The diagram, known as “burning embers,” is an updated version of one that was a central feature of the panel’s preceding climate report in 2001. The main opposition to including the diagram in 2007, they say, came from officials representing the United States, China, Russia and Saudi Arabia.

People who argue that the IPCC is an “alarmist” body forget that virtually all of the world’s governments belong to it. Thus, governments that don’t want to do anything about climate change have just as much input to the report as countries that do.

This tension between the ideological factions of the IPCC actually gives the reports credibility. Only statements that everyone agrees to make it into the report. A few countries that object to some result can keep it out of the report. This is, in fact, why the IPCC process was designed this way.

This is why some people argue that the actual science of climate change is more alarming than that revealed in the IPCC reports. In any event, if you read the IPCC reports and find it alarming, then you can have great confidence that your alarm is warranted.

Interestingly, it seems that just about everybody now agrees water vapor provides a robustly strong and positive feedback. Roy Spencer even sent me email saying that he agrees.

What I want to focus on here is model verification. If you read the blogs, you’ll often see people say things like “the models are completely unvalidated.” What they mean is that no one has produced a 100-year climate run with a model, then waited a hundred years, and evaluated how the model did. There are many practical problems with doing this, but the biggest is that by the time you determine if your model was right or not, it would be too late to take any meaningful action to head off the problem.

Of course, we could compare the last 150 years of observations to climate model runs for that same period. This has been done, and the models do a pretty good job. But because the models are constructed with knowledge of the present climate, this is clearly a weaker test than one in which you do not know what the answer is in advance.

What about comparing the climate models with shorter temperature records? Like 10 or 15 years? This will not work. In order for the models to correctly simulate short timescales like this, the models have to be initialized with the atmosphere’s present state. This is not done, so short-term fluctuations in the model and in the atmosphere may be completely uncorrelated, and over short times the temperature record may diverge significantly.

So how do we get a sense of the reliability of climate models? The approach taken by the scientific community is really the only one available: analyze and validate the individual processes in the climate models. Thus, the focus of my work has been to study the water vapor feedback and validate its incorporation into climate models. What we have found is that the models appear to be doing a pretty good job at getting this key parameter correct.

If you can validate enough processes of the model (water vapor, clouds, ice, oceans, etc.) then you generate confidence that your model is probably making predictions that are at least in the ballpark. In addition, it gives you a good feeling of where the weak points in the model all are. For example, this type of analysis has demonstrated that most of the uncertainty in the model predictions arises due to clouds.

And having identified the most uncertain processes in the model, you can use other physical constraints to bound their magnitude. For example, a strong argument can be made that the cloud feedback is unlikely to be large and negative.

Once you have a good handle on the individual processes that are operating in the climate, then you can actually estimate future warming without a climate model.

Thus, saying that climate models are “unvalidated” sells them short. They may not have been validated in all the ways we would like to validate them, but scientists have indeed spent a lot of time studying and validating the individual physical processes within the models. The result of this is that we can have a reasonably high confidence that we will get a few degrees of warming by the end of the century if emissions are not reduced.

What’s amazing is not that George Will is selectively quoting to mislead the reader, but that he continues to do so after John sent him a copy of the article in question:

When George Will last wrote about this subject, last May, I sent him a copy of the Science News article he misleadingly quoted in the example I used above. I got a nice note back from him thanking me for sharing it.

I’ll leave it to the reader to decide what this reveals about George Will’s journalistic integrity.

I can sense some frustration from Fleck that this argument lives on despite the publication of his nice BAMS article that lays out the actual history of the argument, and which clearly shows it to be false.

All I can say is: Welcome to the club, John.

Most climate scientists, however, are reasonably certain that a negative feedback big enough to overwhelm the well-known positive feedbacks in the climate system, such as the water vapor feedback [PDF], does not exist. Why?

Negative feedbacks tend to dampen out climate change. If you add greenhouse gases to the atmosphere or the sun brightens, then the hypothetical negative feedback will counteract the warming, leaving the climate nearly unchanged. While it may be comforting to believe that a negative feedback exists, it is extremely difficult to reconcile the existence of a big negative feedback with our past observations of climate variability.

For example, the ice ages rely on a carbon dioxide feedback to provide their large amplitude. If there were a big negative feedback in the system, then how do you explain the large swings in to and out of ice ages? No way that I know of.

Similarly, the Paleocene Eocene Thermal Maximum is also thought to be the result of a huge release of greenhouse gases. With a large negative feedback in the system, how do you explain the rapid temperature rise during that event?

