface warming influence of greenhouse gases has been short-circuited by the cooling effects of weather, as just discussed.

When Danny Braswell and I did similar calculations in 1997 to better understand the physics, we found that 1 deg. C of surface warming was true even for the pure radiative equilibrium case (no convective cooling by weather processes). This would mean that the REAL enhancement of the greenhouse effect with 2XCO2 is really only about 1.5%, not 3%, since the natural greenhouse effect is trying to warm the surface by over 60 deg. C, not by 33 deg. C.

Is this Simple Evidence of Negative Feedback?

These climate basics, which have been known since the 1960s, also raises an intriguing question: If the surface warming effect of 2XCO2 before surface cooling by convection is 1 deg. C, and (as even the IPCC knows) 50% of that natural greenhouse warming is then short-circuited by convection, might this then tell us that negative feedbacks in the climate system can be expected to reduce anthropogenic global warming to only 0.5 deg. C?

I believe this is entirely possible.

How could this happen, since there is so much evidence that water vapor feedback is positive? Because, even if water vapor feedback is positive, an increase in the solar shading effect of clouds (negative cloud feedback) could more than overwhelm the positive water vapor feedback, leading to little net warming.

The IPCC already admits feedbacks due to low clouds are the least understood. Indeed, the evidence presented in Spencer and Braswell (2010), at face value, would suggest this could happen.

We already know that the net effect of clouds is to cool the climate system in response to solar heating. Are we to believe that cloud changes turn into a warming influence when temperatures get a little bit higher? Well, that’s what all of the IPCC coupled climate models do now.

The Importance of Convective Cooling Versus Greenhouse Warming

I sometimes get e-mails asking why I don’t mention convection as a cooling mechanism in the context of global warming. Folks, I used to be virtually the only one speaking out on the subject. For years I harped on this issue.

The reason why I have been recently defending the basic physics of the greenhouse effect is because I think the credibility of those who claim that the greenhouse effect of the atmosphere cannot be increased (or doesn’t even exist) is compromised when they object to something that – as far as I have seen – has no alternative explanation.

I’m always upon open to new theories, but as I have said before, until someone puts their alternative physics into an energy-conserving model of the vertical temperature profile of the atmosphere, which then produces the present-day temperature profile as current models do, it is little more than hand-waving.

[NOTE: What follows assumes the direct (no-feedback) infrared radiative effects of greenhouse gases (water vapor, CO2, methane, etc.) on the Earth’s radiative budget are reasonably well understood. If you want to challenge that assumption, your time might be better spent here.]

I was recently asked by a reader to comment on a new paper by Schmidt et al. which put some numbers behind the common question, What fraction of the Earth’s greenhouse effect is due to carbon dioxide?

There are a wide variety of answers to this question depending on how you define “greenhouse effect”, what your assumed baseline is, etc. Conceptually, in any greenhouse atmosphere, greenhouse gases warm the lower layers and cool the upper layers compared to if those gases were not present. That never changes. It’s the way you compute the relative magnitude (say, in percent) of that warming that depends greatly upon your assumptions.

Note that the greenhouse effect can only be calculated based upon theory. The greenhouse effect isn’t a physical variable like temperature that you can measure. It is a radiative process that affects the atmosphere’s energy budget at all altitudes, warms the surface, and whose components must be calculated based upon radiative transfer theory and the IR absorption characteristics of greenhouse gases (and clouds).


The Wrong Question

I will argue that if what we are REALLY interested in is how much the Earth’s greenhouse effect will be enhanced by adding CO2 to the atmosphere (the only reason we are interested in the CO2 issue anyway, right?), then the above question is not very relevant.

In fact, the answer to it can totally mislead us. This is easy to show with 2 simple examples.

First, assume there was NO naturally occurring carbon dioxide in the atmosphere, and we added 300 ppm. In that case, the natural influence of CO2 on the Earth’s greenhouse effect would be zero, but the influence of adding 300 ppm would be quite significant.