Finally, how do you explain the warming of the last few decades if the climate is intrinsically stable?

Climate skeptics, of course, don’t have to look at all the data. In one thread, they can argue “it’s the sun,” while in another thread they can argue “there is a negative feedback.” The problem is that these are mutually contradictory. Any negative feedback working on carbon dioxide would also work on increased solar forcing. One cannot argue both that our present-day warming is due the sun, and that there is a negative feedback that prevents carbon dioxide from warming and climate.

If you look at all the data, the simplest explanation is that there is no negative feedback, and we are experiencing warming due to increases in greenhouse gas concentrations. There is, in fact, no fully consistent, alternative theory.

Marc’s email contained a link to a recent post by Roy Spencer. In it, Spencer claims:

Obviously, the thermostat (feedback) issue is the most critical one that determines whether manmade global warming will be catastrophic or benign. In this context, it is critical for the public and politicians to understand that the vast majority of climate researchers do not work on feedbacks.

In popular political parlance, most climate researchers do not appreciate the nuanced details of how one estimates feedbacks in nature, and therefore they are not qualified to pass judgment on this issue. Therefore, any claims about how many thousands of scientists agree with the IPCC’s official position on global warming are meaningless.

Did I read that right? The only people qualified to make judgments on the science of climate change are experts in climate feedbacks?

I’ll ignore the questionable and obviously self-serving nature of this claim for now. The surprising point here is that Roy has clearly disqualified virtually every member of Inhofe’s list of 650 “experts” who dismiss the IPCC’s view of climate science. Not only are the Inhofe 650 members not experts on climate feedbacks, but also most of them are not experts on any aspect of the climate. (Note, however, that I’m still an expert because I actually do work on climate feedbacks.)

And since Marc Moreno sent out a link to this post, he obviously agrees that Inhofe’s list is a pile of rubbish.

Finally, something Marc and I can agree on.

Recently Harold Ambler, climate crank and proprietor of TalkingAboutTheWeather.com, published an essay on Huffington Post replete with gross factual errors about the science of climate change.

Word is that this was an editorial slip-up on HuffPo’s part; they don’t typically provide a place for this kind of agitprop. The essay is gone from the site’s portal pages and rumor has it The Huff herself may address the issue soon.

Regardless, the essay is out there getting skeptics all twitterpated (again). These folks can’t find a scientific journal with two hands and a flashlight, but nothing escapes their RSS feeds.

So lets examine a few of the claims again. After all, the only thing hucksters need is for the rest of us to get tired of repeating the same damn truths over and over again. Right?

Right off the bat Mr. Ambler recycles a classic, one of the most durable and thoroughly discredited skeptic chestnuts:

Because it turns out that there is an 800-year lag between temperature and carbon dioxide [in the ice age record], unlike the sense conveyed by Mr. Gore’s graph. You are probably wondering by now — and if you are not, you should be — which rises first, carbon dioxide or temperature. The answer? Temperature. In every case, the ice-core data shows that temperature rises precede rises in carbon dioxide by, on average, 800 years.

The basic science of atmospheric carbon dioxide is well explained in the IPCC reports and on numerous web sites, including in Grist’s How to Talk to a Skeptic series. It’s puzzling that it continues to confuse skeptics.

The claim that the CO2 rise begins after the temperature rise is correct but misleading. The cause of the ice ages is well known: slight shifts in the Earth’s orbit. Those shifts, however, are too weak to explain the full temperature swings seen during ice ages. That’s where carbon dioxide comes in. It acts as a feedback, taking the small effects of orbital changes and turbocharging them into the enormous temperature swings observed in the historical record.

So yes, carbon dioxide plays a key role in ice ages. Arguing otherwise demonstrates a lack of understanding of even the most rudimentary climate physics.

Next:

When the ocean-atmosphere system warms, the oceans discharge vast quantities of carbon dioxide in a process known as de-gassing. For this reason, warm and cold years show up on the Mauna Loa CO2 measurements even in the short term. For instance, the post-Pinatubo-eruption year of 1993 shows the lowest CO2 increase since measurements have been kept. When did the highest CO2 increase take place? During the super El Niño year of 1998.

Check out this plot of the Mauna Loa carbon dioxide record and tell me if you see any effect of ocean temperature in 1993 or 1998:

No? Who you going to believe, Mr. Ambler or your lying eyes?

In fact, there’s no question that humans are responsible the atmospheric abundance of carbon dioxide. The strongest evidence comes from measurements of the isotopic signature of carbon dioxide — the amount of carbon-12, -13, and -14 in the atmosphere. Carbon dioxide from fossil fuels has a unique signature not shared by biomass or volcanoes. This is well described in the IPCC reports and in this RealClimate post among other places.