Now, as the second example let’s assume the natural CO2 concentration is high, say 1,000 ppm, and THEN we added 300 ppm. In this second case, the natural role of CO2 in the Earth’s greenhouse effect would be very significant, but our addition of 300 ppm more would have a relatively small direct warming influence.

This is because the more CO2 there is in the atmosphere, the more “saturated” the CO2-portion of the greenhouse effect becomes, a well known feature that has a standard simplified, logarithmic formula for its computation.

Everyone already knows about this mostly saturated condition relative to the radiative effect of carbon dioxide – even the IPCC. Adding more and more CO2 causes incrementally less and less warming (again, assuming no feedback, which is a separate issue)….but the radiative effect of CO2 in the atmosphere is not totally saturated.

And it never can be, for the same reason that you can keep dividing a number by two forever, and the resulting number will get extremely small…but it will never reach zero.

So what do these two examples tell us? If the natural contribution of CO2 to the greenhouse effect was ZERO, then the warming effect of our addition of 300 ppm would be relatively large. But if the natural contribution of CO2 to the greenhouse effect was already large, then the incremental warming effect of adding more will be small.

An extreme example would be Venus, which has 230,000 times as much CO2 in its atmosphere as Earth does. Our addition of CO2 to that atmosphere would have essentially no effect.

The point is that knowing what percentage of the Earth’s natural greenhouse effect comes from carbon dioxide alone tells us little of use in determining how much warming might result from adding more CO2 to the atmosphere.

How Much is the Earth’s Greenhouse Effect Enhanced by Adding More CO2?
This is the question we should be asking, and it can be easily answered with a couple of numbers quoted in the Schmidt et al. article.

Schmidt et al. assumes the commonly quoted 33 deg. C as the amount of surface warming due to the Earth’s greenhouse effect, and for the time being I will assume the same. (In my next blog post, I will explain why this number is NOT a good measure of the Earth’s greenhouse effect.)

Thirteen years ago, Danny Braswell and I did our own calculations to explore the greenhouse effect with a built-from-scratch radiative transfer model, incorporating the IR radiative code developed by Ming Dah Chou at NASA Goddard. The Chou code has also been used in some global climate models.

We calculated, as others have, a direct (no feedback) surface warming of about 1 deg. C as a result of doubling CO2 (“2XCO2”).

So, this immediately gives us numbers we can use to compute a percentage increase in the greenhouse effect: Doubling of atmospheric CO2 (which will probably happen by late in this century) enhances the Earth’s greenhouse effect by about (1/33=) 3%.

This value (3%) for the enhancement of the Earth’s greenhouse effect from our addition of CO2 is much smaller than the 20% value that Schmidt et al. get…but remember that we are addressing two different issues. I claim what we should be interested in is the relative size of our enhancement of the greenhouse effect, rather than how much of the Earth’s natural greenhouse effect is due to CO2. The latter question really proves nothing about how much effect adding MORE CO2 to the atmosphere will have.

Next Time: Why 33 deg. C is a Misleading Number

In my next post, I will discuss why the use of 33 deg. C for surface warming due to the greenhouse effect is very misleading. The issue is not new, as it has been known since the 1960s. I wasn’t aware of its central importance to the global warming debate until Dick Lindzen published his 1990 paper, Some Coolness Concerning Global Warming.