Next:

Meanwhile, the theory that carbon dioxide "drives" climate in any meaningful way is simply wrong and, again, evidence of a "flat-Earth" mentality. Carbon dioxide cannot absorb an unlimited amount of infrared radiation. Why not? Because it only absorbs heat along limited bandwidths, and is already absorbing just about everything it can.

It is true that the forcing due to carbon dioxide is proportional to the logarithm of the concentration. Mr. Ambler takes that fact and concludes that we are therefore at the maximum forcing from carbon dioxide. Say what? While individual spectral lines do indeed saturate, adding more carbon dioxide pushes the level of saturation higher in the atmosphere — leading to additional heating of the surface.

Evidence of this can be found on Venus, which has a surface temperature of 450°C — hot enough to melt lead; hotter even than Mercury, which is closer to the sun. Why so hot? Venus has a thick, carbon-dioxide-rich atmosphere, which Mercury does not. If, as Mr. Ambler claims, carbon dioxide saturates, Venus’ temperature ought to be lower than Earth’s, owing to the thick sulfuric acid clouds that shroud the planet and reflect sunlight. It’s not; Mr. Ambler does not know what he’s talking about.

Next:

Further, the IPCC Fourth Assessment, like all the ones before it, is based on computer models that presume a positive feedback of atmospheric warming via increased water vapor. … This mechanism has never been shown to exist.

This is another skeptic zombie that just won’t stay killed. It could not be more wrong if Sarah Palin herself said it.

In fact, one of us (hint: not the blogger) recently published a paper estimating the magnitude of the water-vapor feedback exclusively from data — no climate models involved. Sure enough, the water vapor feedback is strong and positive. There are several other observation-based analyses that agree with this conclusion (see references in the paper).

Next:

By the way, water vapor is far more prevalent, and relevant, in the atmosphere than carbon dioxide — a trace gas. Water vapor’s absorption spectrum also overlays that of carbon dioxide. They cannot both absorb the same energy!

To give Mr. Ambler some credit, this was the subject of legitimate scientific uncertainty … in the first half of the twentieth century. However, careful spectroscopic measurements settled it about 50 years ago. There is indeed some overlap, but enough lines do not overlap that carbon dioxide is indeed an important greenhouse gas.

Indeed, the case against carbon dioxide is pretty close to airtight — see, e.g., this old post.

Finally, Mr. Ambler shares his theory of why the climate is warming: it’s everything other than carbon dioxide! It appears the climate science community has gotten it as wrong as those kooky tobacco alarmists.

Notwithstanding Mr. Ambler’s confusions and deceits, humans are now in the climatic drivers’ seat, with the pedal to the metal. Maybe it’s time we put our hands on the wheel.

So here is the reasoning that has led me to conclude that business-as-usual carbon dioxide emissions will lead to temperature increases over the next century of around 3 degrees C.

First, it has been known for over 150 years that adding carbon dioxide to the atmosphere will increase the temperature of the planet. In fact, the very small number of credible skeptics out there, such as Dick Lindzen and Pat Michaels, are on record agreeing that adding greenhouse gases to the atmosphere will warm the planet. What they argue is that the warming will be very small. More on that later.

The conclusion that emitting greenhouse gases will result in warming does not rest on the output of climate models, but is a simple physical argument that predates the invention of the computer. And if you don’t believe in physics, take a look at Venus. That planet features a thick carbon dioxide atmosphere and consequently a surface temperature hot enough to melt lead.

So we know that adding carbon dioxide is going to warm the planet. This leads us to the real question: How much warming are we going to get?

Carbon dioxide by itself will only provide somewhere around 1 degree C warming over the next century. In order to get really large warnings over the 21st century, there needs to be strong positive feedbacks to amplify the initial warming from carbon dioxide.

The strongest positive feedback is due to water vapor. The so-called water-vapor feedback refers to the process whereby an initial warming of the planet, caused for example by an increase in atmospheric carbon dioxide, causes an increase in the specific humidity of the atmosphere. Because water vapor is itself a greenhouse gas, the increase in specific humidity causes additional warming.

The water vapor feedback has long been expected to exert a powerful warming effect because of the belief that the atmosphere’s relative humidity would remain roughly constant — meaning that specific humidity would increase rapidly with surface temperature. Models reproduce this, and the water vapor feedback is the most important reason for the models’ large predicted warming for increases in greenhouse gases over the 21st century.

If you read the blogs, you’ll often see the argument made that no data exist to support the models’ strong positive feedback and that they are simply “computer-generated.” This is incorrect. I recently published a paper [PDF] estimating the magnitude of the water-vapor feedback exclusively from data. No climate model involved.

What we found was evidence that the water vapor feedback is indeed strong and positive. And there are several other observation-based analyses that agree with this conclusion (see the references in my paper).

Overall, the water vapor feedback about doubles the Earth’s response to carbon dioxide alone. If you throw in the other feedbacks (albedo, lapse rate, etc.), you’ll get about a 3 degrees C warming for doubled carbon dioxide (compared to 1 degree C for carbon dioxide alone).

While there is significant uncertainty in this number, it’s hard to believe that it will be fall outside a factor of 2 of this number.

The credible skeptics agree that the Earth will warm over the 21st century, but that the warming will be very small (less than 1 degree C). Could they be right? Possibly. The one way that climate change may not be large is if there exists, somewhere in the climate system, a large negative feedback that compensates for the positive feedback provided by water vapor. If such a negative feedback exists, it seems highly likely that it would somehow revolve around clouds.

To their credit, the few credible climate skeptics out there (Lindzen, Spencer) are indeed searching for negative feedbacks. So far, though, their arguments have been pretty weak and not convinced anyone in the scientific community.

One interpretation of the IPCC’s statement that humans are “very likely” responsible for most of the observed recent warming is that there is about a 10 percent chance that a significant negative feedback (or something equivalent) does exist in the climate system and will preclude significant warming over the century.

My personal opinion is that this is conservative, and that the actual chance we will discover a big negative feedback is actually far smaller. There is simply too much evidence in the paleoclimate record showing large swings of the climate, which tends to preclude the existence of stabilizing negative feedbacks.

This is how I reach the conclusion that warming of a few degrees Celsius is very likely unless we do something about greenhouse-gas emissions. Note that this conclusion is not derived from climate models. Rather, it is derived from fundamental physics combined with observations.

To: PEBO
From: Andrew Dessler
Re: What to do about NASA on your first day in office

Two things:

1. Fire Michael Griffin, NASA’s current administrator. He says stupid things about climate change and is going to be an impediment to the change that NASA needs.
2. Put the Earth back in NASA’s mandate. In 2006, the Bush Administration quietly deleted the phrase “to understand and protect our home planet” from the NASA mission statement. This move perfectly encapsulated Bush’s attitude toward the environment, and with a stroke of your pen you can show how things have changed.

DotEarth links to an interview with economist Gary Yohe about, among other things, uncertainty. Here’s the money quote:

e360: You’ve written recently about uncertainty over the future impacts of climate change and how that plays a role in discouraging action in reducing greenhouse gases. How do you spur world action on this issue when there are still questions out there about future levels of CO2 in the atmosphere and the range of future temperature increases?

Yohe: Uncertainly is ubiquitous. There are some fundamental conclusions that we now know: that the planet is warming; that humans are the cause of it. We’ve seen the climate signal and changes in global mean temperature … But there’s some uncertainty that simply will not be resolved in a timely fashion. Yet once you adopt a risk-management perspective, then uncertainty becomes a reason to do something rather than a reason not to do something. And people who argue against doing anything then have to guarantee that humans aren’t changing the climate. They can’t do that, so they can’t argue against enacting some climate policy. At the same time, though, uncertainty is something we need to recognize will be persistent. We have to learn how to make decisions under uncertainty.

Well said!

Over on Rabett Run, Eli looks into Fred Singer’s finances. Turns out you get paid pretty well to be famous skeptic. I should note here that I don’t believe skeptics are doing it for the money. I am quite convinced that they would be saying exactly the same thing even if they were not getting paid for it. The huge amounts of money they get paid (according to Eli, Fred got $143,000 for his work on the NIPCC) is just a nice bonus. Hey Fred, can I get a job with SEPP?

ClimateAudit has a pretty good post on tropical temperatures:

For people that look at data, it is obvious that the data (in each incarnation) is highly autocorrelated; the degrees of freedom in autocorrelated data can be much lower than people think and, accordingly, the confidence intervals can be surprisingly wide (a point made in Santer et al 2008, though there are some defects in their analysis that we discussed before).

This explains why scientists are not terribly interested in the question of temperature trends “since 1998.” Given the large internal variability and autocorrelation in the data, you just can’t conclude anything about trends in such a short time period. What are the implications of this uncertainty? See the DotEarth link above …