YR MON GLOBE NH SH TROPICS
2009 1 0.251 0.472 0.030 -0.068
2009 2 0.247 0.565 -0.071 -0.045
2009 3 0.191 0.324 0.058 -0.159
2009 4 0.162 0.315 0.008 0.012
2009 5 0.139 0.161 0.118 -0.059
2009 6 0.041 -0.021 0.103 0.105
2009 7 0.429 0.190 0.668 0.506
2009 8 0.242 0.236 0.248 0.406
2009 9 0.505 0.597 0.413 0.594
2009 10 0.362 0.332 0.393 0.383
2009 11 0.498 0.453 0.543 0.479
2009 12 0.284 0.358 0.211 0.506
2010 1 0.648 0.860 0.436 0.681
2010 2 0.603 0.720 0.486 0.791
2010 3 0.653 0.850 0.455 0.726
2010 4 0.501 0.799 0.203 0.633
2010 5 0.534 0.775 0.292 0.708
2010 6 0.436 0.550 0.323 0.476
2010 7 0.489 0.635 0.342 0.420
2010 8 0.511 0.672 0.349 0.362


(NOTE: 9/9/10, fixed 13-month running avg…it was 2 months behind)
While the global-average lower tropospheric temperature remained high, +0.51 deg. C in August, 2010, monitoring of the daily Aqua Ch.5 data at the Discover web site suggests that the cooling of global average sea surface temperatures that started several months ago is now causing the troposphere to cool as well. I will probably provide an update of that plot tomorrow.


As of Julian Day 243 (end of August), the race for warmest year in the 32-year satellite period of record is still too close to call with 1998 continuing its lead by only 0.06 C:

YEAR GL
1998 +0.61
2010 +0.55

As a reminder, six months ago we changed to Version 5.3 of our dataset, which accounts for the mismatch between the average seasonal cycle produced by the older MSU and the newer AMSU instruments. This affects the value of the individual monthly departures, but does not affect the year to year variations, and thus the overall trend remains the same as in Version 5.2. ALSO…we have added the NOAA-18 AMSU to the data processing in v5.3, which provides data since June of 2005. The local observation time of NOAA-18 (now close to 2 p.m., ascending node) is similar to that of NASA’s Aqua satellite (about 1:30 p.m.). The temperature anomalies listed above have changed somewhat as a result of adding NOAA-18.

[NOTE: These satellite measurements are not calibrated to surface thermometer data in any way, but instead use on-board redundant precision platinum resistance thermometers (PRTs) carried on the satellite radiometers. The PRT’s are individually calibrated in a laboratory before being installed in the instruments.]

I am seeing increasing chatter about one or more papers that will (or already have) debunked my ideas on feedbacks in the climate system.

Yet, I cannot remember a climate issue of which I have ever been so certain.

I understand that most people interested in the climate debate will simply believe what their favorite science pundits at RealClimate tell them to believe, which is fine, and I can’t do anything about that.

But for those who want to investigate for themselves, I recommend reading only our latest and most comprehensive paper in Journal of Geophysical Research. It takes you from the very basics of feedback estimation — which I found I had to include because even the experts in the field apparently did not understand them — and for the first time explains why satellite observations of the climate system behave the way they do.

No one has ever done this before to anywhere near the level of detail we do.


[Unfortunately, our 2008 paper in Journal of Climate, I now realize, had insufficient evidence to make the case we were trying to make in 2008. I believe our claims were correct, but the evidence we presented could not unequivocally support those claims. Only after finishing our most recent 2010 paper did I realize the insufficiency of that previous work on the subject.]

Then, once you think you understand the main points we make in the new JGR paper, read any other critiques or criticisms that catch your fancy.

As a teaser, one of the clear conclusions the new paper supports is this: The only times that there is clear evidence of feedback in global satellite data, that feedback is strongly negative.

All I ask is that you evaluate whether anyone can come up with a better explanation than what we have given for the structures we see in the satellite observations of natural climate variations. Do not settle for others’ vague arm-waving dismissals based upon preconceived notions or what others have told them.

You engineers and scientists from other fields are capable of understanding this, and I am appealing to you to bring fresh eyes to a field where the research establishment has become hopelessly inbred and too beholden to special interests to see that which is staring them in the face.

This is the main reason why I wrote The Great Global Warming Blunder…the evidence is simple enough for the science-savvy public to understand. But the experts do not see the evidence because they refuse to open their eyes.